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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/mm/filemap.c
3 *
4 * Copyright (C) 1994-1999 Linus Torvalds
5 */
6
7/*
8 * This file handles the generic file mmap semantics used by
9 * most "normal" filesystems (but you don't /have/ to use this:
10 * the NFS filesystem used to do this differently, for example)
11 */
Linus Torvalds1da177e2005-04-16 15:20:36 -070012#include <linux/module.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070013#include <linux/compiler.h>
14#include <linux/fs.h>
Hiro Yoshiokac22ce142006-06-23 02:04:16 -070015#include <linux/uaccess.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070016#include <linux/aio.h>
Randy.Dunlapc59ede72006-01-11 12:17:46 -080017#include <linux/capability.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070018#include <linux/kernel_stat.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090019#include <linux/gfp.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070020#include <linux/mm.h>
21#include <linux/swap.h>
22#include <linux/mman.h>
23#include <linux/pagemap.h>
24#include <linux/file.h>
25#include <linux/uio.h>
26#include <linux/hash.h>
27#include <linux/writeback.h>
Linus Torvalds53253382007-10-18 14:47:32 -070028#include <linux/backing-dev.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070029#include <linux/pagevec.h>
30#include <linux/blkdev.h>
31#include <linux/security.h>
32#include <linux/syscalls.h>
Paul Jackson44110fe2006-03-24 03:16:04 -080033#include <linux/cpuset.h>
Nick Piggin2f718ff2007-10-16 01:24:59 -070034#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
Balbir Singh8a9f3cc2008-02-07 00:13:53 -080035#include <linux/memcontrol.h>
Dan Magenheimerc515e1f2011-05-26 10:01:43 -060036#include <linux/cleancache.h>
Nick Piggin0f8053a2006-03-22 00:08:33 -080037#include "internal.h"
38
Linus Torvalds1da177e2005-04-16 15:20:36 -070039/*
Linus Torvalds1da177e2005-04-16 15:20:36 -070040 * FIXME: remove all knowledge of the buffer layer from the core VM
41 */
Jan Kara148f9482009-08-17 19:52:36 +020042#include <linux/buffer_head.h> /* for try_to_free_buffers */
Linus Torvalds1da177e2005-04-16 15:20:36 -070043
Linus Torvalds1da177e2005-04-16 15:20:36 -070044#include <asm/mman.h>
45
46/*
47 * Shared mappings implemented 30.11.1994. It's not fully working yet,
48 * though.
49 *
50 * Shared mappings now work. 15.8.1995 Bruno.
51 *
52 * finished 'unifying' the page and buffer cache and SMP-threaded the
53 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
54 *
55 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
56 */
57
58/*
59 * Lock ordering:
60 *
Peter Zijlstra3d48ae42011-05-24 17:12:06 -070061 * ->i_mmap_mutex (truncate_pagecache)
Linus Torvalds1da177e2005-04-16 15:20:36 -070062 * ->private_lock (__free_pte->__set_page_dirty_buffers)
Hugh Dickins5d337b92005-09-03 15:54:41 -070063 * ->swap_lock (exclusive_swap_page, others)
64 * ->mapping->tree_lock
Linus Torvalds1da177e2005-04-16 15:20:36 -070065 *
Jes Sorensen1b1dcc12006-01-09 15:59:24 -080066 * ->i_mutex
Peter Zijlstra3d48ae42011-05-24 17:12:06 -070067 * ->i_mmap_mutex (truncate->unmap_mapping_range)
Linus Torvalds1da177e2005-04-16 15:20:36 -070068 *
69 * ->mmap_sem
Peter Zijlstra3d48ae42011-05-24 17:12:06 -070070 * ->i_mmap_mutex
Hugh Dickinsb8072f02005-10-29 18:16:41 -070071 * ->page_table_lock or pte_lock (various, mainly in memory.c)
Linus Torvalds1da177e2005-04-16 15:20:36 -070072 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
73 *
74 * ->mmap_sem
75 * ->lock_page (access_process_vm)
76 *
Nick Piggin82591e62006-10-19 23:29:10 -070077 * ->i_mutex (generic_file_buffered_write)
78 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
Linus Torvalds1da177e2005-04-16 15:20:36 -070079 *
Christoph Hellwigf758eea2011-04-21 18:19:44 -060080 * bdi->wb.list_lock
Dave Chinnera66979a2011-03-22 22:23:41 +110081 * sb_lock (fs/fs-writeback.c)
Linus Torvalds1da177e2005-04-16 15:20:36 -070082 * ->mapping->tree_lock (__sync_single_inode)
83 *
Peter Zijlstra3d48ae42011-05-24 17:12:06 -070084 * ->i_mmap_mutex
Linus Torvalds1da177e2005-04-16 15:20:36 -070085 * ->anon_vma.lock (vma_adjust)
86 *
87 * ->anon_vma.lock
Hugh Dickinsb8072f02005-10-29 18:16:41 -070088 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
Linus Torvalds1da177e2005-04-16 15:20:36 -070089 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -070090 * ->page_table_lock or pte_lock
Hugh Dickins5d337b92005-09-03 15:54:41 -070091 * ->swap_lock (try_to_unmap_one)
Linus Torvalds1da177e2005-04-16 15:20:36 -070092 * ->private_lock (try_to_unmap_one)
93 * ->tree_lock (try_to_unmap_one)
94 * ->zone.lru_lock (follow_page->mark_page_accessed)
Nick Piggin053837f2006-01-18 17:42:27 -080095 * ->zone.lru_lock (check_pte_range->isolate_lru_page)
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 * ->private_lock (page_remove_rmap->set_page_dirty)
97 * ->tree_lock (page_remove_rmap->set_page_dirty)
Christoph Hellwigf758eea2011-04-21 18:19:44 -060098 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
Dave Chinner250df6e2011-03-22 22:23:36 +110099 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
Christoph Hellwigf758eea2011-04-21 18:19:44 -0600100 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
Dave Chinner250df6e2011-03-22 22:23:36 +1100101 * ->inode->i_lock (zap_pte_range->set_page_dirty)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
103 *
Andi Kleen6a460792009-09-16 11:50:15 +0200104 * (code doesn't rely on that order, so you could switch it around)
105 * ->tasklist_lock (memory_failure, collect_procs_ao)
Peter Zijlstra3d48ae42011-05-24 17:12:06 -0700106 * ->i_mmap_mutex
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107 */
108
109/*
Minchan Kime64a7822011-03-22 16:32:44 -0700110 * Delete a page from the page cache and free it. Caller has to make
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111 * sure the page is locked and that nobody else uses it - or that usage
Nick Piggin19fd6232008-07-25 19:45:32 -0700112 * is safe. The caller must hold the mapping's tree_lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113 */
Minchan Kime64a7822011-03-22 16:32:44 -0700114void __delete_from_page_cache(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115{
116 struct address_space *mapping = page->mapping;
117
Dan Magenheimerc515e1f2011-05-26 10:01:43 -0600118 /*
119 * if we're uptodate, flush out into the cleancache, otherwise
120 * invalidate any existing cleancache entries. We can't leave
121 * stale data around in the cleancache once our page is gone
122 */
123 if (PageUptodate(page) && PageMappedToDisk(page))
124 cleancache_put_page(page);
125 else
126 cleancache_flush_page(mapping, page);
127
Linus Torvalds1da177e2005-04-16 15:20:36 -0700128 radix_tree_delete(&mapping->page_tree, page->index);
129 page->mapping = NULL;
Hugh Dickinsb85e0ef2011-07-25 17:12:25 -0700130 /* Leave page->index set: truncation lookup relies upon it */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700131 mapping->nrpages--;
Christoph Lameter347ce432006-06-30 01:55:35 -0700132 __dec_zone_page_state(page, NR_FILE_PAGES);
KOSAKI Motohiro4b021082009-09-21 17:01:33 -0700133 if (PageSwapBacked(page))
134 __dec_zone_page_state(page, NR_SHMEM);
Nick Piggin45426812007-07-15 23:38:12 -0700135 BUG_ON(page_mapped(page));
Linus Torvalds3a692792007-12-19 14:05:13 -0800136
137 /*
138 * Some filesystems seem to re-dirty the page even after
139 * the VM has canceled the dirty bit (eg ext3 journaling).
140 *
141 * Fix it up by doing a final dirty accounting check after
142 * having removed the page entirely.
143 */
144 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
145 dec_zone_page_state(page, NR_FILE_DIRTY);
146 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
147 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700148}
149
Minchan Kim702cfbf2011-03-22 16:32:43 -0700150/**
151 * delete_from_page_cache - delete page from page cache
152 * @page: the page which the kernel is trying to remove from page cache
153 *
154 * This must be called only on pages that have been verified to be in the page
155 * cache and locked. It will never put the page into the free list, the caller
156 * has a reference on the page.
157 */
158void delete_from_page_cache(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159{
160 struct address_space *mapping = page->mapping;
Linus Torvalds6072d132010-12-01 13:35:19 -0500161 void (*freepage)(struct page *);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162
Matt Mackallcd7619d2005-05-01 08:59:01 -0700163 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700164
Linus Torvalds6072d132010-12-01 13:35:19 -0500165 freepage = mapping->a_ops->freepage;
Nick Piggin19fd6232008-07-25 19:45:32 -0700166 spin_lock_irq(&mapping->tree_lock);
Minchan Kime64a7822011-03-22 16:32:44 -0700167 __delete_from_page_cache(page);
Nick Piggin19fd6232008-07-25 19:45:32 -0700168 spin_unlock_irq(&mapping->tree_lock);
Daisuke Nishimurae767e052009-05-28 14:34:28 -0700169 mem_cgroup_uncharge_cache_page(page);
Linus Torvalds6072d132010-12-01 13:35:19 -0500170
171 if (freepage)
172 freepage(page);
Minchan Kim97cecb52011-03-22 16:30:53 -0700173 page_cache_release(page);
174}
175EXPORT_SYMBOL(delete_from_page_cache);
176
Jens Axboe7eaceac2011-03-10 08:52:07 +0100177static int sleep_on_page(void *word)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700179 io_schedule();
180 return 0;
181}
182
Jens Axboe7eaceac2011-03-10 08:52:07 +0100183static int sleep_on_page_killable(void *word)
Matthew Wilcox2687a352007-12-06 11:18:49 -0500184{
Jens Axboe7eaceac2011-03-10 08:52:07 +0100185 sleep_on_page(word);
Matthew Wilcox2687a352007-12-06 11:18:49 -0500186 return fatal_signal_pending(current) ? -EINTR : 0;
187}
188
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189/**
Randy Dunlap485bb992006-06-23 02:03:49 -0700190 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
Martin Waitz67be2dd2005-05-01 08:59:26 -0700191 * @mapping: address space structure to write
192 * @start: offset in bytes where the range starts
Andrew Morton469eb4d2006-03-24 03:17:45 -0800193 * @end: offset in bytes where the range ends (inclusive)
Martin Waitz67be2dd2005-05-01 08:59:26 -0700194 * @sync_mode: enable synchronous operation
Linus Torvalds1da177e2005-04-16 15:20:36 -0700195 *
Randy Dunlap485bb992006-06-23 02:03:49 -0700196 * Start writeback against all of a mapping's dirty pages that lie
197 * within the byte offsets <start, end> inclusive.
198 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700199 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
Randy Dunlap485bb992006-06-23 02:03:49 -0700200 * opposed to a regular memory cleansing writeback. The difference between
Linus Torvalds1da177e2005-04-16 15:20:36 -0700201 * these two operations is that if a dirty page/buffer is encountered, it must
202 * be waited upon, and not just skipped over.
203 */
Andrew Mortonebcf28e2006-03-24 03:18:04 -0800204int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
205 loff_t end, int sync_mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700206{
207 int ret;
208 struct writeback_control wbc = {
209 .sync_mode = sync_mode,
Nick Piggin05fe4782009-01-06 14:39:08 -0800210 .nr_to_write = LONG_MAX,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -0700211 .range_start = start,
212 .range_end = end,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700213 };
214
215 if (!mapping_cap_writeback_dirty(mapping))
216 return 0;
217
218 ret = do_writepages(mapping, &wbc);
219 return ret;
220}
221
222static inline int __filemap_fdatawrite(struct address_space *mapping,
223 int sync_mode)
224{
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -0700225 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700226}
227
228int filemap_fdatawrite(struct address_space *mapping)
229{
230 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
231}
232EXPORT_SYMBOL(filemap_fdatawrite);
233
Jan Karaf4c0a0f2008-07-11 19:27:31 -0400234int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
Andrew Mortonebcf28e2006-03-24 03:18:04 -0800235 loff_t end)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700236{
237 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
238}
Jan Karaf4c0a0f2008-07-11 19:27:31 -0400239EXPORT_SYMBOL(filemap_fdatawrite_range);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700240
Randy Dunlap485bb992006-06-23 02:03:49 -0700241/**
242 * filemap_flush - mostly a non-blocking flush
243 * @mapping: target address_space
244 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700245 * This is a mostly non-blocking flush. Not suitable for data-integrity
246 * purposes - I/O may not be started against all dirty pages.
247 */
248int filemap_flush(struct address_space *mapping)
249{
250 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
251}
252EXPORT_SYMBOL(filemap_flush);
253
Randy Dunlap485bb992006-06-23 02:03:49 -0700254/**
Christoph Hellwig94004ed2009-09-30 22:16:33 +0200255 * filemap_fdatawait_range - wait for writeback to complete
256 * @mapping: address space structure to wait for
257 * @start_byte: offset in bytes where the range starts
258 * @end_byte: offset in bytes where the range ends (inclusive)
Randy Dunlap485bb992006-06-23 02:03:49 -0700259 *
Christoph Hellwig94004ed2009-09-30 22:16:33 +0200260 * Walk the list of under-writeback pages of the given address space
261 * in the given range and wait for all of them.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700262 */
Christoph Hellwig94004ed2009-09-30 22:16:33 +0200263int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
264 loff_t end_byte)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700265{
Christoph Hellwig94004ed2009-09-30 22:16:33 +0200266 pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
267 pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700268 struct pagevec pvec;
269 int nr_pages;
270 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700271
Christoph Hellwig94004ed2009-09-30 22:16:33 +0200272 if (end_byte < start_byte)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700273 return 0;
274
275 pagevec_init(&pvec, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700276 while ((index <= end) &&
277 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
278 PAGECACHE_TAG_WRITEBACK,
279 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
280 unsigned i;
281
282 for (i = 0; i < nr_pages; i++) {
283 struct page *page = pvec.pages[i];
284
285 /* until radix tree lookup accepts end_index */
286 if (page->index > end)
287 continue;
288
289 wait_on_page_writeback(page);
Rik van Riel212260a2011-01-13 15:46:06 -0800290 if (TestClearPageError(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700291 ret = -EIO;
292 }
293 pagevec_release(&pvec);
294 cond_resched();
295 }
296
297 /* Check for outstanding write errors */
298 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
299 ret = -ENOSPC;
300 if (test_and_clear_bit(AS_EIO, &mapping->flags))
301 ret = -EIO;
302
303 return ret;
304}
Jan Karad3bccb62009-08-17 19:30:27 +0200305EXPORT_SYMBOL(filemap_fdatawait_range);
306
307/**
Randy Dunlap485bb992006-06-23 02:03:49 -0700308 * filemap_fdatawait - wait for all under-writeback pages to complete
Linus Torvalds1da177e2005-04-16 15:20:36 -0700309 * @mapping: address space structure to wait for
Randy Dunlap485bb992006-06-23 02:03:49 -0700310 *
311 * Walk the list of under-writeback pages of the given address space
312 * and wait for all of them.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700313 */
314int filemap_fdatawait(struct address_space *mapping)
315{
316 loff_t i_size = i_size_read(mapping->host);
317
318 if (i_size == 0)
319 return 0;
320
Christoph Hellwig94004ed2009-09-30 22:16:33 +0200321 return filemap_fdatawait_range(mapping, 0, i_size - 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700322}
323EXPORT_SYMBOL(filemap_fdatawait);
324
325int filemap_write_and_wait(struct address_space *mapping)
326{
OGAWA Hirofumi28fd1292006-01-08 01:02:14 -0800327 int err = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700328
329 if (mapping->nrpages) {
OGAWA Hirofumi28fd1292006-01-08 01:02:14 -0800330 err = filemap_fdatawrite(mapping);
331 /*
332 * Even if the above returned error, the pages may be
333 * written partially (e.g. -ENOSPC), so we wait for it.
