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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * fs/direct-io.c
3 *
4 * Copyright (C) 2002, Linus Torvalds.
5 *
6 * O_DIRECT
7 *
Francois Camie1f8e872008-10-15 22:01:59 -07008 * 04Jul2002 Andrew Morton
Linus Torvalds1da177e2005-04-16 15:20:36 -07009 * Initial version
10 * 11Sep2002 janetinc@us.ibm.com
11 * added readv/writev support.
Francois Camie1f8e872008-10-15 22:01:59 -070012 * 29Oct2002 Andrew Morton
Linus Torvalds1da177e2005-04-16 15:20:36 -070013 * rewrote bio_add_page() support.
14 * 30Oct2002 pbadari@us.ibm.com
15 * added support for non-aligned IO.
16 * 06Nov2002 pbadari@us.ibm.com
17 * added asynchronous IO support.
18 * 21Jul2003 nathans@sgi.com
19 * added IO completion notifier.
20 */
21
22#include <linux/kernel.h>
23#include <linux/module.h>
24#include <linux/types.h>
25#include <linux/fs.h>
26#include <linux/mm.h>
27#include <linux/slab.h>
28#include <linux/highmem.h>
29#include <linux/pagemap.h>
Andrew Morton98c4d572006-12-10 02:19:47 -080030#include <linux/task_io_accounting_ops.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070031#include <linux/bio.h>
32#include <linux/wait.h>
33#include <linux/err.h>
34#include <linux/blkdev.h>
35#include <linux/buffer_head.h>
36#include <linux/rwsem.h>
37#include <linux/uio.h>
38#include <asm/atomic.h>
39
40/*
41 * How many user pages to map in one call to get_user_pages(). This determines
42 * the size of a structure on the stack.
43 */
44#define DIO_PAGES 64
45
46/*
47 * This code generally works in units of "dio_blocks". A dio_block is
48 * somewhere between the hard sector size and the filesystem block size. it
49 * is determined on a per-invocation basis. When talking to the filesystem
50 * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity
51 * down by dio->blkfactor. Similarly, fs-blocksize quantities are converted
52 * to bio_block quantities by shifting left by blkfactor.
53 *
54 * If blkfactor is zero then the user's request was aligned to the filesystem's
55 * blocksize.
56 *
57 * lock_type is DIO_LOCKING for regular files on direct-IO-naive filesystems.
58 * This determines whether we need to do the fancy locking which prevents
59 * direct-IO from being able to read uninitialised disk blocks. If its zero
Jes Sorensen1b1dcc12006-01-09 15:59:24 -080060 * (blockdev) this locking is not done, and if it is DIO_OWN_LOCKING i_mutex is
Linus Torvalds1da177e2005-04-16 15:20:36 -070061 * not held for the entire direct write (taken briefly, initially, during a
62 * direct read though, but its never held for the duration of a direct-IO).
63 */
64
65struct dio {
66 /* BIO submission state */
67 struct bio *bio; /* bio under assembly */
68 struct inode *inode;
69 int rw;
Daniel McNeil29504ff2005-04-16 15:25:50 -070070 loff_t i_size; /* i_size when submitted */
Linus Torvalds1da177e2005-04-16 15:20:36 -070071 int lock_type; /* doesn't change */
72 unsigned blkbits; /* doesn't change */
73 unsigned blkfactor; /* When we're using an alignment which
74 is finer than the filesystem's soft
75 blocksize, this specifies how much
76 finer. blkfactor=2 means 1/4-block
77 alignment. Does not change */
78 unsigned start_zero_done; /* flag: sub-blocksize zeroing has
79 been performed at the start of a
80 write */
81 int pages_in_io; /* approximate total IO pages */
82 size_t size; /* total request size (doesn't change)*/
83 sector_t block_in_file; /* Current offset into the underlying
84 file in dio_block units. */
85 unsigned blocks_available; /* At block_in_file. changes */
86 sector_t final_block_in_request;/* doesn't change */
87 unsigned first_block_in_page; /* doesn't change, Used only once */
88 int boundary; /* prev block is at a boundary */
89 int reap_counter; /* rate limit reaping */
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -080090 get_block_t *get_block; /* block mapping function */
Linus Torvalds1da177e2005-04-16 15:20:36 -070091 dio_iodone_t *end_io; /* IO completion function */
92 sector_t final_block_in_bio; /* current final block in bio + 1 */
93 sector_t next_block_for_io; /* next block to be put under IO,
94 in dio_blocks units */
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -080095 struct buffer_head map_bh; /* last get_block() result */
Linus Torvalds1da177e2005-04-16 15:20:36 -070096
97 /*
98 * Deferred addition of a page to the dio. These variables are
99 * private to dio_send_cur_page(), submit_page_section() and
100 * dio_bio_add_page().
101 */
102 struct page *cur_page; /* The page */
103 unsigned cur_page_offset; /* Offset into it, in bytes */
104 unsigned cur_page_len; /* Nr of bytes at cur_page_offset */
105 sector_t cur_page_block; /* Where it starts */
106
107 /*
108 * Page fetching state. These variables belong to dio_refill_pages().
109 */
110 int curr_page; /* changes */
111 int total_pages; /* doesn't change */
112 unsigned long curr_user_address;/* changes */
113
114 /*
115 * Page queue. These variables belong to dio_refill_pages() and
116 * dio_get_page().
117 */
118 struct page *pages[DIO_PAGES]; /* page buffer */
119 unsigned head; /* next page to process */
120 unsigned tail; /* last valid page + 1 */
121 int page_errors; /* errno from get_user_pages() */
122
123 /* BIO completion state */
124 spinlock_t bio_lock; /* protects BIO fields below */
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800125 unsigned long refcount; /* direct_io_worker() and bios */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700126 struct bio *bio_list; /* singly linked via bi_private */
127 struct task_struct *waiter; /* waiting task (NULL if none) */
128
129 /* AIO related stuff */
130 struct kiocb *iocb; /* kiocb */
131 int is_async; /* is IO async ? */
Chen, Kenneth W174e27c2006-03-25 03:08:16 -0800132 int io_error; /* IO error in completion path */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700133 ssize_t result; /* IO result */
134};
135
136/*
137 * How many pages are in the queue?
