blob: 477817c00bace86e23e29340257544b27d2843f4 [file] [log] [blame]
Christoph Hellwigae259a92016-06-21 09:23:11 +10001/*
2 * Copyright (C) 2010 Red Hat, Inc.
3 * Copyright (c) 2016 Christoph Hellwig.
4 *
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms and conditions of the GNU General Public License,
7 * version 2, as published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
12 * more details.
13 */
14#include <linux/module.h>
15#include <linux/compiler.h>
16#include <linux/fs.h>
17#include <linux/iomap.h>
18#include <linux/uaccess.h>
19#include <linux/gfp.h>
20#include <linux/mm.h>
21#include <linux/swap.h>
22#include <linux/pagemap.h>
23#include <linux/file.h>
24#include <linux/uio.h>
25#include <linux/backing-dev.h>
26#include <linux/buffer_head.h>
Christoph Hellwig9a286f02016-06-21 09:31:39 +100027#include <linux/dax.h>
Christoph Hellwigae259a92016-06-21 09:23:11 +100028#include "internal.h"
29
30typedef loff_t (*iomap_actor_t)(struct inode *inode, loff_t pos, loff_t len,
31 void *data, struct iomap *iomap);
32
33/*
34 * Execute a iomap write on a segment of the mapping that spans a
35 * contiguous range of pages that have identical block mapping state.
36 *
37 * This avoids the need to map pages individually, do individual allocations
38 * for each page and most importantly avoid the need for filesystem specific
39 * locking per page. Instead, all the operations are amortised over the entire
40 * range of pages. It is assumed that the filesystems will lock whatever
41 * resources they require in the iomap_begin call, and release them in the
42 * iomap_end call.
43 */
44static loff_t
45iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
46 struct iomap_ops *ops, void *data, iomap_actor_t actor)
47{
48 struct iomap iomap = { 0 };
49 loff_t written = 0, ret;
50
51 /*
52 * Need to map a range from start position for length bytes. This can
53 * span multiple pages - it is only guaranteed to return a range of a
54 * single type of pages (e.g. all into a hole, all mapped or all
55 * unwritten). Failure at this point has nothing to undo.
56 *
57 * If allocation is required for this range, reserve the space now so
58 * that the allocation is guaranteed to succeed later on. Once we copy
59 * the data into the page cache pages, then we cannot fail otherwise we
60 * expose transient stale data. If the reserve fails, we can safely
61 * back out at this point as there is nothing to undo.
62 */
63 ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
64 if (ret)
65 return ret;
66 if (WARN_ON(iomap.offset > pos))
67 return -EIO;
68
69 /*
70 * Cut down the length to the one actually provided by the filesystem,
71 * as it might not be able to give us the whole size that we requested.
72 */
73 if (iomap.offset + iomap.length < pos + length)
74 length = iomap.offset + iomap.length - pos;
75
76 /*
77 * Now that we have guaranteed that the space allocation will succeed.
78 * we can do the copy-in page by page without having to worry about
79 * failures exposing transient data.
80 */
81 written = actor(inode, pos, length, data, &iomap);
82
83 /*
84 * Now the data has been copied, commit the range we've copied. This
85 * should not fail unless the filesystem has had a fatal error.
86 */
87 ret = ops->iomap_end(inode, pos, length, written > 0 ? written : 0,
88 flags, &iomap);
89
90 return written ? written : ret;
91}
92
93static void
94iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
95{
96 loff_t i_size = i_size_read(inode);
97
98 /*
99 * Only truncate newly allocated pages beyoned EOF, even if the
100 * write started inside the existing inode size.