334 * But the -EIO is special case, it may indicate the worst
335 * thing (e.g. bug) happened, so we avoid waiting for it.
336 */
337 if (err != -EIO) {
338 int err2 = filemap_fdatawait(mapping);
339 if (!err)
340 err = err2;
341 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342 }
OGAWA Hirofumi28fd1292006-01-08 01:02:14 -0800343 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700344}
OGAWA Hirofumi28fd1292006-01-08 01:02:14 -0800345EXPORT_SYMBOL(filemap_write_and_wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700346
Randy Dunlap485bb992006-06-23 02:03:49 -0700347/**
348 * filemap_write_and_wait_range - write out & wait on a file range
349 * @mapping: the address_space for the pages
350 * @lstart: offset in bytes where the range starts
351 * @lend: offset in bytes where the range ends (inclusive)
352 *
Andrew Morton469eb4d2006-03-24 03:17:45 -0800353 * Write out and wait upon file offsets lstart->lend, inclusive.
354 *
355 * Note that `lend' is inclusive (describes the last byte to be written) so
356 * that this function can be used to write to the very end-of-file (end = -1).
357 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700358int filemap_write_and_wait_range(struct address_space *mapping,
359 loff_t lstart, loff_t lend)
360{
OGAWA Hirofumi28fd1292006-01-08 01:02:14 -0800361 int err = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700362
363 if (mapping->nrpages) {
OGAWA Hirofumi28fd1292006-01-08 01:02:14 -0800364 err = __filemap_fdatawrite_range(mapping, lstart, lend,
365 WB_SYNC_ALL);
366 /* See comment of filemap_write_and_wait() */
367 if (err != -EIO) {
Christoph Hellwig94004ed2009-09-30 22:16:33 +0200368 int err2 = filemap_fdatawait_range(mapping,
369 lstart, lend);
OGAWA Hirofumi28fd1292006-01-08 01:02:14 -0800370 if (!err)
371 err = err2;
372 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700373 }
OGAWA Hirofumi28fd1292006-01-08 01:02:14 -0800374 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375}
Chris Masonf6995582009-04-15 13:22:37 -0400376EXPORT_SYMBOL(filemap_write_and_wait_range);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700377
Randy Dunlap485bb992006-06-23 02:03:49 -0700378/**
Miklos Szeredief6a3c62011-03-22 16:30:52 -0700379 * replace_page_cache_page - replace a pagecache page with a new one
380 * @old: page to be replaced
381 * @new: page to replace with
382 * @gfp_mask: allocation mode
383 *
384 * This function replaces a page in the pagecache with a new one. On
385 * success it acquires the pagecache reference for the new page and
386 * drops it for the old page. Both the old and new pages must be
387 * locked. This function does not add the new page to the LRU, the
388 * caller must do that.
389 *
390 * The remove + add is atomic. The only way this function can fail is
391 * memory allocation failure.
392 */
393int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
394{
395 int error;
396 struct mem_cgroup *memcg = NULL;
397
398 VM_BUG_ON(!PageLocked(old));
399 VM_BUG_ON(!PageLocked(new));
400 VM_BUG_ON(new->mapping);
401
402 /*
403 * This is not page migration, but prepare_migration and
404 * end_migration does enough work for charge replacement.
405 *
406 * In the longer term we probably want a specialized function
407 * for moving the charge from old to new in a more efficient
408 * manner.
409 */
410 error = mem_cgroup_prepare_migration(old, new, &memcg, gfp_mask);
411 if (error)
412 return error;
413
414 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
415 if (!error) {
416 struct address_space *mapping = old->mapping;
417 void (*freepage)(struct page *);
418
419 pgoff_t offset = old->index;
420 freepage = mapping->a_ops->freepage;
421
422 page_cache_get(new);
423 new->mapping = mapping;
424 new->index = offset;
425
426 spin_lock_irq(&mapping->tree_lock);
Minchan Kime64a7822011-03-22 16:32:44 -0700427 __delete_from_page_cache(old);
Miklos Szeredief6a3c62011-03-22 16:30:52 -0700428 error = radix_tree_insert(&mapping->page_tree, offset, new);
429 BUG_ON(error);
430 mapping->nrpages++;
431 __inc_zone_page_state(new, NR_FILE_PAGES);
432 if (PageSwapBacked(new))
433 __inc_zone_page_state(new, NR_SHMEM);
434 spin_unlock_irq(&mapping->tree_lock);
435 radix_tree_preload_end();
436 if (freepage)
437 freepage(old);
438 page_cache_release(old);
439 mem_cgroup_end_migration(memcg, old, new, true);
440 } else {
441 mem_cgroup_end_migration(memcg, old, new, false);
442 }
443
444 return error;
445}
446EXPORT_SYMBOL_GPL(replace_page_cache_page);
447
448/**
Nick Piggine2867812008-07-25 19:45:30 -0700449 * add_to_page_cache_locked - add a locked page to the pagecache
Randy Dunlap485bb992006-06-23 02:03:49 -0700450 * @page: page to add
451 * @mapping: the page's address_space
452 * @offset: page index
453 * @gfp_mask: page allocation mode
454 *
Nick Piggine2867812008-07-25 19:45:30 -0700455 * This function is used to add a page to the pagecache. It must be locked.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700456 * This function does not add the page to the LRU. The caller must do that.
457 */
Nick Piggine2867812008-07-25 19:45:30 -0700458int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
Al Viro6daa0e22005-10-21 03:18:50 -0400459 pgoff_t offset, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700460{
Nick Piggine2867812008-07-25 19:45:30 -0700461 int error;
462
463 VM_BUG_ON(!PageLocked(page));
Hugh Dickins31475dd2011-08-03 16:21:27 -0700464 VM_BUG_ON(PageSwapBacked(page));
Nick Piggine2867812008-07-25 19:45:30 -0700465
466 error = mem_cgroup_cache_charge(page, current->mm,
KAMEZAWA Hiroyuki2c26fdd2009-01-07 18:08:10 -0800467 gfp_mask & GFP_RECLAIM_MASK);
Balbir Singh35c754d2008-02-07 00:14:05 -0800468 if (error)
469 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700470
Balbir Singh35c754d2008-02-07 00:14:05 -0800471 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700472 if (error == 0) {
Nick Piggine2867812008-07-25 19:45:30 -0700473 page_cache_get(page);
474 page->mapping = mapping;
475 page->index = offset;
476
Nick Piggin19fd6232008-07-25 19:45:32 -0700477 spin_lock_irq(&mapping->tree_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700478 error = radix_tree_insert(&mapping->page_tree, offset, page);
Nick Piggine2867812008-07-25 19:45:30 -0700479 if (likely(!error)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700480 mapping->nrpages++;
Christoph Lameter347ce432006-06-30 01:55:35 -0700481 __inc_zone_page_state(page, NR_FILE_PAGES);
Daisuke Nishimurae767e052009-05-28 14:34:28 -0700482 spin_unlock_irq(&mapping->tree_lock);
Nick Piggine2867812008-07-25 19:45:30 -0700483 } else {
484 page->mapping = NULL;
Hugh Dickinsb85e0ef2011-07-25 17:12:25 -0700485 /* Leave page->index set: truncation relies upon it */
Daisuke Nishimurae767e052009-05-28 14:34:28 -0700486 spin_unlock_irq(&mapping->tree_lock);
KAMEZAWA Hiroyuki69029cd2008-07-25 01:47:14 -0700487 mem_cgroup_uncharge_cache_page(page);
Nick Piggine2867812008-07-25 19:45:30 -0700488 page_cache_release(page);
489 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700490 radix_tree_preload_end();
Balbir Singh35c754d2008-02-07 00:14:05 -0800491 } else
KAMEZAWA Hiroyuki69029cd2008-07-25 01:47:14 -0700492 mem_cgroup_uncharge_cache_page(page);
Balbir Singh8a9f3cc2008-02-07 00:13:53 -0800493out:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700494 return error;
495}
Nick Piggine2867812008-07-25 19:45:30 -0700496EXPORT_SYMBOL(add_to_page_cache_locked);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700497
498int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
Al Viro6daa0e22005-10-21 03:18:50 -0400499 pgoff_t offset, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700500{
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700501 int ret;
502
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700503 ret = add_to_page_cache(page, mapping, offset, gfp_mask);
Hugh Dickins31475dd2011-08-03 16:21:27 -0700504 if (ret == 0)
505 lru_cache_add_file(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506 return ret;
507}
Evgeniy Polyakov18bc0bb2009-02-09 17:02:42 +0300508EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509
Paul Jackson44110fe2006-03-24 03:16:04 -0800510#ifdef CONFIG_NUMA
Nick Piggin2ae88142006-10-28 10:38:23 -0700511struct page *__page_cache_alloc(gfp_t gfp)
Paul Jackson44110fe2006-03-24 03:16:04 -0800512{
Miao Xiec0ff7452010-05-24 14:32:08 -0700513 int n;
514 struct page *page;
515
Paul Jackson44110fe2006-03-24 03:16:04 -0800516 if (cpuset_do_page_mem_spread()) {
Miao Xiec0ff7452010-05-24 14:32:08 -0700517 get_mems_allowed();
518 n = cpuset_mem_spread_node();
519 page = alloc_pages_exact_node(n, gfp, 0);
520 put_mems_allowed();
521 return page;
Paul Jackson44110fe2006-03-24 03:16:04 -0800522 }
Nick Piggin2ae88142006-10-28 10:38:23 -0700523 return alloc_pages(gfp, 0);
Paul Jackson44110fe2006-03-24 03:16:04 -0800524}
Nick Piggin2ae88142006-10-28 10:38:23 -0700525EXPORT_SYMBOL(__page_cache_alloc);
Paul Jackson44110fe2006-03-24 03:16:04 -0800526#endif
527
Linus Torvalds1da177e2005-04-16 15:20:36 -0700528/*
529 * In order to wait for pages to become available there must be
530 * waitqueues associated with pages. By using a hash table of
531 * waitqueues where the bucket discipline is to maintain all
532 * waiters on the same queue and wake all when any of the pages
533 * become available, and for the woken contexts to check to be
534 * sure the appropriate page became available, this saves space
535 * at a cost of "thundering herd" phenomena during rare hash
536 * collisions.
537 */
538static wait_queue_head_t *page_waitqueue(struct page *page)
539{
540 const struct zone *zone = page_zone(page);
541
542 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
543}
544
545static inline void wake_up_page(struct page *page, int bit)
546{
547 __wake_up_bit(page_waitqueue(page), &page->flags, bit);
548}
549
Harvey Harrison920c7a52008-02-04 22:29:26 -0800550void wait_on_page_bit(struct page *page, int bit_nr)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700551{
552 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
553
554 if (test_bit(bit_nr, &page->flags))
Jens Axboe7eaceac2011-03-10 08:52:07 +0100555 __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700556 TASK_UNINTERRUPTIBLE);
557}
558EXPORT_SYMBOL(wait_on_page_bit);
559
KOSAKI Motohirof62e00c2011-05-24 17:11:29 -0700560int wait_on_page_bit_killable(struct page *page, int bit_nr)
561{
562 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
563
564 if (!test_bit(bit_nr, &page->flags))
565 return 0;
566
567 return __wait_on_bit(page_waitqueue(page), &wait,
568 sleep_on_page_killable, TASK_KILLABLE);
569}
570
Linus Torvalds1da177e2005-04-16 15:20:36 -0700571/**
David Howells385e1ca2009-04-03 16:42:39 +0100572 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
Randy Dunlap697f6192009-04-13 14:39:54 -0700573 * @page: Page defining the wait queue of interest
574 * @waiter: Waiter to add to the queue
David Howells385e1ca2009-04-03 16:42:39 +0100575 *
576 * Add an arbitrary @waiter to the wait queue for the nominated @page.
577 */
578void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
579{
580 wait_queue_head_t *q = page_waitqueue(page);
581 unsigned long flags;
582
583 spin_lock_irqsave(&q->lock, flags);
584 __add_wait_queue(q, waiter);
585 spin_unlock_irqrestore(&q->lock, flags);
586}
587EXPORT_SYMBOL_GPL(add_page_wait_queue);
588
589/**
Randy Dunlap485bb992006-06-23 02:03:49 -0700590 * unlock_page - unlock a locked page
Linus Torvalds1da177e2005-04-16 15:20:36 -0700591 * @page: the page
592 *
593 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
594 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
595 * mechananism between PageLocked pages and PageWriteback pages is shared.