138 */
139static inline unsigned dio_pages_present(struct dio *dio)
140{
141 return dio->tail - dio->head;
142}
143
144/*
145 * Go grab and pin some userspace pages. Typically we'll get 64 at a time.
146 */
147static int dio_refill_pages(struct dio *dio)
148{
149 int ret;
150 int nr_pages;
151
152 nr_pages = min(dio->total_pages - dio->curr_page, DIO_PAGES);
Nick Pigginf5dd33c2008-07-25 19:45:25 -0700153 ret = get_user_pages_fast(
Linus Torvalds1da177e2005-04-16 15:20:36 -0700154 dio->curr_user_address, /* Where from? */
155 nr_pages, /* How many pages? */
156 dio->rw == READ, /* Write to memory? */
Nick Pigginf5dd33c2008-07-25 19:45:25 -0700157 &dio->pages[0]); /* Put results here */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700158
Jens Axboeb31dc662006-06-13 08:26:10 +0200159 if (ret < 0 && dio->blocks_available && (dio->rw & WRITE)) {
Nick Piggin557ed1f2007-10-16 01:24:40 -0700160 struct page *page = ZERO_PAGE(0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161 /*
162 * A memory fault, but the filesystem has some outstanding
163 * mapped blocks. We need to use those blocks up to avoid
164 * leaking stale data in the file.
165 */
166 if (dio->page_errors == 0)
167 dio->page_errors = ret;
Nick Pigginb5810032005-10-29 18:16:12 -0700168 page_cache_get(page);
169 dio->pages[0] = page;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170 dio->head = 0;
171 dio->tail = 1;
172 ret = 0;
173 goto out;
174 }
175
176 if (ret >= 0) {
177 dio->curr_user_address += ret * PAGE_SIZE;
178 dio->curr_page += ret;
179 dio->head = 0;
180 dio->tail = ret;
181 ret = 0;
182 }
183out:
184 return ret;
185}
186
187/*
188 * Get another userspace page. Returns an ERR_PTR on error. Pages are
189 * buffered inside the dio so that we can call get_user_pages() against a
190 * decent number of pages, less frequently. To provide nicer use of the
191 * L1 cache.
192 */
193static struct page *dio_get_page(struct dio *dio)
194{
195 if (dio_pages_present(dio) == 0) {
196 int ret;
197
198 ret = dio_refill_pages(dio);
199 if (ret)
200 return ERR_PTR(ret);
201 BUG_ON(dio_pages_present(dio) == 0);
202 }
203 return dio->pages[dio->head++];
204}
205
Zach Brown6d544bb2006-12-10 02:20:54 -0800206/**
207 * dio_complete() - called when all DIO BIO I/O has been completed
208 * @offset: the byte offset in the file of the completed operation
209 *
210 * This releases locks as dictated by the locking type, lets interested parties
211 * know that a DIO operation has completed, and calculates the resulting return
212 * code for the operation.
213 *
214 * It lets the filesystem know if it registered an interest earlier via
215 * get_block. Pass the private field of the map buffer_head so that
216 * filesystems can use it to hold additional state between get_block calls and
217 * dio_complete.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700218 */
Zach Brown6d544bb2006-12-10 02:20:54 -0800219static int dio_complete(struct dio *dio, loff_t offset, int ret)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700220{
Zach Brown6d544bb2006-12-10 02:20:54 -0800221 ssize_t transferred = 0;
222
Zach Brown8459d862006-12-10 02:21:05 -0800223 /*
224 * AIO submission can race with bio completion to get here while
225 * expecting to have the last io completed by bio completion.
226 * In that case -EIOCBQUEUED is in fact not an error we want
227 * to preserve through this call.
228 */
229 if (ret == -EIOCBQUEUED)
230 ret = 0;
231
Zach Brown6d544bb2006-12-10 02:20:54 -0800232 if (dio->result) {
233 transferred = dio->result;
234
235 /* Check for short read case */
236 if ((dio->rw == READ) && ((offset + transferred) > dio->i_size))
237 transferred = dio->i_size - offset;
238 }
239
Linus Torvalds1da177e2005-04-16 15:20:36 -0700240 if (dio->end_io && dio->result)
Zach Brown6d544bb2006-12-10 02:20:54 -0800241 dio->end_io(dio->iocb, offset, transferred,
242 dio->map_bh.b_private);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700243 if (dio->lock_type == DIO_LOCKING)
Ingo Molnard8aa9052006-07-03 00:25:02 -0700244 /* lockdep: non-owner release */
245 up_read_non_owner(&dio->inode->i_alloc_sem);
Zach Brown6d544bb2006-12-10 02:20:54 -0800246
247 if (ret == 0)
248 ret = dio->page_errors;
249 if (ret == 0)
250 ret = dio->io_error;
251 if (ret == 0)
252 ret = transferred;
253
254 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700255}
256
Linus Torvalds1da177e2005-04-16 15:20:36 -0700257static int dio_bio_complete(struct dio *dio, struct bio *bio);
258/*
259 * Asynchronous IO callback.
260 */
NeilBrown6712ecf2007-09-27 12:47:43 +0200261static void dio_bio_end_aio(struct bio *bio, int error)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700262{
263 struct dio *dio = bio->bi_private;
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800264 unsigned long remaining;
265 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267 /* cleanup the bio */
268 dio_bio_complete(dio, bio);
Zach Brown02732012006-12-10 02:20:59 -0800269
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800270 spin_lock_irqsave(&dio->bio_lock, flags);
271 remaining = --dio->refcount;
272 if (remaining == 1 && dio->waiter)
Zach Brown20258b2b2006-12-10 02:21:01 -0800273 wake_up_process(dio->waiter);
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800274 spin_unlock_irqrestore(&dio->bio_lock, flags);
Zach Brown20258b2b2006-12-10 02:21:01 -0800275
Zach Brown8459d862006-12-10 02:21:05 -0800276 if (remaining == 0) {
277 int ret = dio_complete(dio, dio->iocb->ki_pos, 0);
278 aio_complete(dio->iocb, ret, 0);
279 kfree(dio);
280 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700281}
282
283/*
284 * The BIO completion handler simply queues the BIO up for the process-context
285 * handler.