101 */
102 if (pos + len > i_size)
103 truncate_pagecache_range(inode, max(pos, i_size), pos + len);
104}
105
106static int
107iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
108 struct page **pagep, struct iomap *iomap)
109{
110 pgoff_t index = pos >> PAGE_SHIFT;
111 struct page *page;
112 int status = 0;
113
114 BUG_ON(pos + len > iomap->offset + iomap->length);
115
116 page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
117 if (!page)
118 return -ENOMEM;
119
120 status = __block_write_begin_int(page, pos, len, NULL, iomap);
121 if (unlikely(status)) {
122 unlock_page(page);
123 put_page(page);
124 page = NULL;
125
126 iomap_write_failed(inode, pos, len);
127 }
128
129 *pagep = page;
130 return status;
131}
132
133static int
134iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
135 unsigned copied, struct page *page)
136{
137 int ret;
138
139 ret = generic_write_end(NULL, inode->i_mapping, pos, len,
140 copied, page, NULL);
141 if (ret < len)
142 iomap_write_failed(inode, pos, len);
143 return ret;
144}
145
146static loff_t
147iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
148 struct iomap *iomap)
149{
150 struct iov_iter *i = data;
151 long status = 0;
152 ssize_t written = 0;
153 unsigned int flags = AOP_FLAG_NOFS;
154
155 /*
156 * Copies from kernel address space cannot fail (NFSD is a big user).
157 */
158 if (!iter_is_iovec(i))
159 flags |= AOP_FLAG_UNINTERRUPTIBLE;
160
161 do {
162 struct page *page;
163 unsigned long offset; /* Offset into pagecache page */
164 unsigned long bytes; /* Bytes to write to page */
165 size_t copied; /* Bytes copied from user */
166
167 offset = (pos & (PAGE_SIZE - 1));
168 bytes = min_t(unsigned long, PAGE_SIZE - offset,
169 iov_iter_count(i));
170again:
171 if (bytes > length)
172 bytes = length;
173
174 /*
175 * Bring in the user page that we will copy from _first_.
176 * Otherwise there's a nasty deadlock on copying from the
177 * same page as we're writing to, without it being marked
178 * up-to-date.
179 *
180 * Not only is this an optimisation, but it is also required
181 * to check that the address is actually valid, when atomic
182 * usercopies are used, below.
183 */
184 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
185 status = -EFAULT;
186 break;
187 }
188
189 status = iomap_write_begin(inode, pos, bytes, flags, &page,
190 iomap);
191 if (unlikely(status))
192 break;
193
194 if (mapping_writably_mapped(inode->i_mapping))
195 flush_dcache_page(page);
196
197 pagefault_disable();
198 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
199 pagefault_enable();
200
201 flush_dcache_page(page);
202 mark_page_accessed(page);
203
204 status = iomap_write_end(inode, pos, bytes, copied, page);
205 if (unlikely(status < 0))
206 break;
207 copied = status;
208
209 cond_resched();
210
211 iov_iter_advance(i, copied);
212 if (unlikely(copied == 0)) {
213 /*
214 * If we were unable to copy any data at all, we must
215 * fall back to a single segment length write.
216 *
217 * If we didn't fallback here, we could livelock
218 * because not all segments in the iov can be copied at
219 * once without a pagefault.
220 */
221 bytes = min_t(unsigned long, PAGE_SIZE - offset,
222 iov_iter_single_seg_count(i));
223 goto again;
224 }
225 pos += copied;
226 written += copied;
227 length -= copied;
228
229 balance_dirty_pages_ratelimited(inode->i_mapping);
230 } while (iov_iter_count(i) && length);
231
232 return written ? written : status;
233}
234
235ssize_t
236iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter,
237 struct iomap_ops *ops)
238{
239 struct inode *inode = iocb->ki_filp->f_mapping->host;
240 loff_t pos = iocb->ki_pos, ret = 0, written = 0;
241
242 while (iov_iter_count(iter)) {
243 ret = iomap_apply(inode, pos, iov_iter_count(iter),
244 IOMAP_WRITE, ops, iter, iomap_write_actor);
245 if (ret <= 0)
246 break;
247 pos += ret;
248 written += ret;
249 }
250
251 return written ? written : ret;
252}
253EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
254
255static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
256 unsigned bytes, struct iomap *iomap)
257{
258 struct page *page;
259 int status;
260
261 status = iomap_write_begin(inode, pos, bytes,
262 AOP_FLAG_UNINTERRUPTIBLE | AOP_FLAG_NOFS, &page, iomap);
263 if (status)
264 return status;
265
266 zero_user(page, offset, bytes);
267 mark_page_accessed(page);
268
269 return iomap_write_end(inode, pos, bytes, bytes, page);
270}
271
Christoph Hellwig9a286f02016-06-21 09:31:39 +1000272static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
273 struct iomap *iomap)
274{
275 sector_t sector = iomap->blkno +
276 (((pos & ~(PAGE_SIZE - 1)) - iomap->offset) >> 9);
277
278 return __dax_zero_page_range(iomap->bdev, sector, offset, bytes);
279}
280
Christoph Hellwigae259a92016-06-21 09:23:11 +1000281static loff_t
282iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
283 void *data, struct iomap *iomap)
284{
285 bool *did_zero = data;
286 loff_t written = 0;
287 int status;
288
289 /* already zeroed? we're done. */
290 if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
291 return count;
292
293 do {
294 unsigned offset, bytes;
295
296 offset = pos & (PAGE_SIZE - 1); /* Within page */
297 bytes = min_t(unsigned, PAGE_SIZE - offset, count);
298
Christoph Hellwig9a286f02016-06-21 09:31:39 +1000299 if (IS_DAX(inode))
300 status = iomap_dax_zero(pos, offset, bytes, iomap);
301 else
302 status = iomap_zero(inode, pos, offset, bytes, iomap);
Christoph Hellwigae259a92016-06-21 09:23:11 +1000303 if (status < 0)
304 return status;
305
306 pos += bytes;
307 count -= bytes;
308 written += bytes;
309 if (did_zero)
310 *did_zero = true;
311 } while (count > 0);
312
313 return written;
314}
315
316int
317iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
318 struct iomap_ops *ops)
319{
320 loff_t ret;
321
322 while (len > 0) {
323 ret = iomap_apply(inode, pos, len, IOMAP_ZERO,
324 ops, did_zero, iomap_zero_range_actor);
325 if (ret <= 0)
326 return ret;
327
328 pos += ret;
329 len -= ret;
330 }
331
332 return 0;
333}
334EXPORT_SYMBOL_GPL(iomap_zero_range);
335
336int
337iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
338 struct iomap_ops *ops)
339{
340 unsigned blocksize = (1 << inode->i_blkbits);
341 unsigned off = pos & (blocksize - 1);
342
343 /* Block boundary? Nothing to do */
344 if (!off)
345 return 0;
346 return iomap_zero_range(inode, pos, blocksize - off, did_zero, ops);
347}
348EXPORT_SYMBOL_GPL(iomap_truncate_page);
349
350static loff_t
351iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length,
352 void *data, struct iomap *iomap)
353{
354 struct page *page = data;
355 int ret;
356
357 ret = __block_write_begin_int(page, pos & ~PAGE_MASK, length,
358 NULL, iomap);
359 if (ret)
360 return ret;
361
362 block_commit_write(page, 0, length);
363 return length;
364}
365
366int iomap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
367 struct iomap_ops *ops)
368{
369 struct page *page = vmf->page;
370 struct inode *inode = file_inode(vma->vm_file);
371 unsigned long length;
372 loff_t offset, size;
373 ssize_t ret;
374
375 lock_page(page);
376 size = i_size_read(inode);
377 if ((page->mapping != inode->i_mapping) ||
378 (page_offset(page) > size)) {
379 /* We overload EFAULT to mean page got truncated */
380 ret = -EFAULT;
381 goto out_unlock;
382 }
383
384 /* page is wholly or partially inside EOF */
385 if (((page->index + 1) << PAGE_SHIFT) > size)
386 length = size & ~PAGE_MASK;
387 else
388 length = PAGE_SIZE;
389
390 offset = page_offset(page);
391 while (length > 0) {
392 ret = iomap_apply(inode, offset, length, IOMAP_WRITE,
393 ops, page, iomap_page_mkwrite_actor);
394 if (unlikely(ret <= 0))
395 goto out_unlock;
396 offset += ret;
397 length -= ret;
398 }
399
400 set_page_dirty(page);
401 wait_for_stable_page(page);
402 return 0;
403out_unlock:
404 unlock_page(page);
405 return ret;
406}
407EXPORT_SYMBOL_GPL(iomap_page_mkwrite);