596 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
597 *
Nick Piggin8413ac92008-10-18 20:26:59 -0700598 * The mb is necessary to enforce ordering between the clear_bit and the read
599 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700600 */
Harvey Harrison920c7a52008-02-04 22:29:26 -0800601void unlock_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700602{
Nick Piggin8413ac92008-10-18 20:26:59 -0700603 VM_BUG_ON(!PageLocked(page));
604 clear_bit_unlock(PG_locked, &page->flags);
605 smp_mb__after_clear_bit();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700606 wake_up_page(page, PG_locked);
607}
608EXPORT_SYMBOL(unlock_page);
609
Randy Dunlap485bb992006-06-23 02:03:49 -0700610/**
611 * end_page_writeback - end writeback against a page
612 * @page: the page
Linus Torvalds1da177e2005-04-16 15:20:36 -0700613 */
614void end_page_writeback(struct page *page)
615{
Miklos Szerediac6aadb2008-04-28 02:12:38 -0700616 if (TestClearPageReclaim(page))
617 rotate_reclaimable_page(page);
618
619 if (!test_clear_page_writeback(page))
620 BUG();
621
Linus Torvalds1da177e2005-04-16 15:20:36 -0700622 smp_mb__after_clear_bit();
623 wake_up_page(page, PG_writeback);
624}
625EXPORT_SYMBOL(end_page_writeback);
626
Randy Dunlap485bb992006-06-23 02:03:49 -0700627/**
628 * __lock_page - get a lock on the page, assuming we need to sleep to get it
629 * @page: the page to lock
Linus Torvalds1da177e2005-04-16 15:20:36 -0700630 */
Harvey Harrison920c7a52008-02-04 22:29:26 -0800631void __lock_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700632{
633 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
634
Jens Axboe7eaceac2011-03-10 08:52:07 +0100635 __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700636 TASK_UNINTERRUPTIBLE);
637}
638EXPORT_SYMBOL(__lock_page);
639
Harvey Harrisonb5606c22008-02-13 15:03:16 -0800640int __lock_page_killable(struct page *page)
Matthew Wilcox2687a352007-12-06 11:18:49 -0500641{
642 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
643
644 return __wait_on_bit_lock(page_waitqueue(page), &wait,
Jens Axboe7eaceac2011-03-10 08:52:07 +0100645 sleep_on_page_killable, TASK_KILLABLE);
Matthew Wilcox2687a352007-12-06 11:18:49 -0500646}
Evgeniy Polyakov18bc0bb2009-02-09 17:02:42 +0300647EXPORT_SYMBOL_GPL(__lock_page_killable);
Matthew Wilcox2687a352007-12-06 11:18:49 -0500648
Michel Lespinassed065bd82010-10-26 14:21:57 -0700649int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
650 unsigned int flags)
651{
KOSAKI Motohiro37b23e02011-05-24 17:11:30 -0700652 if (flags & FAULT_FLAG_ALLOW_RETRY) {
653 /*
654 * CAUTION! In this case, mmap_sem is not released
655 * even though return 0.
656 */
657 if (flags & FAULT_FLAG_RETRY_NOWAIT)
658 return 0;
659
660 up_read(&mm->mmap_sem);
661 if (flags & FAULT_FLAG_KILLABLE)
662 wait_on_page_locked_killable(page);
663 else
Gleb Natapov318b2752011-03-22 16:30:51 -0700664 wait_on_page_locked(page);
Michel Lespinassed065bd82010-10-26 14:21:57 -0700665 return 0;
KOSAKI Motohiro37b23e02011-05-24 17:11:30 -0700666 } else {
667 if (flags & FAULT_FLAG_KILLABLE) {
668 int ret;
669
670 ret = __lock_page_killable(page);
671 if (ret) {
672 up_read(&mm->mmap_sem);
673 return 0;
674 }
675 } else
676 __lock_page(page);
677 return 1;
Michel Lespinassed065bd82010-10-26 14:21:57 -0700678 }
679}
680
Randy Dunlap485bb992006-06-23 02:03:49 -0700681/**
682 * find_get_page - find and get a page reference
683 * @mapping: the address_space to search
684 * @offset: the page index
685 *
Nick Pigginda6052f2006-09-25 23:31:35 -0700686 * Is there a pagecache struct page at the given (mapping, offset) tuple?
687 * If yes, increment its refcount and return it; if no, return NULL.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700688 */
Nick Piggina60637c2008-07-25 19:45:31 -0700689struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700690{
Nick Piggina60637c2008-07-25 19:45:31 -0700691 void **pagep;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700692 struct page *page;
693
Nick Piggina60637c2008-07-25 19:45:31 -0700694 rcu_read_lock();
695repeat:
696 page = NULL;
697 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
698 if (pagep) {
699 page = radix_tree_deref_slot(pagep);
Nick Piggin27d20fd2010-11-11 14:05:19 -0800700 if (unlikely(!page))
701 goto out;
Hugh Dickinsa2c16d62011-08-03 16:21:19 -0700702 if (radix_tree_exception(page)) {
Hugh Dickins8079b1c2011-08-03 16:21:28 -0700703 if (radix_tree_deref_retry(page))
704 goto repeat;
705 /*
706 * Otherwise, shmem/tmpfs must be storing a swap entry
707 * here as an exceptional entry: so return it without
708 * attempting to raise page count.
709 */
710 goto out;
Hugh Dickinsa2c16d62011-08-03 16:21:19 -0700711 }
Nick Piggina60637c2008-07-25 19:45:31 -0700712 if (!page_cache_get_speculative(page))
713 goto repeat;
714
715 /*
716 * Has the page moved?
717 * This is part of the lockless pagecache protocol. See
718 * include/linux/pagemap.h for details.
719 */
720 if (unlikely(page != *pagep)) {
721 page_cache_release(page);
722 goto repeat;
723 }
724 }
Nick Piggin27d20fd2010-11-11 14:05:19 -0800725out:
Nick Piggina60637c2008-07-25 19:45:31 -0700726 rcu_read_unlock();
727
Linus Torvalds1da177e2005-04-16 15:20:36 -0700728 return page;
729}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700730EXPORT_SYMBOL(find_get_page);
731
Randy Dunlap485bb992006-06-23 02:03:49 -0700732/**
Linus Torvalds1da177e2005-04-16 15:20:36 -0700733 * find_lock_page - locate, pin and lock a pagecache page
Martin Waitz67be2dd2005-05-01 08:59:26 -0700734 * @mapping: the address_space to search
735 * @offset: the page index
Linus Torvalds1da177e2005-04-16 15:20:36 -0700736 *
737 * Locates the desired pagecache page, locks it, increments its reference
738 * count and returns its address.
739 *
740 * Returns zero if the page was not present. find_lock_page() may sleep.
741 */
Nick Piggina60637c2008-07-25 19:45:31 -0700742struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700743{
744 struct page *page;
745
Linus Torvalds1da177e2005-04-16 15:20:36 -0700746repeat:
Nick Piggina60637c2008-07-25 19:45:31 -0700747 page = find_get_page(mapping, offset);
Hugh Dickinsa2c16d62011-08-03 16:21:19 -0700748 if (page && !radix_tree_exception(page)) {
Nick Piggina60637c2008-07-25 19:45:31 -0700749 lock_page(page);
750 /* Has the page been truncated? */
751 if (unlikely(page->mapping != mapping)) {
752 unlock_page(page);
753 page_cache_release(page);
754 goto repeat;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700755 }
Nick Piggina60637c2008-07-25 19:45:31 -0700756 VM_BUG_ON(page->index != offset);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700757 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700758 return page;
759}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700760EXPORT_SYMBOL(find_lock_page);
761
762/**
763 * find_or_create_page - locate or add a pagecache page
Martin Waitz67be2dd2005-05-01 08:59:26 -0700764 * @mapping: the page's address_space
765 * @index: the page's index into the mapping
766 * @gfp_mask: page allocation mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700767 *
768 * Locates a page in the pagecache. If the page is not present, a new page
769 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
770 * LRU list. The returned page is locked and has its reference count
771 * incremented.
772 *
773 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
774 * allocation!
775 *
776 * find_or_create_page() returns the desired page's address, or zero on
777 * memory exhaustion.
778 */
779struct page *find_or_create_page(struct address_space *mapping,
Fengguang Wu57f6b962007-10-16 01:24:37 -0700780 pgoff_t index, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700781{
Nick Piggineb2be182007-10-16 01:24:57 -0700782 struct page *page;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700783 int err;
784repeat:
785 page = find_lock_page(mapping, index);
786 if (!page) {
Nick Piggineb2be182007-10-16 01:24:57 -0700787 page = __page_cache_alloc(gfp_mask);
788 if (!page)
789 return NULL;
Nick Piggin67d58ac2009-01-06 14:40:28 -0800790 /*
791 * We want a regular kernel memory (not highmem or DMA etc)
792 * allocation for the radix tree nodes, but we need to honour
793 * the context-specific requirements the caller has asked for.
794 * GFP_RECLAIM_MASK collects those requirements.
795 */
796 err = add_to_page_cache_lru(page, mapping, index,
797 (gfp_mask & GFP_RECLAIM_MASK));
Nick Piggineb2be182007-10-16 01:24:57 -0700798 if (unlikely(err)) {
799 page_cache_release(page);
800 page = NULL;
801 if (err == -EEXIST)
802 goto repeat;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700803 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700804 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700805 return page;
806}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700807EXPORT_SYMBOL(find_or_create_page);
808
809/**
810 * find_get_pages - gang pagecache lookup
811 * @mapping: The address_space to search
812 * @start: The starting page index
813 * @nr_pages: The maximum number of pages
814 * @pages: Where the resulting pages are placed
815 *
816 * find_get_pages() will search for and return a group of up to
817 * @nr_pages pages in the mapping. The pages are placed at @pages.
818 * find_get_pages() takes a reference against the returned pages.
819 *
820 * The search returns a group of mapping-contiguous pages with ascending
821 * indexes. There may be holes in the indices due to not-present pages.
822 *
823 * find_get_pages() returns the number of pages which were found.
824 */
825unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
826 unsigned int nr_pages, struct page **pages)
827{
828 unsigned int i;
829 unsigned int ret;
Nick Piggina60637c2008-07-25 19:45:31 -0700830 unsigned int nr_found;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700831
Nick Piggina60637c2008-07-25 19:45:31 -0700832 rcu_read_lock();
833restart:
834 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
Hugh Dickins63286502011-08-03 16:21:18 -0700835 (void ***)pages, NULL, start, nr_pages);
Nick Piggina60637c2008-07-25 19:45:31 -0700836 ret = 0;
837 for (i = 0; i < nr_found; i++) {
838 struct page *page;
839repeat:
840 page = radix_tree_deref_slot((void **)pages[i]);
841 if (unlikely(!page))
842 continue;
Hugh Dickins9d8aa4e2011-03-22 16:33:06 -0700843
Hugh Dickinsa2c16d62011-08-03 16:21:19 -0700844 if (radix_tree_exception(page)) {
Hugh Dickins8079b1c2011-08-03 16:21:28 -0700845 if (radix_tree_deref_retry(page)) {
846 /*
847 * Transient condition which can only trigger
848 * when entry at index 0 moves out of or back
849 * to root: none yet gotten, safe to restart.
850 */
851 WARN_ON(start | i);
852 goto restart;
853 }
Hugh Dickinsa2c16d62011-08-03 16:21:19 -0700854 /*
Hugh Dickins8079b1c2011-08-03 16:21:28 -0700855 * Otherwise, shmem/tmpfs must be storing a swap entry
856 * here as an exceptional entry: so skip over it -
857 * we only reach this from invalidate_mapping_pages().
Hugh Dickinsa2c16d62011-08-03 16:21:19 -0700858 */
Hugh Dickins8079b1c2011-08-03 16:21:28 -0700859 continue;
Nick Piggin27d20fd2010-11-11 14:05:19 -0800860 }
Nick Piggina60637c2008-07-25 19:45:31 -0700861
862 if (!page_cache_get_speculative(page))
863 goto repeat;
864
865 /* Has the page moved? */
866 if (unlikely(page != *((void **)pages[i]))) {
867 page_cache_release(page);
868 goto repeat;
869 }
870
871 pages[ret] = page;
872 ret++;
873 }
Hugh Dickins5b280c02011-03-22 16:33:07 -0700874
875 /*
876 * If all entries were removed before we could secure them,
877 * try again, because callers stop trying once 0 is returned.
878 */
879 if (unlikely(!ret && nr_found))
880 goto restart;
Nick Piggina60637c2008-07-25 19:45:31 -0700881 rcu_read_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700882 return ret;
883}
884
Jens Axboeebf43502006-04-27 08:46:01 +0200885/**
886 * find_get_pages_contig - gang contiguous pagecache lookup
887 * @mapping: The address_space to search
888 * @index: The starting page index
889 * @nr_pages: The maximum number of pages
890 * @pages: Where the resulting pages are placed
891 *
892 * find_get_pages_contig() works exactly like find_get_pages(), except
893 * that the returned number of pages are guaranteed to be contiguous.
894 *
895 * find_get_pages_contig() returns the number of pages which were found.
896 */
897unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
898 unsigned int nr_pages, struct page **pages)
899{
900 unsigned int i;
901 unsigned int ret;
Nick Piggina60637c2008-07-25 19:45:31 -0700902 unsigned int nr_found;
Jens Axboeebf43502006-04-27 08:46:01 +0200903
Nick Piggina60637c2008-07-25 19:45:31 -0700904 rcu_read_lock();
905restart:
906 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
Hugh Dickins63286502011-08-03 16:21:18 -0700907 (void ***)pages, NULL, index, nr_pages);
Nick Piggina60637c2008-07-25 19:45:31 -0700908 ret = 0;
909 for (i = 0; i < nr_found; i++) {
910 struct page *page;
911repeat:
912 page = radix_tree_deref_slot((void **)pages[i]);
913 if (unlikely(!page))
914 continue;
Hugh Dickins9d8aa4e2011-03-22 16:33:06 -0700915
Hugh Dickinsa2c16d62011-08-03 16:21:19 -0700916 if (radix_tree_exception(page)) {
Hugh Dickins8079b1c2011-08-03 16:21:28 -0700917 if (radix_tree_deref_retry(page)) {
918 /*
919 * Transient condition which can only trigger
920 * when entry at index 0 moves out of or back
921 * to root: none yet gotten, safe to restart.
922 */
923 goto restart;
924 }
Hugh Dickinsa2c16d62011-08-03 16:21:19 -0700925 /*
Hugh Dickins8079b1c2011-08-03 16:21:28 -0700926 * Otherwise, shmem/tmpfs must be storing a swap entry
927 * here as an exceptional entry: so stop looking for
928 * contiguous pages.
Hugh Dickinsa2c16d62011-08-03 16:21:19 -0700929 */
Hugh Dickins8079b1c2011-08-03 16:21:28 -0700930 break;
Hugh Dickinsa2c16d62011-08-03 16:21:19 -0700931 }
Nick Piggina60637c2008-07-25 19:45:31 -0700932
Nick Piggina60637c2008-07-25 19:45:31 -0700933 if (!page_cache_get_speculative(page))
934 goto repeat;
935
936 /* Has the page moved? */
937 if (unlikely(page != *((void **)pages[i]))) {
938 page_cache_release(page);
939 goto repeat;
940 }
941
Nick Piggin9cbb4cb2011-01-13 15:45:51 -0800942 /*
943 * must check mapping and index after taking the ref.
944 * otherwise we can get both false positives and false
945 * negatives, which is just confusing to the caller.