286 *
287 * During I/O bi_private points at the dio. After I/O, bi_private is used to
288 * implement a singly-linked list of completed BIOs, at dio->bio_list.
289 */
NeilBrown6712ecf2007-09-27 12:47:43 +0200290static void dio_bio_end_io(struct bio *bio, int error)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700291{
292 struct dio *dio = bio->bi_private;
293 unsigned long flags;
294
Linus Torvalds1da177e2005-04-16 15:20:36 -0700295 spin_lock_irqsave(&dio->bio_lock, flags);
296 bio->bi_private = dio->bio_list;
297 dio->bio_list = bio;
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800298 if (--dio->refcount == 1 && dio->waiter)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700299 wake_up_process(dio->waiter);
300 spin_unlock_irqrestore(&dio->bio_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700301}
302
303static int
304dio_bio_alloc(struct dio *dio, struct block_device *bdev,
305 sector_t first_sector, int nr_vecs)
306{
307 struct bio *bio;
308
309 bio = bio_alloc(GFP_KERNEL, nr_vecs);
310 if (bio == NULL)
311 return -ENOMEM;
312
313 bio->bi_bdev = bdev;
314 bio->bi_sector = first_sector;
315 if (dio->is_async)
316 bio->bi_end_io = dio_bio_end_aio;
317 else
318 bio->bi_end_io = dio_bio_end_io;
319
320 dio->bio = bio;
321 return 0;
322}
323
324/*
325 * In the AIO read case we speculatively dirty the pages before starting IO.
326 * During IO completion, any of these pages which happen to have been written
327 * back will be redirtied by bio_check_pages_dirty().
Zach Brown02732012006-12-10 02:20:59 -0800328 *
329 * bios hold a dio reference between submit_bio and ->end_io.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700330 */
331static void dio_bio_submit(struct dio *dio)
332{
333 struct bio *bio = dio->bio;
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800334 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700335
336 bio->bi_private = dio;
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800337
338 spin_lock_irqsave(&dio->bio_lock, flags);
339 dio->refcount++;
340 spin_unlock_irqrestore(&dio->bio_lock, flags);
341
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342 if (dio->is_async && dio->rw == READ)
343 bio_set_pages_dirty(bio);
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800344
Linus Torvalds1da177e2005-04-16 15:20:36 -0700345 submit_bio(dio->rw, bio);
346
347 dio->bio = NULL;
348 dio->boundary = 0;
349}
350
351/*
352 * Release any resources in case of a failure
353 */
354static void dio_cleanup(struct dio *dio)
355{
356 while (dio_pages_present(dio))
357 page_cache_release(dio_get_page(dio));
358}
359
360/*
Zach Brown02732012006-12-10 02:20:59 -0800361 * Wait for the next BIO to complete. Remove it and return it. NULL is
362 * returned once all BIOs have been completed. This must only be called once
363 * all bios have been issued so that dio->refcount can only decrease. This
364 * requires that that the caller hold a reference on the dio.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700365 */
366static struct bio *dio_await_one(struct dio *dio)
367{
368 unsigned long flags;
Zach Brown02732012006-12-10 02:20:59 -0800369 struct bio *bio = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700370
371 spin_lock_irqsave(&dio->bio_lock, flags);
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800372
373 /*
374 * Wait as long as the list is empty and there are bios in flight. bio
375 * completion drops the count, maybe adds to the list, and wakes while
376 * holding the bio_lock so we don't need set_current_state()'s barrier
377 * and can call it after testing our condition.
378 */
379 while (dio->refcount > 1 && dio->bio_list == NULL) {
380 __set_current_state(TASK_UNINTERRUPTIBLE);
381 dio->waiter = current;
382 spin_unlock_irqrestore(&dio->bio_lock, flags);
383 io_schedule();
384 /* wake up sets us TASK_RUNNING */
385 spin_lock_irqsave(&dio->bio_lock, flags);
386 dio->waiter = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387 }
Zach Brown02732012006-12-10 02:20:59 -0800388 if (dio->bio_list) {
389 bio = dio->bio_list;
390 dio->bio_list = bio->bi_private;
391 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700392 spin_unlock_irqrestore(&dio->bio_lock, flags);
393 return bio;
394}
395
396/*
397 * Process one completed BIO. No locks are held.
398 */
399static int dio_bio_complete(struct dio *dio, struct bio *bio)
400{
401 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
402 struct bio_vec *bvec = bio->bi_io_vec;
403 int page_no;
404
405 if (!uptodate)
Chen, Kenneth W174e27c2006-03-25 03:08:16 -0800406 dio->io_error = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700407
408 if (dio->is_async && dio->rw == READ) {
409 bio_check_pages_dirty(bio); /* transfers ownership */
410 } else {
411 for (page_no = 0; page_no < bio->bi_vcnt; page_no++) {
412 struct page *page = bvec[page_no].bv_page;
413
414 if (dio->rw == READ && !PageCompound(page))
415 set_page_dirty_lock(page);
416 page_cache_release(page);
417 }
418 bio_put(bio);
419 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700420 return uptodate ? 0 : -EIO;
421}
422
423/*
Zach Brown02732012006-12-10 02:20:59 -0800424 * Wait on and process all in-flight BIOs. This must only be called once
425 * all bios have been issued so that the refcount can only decrease.
426 * This just waits for all bios to make it through dio_bio_complete. IO
Robert P. J. Daybeb7dd82007-05-09 07:14:03 +0200427 * errors are propagated through dio->io_error and should be propagated via
Zach Brown02732012006-12-10 02:20:59 -0800428 * dio_complete().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700429 */
Zach Brown6d544bb2006-12-10 02:20:54 -0800430static void dio_await_completion(struct dio *dio)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700431{
Zach Brown02732012006-12-10 02:20:59 -0800432 struct bio *bio;
433 do {
434 bio = dio_await_one(dio);
435 if (bio)
436 dio_bio_complete(dio, bio);
437 } while (bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700438}
439
440/*
441 * A really large O_DIRECT read or write can generate a lot of BIOs. So
442 * to keep the memory consumption sane we periodically reap any completed BIOs
443 * during the BIO generation phase.