946 */
947 if (page->mapping == NULL || page->index != index) {
948 page_cache_release(page);
949 break;
950 }
951
Nick Piggina60637c2008-07-25 19:45:31 -0700952 pages[ret] = page;
953 ret++;
Jens Axboeebf43502006-04-27 08:46:01 +0200954 index++;
955 }
Nick Piggina60637c2008-07-25 19:45:31 -0700956 rcu_read_unlock();
957 return ret;
Jens Axboeebf43502006-04-27 08:46:01 +0200958}
David Howellsef71c152007-05-09 02:33:44 -0700959EXPORT_SYMBOL(find_get_pages_contig);
Jens Axboeebf43502006-04-27 08:46:01 +0200960
Randy Dunlap485bb992006-06-23 02:03:49 -0700961/**
962 * find_get_pages_tag - find and return pages that match @tag
963 * @mapping: the address_space to search
964 * @index: the starting page index
965 * @tag: the tag index
966 * @nr_pages: the maximum number of pages
967 * @pages: where the resulting pages are placed
968 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700969 * Like find_get_pages, except we only return pages which are tagged with
Randy Dunlap485bb992006-06-23 02:03:49 -0700970 * @tag. We update @index to index the next page for the traversal.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700971 */
972unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
973 int tag, unsigned int nr_pages, struct page **pages)
974{
975 unsigned int i;
976 unsigned int ret;
Nick Piggina60637c2008-07-25 19:45:31 -0700977 unsigned int nr_found;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700978
Nick Piggina60637c2008-07-25 19:45:31 -0700979 rcu_read_lock();
980restart:
981 nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
982 (void ***)pages, *index, nr_pages, tag);
983 ret = 0;
984 for (i = 0; i < nr_found; i++) {
985 struct page *page;
986repeat:
987 page = radix_tree_deref_slot((void **)pages[i]);
988 if (unlikely(!page))
989 continue;
Hugh Dickins9d8aa4e2011-03-22 16:33:06 -0700990
Hugh Dickinsa2c16d62011-08-03 16:21:19 -0700991 if (radix_tree_exception(page)) {
Hugh Dickins8079b1c2011-08-03 16:21:28 -0700992 if (radix_tree_deref_retry(page)) {
993 /*
994 * Transient condition which can only trigger
995 * when entry at index 0 moves out of or back
996 * to root: none yet gotten, safe to restart.
997 */
998 goto restart;
999 }
Hugh Dickinsa2c16d62011-08-03 16:21:19 -07001000 /*
Hugh Dickins8079b1c2011-08-03 16:21:28 -07001001 * This function is never used on a shmem/tmpfs
1002 * mapping, so a swap entry won't be found here.
Hugh Dickinsa2c16d62011-08-03 16:21:19 -07001003 */
Hugh Dickins8079b1c2011-08-03 16:21:28 -07001004 BUG();
Hugh Dickinsa2c16d62011-08-03 16:21:19 -07001005 }
Nick Piggina60637c2008-07-25 19:45:31 -07001006
1007 if (!page_cache_get_speculative(page))
1008 goto repeat;
1009
1010 /* Has the page moved? */
1011 if (unlikely(page != *((void **)pages[i]))) {
1012 page_cache_release(page);
1013 goto repeat;
1014 }
1015
1016 pages[ret] = page;
1017 ret++;
1018 }
Hugh Dickins5b280c02011-03-22 16:33:07 -07001019
1020 /*
1021 * If all entries were removed before we could secure them,
1022 * try again, because callers stop trying once 0 is returned.
1023 */
1024 if (unlikely(!ret && nr_found))
1025 goto restart;
Nick Piggina60637c2008-07-25 19:45:31 -07001026 rcu_read_unlock();
1027
Linus Torvalds1da177e2005-04-16 15:20:36 -07001028 if (ret)
1029 *index = pages[ret - 1]->index + 1;
Nick Piggina60637c2008-07-25 19:45:31 -07001030
Linus Torvalds1da177e2005-04-16 15:20:36 -07001031 return ret;
1032}
David Howellsef71c152007-05-09 02:33:44 -07001033EXPORT_SYMBOL(find_get_pages_tag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001034
Randy Dunlap485bb992006-06-23 02:03:49 -07001035/**
1036 * grab_cache_page_nowait - returns locked page at given index in given cache
1037 * @mapping: target address_space
1038 * @index: the page index
1039 *
Robert P. J. Day72fd4a32007-02-10 01:45:59 -08001040 * Same as grab_cache_page(), but do not wait if the page is unavailable.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041 * This is intended for speculative data generators, where the data can
1042 * be regenerated if the page couldn't be grabbed. This routine should
1043 * be safe to call while holding the lock for another page.
1044 *
1045 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1046 * and deadlock against the caller's locked page.
1047 */
1048struct page *
Fengguang Wu57f6b962007-10-16 01:24:37 -07001049grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001050{
1051 struct page *page = find_get_page(mapping, index);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001052
1053 if (page) {
Nick Piggin529ae9a2008-08-02 12:01:03 +02001054 if (trylock_page(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001055 return page;
1056 page_cache_release(page);
1057 return NULL;
1058 }
Nick Piggin2ae88142006-10-28 10:38:23 -07001059 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
Nick Piggin67d58ac2009-01-06 14:40:28 -08001060 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001061 page_cache_release(page);
1062 page = NULL;
1063 }
1064 return page;
1065}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001066EXPORT_SYMBOL(grab_cache_page_nowait);
1067
Wu Fengguang76d42bd2006-06-25 05:48:43 -07001068/*
1069 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1070 * a _large_ part of the i/o request. Imagine the worst scenario:
1071 *
1072 * ---R__________________________________________B__________
1073 * ^ reading here ^ bad block(assume 4k)
1074 *
1075 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1076 * => failing the whole request => read(R) => read(R+1) =>
1077 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1078 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1079 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1080 *
1081 * It is going insane. Fix it by quickly scaling down the readahead size.
1082 */
1083static void shrink_readahead_size_eio(struct file *filp,
1084 struct file_ra_state *ra)
1085{
Wu Fengguang76d42bd2006-06-25 05:48:43 -07001086 ra->ra_pages /= 4;
Wu Fengguang76d42bd2006-06-25 05:48:43 -07001087}
1088
Randy Dunlap485bb992006-06-23 02:03:49 -07001089/**
Christoph Hellwig36e78912008-02-08 04:21:24 -08001090 * do_generic_file_read - generic file read routine
Randy Dunlap485bb992006-06-23 02:03:49 -07001091 * @filp: the file to read
1092 * @ppos: current file position
1093 * @desc: read_descriptor
1094 * @actor: read method
1095 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001096 * This is a generic file read routine, and uses the
Randy Dunlap485bb992006-06-23 02:03:49 -07001097 * mapping->a_ops->readpage() function for the actual low-level stuff.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001098 *
1099 * This is really ugly. But the goto's actually try to clarify some
1100 * of the logic when it comes to error handling etc.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001101 */
Christoph Hellwig36e78912008-02-08 04:21:24 -08001102static void do_generic_file_read(struct file *filp, loff_t *ppos,
1103 read_descriptor_t *desc, read_actor_t actor)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001104{
Christoph Hellwig36e78912008-02-08 04:21:24 -08001105 struct address_space *mapping = filp->f_mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001106 struct inode *inode = mapping->host;
Christoph Hellwig36e78912008-02-08 04:21:24 -08001107 struct file_ra_state *ra = &filp->f_ra;
Fengguang Wu57f6b962007-10-16 01:24:37 -07001108 pgoff_t index;
1109 pgoff_t last_index;
1110 pgoff_t prev_index;
1111 unsigned long offset; /* offset into pagecache page */
Jan Karaec0f1632007-05-06 14:49:25 -07001112 unsigned int prev_offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001113 int error;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001114
Linus Torvalds1da177e2005-04-16 15:20:36 -07001115 index = *ppos >> PAGE_CACHE_SHIFT;
Fengguang Wu7ff81072007-10-16 01:24:35 -07001116 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1117 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001118 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1119 offset = *ppos & ~PAGE_CACHE_MASK;
1120
Linus Torvalds1da177e2005-04-16 15:20:36 -07001121 for (;;) {
1122 struct page *page;
Fengguang Wu57f6b962007-10-16 01:24:37 -07001123 pgoff_t end_index;
NeilBrowna32ea1e2007-07-17 04:03:04 -07001124 loff_t isize;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001125 unsigned long nr, ret;
1126
Linus Torvalds1da177e2005-04-16 15:20:36 -07001127 cond_resched();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001128find_page:
1129 page = find_get_page(mapping, index);
Fengguang Wu3ea89ee2007-07-19 01:48:02 -07001130 if (!page) {
Rusty Russellcf914a72007-07-19 01:48:08 -07001131 page_cache_sync_readahead(mapping,
Fengguang Wu7ff81072007-10-16 01:24:35 -07001132 ra, filp,
Fengguang Wu3ea89ee2007-07-19 01:48:02 -07001133 index, last_index - index);
1134 page = find_get_page(mapping, index);
1135 if (unlikely(page == NULL))
1136 goto no_cached_page;
1137 }
1138 if (PageReadahead(page)) {
Rusty Russellcf914a72007-07-19 01:48:08 -07001139 page_cache_async_readahead(mapping,
Fengguang Wu7ff81072007-10-16 01:24:35 -07001140 ra, filp, page,
Fengguang Wu3ea89ee2007-07-19 01:48:02 -07001141 index, last_index - index);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001142 }
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07001143 if (!PageUptodate(page)) {
1144 if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1145 !mapping->a_ops->is_partially_uptodate)
1146 goto page_not_up_to_date;
Nick Piggin529ae9a2008-08-02 12:01:03 +02001147 if (!trylock_page(page))
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07001148 goto page_not_up_to_date;
Dave Hansen8d056cb2010-11-11 14:05:15 -08001149 /* Did it get truncated before we got the lock? */
1150 if (!page->mapping)
1151 goto page_not_up_to_date_locked;
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07001152 if (!mapping->a_ops->is_partially_uptodate(page,
1153 desc, offset))
1154 goto page_not_up_to_date_locked;
1155 unlock_page(page);
1156 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001157page_ok:
NeilBrowna32ea1e2007-07-17 04:03:04 -07001158 /*
1159 * i_size must be checked after we know the page is Uptodate.
1160 *
1161 * Checking i_size after the check allows us to calculate
1162 * the correct value for "nr", which means the zero-filled
1163 * part of the page is not copied back to userspace (unless
1164 * another truncate extends the file - this is desired though).
1165 */
1166
1167 isize = i_size_read(inode);
1168 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1169 if (unlikely(!isize || index > end_index)) {
1170 page_cache_release(page);
1171 goto out;
1172 }
1173
1174 /* nr is the maximum number of bytes to copy from this page */
1175 nr = PAGE_CACHE_SIZE;
1176 if (index == end_index) {
1177 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1178 if (nr <= offset) {
1179 page_cache_release(page);
1180 goto out;
1181 }
1182 }
1183 nr = nr - offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001184
1185 /* If users can be writing to this page using arbitrary
1186 * virtual addresses, take care about potential aliasing
1187 * before reading the page on the kernel side.
1188 */
1189 if (mapping_writably_mapped(mapping))
1190 flush_dcache_page(page);
1191
1192 /*
Jan Karaec0f1632007-05-06 14:49:25 -07001193 * When a sequential read accesses a page several times,
1194 * only mark it as accessed the first time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001195 */
Jan Karaec0f1632007-05-06 14:49:25 -07001196 if (prev_index != index || offset != prev_offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001197 mark_page_accessed(page);
1198 prev_index = index;
1199
1200 /*
1201 * Ok, we have the page, and it's up-to-date, so
1202 * now we can copy it to user space...
1203 *
1204 * The actor routine returns how many bytes were actually used..
1205 * NOTE! This may not be the same as how much of a user buffer
1206 * we filled up (we may be padding etc), so we can only update
1207 * "pos" here (the actor routine has to update the user buffer
1208 * pointers and the remaining count).
1209 */
1210 ret = actor(desc, page, offset, nr);
1211 offset += ret;
1212 index += offset >> PAGE_CACHE_SHIFT;
1213 offset &= ~PAGE_CACHE_MASK;
Jan Kara6ce745e2007-05-06 14:49:26 -07001214 prev_offset = offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001215
1216 page_cache_release(page);
1217 if (ret == nr && desc->count)
1218 continue;
1219 goto out;
1220
1221page_not_up_to_date:
1222 /* Get exclusive access to the page ... */
Oleg Nesterov85462322008-06-08 21:20:43 +04001223 error = lock_page_killable(page);
1224 if (unlikely(error))
1225 goto readpage_error;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001226
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07001227page_not_up_to_date_locked:
Nick Pigginda6052f2006-09-25 23:31:35 -07001228 /* Did it get truncated before we got the lock? */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001229 if (!page->mapping) {
1230 unlock_page(page);
1231 page_cache_release(page);
1232 continue;
1233 }
1234
1235 /* Did somebody else fill it already? */
1236 if (PageUptodate(page)) {
1237 unlock_page(page);
1238 goto page_ok;
1239 }
1240
1241readpage:
Jeff Moyer91803b42010-05-26 11:49:40 -04001242 /*
1243 * A previous I/O error may have been due to temporary
1244 * failures, eg. multipath errors.
1245 * PG_error will be set again if readpage fails.
1246 */
1247 ClearPageError(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001248 /* Start the actual read. The read will unlock the page. */
1249 error = mapping->a_ops->readpage(filp, page);
1250
Zach Brown994fc28c2005-12-15 14:28:17 -08001251 if (unlikely(error)) {
1252 if (error == AOP_TRUNCATED_PAGE) {
1253 page_cache_release(page);
1254 goto find_page;
1255 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001256 goto readpage_error;
Zach Brown994fc28c2005-12-15 14:28:17 -08001257 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001258
1259 if (!PageUptodate(page)) {
Oleg Nesterov85462322008-06-08 21:20:43 +04001260 error = lock_page_killable(page);
1261 if (unlikely(error))
1262 goto readpage_error;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001263 if (!PageUptodate(page)) {
1264 if (page->mapping == NULL) {
1265 /*
Christoph Hellwig2ecdc822010-01-26 17:27:20 +01001266 * invalidate_mapping_pages got it
Linus Torvalds1da177e2005-04-16 15:20:36 -07001267 */
1268 unlock_page(page);
1269 page_cache_release(page);
1270 goto find_page;
1271 }
1272 unlock_page(page);
Fengguang Wu7ff81072007-10-16 01:24:35 -07001273 shrink_readahead_size_eio(filp, ra);
Oleg Nesterov85462322008-06-08 21:20:43 +04001274 error = -EIO;
1275 goto readpage_error;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001276 }
1277 unlock_page(page);
1278 }
1279
Linus Torvalds1da177e2005-04-16 15:20:36 -07001280 goto page_ok;
1281
1282readpage_error:
1283 /* UHHUH! A synchronous read error occurred. Report it */
1284 desc->error = error;
1285 page_cache_release(page);
1286 goto out;
1287
1288no_cached_page:
1289 /*
1290 * Ok, it wasn't cached, so we need to create a new
1291 * page..
1292 */
Nick Piggineb2be182007-10-16 01:24:57 -07001293 page = page_cache_alloc_cold(mapping);
1294 if (!page) {
1295 desc->error = -ENOMEM;
1296 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001297 }
Nick Piggineb2be182007-10-16 01:24:57 -07001298 error = add_to_page_cache_lru(page, mapping,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001299 index, GFP_KERNEL);
1300 if (error) {
Nick Piggineb2be182007-10-16 01:24:57 -07001301 page_cache_release(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001302 if (error == -EEXIST)
1303 goto find_page;
1304 desc->error = error;
1305 goto out;
1306 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001307 goto readpage;
1308 }
1309
1310out:
Fengguang Wu7ff81072007-10-16 01:24:35 -07001311 ra->prev_pos = prev_index;
1312 ra->prev_pos <<= PAGE_CACHE_SHIFT;
1313 ra->prev_pos |= prev_offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001314
Fengguang Wuf4e6b492007-10-16 01:24:33 -07001315 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
Krishna Kumar0c6aa262008-10-15 22:01:13 -07001316 file_accessed(filp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001317}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001318
1319int file_read_actor(read_descriptor_t *desc, struct page *page,
1320 unsigned long offset, unsigned long size)
1321{
1322 char *kaddr;
1323 unsigned long left, count = desc->count;
1324
1325 if (size > count)
1326 size = count;
1327
1328 /*
1329 * Faults on the destination of a read are common, so do it before
1330 * taking the kmap.