444 *
445 * This also helps to limit the peak amount of pinned userspace memory.
446 */
447static int dio_bio_reap(struct dio *dio)
448{
449 int ret = 0;
450
451 if (dio->reap_counter++ >= 64) {
452 while (dio->bio_list) {
453 unsigned long flags;
454 struct bio *bio;
455 int ret2;
456
457 spin_lock_irqsave(&dio->bio_lock, flags);
458 bio = dio->bio_list;
459 dio->bio_list = bio->bi_private;
460 spin_unlock_irqrestore(&dio->bio_lock, flags);
461 ret2 = dio_bio_complete(dio, bio);
462 if (ret == 0)
463 ret = ret2;
464 }
465 dio->reap_counter = 0;
466 }
467 return ret;
468}
469
470/*
471 * Call into the fs to map some more disk blocks. We record the current number
472 * of available blocks at dio->blocks_available. These are in units of the
473 * fs blocksize, (1 << inode->i_blkbits).
474 *
475 * The fs is allowed to map lots of blocks at once. If it wants to do that,
476 * it uses the passed inode-relative block number as the file offset, as usual.
477 *
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -0800478 * get_block() is passed the number of i_blkbits-sized blocks which direct_io
Linus Torvalds1da177e2005-04-16 15:20:36 -0700479 * has remaining to do. The fs should not map more than this number of blocks.
480 *
481 * If the fs has mapped a lot of blocks, it should populate bh->b_size to
482 * indicate how much contiguous disk space has been made available at
483 * bh->b_blocknr.
484 *
485 * If *any* of the mapped blocks are new, then the fs must set buffer_new().
486 * This isn't very efficient...
487 *
488 * In the case of filesystem holes: the fs may return an arbitrarily-large
489 * hole by returning an appropriate value in b_size and by clearing
490 * buffer_mapped(). However the direct-io code will only process holes one
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -0800491 * block at a time - it will repeatedly call get_block() as it walks the hole.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700492 */
493static int get_more_blocks(struct dio *dio)
494{
495 int ret;
496 struct buffer_head *map_bh = &dio->map_bh;
497 sector_t fs_startblk; /* Into file, in filesystem-sized blocks */
498 unsigned long fs_count; /* Number of filesystem-sized blocks */
499 unsigned long dio_count;/* Number of dio_block-sized blocks */
500 unsigned long blkmask;
501 int create;
502
503 /*
504 * If there was a memory error and we've overwritten all the
505 * mapped blocks then we can now return that memory error
506 */
507 ret = dio->page_errors;
508 if (ret == 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509 BUG_ON(dio->block_in_file >= dio->final_block_in_request);
510 fs_startblk = dio->block_in_file >> dio->blkfactor;
511 dio_count = dio->final_block_in_request - dio->block_in_file;
512 fs_count = dio_count >> dio->blkfactor;
513 blkmask = (1 << dio->blkfactor) - 1;
514 if (dio_count & blkmask)
515 fs_count++;
516
Nathan Scott3c674e72006-03-29 09:26:15 +1000517 map_bh->b_state = 0;
518 map_bh->b_size = fs_count << dio->inode->i_blkbits;
519
Jens Axboeb31dc662006-06-13 08:26:10 +0200520 create = dio->rw & WRITE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700521 if (dio->lock_type == DIO_LOCKING) {
522 if (dio->block_in_file < (i_size_read(dio->inode) >>
523 dio->blkbits))
524 create = 0;
525 } else if (dio->lock_type == DIO_NO_LOCKING) {
526 create = 0;
527 }
Nathan Scott3c674e72006-03-29 09:26:15 +1000528
Linus Torvalds1da177e2005-04-16 15:20:36 -0700529 /*
530 * For writes inside i_size we forbid block creations: only
531 * overwrites are permitted. We fall back to buffered writes
532 * at a higher level for inside-i_size block-instantiating
533 * writes.
534 */
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -0800535 ret = (*dio->get_block)(dio->inode, fs_startblk,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700536 map_bh, create);
537 }
538 return ret;
539}
540
541/*
542 * There is no bio. Make one now.
543 */
544static int dio_new_bio(struct dio *dio, sector_t start_sector)
545{
546 sector_t sector;
547 int ret, nr_pages;
548
549 ret = dio_bio_reap(dio);
550 if (ret)
551 goto out;
552 sector = start_sector << (dio->blkbits - 9);
553 nr_pages = min(dio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev));
554 BUG_ON(nr_pages <= 0);
555 ret = dio_bio_alloc(dio, dio->map_bh.b_bdev, sector, nr_pages);
556 dio->boundary = 0;
557out:
558 return ret;
559}
560
561/*
562 * Attempt to put the current chunk of 'cur_page' into the current BIO. If
563 * that was successful then update final_block_in_bio and take a ref against
564 * the just-added page.
565 *
566 * Return zero on success. Non-zero means the caller needs to start a new BIO.
567 */
568static int dio_bio_add_page(struct dio *dio)
569{
570 int ret;
571
572 ret = bio_add_page(dio->bio, dio->cur_page,
573 dio->cur_page_len, dio->cur_page_offset);
574 if (ret == dio->cur_page_len) {
575 /*
576 * Decrement count only, if we are done with this page
577 */
578 if ((dio->cur_page_len + dio->cur_page_offset) == PAGE_SIZE)
579 dio->pages_in_io--;
580 page_cache_get(dio->cur_page);
581 dio->final_block_in_bio = dio->cur_page_block +
582 (dio->cur_page_len >> dio->blkbits);
583 ret = 0;
584 } else {
585 ret = 1;
586 }
587 return ret;
588}
589
590/*
591 * Put cur_page under IO. The section of cur_page which is described by
592 * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page
593 * starts on-disk at cur_page_block.
594 *
595 * We take a ref against the page here (on behalf of its presence in the bio).
596 *
597 * The caller of this function is responsible for removing cur_page from the
598 * dio, and for dropping the refcount which came from that presence.
599 */
600static int dio_send_cur_page(struct dio *dio)
601{
602 int ret = 0;
603
604 if (dio->bio) {
605 /*
606 * See whether this new request is contiguous with the old
607 */
608 if (dio->final_block_in_bio != dio->cur_page_block)
609 dio_bio_submit(dio);
610 /*
611 * Submit now if the underlying fs is about to perform a
612 * metadata read
613 */
614 if (dio->boundary)
615 dio_bio_submit(dio);
616 }
617
618 if (dio->bio == NULL) {
619 ret = dio_new_bio(dio, dio->cur_page_block);
620 if (ret)
621 goto out;
622 }
623
624 if (dio_bio_add_page(dio) != 0) {
625 dio_bio_submit(dio);
626 ret = dio_new_bio(dio, dio->cur_page_block);
627 if (ret == 0) {
628 ret = dio_bio_add_page(dio);
629 BUG_ON(ret != 0);
630 }
631 }
632out:
633 return ret;
634}
635
636/*
637 * An autonomous function to put a chunk of a page under deferred IO.
638 *
639 * The caller doesn't actually know (or care) whether this piece of page is in
640 * a BIO, or is under IO or whatever. We just take care of all possible
641 * situations here. The separation between the logic of do_direct_IO() and
642 * that of submit_page_section() is important for clarity. Please don't break.
643 *
644 * The chunk of page starts on-disk at blocknr.
645 *
646 * We perform deferred IO, by recording the last-submitted page inside our
647 * private part of the dio structure. If possible, we just expand the IO
648 * across that page here.
649 *
650 * If that doesn't work out then we put the old page into the bio and add this
651 * page to the dio instead.
652 */
653static int
654submit_page_section(struct dio *dio, struct page *page,
655 unsigned offset, unsigned len, sector_t blocknr)
656{
657 int ret = 0;
658
Andrew Morton98c4d572006-12-10 02:19:47 -0800659 if (dio->rw & WRITE) {
660 /*
661 * Read accounting is performed in submit_bio()
662 */
663 task_io_account_write(len);
664 }
665
Linus Torvalds1da177e2005-04-16 15:20:36 -0700666 /*
667 * Can we just grow the current page's presence in the dio?
668 */
669 if ( (dio->cur_page == page) &&
670 (dio->cur_page_offset + dio->cur_page_len == offset) &&
671 (dio->cur_page_block +
672 (dio->cur_page_len >> dio->blkbits) == blocknr)) {
673 dio->cur_page_len += len;
674
675 /*
676 * If dio->boundary then we want to schedule the IO now to
677 * avoid metadata seeks.
678 */
679 if (dio->boundary) {
680 ret = dio_send_cur_page(dio);
681 page_cache_release(dio->cur_page);
682 dio->cur_page = NULL;
683 }
684 goto out;
685 }
686
687 /*
688 * If there's a deferred page already there then send it.
689 */
690 if (dio->cur_page) {
691 ret = dio_send_cur_page(dio);
692 page_cache_release(dio->cur_page);
693 dio->cur_page = NULL;
694 if (ret)
695 goto out;
696 }
697
698 page_cache_get(page); /* It is in dio */
699 dio->cur_page = page;
700 dio->cur_page_offset = offset;
701 dio->cur_page_len = len;
702 dio->cur_page_block = blocknr;
703out:
704 return ret;
705}
706
707/*
708 * Clean any dirty buffers in the blockdev mapping which alias newly-created
709 * file blocks. Only called for S_ISREG files - blockdevs do not set
710 * buffer_new
711 */
712static void clean_blockdev_aliases(struct dio *dio)
713{
714 unsigned i;
715 unsigned nblocks;
716
717 nblocks = dio->map_bh.b_size >> dio->inode->i_blkbits;
718
719 for (i = 0; i < nblocks; i++) {
720 unmap_underlying_metadata(dio->map_bh.b_bdev,
721 dio->map_bh.b_blocknr + i);
722 }
723}
724
725/*
726 * If we are not writing the entire block and get_block() allocated
727 * the block for us, we need to fill-in the unused portion of the
728 * block with zeros. This happens only if user-buffer, fileoffset or
729 * io length is not filesystem block-size multiple.
730 *
731 * `end' is zero if we're doing the start of the IO, 1 at the end of the
732 * IO.
733 */
734static void dio_zero_block(struct dio *dio, int end)
735{
736 unsigned dio_blocks_per_fs_block;
737 unsigned this_chunk_blocks; /* In dio_blocks */
738 unsigned this_chunk_bytes;
739 struct page *page;
740
741 dio->start_zero_done = 1;
742 if (!dio->blkfactor || !buffer_new(&dio->map_bh))
743 return;
744
745 dio_blocks_per_fs_block = 1 << dio->blkfactor;
746 this_chunk_blocks = dio->block_in_file & (dio_blocks_per_fs_block - 1);
747
748 if (!this_chunk_blocks)
749 return;
750
751 /*
752 * We need to zero out part of an fs block. It is either at the
753 * beginning or the end of the fs block.
754 */
755 if (end)
756 this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks;
757
758 this_chunk_bytes = this_chunk_blocks << dio->blkbits;
759
Nick Piggin557ed1f2007-10-16 01:24:40 -0700760 page = ZERO_PAGE(0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700761 if (submit_page_section(dio, page, 0, this_chunk_bytes,
762 dio->next_block_for_io))
763 return;
764
765 dio->next_block_for_io += this_chunk_blocks;
766}
767
768/*
769 * Walk the user pages, and the file, mapping blocks to disk and generating
770 * a sequence of (page,offset,len,block) mappings. These mappings are injected
771 * into submit_page_section(), which takes care of the next stage of submission
772 *
773 * Direct IO against a blockdev is different from a file. Because we can
774 * happily perform page-sized but 512-byte aligned IOs. It is important that
775 * blockdev IO be able to have fine alignment and large sizes.