1331 */
1332 if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1333 kaddr = kmap_atomic(page, KM_USER0);
1334 left = __copy_to_user_inatomic(desc->arg.buf,
1335 kaddr + offset, size);
1336 kunmap_atomic(kaddr, KM_USER0);
1337 if (left == 0)
1338 goto success;
1339 }
1340
1341 /* Do it the slow way */
1342 kaddr = kmap(page);
1343 left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1344 kunmap(page);
1345
1346 if (left) {
1347 size -= left;
1348 desc->error = -EFAULT;
1349 }
1350success:
1351 desc->count = count - size;
1352 desc->written += size;
1353 desc->arg.buf += size;
1354 return size;
1355}
1356
Dmitriy Monakhov0ceb3312007-05-08 00:23:02 -07001357/*
1358 * Performs necessary checks before doing a write
1359 * @iov: io vector request
1360 * @nr_segs: number of segments in the iovec
1361 * @count: number of bytes to write
1362 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1363 *
1364 * Adjust number of segments and amount of bytes to write (nr_segs should be
1365 * properly initialized first). Returns appropriate error code that caller
1366 * should return or zero in case that write should be allowed.
1367 */
1368int generic_segment_checks(const struct iovec *iov,
1369 unsigned long *nr_segs, size_t *count, int access_flags)
1370{
1371 unsigned long seg;
1372 size_t cnt = 0;
1373 for (seg = 0; seg < *nr_segs; seg++) {
1374 const struct iovec *iv = &iov[seg];
1375
1376 /*
1377 * If any segment has a negative length, or the cumulative
1378 * length ever wraps negative then return -EINVAL.
1379 */
1380 cnt += iv->iov_len;
1381 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1382 return -EINVAL;
1383 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1384 continue;
1385 if (seg == 0)
1386 return -EFAULT;
1387 *nr_segs = seg;
1388 cnt -= iv->iov_len; /* This segment is no good */
1389 break;
1390 }
1391 *count = cnt;
1392 return 0;
1393}
1394EXPORT_SYMBOL(generic_segment_checks);
1395
Randy Dunlap485bb992006-06-23 02:03:49 -07001396/**
Henrik Kretzschmarb2abacf2006-10-04 02:15:22 -07001397 * generic_file_aio_read - generic filesystem read routine
Randy Dunlap485bb992006-06-23 02:03:49 -07001398 * @iocb: kernel I/O control block
1399 * @iov: io vector request
1400 * @nr_segs: number of segments in the iovec
Henrik Kretzschmarb2abacf2006-10-04 02:15:22 -07001401 * @pos: current file position
Randy Dunlap485bb992006-06-23 02:03:49 -07001402 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001403 * This is the "read()" routine for all filesystems
1404 * that can use the page cache directly.
1405 */
1406ssize_t
Badari Pulavarty543ade12006-09-30 23:28:48 -07001407generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1408 unsigned long nr_segs, loff_t pos)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001409{
1410 struct file *filp = iocb->ki_filp;
1411 ssize_t retval;
Josef Bacik66f998f2010-05-23 11:00:54 -04001412 unsigned long seg = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001413 size_t count;
Badari Pulavarty543ade12006-09-30 23:28:48 -07001414 loff_t *ppos = &iocb->ki_pos;
Jens Axboe55602dd2010-06-24 15:05:37 +02001415 struct blk_plug plug;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001416
1417 count = 0;
Dmitriy Monakhov0ceb3312007-05-08 00:23:02 -07001418 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1419 if (retval)
1420 return retval;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001421
Jens Axboe55602dd2010-06-24 15:05:37 +02001422 blk_start_plug(&plug);
1423
Linus Torvalds1da177e2005-04-16 15:20:36 -07001424 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1425 if (filp->f_flags & O_DIRECT) {
Badari Pulavarty543ade12006-09-30 23:28:48 -07001426 loff_t size;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001427 struct address_space *mapping;
1428 struct inode *inode;
1429
1430 mapping = filp->f_mapping;
1431 inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001432 if (!count)
1433 goto out; /* skip atime */
1434 size = i_size_read(inode);
1435 if (pos < size) {
Nick Piggin48b47c52009-01-06 14:40:22 -08001436 retval = filemap_write_and_wait_range(mapping, pos,
1437 pos + iov_length(iov, nr_segs) - 1);
Christoph Hellwiga969e902008-07-23 21:27:04 -07001438 if (!retval) {
1439 retval = mapping->a_ops->direct_IO(READ, iocb,
1440 iov, pos, nr_segs);
1441 }
Josef Bacik66f998f2010-05-23 11:00:54 -04001442 if (retval > 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001443 *ppos = pos + retval;
Josef Bacik66f998f2010-05-23 11:00:54 -04001444 count -= retval;
1445 }
1446
1447 /*
1448 * Btrfs can have a short DIO read if we encounter
1449 * compressed extents, so if there was an error, or if
1450 * we've already read everything we wanted to, or if
1451 * there was a short read because we hit EOF, go ahead
1452 * and return. Otherwise fallthrough to buffered io for
1453 * the rest of the read.
1454 */
1455 if (retval < 0 || !count || *ppos >= size) {
Hugh Dickins11fa9772008-07-23 21:27:34 -07001456 file_accessed(filp);
1457 goto out;
1458 }
Steven Whitehouse0e0bcae2006-09-27 14:45:07 -04001459 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001460 }
1461
Josef Bacik66f998f2010-05-23 11:00:54 -04001462 count = retval;
Hugh Dickins11fa9772008-07-23 21:27:34 -07001463 for (seg = 0; seg < nr_segs; seg++) {
1464 read_descriptor_t desc;
Josef Bacik66f998f2010-05-23 11:00:54 -04001465 loff_t offset = 0;
1466
1467 /*
1468 * If we did a short DIO read we need to skip the section of the
1469 * iov that we've already read data into.
1470 */
1471 if (count) {
1472 if (count > iov[seg].iov_len) {
1473 count -= iov[seg].iov_len;
1474 continue;
1475 }
1476 offset = count;
1477 count = 0;
1478 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001479
Hugh Dickins11fa9772008-07-23 21:27:34 -07001480 desc.written = 0;
Josef Bacik66f998f2010-05-23 11:00:54 -04001481 desc.arg.buf = iov[seg].iov_base + offset;
1482 desc.count = iov[seg].iov_len - offset;
Hugh Dickins11fa9772008-07-23 21:27:34 -07001483 if (desc.count == 0)
1484 continue;
1485 desc.error = 0;
1486 do_generic_file_read(filp, ppos, &desc, file_read_actor);
1487 retval += desc.written;
1488 if (desc.error) {
1489 retval = retval ?: desc.error;
1490 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001491 }
Hugh Dickins11fa9772008-07-23 21:27:34 -07001492 if (desc.count > 0)
1493 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001494 }
1495out:
Jens Axboe55602dd2010-06-24 15:05:37 +02001496 blk_finish_plug(&plug);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001497 return retval;
1498}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001499EXPORT_SYMBOL(generic_file_aio_read);
1500
Linus Torvalds1da177e2005-04-16 15:20:36 -07001501static ssize_t
1502do_readahead(struct address_space *mapping, struct file *filp,
Fengguang Wu57f6b962007-10-16 01:24:37 -07001503 pgoff_t index, unsigned long nr)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001504{
1505 if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1506 return -EINVAL;
1507
Wu Fengguangf7e839d2009-06-16 15:31:20 -07001508 force_page_cache_readahead(mapping, filp, index, nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001509 return 0;
1510}
1511
Heiko Carstens6673e0c2009-01-14 14:14:02 +01001512SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001513{
1514 ssize_t ret;
1515 struct file *file;
1516
1517 ret = -EBADF;
1518 file = fget(fd);
1519 if (file) {
1520 if (file->f_mode & FMODE_READ) {
1521 struct address_space *mapping = file->f_mapping;
Fengguang Wu57f6b962007-10-16 01:24:37 -07001522 pgoff_t start = offset >> PAGE_CACHE_SHIFT;
1523 pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001524 unsigned long len = end - start + 1;
1525 ret = do_readahead(mapping, file, start, len);
1526 }
1527 fput(file);
1528 }
1529 return ret;
1530}
Heiko Carstens6673e0c2009-01-14 14:14:02 +01001531#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1532asmlinkage long SyS_readahead(long fd, loff_t offset, long count)
1533{
1534 return SYSC_readahead((int) fd, offset, (size_t) count);
1535}
1536SYSCALL_ALIAS(sys_readahead, SyS_readahead);
1537#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -07001538
1539#ifdef CONFIG_MMU
Randy Dunlap485bb992006-06-23 02:03:49 -07001540/**
1541 * page_cache_read - adds requested page to the page cache if not already there
1542 * @file: file to read
1543 * @offset: page index
1544 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001545 * This adds the requested page to the page cache if it isn't already there,
1546 * and schedules an I/O to read in its contents from disk.
1547 */
Harvey Harrison920c7a52008-02-04 22:29:26 -08001548static int page_cache_read(struct file *file, pgoff_t offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001549{
1550 struct address_space *mapping = file->f_mapping;
1551 struct page *page;
Zach Brown994fc28c2005-12-15 14:28:17 -08001552 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001553
Zach Brown994fc28c2005-12-15 14:28:17 -08001554 do {
1555 page = page_cache_alloc_cold(mapping);
1556 if (!page)
1557 return -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001558
Zach Brown994fc28c2005-12-15 14:28:17 -08001559 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1560 if (ret == 0)
1561 ret = mapping->a_ops->readpage(file, page);
1562 else if (ret == -EEXIST)
1563 ret = 0; /* losing race to add is OK */
1564
Linus Torvalds1da177e2005-04-16 15:20:36 -07001565 page_cache_release(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001566
Zach Brown994fc28c2005-12-15 14:28:17 -08001567 } while (ret == AOP_TRUNCATED_PAGE);
1568
1569 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001570}
1571
1572#define MMAP_LOTSAMISS (100)
1573
Linus Torvaldsef00e082009-06-16 15:31:25 -07001574/*
1575 * Synchronous readahead happens when we don't even find
1576 * a page in the page cache at all.
1577 */
1578static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1579 struct file_ra_state *ra,
1580 struct file *file,
1581 pgoff_t offset)
1582{
1583 unsigned long ra_pages;
1584 struct address_space *mapping = file->f_mapping;
1585
1586 /* If we don't want any read-ahead, don't bother */
1587 if (VM_RandomReadHint(vma))
1588 return;
Wu Fengguang275b12b2011-05-24 17:12:28 -07001589 if (!ra->ra_pages)
1590 return;
Linus Torvaldsef00e082009-06-16 15:31:25 -07001591
Wu Fengguang2cbea1d2011-05-24 17:12:30 -07001592 if (VM_SequentialReadHint(vma)) {
Wu Fengguang7ffc59b2009-06-16 15:31:38 -07001593 page_cache_sync_readahead(mapping, ra, file, offset,
1594 ra->ra_pages);
Linus Torvaldsef00e082009-06-16 15:31:25 -07001595 return;
1596 }
1597
Andi Kleen207d04b2011-05-24 17:12:29 -07001598 /* Avoid banging the cache line if not needed */
1599 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
Linus Torvaldsef00e082009-06-16 15:31:25 -07001600 ra->mmap_miss++;
1601
1602 /*
1603 * Do we miss much more than hit in this file? If so,
1604 * stop bothering with read-ahead. It will only hurt.
1605 */
1606 if (ra->mmap_miss > MMAP_LOTSAMISS)
1607 return;
1608
Wu Fengguangd30a1102009-06-16 15:31:30 -07001609 /*
1610 * mmap read-around
1611 */
Linus Torvaldsef00e082009-06-16 15:31:25 -07001612 ra_pages = max_sane_readahead(ra->ra_pages);
Wu Fengguang275b12b2011-05-24 17:12:28 -07001613 ra->start = max_t(long, 0, offset - ra_pages / 2);
1614 ra->size = ra_pages;
Wu Fengguang2cbea1d2011-05-24 17:12:30 -07001615 ra->async_size = ra_pages / 4;
Wu Fengguang275b12b2011-05-24 17:12:28 -07001616 ra_submit(ra, mapping, file);
Linus Torvaldsef00e082009-06-16 15:31:25 -07001617}
1618
1619/*
1620 * Asynchronous readahead happens when we find the page and PG_readahead,
1621 * so we want to possibly extend the readahead further..
1622 */
1623static void do_async_mmap_readahead(struct vm_area_struct *vma,
1624 struct file_ra_state *ra,
1625 struct file *file,
1626 struct page *page,
1627 pgoff_t offset)
1628{
1629 struct address_space *mapping = file->f_mapping;
1630
1631 /* If we don't want any read-ahead, don't bother */
1632 if (VM_RandomReadHint(vma))
1633 return;
1634 if (ra->mmap_miss > 0)
1635 ra->mmap_miss--;
1636 if (PageReadahead(page))
Wu Fengguang2fad6f52009-06-16 15:31:29 -07001637 page_cache_async_readahead(mapping, ra, file,
1638 page, offset, ra->ra_pages);
Linus Torvaldsef00e082009-06-16 15:31:25 -07001639}
1640
Randy Dunlap485bb992006-06-23 02:03:49 -07001641/**
Nick Piggin54cb8822007-07-19 01:46:59 -07001642 * filemap_fault - read in file data for page fault handling
Nick Piggind0217ac2007-07-19 01:47:03 -07001643 * @vma: vma in which the fault was taken
1644 * @vmf: struct vm_fault containing details of the fault
Randy Dunlap485bb992006-06-23 02:03:49 -07001645 *
Nick Piggin54cb8822007-07-19 01:46:59 -07001646 * filemap_fault() is invoked via the vma operations vector for a
Linus Torvalds1da177e2005-04-16 15:20:36 -07001647 * mapped memory region to read in file data during a page fault.
1648 *
1649 * The goto's are kind of ugly, but this streamlines the normal case of having
1650 * it in the page cache, and handles the special cases reasonably without
1651 * having a lot of duplicated code.
1652 */
Nick Piggind0217ac2007-07-19 01:47:03 -07001653int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001654{
1655 int error;
Nick Piggin54cb8822007-07-19 01:46:59 -07001656 struct file *file = vma->vm_file;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001657 struct address_space *mapping = file->f_mapping;
1658 struct file_ra_state *ra = &file->f_ra;
1659 struct inode *inode = mapping->host;
Linus Torvaldsef00e082009-06-16 15:31:25 -07001660 pgoff_t offset = vmf->pgoff;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001661 struct page *page;
Jan Kara2004dc82008-02-08 04:20:11 -08001662 pgoff_t size;
Nick Piggin83c54072007-07-19 01:47:05 -07001663 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001664
Linus Torvalds1da177e2005-04-16 15:20:36 -07001665 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
Linus Torvaldsef00e082009-06-16 15:31:25 -07001666 if (offset >= size)
Linus Torvalds5307cc12007-10-31 09:19:46 -07001667 return VM_FAULT_SIGBUS;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001668
Linus Torvalds1da177e2005-04-16 15:20:36 -07001669 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001670 * Do we have something in the page cache already?
1671 */
Linus Torvaldsef00e082009-06-16 15:31:25 -07001672 page = find_get_page(mapping, offset);
1673 if (likely(page)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001674 /*
Linus Torvaldsef00e082009-06-16 15:31:25 -07001675 * We found the page, so try async readahead before
1676 * waiting for the lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001677 */
Linus Torvaldsef00e082009-06-16 15:31:25 -07001678 do_async_mmap_readahead(vma, ra, file, page, offset);
Linus Torvaldsef00e082009-06-16 15:31:25 -07001679 } else {
1680 /* No page in the page cache at all */
1681 do_sync_mmap_readahead(vma, ra, file, offset);
1682 count_vm_event(PGMAJFAULT);
Ying Han456f9982011-05-26 16:25:38 -07001683 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
Linus Torvaldsef00e082009-06-16 15:31:25 -07001684 ret = VM_FAULT_MAJOR;
1685retry_find:
Michel Lespinasseb522c942010-10-26 14:21:56 -07001686 page = find_get_page(mapping, offset);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001687 if (!page)
1688 goto no_cached_page;
1689 }
1690
Michel Lespinassed88c0922010-11-02 13:05:18 -07001691 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1692 page_cache_release(page);
Michel Lespinassed065bd82010-10-26 14:21:57 -07001693 return ret | VM_FAULT_RETRY;
Michel Lespinassed88c0922010-11-02 13:05:18 -07001694 }
Michel Lespinasseb522c942010-10-26 14:21:56 -07001695
1696 /* Did it get truncated? */
1697 if (unlikely(page->mapping != mapping)) {
1698 unlock_page(page);
1699 put_page(page);
1700 goto retry_find;
1701 }
1702 VM_BUG_ON(page->index != offset);
1703
Linus Torvalds1da177e2005-04-16 15:20:36 -07001704 /*
Nick Piggind00806b2007-07-19 01:46:57 -07001705 * We have a locked page in the page cache, now we need to check
1706 * that it's up-to-date. If not, it is going to be due to an error.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001707 */
Nick Piggind00806b2007-07-19 01:46:57 -07001708 if (unlikely(!PageUptodate(page)))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001709 goto page_not_uptodate;
1710
Linus Torvaldsef00e082009-06-16 15:31:25 -07001711 /*
1712 * Found the page and have a reference on it.
1713 * We must recheck i_size under page lock.
1714 */
Nick Piggind00806b2007-07-19 01:46:57 -07001715 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
Linus Torvaldsef00e082009-06-16 15:31:25 -07001716 if (unlikely(offset >= size)) {
Nick Piggind00806b2007-07-19 01:46:57 -07001717 unlock_page(page);
Yan Zheng745ad482007-10-08 10:08:37 -07001718 page_cache_release(page);
Linus Torvalds5307cc12007-10-31 09:19:46 -07001719 return VM_FAULT_SIGBUS;
Nick Piggind00806b2007-07-19 01:46:57 -07001720 }
1721
Nick Piggind0217ac2007-07-19 01:47:03 -07001722 vmf->page = page;
Nick Piggin83c54072007-07-19 01:47:05 -07001723 return ret | VM_FAULT_LOCKED;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001724
Linus Torvalds1da177e2005-04-16 15:20:36 -07001725no_cached_page:
1726 /*
1727 * We're only likely to ever get here if MADV_RANDOM is in
1728 * effect.
1729 */
Linus Torvaldsef00e082009-06-16 15:31:25 -07001730 error = page_cache_read(file, offset);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001731
1732 /*
1733 * The page we want has now been added to the page cache.
1734 * In the unlikely event that someone removed it in the
1735 * meantime, we'll just come back here and read it again.
1736 */
1737 if (error >= 0)
1738 goto retry_find;
1739
1740 /*
1741 * An error return from page_cache_read can result if the
1742 * system is low on memory, or a problem occurs while trying
1743 * to schedule I/O.
1744 */
1745 if (error == -ENOMEM)
Nick Piggind0217ac2007-07-19 01:47:03 -07001746 return VM_FAULT_OOM;
1747 return VM_FAULT_SIGBUS;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001748
1749page_not_uptodate:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001750 /*
1751 * Umm, take care of errors if the page isn't up-to-date.
1752 * Try to re-read it _once_. We do this synchronously,
1753 * because there really aren't any performance issues here
1754 * and we need to check for errors.
1755 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001756 ClearPageError(page);
Zach Brown994fc28c2005-12-15 14:28:17 -08001757 error = mapping->a_ops->readpage(file, page);
Miklos Szeredi3ef0f722008-05-14 16:05:37 -07001758 if (!error) {
1759 wait_on_page_locked(page);
1760 if (!PageUptodate(page))
1761 error = -EIO;
1762 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001763 page_cache_release(page);
Nick Piggind00806b2007-07-19 01:46:57 -07001764
1765 if (!error || error == AOP_TRUNCATED_PAGE)
1766 goto retry_find;
1767
1768 /* Things didn't work out. Return zero to tell the mm layer so. */
1769 shrink_readahead_size_eio(file, ra);
Nick Piggind0217ac2007-07-19 01:47:03 -07001770 return VM_FAULT_SIGBUS;
Nick Piggin54cb8822007-07-19 01:46:59 -07001771}
1772EXPORT_SYMBOL(filemap_fault);
1773
Alexey Dobriyanf0f37e22009-09-27 22:29:37 +04001774const struct vm_operations_struct generic_file_vm_ops = {
Nick Piggin54cb8822007-07-19 01:46:59 -07001775 .fault = filemap_fault,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001776};
1777
1778/* This is used for a general mmap of a disk file */
1779
1780int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1781{
1782 struct address_space *mapping = file->f_mapping;
1783
1784 if (!mapping->a_ops->readpage)
1785 return -ENOEXEC;
1786 file_accessed(file);
1787 vma->vm_ops = &generic_file_vm_ops;
Nick Piggind0217ac2007-07-19 01:47:03 -07001788 vma->vm_flags |= VM_CAN_NONLINEAR;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001789 return 0;
1790}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001791
1792/*
1793 * This is for filesystems which do not implement ->writepage.
1794 */
1795int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1796{
1797 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1798 return -EINVAL;
1799 return generic_file_mmap(file, vma);
1800}
1801#else
1802int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1803{
1804 return -ENOSYS;
1805}
1806int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1807{
1808 return -ENOSYS;
1809}
1810#endif /* CONFIG_MMU */
1811
1812EXPORT_SYMBOL(generic_file_mmap);
1813EXPORT_SYMBOL(generic_file_readonly_mmap);
1814
Nick Piggin6fe69002007-05-06 14:49:04 -07001815static struct page *__read_cache_page(struct address_space *mapping,
Fengguang Wu57f6b962007-10-16 01:24:37 -07001816 pgoff_t index,
Hugh Dickins5e5358e2011-07-25 17:12:23 -07001817 int (*filler)(void *, struct page *),
Linus Torvalds0531b2a2010-01-27 09:20:03 -08001818 void *data,
1819 gfp_t gfp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001820{
Nick Piggineb2be182007-10-16 01:24:57 -07001821 struct page *page;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001822 int err;
1823repeat:
1824 page = find_get_page(mapping, index);
1825 if (!page) {
Linus Torvalds0531b2a2010-01-27 09:20:03 -08001826 page = __page_cache_alloc(gfp | __GFP_COLD);
Nick Piggineb2be182007-10-16 01:24:57 -07001827 if (!page)
1828 return ERR_PTR(-ENOMEM);
1829 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
1830 if (unlikely(err)) {
1831 page_cache_release(page);
1832 if (err == -EEXIST)
1833 goto repeat;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001834 /* Presumably ENOMEM for radix tree node */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001835 return ERR_PTR(err);
1836 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001837 err = filler(data, page);
1838 if (err < 0) {
1839 page_cache_release(page);
1840 page = ERR_PTR(err);
1841 }
1842 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001843 return page;
1844}
1845
Linus Torvalds0531b2a2010-01-27 09:20:03 -08001846static struct page *do_read_cache_page(struct address_space *mapping,
Fengguang Wu57f6b962007-10-16 01:24:37 -07001847 pgoff_t index,
Hugh Dickins5e5358e2011-07-25 17:12:23 -07001848 int (*filler)(void *, struct page *),
Linus Torvalds0531b2a2010-01-27 09:20:03 -08001849 void *data,
1850 gfp_t gfp)
1851
Linus Torvalds1da177e2005-04-16 15:20:36 -07001852{
1853 struct page *page;
1854 int err;
1855
1856retry:
Linus Torvalds0531b2a2010-01-27 09:20:03 -08001857 page = __read_cache_page(mapping, index, filler, data, gfp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001858 if (IS_ERR(page))
David Howellsc855ff32007-05-09 13:42:20 +01001859 return page;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001860 if (PageUptodate(page))
1861 goto out;
1862
1863 lock_page(page);
1864 if (!page->mapping) {
1865 unlock_page(page);
1866 page_cache_release(page);
1867 goto retry;
1868 }
1869 if (PageUptodate(page)) {
1870 unlock_page(page);
1871 goto out;
1872 }
1873 err = filler(data, page);
1874 if (err < 0) {
1875 page_cache_release(page);
David Howellsc855ff32007-05-09 13:42:20 +01001876 return ERR_PTR(err);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001877 }
David Howellsc855ff32007-05-09 13:42:20 +01001878out:
Nick Piggin6fe69002007-05-06 14:49:04 -07001879 mark_page_accessed(page);
1880 return page;
1881}
Linus Torvalds0531b2a2010-01-27 09:20:03 -08001882
1883/**
1884 * read_cache_page_async - read into page cache, fill it if needed
1885 * @mapping: the page's address_space
1886 * @index: the page index
1887 * @filler: function to perform the read
Hugh Dickins5e5358e2011-07-25 17:12:23 -07001888 * @data: first arg to filler(data, page) function, often left as NULL
Linus Torvalds0531b2a2010-01-27 09:20:03 -08001889 *
1890 * Same as read_cache_page, but don't wait for page to become unlocked
1891 * after submitting it to the filler.
1892 *
1893 * Read into the page cache. If a page already exists, and PageUptodate() is
1894 * not set, try to fill the page but don't wait for it to become unlocked.
1895 *
1896 * If the page does not get brought uptodate, return -EIO.
1897 */
1898struct page *read_cache_page_async(struct address_space *mapping,
1899 pgoff_t index,
Hugh Dickins5e5358e2011-07-25 17:12:23 -07001900 int (*filler)(void *, struct page *),
Linus Torvalds0531b2a2010-01-27 09:20:03 -08001901 void *data)
1902{
1903 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
1904}
Nick Piggin6fe69002007-05-06 14:49:04 -07001905EXPORT_SYMBOL(read_cache_page_async);
1906
Linus Torvalds0531b2a2010-01-27 09:20:03 -08001907static struct page *wait_on_page_read(struct page *page)
1908{
1909 if (!IS_ERR(page)) {
1910 wait_on_page_locked(page);
1911 if (!PageUptodate(page)) {
1912 page_cache_release(page);
1913 page = ERR_PTR(-EIO);
1914 }
1915 }
1916 return page;
1917}
1918
1919/**
1920 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1921 * @mapping: the page's address_space
1922 * @index: the page index
1923 * @gfp: the page allocator flags to use if allocating
1924 *
1925 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1926 * any new page allocations done using the specified allocation flags. Note
1927 * that the Radix tree operations will still use GFP_KERNEL, so you can't
1928 * expect to do this atomically or anything like that - but you can pass in
1929 * other page requirements.
1930 *
1931 * If the page does not get brought uptodate, return -EIO.
1932 */
1933struct page *read_cache_page_gfp(struct address_space *mapping,
1934 pgoff_t index,
1935 gfp_t gfp)
1936{
1937 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
1938
1939 return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
1940}
1941EXPORT_SYMBOL(read_cache_page_gfp);
1942
Nick Piggin6fe69002007-05-06 14:49:04 -07001943/**
1944 * read_cache_page - read into page cache, fill it if needed
1945 * @mapping: the page's address_space
1946 * @index: the page index
1947 * @filler: function to perform the read
Hugh Dickins5e5358e2011-07-25 17:12:23 -07001948 * @data: first arg to filler(data, page) function, often left as NULL
Nick Piggin6fe69002007-05-06 14:49:04 -07001949 *
1950 * Read into the page cache. If a page already exists, and PageUptodate() is
1951 * not set, try to fill the page then wait for it to become unlocked.
1952 *
1953 * If the page does not get brought uptodate, return -EIO.
1954 */
1955struct page *read_cache_page(struct address_space *mapping,
Fengguang Wu57f6b962007-10-16 01:24:37 -07001956 pgoff_t index,
Hugh Dickins5e5358e2011-07-25 17:12:23 -07001957 int (*filler)(void *, struct page *),
Nick Piggin6fe69002007-05-06 14:49:04 -07001958 void *data)
1959{
Linus Torvalds0531b2a2010-01-27 09:20:03 -08001960 return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001961}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001962EXPORT_SYMBOL(read_cache_page);
1963
1964/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001965 * The logic we want is
1966 *
1967 * if suid or (sgid and xgrp)
1968 * remove privs
1969 */
Jens Axboe01de85e2006-10-17 19:50:36 +02001970int should_remove_suid(struct dentry *dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001971{
1972 mode_t mode = dentry->d_inode->i_mode;
1973 int kill = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001974
1975 /* suid always must be killed */
1976 if (unlikely(mode & S_ISUID))
1977 kill = ATTR_KILL_SUID;
1978
1979 /*
1980 * sgid without any exec bits is just a mandatory locking mark; leave
1981 * it alone. If some exec bits are set, it's a real sgid; kill it.