776 *
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -0800777 * So what we do is to permit the ->get_block function to populate bh.b_size
Linus Torvalds1da177e2005-04-16 15:20:36 -0700778 * with the size of IO which is permitted at this offset and this i_blkbits.
779 *
780 * For best results, the blockdev should be set up with 512-byte i_blkbits and
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -0800781 * it should set b_size to PAGE_SIZE or more inside get_block(). This gives
Linus Torvalds1da177e2005-04-16 15:20:36 -0700782 * fine alignment but still allows this function to work in PAGE_SIZE units.
783 */
784static int do_direct_IO(struct dio *dio)
785{
786 const unsigned blkbits = dio->blkbits;
787 const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
788 struct page *page;
789 unsigned block_in_page;
790 struct buffer_head *map_bh = &dio->map_bh;
791 int ret = 0;
792
793 /* The I/O can start at any block offset within the first page */
794 block_in_page = dio->first_block_in_page;
795
796 while (dio->block_in_file < dio->final_block_in_request) {
797 page = dio_get_page(dio);
798 if (IS_ERR(page)) {
799 ret = PTR_ERR(page);
800 goto out;
801 }
802
803 while (block_in_page < blocks_per_page) {
804 unsigned offset_in_page = block_in_page << blkbits;
805 unsigned this_chunk_bytes; /* # of bytes mapped */
806 unsigned this_chunk_blocks; /* # of blocks */
807 unsigned u;
808
809 if (dio->blocks_available == 0) {
810 /*
811 * Need to go and map some more disk
812 */
813 unsigned long blkmask;
814 unsigned long dio_remainder;
815
816 ret = get_more_blocks(dio);
817 if (ret) {
818 page_cache_release(page);
819 goto out;
820 }
821 if (!buffer_mapped(map_bh))
822 goto do_holes;
823
824 dio->blocks_available =
825 map_bh->b_size >> dio->blkbits;
826 dio->next_block_for_io =
827 map_bh->b_blocknr << dio->blkfactor;
828 if (buffer_new(map_bh))
829 clean_blockdev_aliases(dio);
830
831 if (!dio->blkfactor)
832 goto do_holes;
833
834 blkmask = (1 << dio->blkfactor) - 1;
835 dio_remainder = (dio->block_in_file & blkmask);
836
837 /*
838 * If we are at the start of IO and that IO
839 * starts partway into a fs-block,
840 * dio_remainder will be non-zero. If the IO
841 * is a read then we can simply advance the IO
842 * cursor to the first block which is to be
843 * read. But if the IO is a write and the
844 * block was newly allocated we cannot do that;
845 * the start of the fs block must be zeroed out
846 * on-disk
847 */
848 if (!buffer_new(map_bh))
849 dio->next_block_for_io += dio_remainder;
850 dio->blocks_available -= dio_remainder;
851 }
852do_holes:
853 /* Handle holes */
854 if (!buffer_mapped(map_bh)) {
Jeff Moyer35dc8162006-02-03 03:04:27 -0800855 loff_t i_size_aligned;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700856
857 /* AKPM: eargh, -ENOTBLK is a hack */
Jens Axboeb31dc662006-06-13 08:26:10 +0200858 if (dio->rw & WRITE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700859 page_cache_release(page);
860 return -ENOTBLK;
861 }
862
Jeff Moyer35dc8162006-02-03 03:04:27 -0800863 /*
864 * Be sure to account for a partial block as the
865 * last block in the file
866 */
867 i_size_aligned = ALIGN(i_size_read(dio->inode),
868 1 << blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700869 if (dio->block_in_file >=
Jeff Moyer35dc8162006-02-03 03:04:27 -0800870 i_size_aligned >> blkbits) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700871 /* We hit eof */
872 page_cache_release(page);
873 goto out;
874 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -0800875 zero_user(page, block_in_page << blkbits,
876 1 << blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700877 dio->block_in_file++;
878 block_in_page++;
879 goto next_block;
880 }
881
882 /*
883 * If we're performing IO which has an alignment which
884 * is finer than the underlying fs, go check to see if
885 * we must zero out the start of this block.
886 */
887 if (unlikely(dio->blkfactor && !dio->start_zero_done))
888 dio_zero_block(dio, 0);
889
890 /*
891 * Work out, in this_chunk_blocks, how much disk we
892 * can add to this page
893 */
894 this_chunk_blocks = dio->blocks_available;
895 u = (PAGE_SIZE - offset_in_page) >> blkbits;
896 if (this_chunk_blocks > u)
897 this_chunk_blocks = u;
898 u = dio->final_block_in_request - dio->block_in_file;
899 if (this_chunk_blocks > u)
900 this_chunk_blocks = u;
901 this_chunk_bytes = this_chunk_blocks << blkbits;
902 BUG_ON(this_chunk_bytes == 0);
903
904 dio->boundary = buffer_boundary(map_bh);
905 ret = submit_page_section(dio, page, offset_in_page,
906 this_chunk_bytes, dio->next_block_for_io);
907 if (ret) {
908 page_cache_release(page);
909 goto out;
910 }
911 dio->next_block_for_io += this_chunk_blocks;
912
913 dio->block_in_file += this_chunk_blocks;
914 block_in_page += this_chunk_blocks;
915 dio->blocks_available -= this_chunk_blocks;
916next_block:
Eric Sesterhennd4569d22006-04-01 01:10:13 +0200917 BUG_ON(dio->block_in_file > dio->final_block_in_request);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700918 if (dio->block_in_file == dio->final_block_in_request)
919 break;
920 }
921
922 /* Drop the ref which was taken in get_user_pages() */
923 page_cache_release(page);
924 block_in_page = 0;
925 }
926out:
927 return ret;
928}
929
930/*
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800931 * Releases both i_mutex and i_alloc_sem
Linus Torvalds1da177e2005-04-16 15:20:36 -0700932 */
933static ssize_t
934direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
935 const struct iovec *iov, loff_t offset, unsigned long nr_segs,
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -0800936 unsigned blkbits, get_block_t get_block, dio_iodone_t end_io,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700937 struct dio *dio)
938{
939 unsigned long user_addr;
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800940 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700941 int seg;
942 ssize_t ret = 0;
943 ssize_t ret2;
944 size_t bytes;
945
Linus Torvalds1da177e2005-04-16 15:20:36 -0700946 dio->inode = inode;
947 dio->rw = rw;
948 dio->blkbits = blkbits;
949 dio->blkfactor = inode->i_blkbits - blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700950 dio->block_in_file = offset >> blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700951
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -0800952 dio->get_block = get_block;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700953 dio->end_io = end_io;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700954 dio->final_block_in_bio = -1;
955 dio->next_block_for_io = -1;
956
Linus Torvalds1da177e2005-04-16 15:20:36 -0700957 dio->iocb = iocb;
Daniel McNeil29504ff2005-04-16 15:25:50 -0700958 dio->i_size = i_size_read(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700959
Linus Torvalds1da177e2005-04-16 15:20:36 -0700960 spin_lock_init(&dio->bio_lock);
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800961 dio->refcount = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700962
963 /*
964 * In case of non-aligned buffers, we may need 2 more
965 * pages since we need to zero out first and last block.