1982 */
1983 if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1984 kill |= ATTR_KILL_SGID;
1985
Dmitri Monakhov7f5ff762008-12-01 14:34:56 -08001986 if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
Jens Axboe01de85e2006-10-17 19:50:36 +02001987 return kill;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001988
Jens Axboe01de85e2006-10-17 19:50:36 +02001989 return 0;
1990}
Mark Fashehd23a1472006-10-17 17:05:18 -07001991EXPORT_SYMBOL(should_remove_suid);
Jens Axboe01de85e2006-10-17 19:50:36 +02001992
Miklos Szeredi7f3d4ee2008-05-07 09:22:39 +02001993static int __remove_suid(struct dentry *dentry, int kill)
Jens Axboe01de85e2006-10-17 19:50:36 +02001994{
1995 struct iattr newattrs;
1996
1997 newattrs.ia_valid = ATTR_FORCE | kill;
1998 return notify_change(dentry, &newattrs);
1999}
2000
Miklos Szeredi2f1936b2008-06-24 16:50:14 +02002001int file_remove_suid(struct file *file)
Jens Axboe01de85e2006-10-17 19:50:36 +02002002{
Miklos Szeredi2f1936b2008-06-24 16:50:14 +02002003 struct dentry *dentry = file->f_path.dentry;
Andi Kleen69b45732011-05-28 08:25:51 -07002004 struct inode *inode = dentry->d_inode;
2005 int killsuid;
2006 int killpriv;
Serge E. Hallynb5376772007-10-16 23:31:36 -07002007 int error = 0;
Jens Axboe01de85e2006-10-17 19:50:36 +02002008
Andi Kleen69b45732011-05-28 08:25:51 -07002009 /* Fast path for nothing security related */
2010 if (IS_NOSEC(inode))
2011 return 0;
2012
2013 killsuid = should_remove_suid(dentry);
2014 killpriv = security_inode_need_killpriv(dentry);
2015
Serge E. Hallynb5376772007-10-16 23:31:36 -07002016 if (killpriv < 0)
2017 return killpriv;
2018 if (killpriv)
2019 error = security_inode_killpriv(dentry);
2020 if (!error && killsuid)
2021 error = __remove_suid(dentry, killsuid);
Al Viro9e1f1de2011-06-03 18:24:58 -04002022 if (!error && (inode->i_sb->s_flags & MS_NOSEC))
Andi Kleen69b45732011-05-28 08:25:51 -07002023 inode->i_flags |= S_NOSEC;
Jens Axboe01de85e2006-10-17 19:50:36 +02002024
Serge E. Hallynb5376772007-10-16 23:31:36 -07002025 return error;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002026}
Miklos Szeredi2f1936b2008-06-24 16:50:14 +02002027EXPORT_SYMBOL(file_remove_suid);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002028
Nick Piggin2f718ff2007-10-16 01:24:59 -07002029static size_t __iovec_copy_from_user_inatomic(char *vaddr,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002030 const struct iovec *iov, size_t base, size_t bytes)
2031{
Ingo Molnarf1800532009-03-02 11:00:57 +01002032 size_t copied = 0, left = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002033
2034 while (bytes) {
2035 char __user *buf = iov->iov_base + base;
2036 int copy = min(bytes, iov->iov_len - base);
2037
2038 base = 0;
Ingo Molnarf1800532009-03-02 11:00:57 +01002039 left = __copy_from_user_inatomic(vaddr, buf, copy);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002040 copied += copy;
2041 bytes -= copy;
2042 vaddr += copy;
2043 iov++;
2044
NeilBrown01408c42006-06-25 05:47:58 -07002045 if (unlikely(left))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002046 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002047 }
2048 return copied - left;
2049}
2050
2051/*
Nick Piggin2f718ff2007-10-16 01:24:59 -07002052 * Copy as much as we can into the page and return the number of bytes which
André Goddard Rosaaf901ca2009-11-14 13:09:05 -02002053 * were successfully copied. If a fault is encountered then return the number of
Nick Piggin2f718ff2007-10-16 01:24:59 -07002054 * bytes which were copied.
2055 */
2056size_t iov_iter_copy_from_user_atomic(struct page *page,
2057 struct iov_iter *i, unsigned long offset, size_t bytes)
2058{
2059 char *kaddr;
2060 size_t copied;
2061
2062 BUG_ON(!in_atomic());
2063 kaddr = kmap_atomic(page, KM_USER0);
2064 if (likely(i->nr_segs == 1)) {
2065 int left;
2066 char __user *buf = i->iov->iov_base + i->iov_offset;
Ingo Molnarf1800532009-03-02 11:00:57 +01002067 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
Nick Piggin2f718ff2007-10-16 01:24:59 -07002068 copied = bytes - left;
2069 } else {
2070 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2071 i->iov, i->iov_offset, bytes);
2072 }
2073 kunmap_atomic(kaddr, KM_USER0);
2074
2075 return copied;
2076}
Nick Piggin89e10782007-10-16 01:25:07 -07002077EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
Nick Piggin2f718ff2007-10-16 01:24:59 -07002078
2079/*
2080 * This has the same sideeffects and return value as
2081 * iov_iter_copy_from_user_atomic().
2082 * The difference is that it attempts to resolve faults.
2083 * Page must not be locked.
2084 */
2085size_t iov_iter_copy_from_user(struct page *page,
2086 struct iov_iter *i, unsigned long offset, size_t bytes)
2087{
2088 char *kaddr;
2089 size_t copied;
2090
2091 kaddr = kmap(page);
2092 if (likely(i->nr_segs == 1)) {
2093 int left;
2094 char __user *buf = i->iov->iov_base + i->iov_offset;
Ingo Molnarf1800532009-03-02 11:00:57 +01002095 left = __copy_from_user(kaddr + offset, buf, bytes);
Nick Piggin2f718ff2007-10-16 01:24:59 -07002096 copied = bytes - left;
2097 } else {
2098 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2099 i->iov, i->iov_offset, bytes);
2100 }
2101 kunmap(page);
2102 return copied;
2103}
Nick Piggin89e10782007-10-16 01:25:07 -07002104EXPORT_SYMBOL(iov_iter_copy_from_user);
Nick Piggin2f718ff2007-10-16 01:24:59 -07002105
Nick Pigginf7009262008-03-10 11:43:59 -07002106void iov_iter_advance(struct iov_iter *i, size_t bytes)
Nick Piggin2f718ff2007-10-16 01:24:59 -07002107{
Nick Pigginf7009262008-03-10 11:43:59 -07002108 BUG_ON(i->count < bytes);
2109
Nick Piggin2f718ff2007-10-16 01:24:59 -07002110 if (likely(i->nr_segs == 1)) {
2111 i->iov_offset += bytes;
Nick Pigginf7009262008-03-10 11:43:59 -07002112 i->count -= bytes;
Nick Piggin2f718ff2007-10-16 01:24:59 -07002113 } else {
2114 const struct iovec *iov = i->iov;
2115 size_t base = i->iov_offset;
2116
Nick Piggin124d3b72008-02-02 15:01:17 +01002117 /*
2118 * The !iov->iov_len check ensures we skip over unlikely
Nick Pigginf7009262008-03-10 11:43:59 -07002119 * zero-length segments (without overruning the iovec).
Nick Piggin124d3b72008-02-02 15:01:17 +01002120 */
Linus Torvalds94ad3742008-07-30 14:45:12 -07002121 while (bytes || unlikely(i->count && !iov->iov_len)) {
Nick Pigginf7009262008-03-10 11:43:59 -07002122 int copy;
Nick Piggin2f718ff2007-10-16 01:24:59 -07002123
Nick Pigginf7009262008-03-10 11:43:59 -07002124 copy = min(bytes, iov->iov_len - base);
2125 BUG_ON(!i->count || i->count < copy);
2126 i->count -= copy;
Nick Piggin2f718ff2007-10-16 01:24:59 -07002127 bytes -= copy;
2128 base += copy;
2129 if (iov->iov_len == base) {
2130 iov++;
2131 base = 0;
2132 }
2133 }
2134 i->iov = iov;
2135 i->iov_offset = base;
2136 }
2137}
Nick Piggin89e10782007-10-16 01:25:07 -07002138EXPORT_SYMBOL(iov_iter_advance);
Nick Piggin2f718ff2007-10-16 01:24:59 -07002139
Nick Pigginafddba42007-10-16 01:25:01 -07002140/*
2141 * Fault in the first iovec of the given iov_iter, to a maximum length
2142 * of bytes. Returns 0 on success, or non-zero if the memory could not be
2143 * accessed (ie. because it is an invalid address).
2144 *
2145 * writev-intensive code may want this to prefault several iovecs -- that
2146 * would be possible (callers must not rely on the fact that _only_ the
2147 * first iovec will be faulted with the current implementation).
2148 */
2149int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
Nick Piggin2f718ff2007-10-16 01:24:59 -07002150{
Nick Piggin2f718ff2007-10-16 01:24:59 -07002151 char __user *buf = i->iov->iov_base + i->iov_offset;
Nick Pigginafddba42007-10-16 01:25:01 -07002152 bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2153 return fault_in_pages_readable(buf, bytes);
Nick Piggin2f718ff2007-10-16 01:24:59 -07002154}
Nick Piggin89e10782007-10-16 01:25:07 -07002155EXPORT_SYMBOL(iov_iter_fault_in_readable);
Nick Piggin2f718ff2007-10-16 01:24:59 -07002156
2157/*
2158 * Return the count of just the current iov_iter segment.
2159 */
2160size_t iov_iter_single_seg_count(struct iov_iter *i)
2161{
2162 const struct iovec *iov = i->iov;
2163 if (i->nr_segs == 1)
2164 return i->count;
2165 else
2166 return min(i->count, iov->iov_len - i->iov_offset);
2167}
Nick Piggin89e10782007-10-16 01:25:07 -07002168EXPORT_SYMBOL(iov_iter_single_seg_count);
Nick Piggin2f718ff2007-10-16 01:24:59 -07002169
2170/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002171 * Performs necessary checks before doing a write
2172 *
Randy Dunlap485bb992006-06-23 02:03:49 -07002173 * Can adjust writing position or amount of bytes to write.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002174 * Returns appropriate error code that caller should return or
2175 * zero in case that write should be allowed.
2176 */
2177inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2178{
2179 struct inode *inode = file->f_mapping->host;
Jiri Slaby59e99e52010-03-05 13:41:44 -08002180 unsigned long limit = rlimit(RLIMIT_FSIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002181
2182 if (unlikely(*pos < 0))
2183 return -EINVAL;
2184
Linus Torvalds1da177e2005-04-16 15:20:36 -07002185 if (!isblk) {
2186 /* FIXME: this is for backwards compatibility with 2.4 */
2187 if (file->f_flags & O_APPEND)
2188 *pos = i_size_read(inode);
2189
2190 if (limit != RLIM_INFINITY) {
2191 if (*pos >= limit) {
2192 send_sig(SIGXFSZ, current, 0);
2193 return -EFBIG;
2194 }
2195 if (*count > limit - (typeof(limit))*pos) {
2196 *count = limit - (typeof(limit))*pos;
2197 }
2198 }
2199 }
2200
2201 /*
2202 * LFS rule
2203 */
2204 if (unlikely(*pos + *count > MAX_NON_LFS &&
2205 !(file->f_flags & O_LARGEFILE))) {
2206 if (*pos >= MAX_NON_LFS) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002207 return -EFBIG;
2208 }
2209 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2210 *count = MAX_NON_LFS - (unsigned long)*pos;
2211 }
2212 }
2213
2214 /*
2215 * Are we about to exceed the fs block limit ?
2216 *
2217 * If we have written data it becomes a short write. If we have
2218 * exceeded without writing data we send a signal and return EFBIG.
2219 * Linus frestrict idea will clean these up nicely..
2220 */
2221 if (likely(!isblk)) {
2222 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2223 if (*count || *pos > inode->i_sb->s_maxbytes) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002224 return -EFBIG;
2225 }
2226 /* zero-length writes at ->s_maxbytes are OK */
2227 }
2228
2229 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2230 *count = inode->i_sb->s_maxbytes - *pos;
2231 } else {
David Howells93614012006-09-30 20:45:40 +02002232#ifdef CONFIG_BLOCK
Linus Torvalds1da177e2005-04-16 15:20:36 -07002233 loff_t isize;
2234 if (bdev_read_only(I_BDEV(inode)))
2235 return -EPERM;
2236 isize = i_size_read(inode);
2237 if (*pos >= isize) {
2238 if (*count || *pos > isize)
2239 return -ENOSPC;
2240 }
2241
2242 if (*pos + *count > isize)
2243 *count = isize - *pos;
David Howells93614012006-09-30 20:45:40 +02002244#else
2245 return -EPERM;
2246#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -07002247 }
2248 return 0;
2249}
2250EXPORT_SYMBOL(generic_write_checks);
2251
Nick Pigginafddba42007-10-16 01:25:01 -07002252int pagecache_write_begin(struct file *file, struct address_space *mapping,
2253 loff_t pos, unsigned len, unsigned flags,
2254 struct page **pagep, void **fsdata)
2255{
2256 const struct address_space_operations *aops = mapping->a_ops;
2257
Nick Piggin4e02ed42008-10-29 14:00:55 -07002258 return aops->write_begin(file, mapping, pos, len, flags,
Nick Pigginafddba42007-10-16 01:25:01 -07002259 pagep, fsdata);
Nick Pigginafddba42007-10-16 01:25:01 -07002260}
2261EXPORT_SYMBOL(pagecache_write_begin);
2262
2263int pagecache_write_end(struct file *file, struct address_space *mapping,
2264 loff_t pos, unsigned len, unsigned copied,
2265 struct page *page, void *fsdata)
2266{
2267 const struct address_space_operations *aops = mapping->a_ops;
Nick Pigginafddba42007-10-16 01:25:01 -07002268
Nick Piggin4e02ed42008-10-29 14:00:55 -07002269 mark_page_accessed(page);
2270 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
Nick Pigginafddba42007-10-16 01:25:01 -07002271}
2272EXPORT_SYMBOL(pagecache_write_end);
2273
Linus Torvalds1da177e2005-04-16 15:20:36 -07002274ssize_t
2275generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2276 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2277 size_t count, size_t ocount)
2278{
2279 struct file *file = iocb->ki_filp;
2280 struct address_space *mapping = file->f_mapping;
2281 struct inode *inode = mapping->host;
2282 ssize_t written;
Christoph Hellwiga969e902008-07-23 21:27:04 -07002283 size_t write_len;
2284 pgoff_t end;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002285
2286 if (count != ocount)
2287 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2288
Christoph Hellwiga969e902008-07-23 21:27:04 -07002289 write_len = iov_length(iov, *nr_segs);
2290 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
Christoph Hellwiga969e902008-07-23 21:27:04 -07002291
Nick Piggin48b47c52009-01-06 14:40:22 -08002292 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
Christoph Hellwiga969e902008-07-23 21:27:04 -07002293 if (written)
2294 goto out;
2295
2296 /*
2297 * After a write we want buffered reads to be sure to go to disk to get
2298 * the new data. We invalidate clean cached page from the region we're
2299 * about to write. We do this *before* the write so that we can return
Hisashi Hifumi6ccfa802008-09-02 14:35:40 -07002300 * without clobbering -EIOCBQUEUED from ->direct_IO().
Christoph Hellwiga969e902008-07-23 21:27:04 -07002301 */
2302 if (mapping->nrpages) {
2303 written = invalidate_inode_pages2_range(mapping,
2304 pos >> PAGE_CACHE_SHIFT, end);
Hisashi Hifumi6ccfa802008-09-02 14:35:40 -07002305 /*
2306 * If a page can not be invalidated, return 0 to fall back
2307 * to buffered write.
2308 */
2309 if (written) {
2310 if (written == -EBUSY)
2311 return 0;
Christoph Hellwiga969e902008-07-23 21:27:04 -07002312 goto out;
Hisashi Hifumi6ccfa802008-09-02 14:35:40 -07002313 }
Christoph Hellwiga969e902008-07-23 21:27:04 -07002314 }
2315
2316 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2317
2318 /*
2319 * Finally, try again to invalidate clean pages which might have been
2320 * cached by non-direct readahead, or faulted in by get_user_pages()
2321 * if the source of the write was an mmap'ed region of the file
2322 * we're writing. Either one is a pretty crazy thing to do,
2323 * so we don't support it 100%. If this invalidation
2324 * fails, tough, the write still worked...