966 */
967 if (unlikely(dio->blkfactor))
968 dio->pages_in_io = 2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700969
970 for (seg = 0; seg < nr_segs; seg++) {
971 user_addr = (unsigned long)iov[seg].iov_base;
972 dio->pages_in_io +=
973 ((user_addr+iov[seg].iov_len +PAGE_SIZE-1)/PAGE_SIZE
974 - user_addr/PAGE_SIZE);
975 }
976
977 for (seg = 0; seg < nr_segs; seg++) {
978 user_addr = (unsigned long)iov[seg].iov_base;
979 dio->size += bytes = iov[seg].iov_len;
980
981 /* Index into the first page of the first block */
982 dio->first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits;
983 dio->final_block_in_request = dio->block_in_file +
984 (bytes >> blkbits);
985 /* Page fetching state */
986 dio->head = 0;
987 dio->tail = 0;
988 dio->curr_page = 0;
989
990 dio->total_pages = 0;
991 if (user_addr & (PAGE_SIZE-1)) {
992 dio->total_pages++;
993 bytes -= PAGE_SIZE - (user_addr & (PAGE_SIZE - 1));
994 }
995 dio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
996 dio->curr_user_address = user_addr;
997
998 ret = do_direct_IO(dio);
999
1000 dio->result += iov[seg].iov_len -
1001 ((dio->final_block_in_request - dio->block_in_file) <<
1002 blkbits);
1003
1004 if (ret) {
1005 dio_cleanup(dio);
1006 break;
1007 }
1008 } /* end iovec loop */
1009
Jens Axboeb31dc662006-06-13 08:26:10 +02001010 if (ret == -ENOTBLK && (rw & WRITE)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001011 /*
1012 * The remaining part of the request will be
1013 * be handled by buffered I/O when we return
1014 */
1015 ret = 0;
1016 }
1017 /*
1018 * There may be some unwritten disk at the end of a part-written
1019 * fs-block-sized block. Go zero that now.
1020 */
1021 dio_zero_block(dio, 1);
1022
1023 if (dio->cur_page) {
1024 ret2 = dio_send_cur_page(dio);
1025 if (ret == 0)
1026 ret = ret2;
1027 page_cache_release(dio->cur_page);
1028 dio->cur_page = NULL;
1029 }
1030 if (dio->bio)
1031 dio_bio_submit(dio);
1032
Zach Brown17a7b1d2006-12-10 02:20:56 -08001033 /* All IO is now issued, send it on its way */
1034 blk_run_address_space(inode->i_mapping);
1035
Linus Torvalds1da177e2005-04-16 15:20:36 -07001036 /*
1037 * It is possible that, we return short IO due to end of file.
1038 * In that case, we need to release all the pages we got hold on.
1039 */
1040 dio_cleanup(dio);
1041
1042 /*
1043 * All block lookups have been performed. For READ requests
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001044 * we can let i_mutex go now that its achieved its purpose
Linus Torvalds1da177e2005-04-16 15:20:36 -07001045 * of protecting us from looking up uninitialized blocks.
1046 */
1047 if ((rw == READ) && (dio->lock_type == DIO_LOCKING))
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001048 mutex_unlock(&dio->inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001049
1050 /*
Zach Brown8459d862006-12-10 02:21:05 -08001051 * The only time we want to leave bios in flight is when a successful
1052 * partial aio read or full aio write have been setup. In that case
1053 * bio completion will call aio_complete. The only time it's safe to
1054 * call aio_complete is when we return -EIOCBQUEUED, so we key on that.
1055 * This had *better* be the only place that raises -EIOCBQUEUED.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001056 */
Zach Brown8459d862006-12-10 02:21:05 -08001057 BUG_ON(ret == -EIOCBQUEUED);
1058 if (dio->is_async && ret == 0 && dio->result &&
1059 ((rw & READ) || (dio->result == dio->size)))
1060 ret = -EIOCBQUEUED;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001061
Zach Brown8459d862006-12-10 02:21:05 -08001062 if (ret != -EIOCBQUEUED)
Zach Brown6d544bb2006-12-10 02:20:54 -08001063 dio_await_completion(dio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001064
Zach Brown8459d862006-12-10 02:21:05 -08001065 /*
1066 * Sync will always be dropping the final ref and completing the
Zach Brown5eb6c7a2006-12-10 02:21:07 -08001067 * operation. AIO can if it was a broken operation described above or
1068 * in fact if all the bios race to complete before we get here. In
1069 * that case dio_complete() translates the EIOCBQUEUED into the proper
1070 * return code that the caller will hand to aio_complete().
1071 *
1072 * This is managed by the bio_lock instead of being an atomic_t so that
1073 * completion paths can drop their ref and use the remaining count to
1074 * decide to wake the submission path atomically.