2325 */
2326 if (mapping->nrpages) {
2327 invalidate_inode_pages2_range(mapping,
2328 pos >> PAGE_CACHE_SHIFT, end);
2329 }
2330
Linus Torvalds1da177e2005-04-16 15:20:36 -07002331 if (written > 0) {
Namhyung Kim01166512010-10-26 14:21:58 -07002332 pos += written;
2333 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2334 i_size_write(inode, pos);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002335 mark_inode_dirty(inode);
2336 }
Namhyung Kim01166512010-10-26 14:21:58 -07002337 *ppos = pos;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002338 }
Christoph Hellwiga969e902008-07-23 21:27:04 -07002339out:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002340 return written;
2341}
2342EXPORT_SYMBOL(generic_file_direct_write);
2343
Nick Piggineb2be182007-10-16 01:24:57 -07002344/*
2345 * Find or create a page at the given pagecache position. Return the locked
2346 * page. This function is specifically for buffered writes.
2347 */
Nick Piggin54566b22009-01-04 12:00:53 -08002348struct page *grab_cache_page_write_begin(struct address_space *mapping,
2349 pgoff_t index, unsigned flags)
Nick Piggineb2be182007-10-16 01:24:57 -07002350{
2351 int status;
2352 struct page *page;
Nick Piggin54566b22009-01-04 12:00:53 -08002353 gfp_t gfp_notmask = 0;
2354 if (flags & AOP_FLAG_NOFS)
2355 gfp_notmask = __GFP_FS;
Nick Piggineb2be182007-10-16 01:24:57 -07002356repeat:
2357 page = find_lock_page(mapping, index);
Steven Rostedtc585a262011-01-13 15:46:18 -08002358 if (page)
Darrick J. Wong3d08bcc2011-05-27 12:23:34 -07002359 goto found;
Nick Piggineb2be182007-10-16 01:24:57 -07002360
Nick Piggin54566b22009-01-04 12:00:53 -08002361 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
Nick Piggineb2be182007-10-16 01:24:57 -07002362 if (!page)
2363 return NULL;
Nick Piggin54566b22009-01-04 12:00:53 -08002364 status = add_to_page_cache_lru(page, mapping, index,
2365 GFP_KERNEL & ~gfp_notmask);
Nick Piggineb2be182007-10-16 01:24:57 -07002366 if (unlikely(status)) {
2367 page_cache_release(page);
2368 if (status == -EEXIST)
2369 goto repeat;
2370 return NULL;
2371 }
Darrick J. Wong3d08bcc2011-05-27 12:23:34 -07002372found:
2373 wait_on_page_writeback(page);
Nick Piggineb2be182007-10-16 01:24:57 -07002374 return page;
2375}
Nick Piggin54566b22009-01-04 12:00:53 -08002376EXPORT_SYMBOL(grab_cache_page_write_begin);
Nick Piggineb2be182007-10-16 01:24:57 -07002377
Nick Pigginafddba42007-10-16 01:25:01 -07002378static ssize_t generic_perform_write(struct file *file,
2379 struct iov_iter *i, loff_t pos)
2380{
2381 struct address_space *mapping = file->f_mapping;
2382 const struct address_space_operations *a_ops = mapping->a_ops;
2383 long status = 0;
2384 ssize_t written = 0;
Nick Piggin674b8922007-10-16 01:25:03 -07002385 unsigned int flags = 0;
2386
2387 /*
2388 * Copies from kernel address space cannot fail (NFSD is a big user).
2389 */
2390 if (segment_eq(get_fs(), KERNEL_DS))
2391 flags |= AOP_FLAG_UNINTERRUPTIBLE;
Nick Pigginafddba42007-10-16 01:25:01 -07002392
2393 do {
2394 struct page *page;
Nick Pigginafddba42007-10-16 01:25:01 -07002395 unsigned long offset; /* Offset into pagecache page */
2396 unsigned long bytes; /* Bytes to write to page */
2397 size_t copied; /* Bytes copied from user */
2398 void *fsdata;
2399
2400 offset = (pos & (PAGE_CACHE_SIZE - 1));
Nick Pigginafddba42007-10-16 01:25:01 -07002401 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2402 iov_iter_count(i));
2403
2404again:
2405
2406 /*
2407 * Bring in the user page that we will copy from _first_.
2408 * Otherwise there's a nasty deadlock on copying from the
2409 * same page as we're writing to, without it being marked
2410 * up-to-date.
2411 *
2412 * Not only is this an optimisation, but it is also required
2413 * to check that the address is actually valid, when atomic
2414 * usercopies are used, below.
2415 */
2416 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2417 status = -EFAULT;
2418 break;
2419 }
2420
Nick Piggin674b8922007-10-16 01:25:03 -07002421 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
Nick Pigginafddba42007-10-16 01:25:01 -07002422 &page, &fsdata);
2423 if (unlikely(status))
2424 break;
2425
anfei zhou931e80e2010-02-02 13:44:02 -08002426 if (mapping_writably_mapped(mapping))
2427 flush_dcache_page(page);
2428
Nick Pigginafddba42007-10-16 01:25:01 -07002429 pagefault_disable();
2430 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2431 pagefault_enable();
2432 flush_dcache_page(page);
2433
Josef Bacikc8236db2009-07-05 12:08:18 -07002434 mark_page_accessed(page);
Nick Pigginafddba42007-10-16 01:25:01 -07002435 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2436 page, fsdata);
2437 if (unlikely(status < 0))
2438 break;
2439 copied = status;
2440
2441 cond_resched();
2442
Nick Piggin124d3b72008-02-02 15:01:17 +01002443 iov_iter_advance(i, copied);
Nick Pigginafddba42007-10-16 01:25:01 -07002444 if (unlikely(copied == 0)) {
2445 /*
2446 * If we were unable to copy any data at all, we must
2447 * fall back to a single segment length write.
2448 *
2449 * If we didn't fallback here, we could livelock
2450 * because not all segments in the iov can be copied at
2451 * once without a pagefault.
2452 */
2453 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2454 iov_iter_single_seg_count(i));
2455 goto again;
2456 }
Nick Pigginafddba42007-10-16 01:25:01 -07002457 pos += copied;
2458 written += copied;
2459
2460 balance_dirty_pages_ratelimited(mapping);
2461
2462 } while (iov_iter_count(i));
2463
2464 return written ? written : status;
2465}
2466
2467ssize_t
2468generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2469 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2470 size_t count, ssize_t written)
2471{
2472 struct file *file = iocb->ki_filp;
Nick Pigginafddba42007-10-16 01:25:01 -07002473 ssize_t status;
2474 struct iov_iter i;
2475
2476 iov_iter_init(&i, iov, nr_segs, count, written);
Nick Piggin4e02ed42008-10-29 14:00:55 -07002477 status = generic_perform_write(file, &i, pos);
Nick Pigginafddba42007-10-16 01:25:01 -07002478
Linus Torvalds1da177e2005-04-16 15:20:36 -07002479 if (likely(status >= 0)) {
Nick Pigginafddba42007-10-16 01:25:01 -07002480 written += status;
2481 *ppos = pos + status;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002482 }
2483
Linus Torvalds1da177e2005-04-16 15:20:36 -07002484 return written ? written : status;
2485}
2486EXPORT_SYMBOL(generic_file_buffered_write);
2487
Jan Karae4dd9de2009-08-17 18:10:06 +02002488/**
2489 * __generic_file_aio_write - write data to a file
2490 * @iocb: IO state structure (file, offset, etc.)
2491 * @iov: vector with data to write
2492 * @nr_segs: number of segments in the vector
2493 * @ppos: position where to write
2494 *
2495 * This function does all the work needed for actually writing data to a
2496 * file. It does all basic checks, removes SUID from the file, updates
2497 * modification times and calls proper subroutines depending on whether we
2498 * do direct IO or a standard buffered write.
2499 *
2500 * It expects i_mutex to be grabbed unless we work on a block device or similar
2501 * object which does not need locking at all.
2502 *
2503 * This function does *not* take care of syncing data in case of O_SYNC write.
2504 * A caller has to handle it. This is mainly due to the fact that we want to
2505 * avoid syncing under i_mutex.
2506 */
2507ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2508 unsigned long nr_segs, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002509{
2510 struct file *file = iocb->ki_filp;
Jeff Moyerfb5527e2006-10-19 23:28:13 -07002511 struct address_space * mapping = file->f_mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002512 size_t ocount; /* original count */
2513 size_t count; /* after file limit checks */
2514 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002515 loff_t pos;
2516 ssize_t written;
2517 ssize_t err;
2518
2519 ocount = 0;
Dmitriy Monakhov0ceb3312007-05-08 00:23:02 -07002520 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2521 if (err)
2522 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002523
2524 count = ocount;
2525 pos = *ppos;
2526
2527 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2528
2529 /* We can write back this queue in page reclaim */
2530 current->backing_dev_info = mapping->backing_dev_info;
2531 written = 0;
2532
2533 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2534 if (err)
2535 goto out;
2536
2537 if (count == 0)
2538 goto out;
2539
Miklos Szeredi2f1936b2008-06-24 16:50:14 +02002540 err = file_remove_suid(file);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002541 if (err)
2542 goto out;
2543
Christoph Hellwig870f4812006-01-09 20:52:01 -08002544 file_update_time(file);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002545
2546 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2547 if (unlikely(file->f_flags & O_DIRECT)) {
Jeff Moyerfb5527e2006-10-19 23:28:13 -07002548 loff_t endbyte;
2549 ssize_t written_buffered;
2550
2551 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2552 ppos, count, ocount);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002553 if (written < 0 || written == count)
2554 goto out;
2555 /*
2556 * direct-io write to a hole: fall through to buffered I/O
2557 * for completing the rest of the request.
2558 */
2559 pos += written;
2560 count -= written;
Jeff Moyerfb5527e2006-10-19 23:28:13 -07002561 written_buffered = generic_file_buffered_write(iocb, iov,
2562 nr_segs, pos, ppos, count,
2563 written);
2564 /*
2565 * If generic_file_buffered_write() retuned a synchronous error
2566 * then we want to return the number of bytes which were
2567 * direct-written, or the error code if that was zero. Note
2568 * that this differs from normal direct-io semantics, which
2569 * will return -EFOO even if some bytes were written.
2570 */
2571 if (written_buffered < 0) {
2572 err = written_buffered;
2573 goto out;
2574 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002575
Jeff Moyerfb5527e2006-10-19 23:28:13 -07002576 /*
2577 * We need to ensure that the page cache pages are written to
2578 * disk and invalidated to preserve the expected O_DIRECT
2579 * semantics.
2580 */
2581 endbyte = pos + written_buffered - written - 1;
Christoph Hellwigc05c4ed2009-09-23 15:07:30 +02002582 err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
Jeff Moyerfb5527e2006-10-19 23:28:13 -07002583 if (err == 0) {
2584 written = written_buffered;
2585 invalidate_mapping_pages(mapping,
2586 pos >> PAGE_CACHE_SHIFT,
2587 endbyte >> PAGE_CACHE_SHIFT);
2588 } else {
2589 /*
2590 * We don't know how much we wrote, so just return
2591 * the number of bytes which were direct-written
2592 */
2593 }
2594 } else {
2595 written = generic_file_buffered_write(iocb, iov, nr_segs,
2596 pos, ppos, count, written);
2597 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002598out:
2599 current->backing_dev_info = NULL;
2600 return written ? written : err;
2601}
Jan Karae4dd9de2009-08-17 18:10:06 +02002602EXPORT_SYMBOL(__generic_file_aio_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002603
Jan Karae4dd9de2009-08-17 18:10:06 +02002604/**
2605 * generic_file_aio_write - write data to a file
2606 * @iocb: IO state structure
2607 * @iov: vector with data to write
2608 * @nr_segs: number of segments in the vector
2609 * @pos: position in file where to write
2610 *
2611 * This is a wrapper around __generic_file_aio_write() to be used by most
2612 * filesystems. It takes care of syncing the file in case of O_SYNC file
2613 * and acquires i_mutex as needed.
2614 */
Badari Pulavarty027445c2006-09-30 23:28:46 -07002615ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2616 unsigned long nr_segs, loff_t pos)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002617{
2618 struct file *file = iocb->ki_filp;
Jan Kara148f9482009-08-17 19:52:36 +02002619 struct inode *inode = file->f_mapping->host;
Jens Axboe55602dd2010-06-24 15:05:37 +02002620 struct blk_plug plug;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002621 ssize_t ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002622
2623 BUG_ON(iocb->ki_pos != pos);
2624
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08002625 mutex_lock(&inode->i_mutex);
Jens Axboe55602dd2010-06-24 15:05:37 +02002626 blk_start_plug(&plug);
Jan Karae4dd9de2009-08-17 18:10:06 +02002627 ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08002628 mutex_unlock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002629
Jan Kara148f9482009-08-17 19:52:36 +02002630 if (ret > 0 || ret == -EIOCBQUEUED) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002631 ssize_t err;
2632
Jan Kara148f9482009-08-17 19:52:36 +02002633 err = generic_write_sync(file, pos, ret);
Jan Karac7b50db2009-08-18 16:18:20 +02002634 if (err < 0 && ret > 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002635 ret = err;
2636 }
Jens Axboe55602dd2010-06-24 15:05:37 +02002637 blk_finish_plug(&plug);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002638 return ret;
2639}
2640EXPORT_SYMBOL(generic_file_aio_write);
2641
David Howellscf9a2ae2006-08-29 19:05:54 +01002642/**
2643 * try_to_release_page() - release old fs-specific metadata on a page
2644 *
2645 * @page: the page which the kernel is trying to free
2646 * @gfp_mask: memory allocation flags (and I/O mode)
2647 *
2648 * The address_space is to try to release any data against the page
2649 * (presumably at page->private). If the release was successful, return `1'.
2650 * Otherwise return zero.
2651 *
David Howells266cf652009-04-03 16:42:36 +01002652 * This may also be called if PG_fscache is set on a page, indicating that the
2653 * page is known to the local caching routines.
2654 *
David Howellscf9a2ae2006-08-29 19:05:54 +01002655 * The @gfp_mask argument specifies whether I/O may be performed to release
Mingming Cao3f31fdd2008-07-25 01:46:22 -07002656 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
David Howellscf9a2ae2006-08-29 19:05:54 +01002657 *
David Howellscf9a2ae2006-08-29 19:05:54 +01002658 */
2659int try_to_release_page(struct page *page, gfp_t gfp_mask)
2660{
2661 struct address_space * const mapping = page->mapping;
2662
2663 BUG_ON(!PageLocked(page));
2664 if (PageWriteback(page))
2665 return 0;
2666
2667 if (mapping && mapping->a_ops->releasepage)
2668 return mapping->a_ops->releasepage(page, gfp_mask);
2669 return try_to_free_buffers(page);
2670}
2671
2672EXPORT_SYMBOL(try_to_release_page);