Zach Brown8459d862006-12-10 02:21:05 -08001075 */
Zach Brown5eb6c7a2006-12-10 02:21:07 -08001076 spin_lock_irqsave(&dio->bio_lock, flags);
1077 ret2 = --dio->refcount;
1078 spin_unlock_irqrestore(&dio->bio_lock, flags);
Zach Brownfcb82f82007-07-03 15:28:55 -07001079
Zach Brown5eb6c7a2006-12-10 02:21:07 -08001080 if (ret2 == 0) {
Zach Brown6d544bb2006-12-10 02:20:54 -08001081 ret = dio_complete(dio, offset, ret);
Zach Brown8459d862006-12-10 02:21:05 -08001082 kfree(dio);
1083 } else
1084 BUG_ON(ret != -EIOCBQUEUED);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001085
Linus Torvalds1da177e2005-04-16 15:20:36 -07001086 return ret;
1087}
1088
1089/*
1090 * This is a library function for use by filesystem drivers.
1091 * The locking rules are governed by the dio_lock_type parameter.
1092 *
1093 * DIO_NO_LOCKING (no locking, for raw block device access)
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001094 * For writes, i_mutex is not held on entry; it is never taken.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001095 *
1096 * DIO_LOCKING (simple locking for regular files)
Nathan Scott3fb962b2006-03-15 15:14:45 +11001097 * For writes we are called under i_mutex and return with i_mutex held, even
1098 * though it is internally dropped.
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001099 * For reads, i_mutex is not held on entry, but it is taken and dropped before
Linus Torvalds1da177e2005-04-16 15:20:36 -07001100 * returning.
1101 *
1102 * DIO_OWN_LOCKING (filesystem provides synchronisation and handling of
1103 * uninitialised data, allowing parallel direct readers and writers)
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001104 * For writes we are called without i_mutex, return without it, never touch it.
Nathan Scott3fb962b2006-03-15 15:14:45 +11001105 * For reads we are called under i_mutex and return with i_mutex held, even
1106 * though it may be internally dropped.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001107 *
1108 * Additional i_alloc_sem locking requirements described inline below.
1109 */
1110ssize_t
1111__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
1112 struct block_device *bdev, const struct iovec *iov, loff_t offset,
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -08001113 unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001114 int dio_lock_type)
1115{
1116 int seg;
1117 size_t size;
1118 unsigned long addr;
1119 unsigned blkbits = inode->i_blkbits;
1120 unsigned bdev_blkbits = 0;
1121 unsigned blocksize_mask = (1 << blkbits) - 1;
1122 ssize_t retval = -EINVAL;
1123 loff_t end = offset;
1124 struct dio *dio;
Nathan Scott3fb962b2006-03-15 15:14:45 +11001125 int release_i_mutex = 0;
1126 int acquire_i_mutex = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001127
1128 if (rw & WRITE)
Jens Axboeb31dc662006-06-13 08:26:10 +02001129 rw = WRITE_SYNC;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001130
1131 if (bdev)
1132 bdev_blkbits = blksize_bits(bdev_hardsect_size(bdev));
1133
1134 if (offset & blocksize_mask) {
1135 if (bdev)
1136 blkbits = bdev_blkbits;
1137 blocksize_mask = (1 << blkbits) - 1;
1138 if (offset & blocksize_mask)
1139 goto out;
1140 }
1141
1142 /* Check the memory alignment. Blocks cannot straddle pages */
1143 for (seg = 0; seg < nr_segs; seg++) {
1144 addr = (unsigned long)iov[seg].iov_base;
1145 size = iov[seg].iov_len;
1146 end += size;
1147 if ((addr & blocksize_mask) || (size & blocksize_mask)) {
1148 if (bdev)
1149 blkbits = bdev_blkbits;
1150 blocksize_mask = (1 << blkbits) - 1;
1151 if ((addr & blocksize_mask) || (size & blocksize_mask))
1152 goto out;
1153 }
1154 }
1155
Zach Brown848c4dd2007-08-20 17:12:01 -07001156 dio = kzalloc(sizeof(*dio), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001157 retval = -ENOMEM;
1158 if (!dio)
1159 goto out;
1160
1161 /*
1162 * For block device access DIO_NO_LOCKING is used,
1163 * neither readers nor writers do any locking at all
1164 * For regular files using DIO_LOCKING,
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001165 * readers need to grab i_mutex and i_alloc_sem
1166 * writers need to grab i_alloc_sem only (i_mutex is already held)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001167 * For regular files using DIO_OWN_LOCKING,
1168 * neither readers nor writers take any locks here
Linus Torvalds1da177e2005-04-16 15:20:36 -07001169 */
1170 dio->lock_type = dio_lock_type;
1171 if (dio_lock_type != DIO_NO_LOCKING) {
1172 /* watch out for a 0 len io from a tricksy fs */
1173 if (rw == READ && end > offset) {
1174 struct address_space *mapping;
1175
1176 mapping = iocb->ki_filp->f_mapping;
1177 if (dio_lock_type != DIO_OWN_LOCKING) {
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001178 mutex_lock(&inode->i_mutex);
Nathan Scott3fb962b2006-03-15 15:14:45 +11001179 release_i_mutex = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001180 }
1181
1182 retval = filemap_write_and_wait_range(mapping, offset,
1183 end - 1);
1184 if (retval) {
1185 kfree(dio);
1186 goto out;
1187 }
1188
1189 if (dio_lock_type == DIO_OWN_LOCKING) {
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001190 mutex_unlock(&inode->i_mutex);
Nathan Scott3fb962b2006-03-15 15:14:45 +11001191 acquire_i_mutex = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001192 }
1193 }
1194
1195 if (dio_lock_type == DIO_LOCKING)
Ingo Molnard8aa9052006-07-03 00:25:02 -07001196 /* lockdep: not the owner will release it */
1197 down_read_non_owner(&inode->i_alloc_sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001198 }
1199
1200 /*
1201 * For file extending writes updating i_size before data
1202 * writeouts complete can expose uninitialized blocks. So
1203 * even for AIO, we need to wait for i/o to complete before
1204 * returning in this case.
1205 */
Jens Axboeb31dc662006-06-13 08:26:10 +02001206 dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001207 (end > i_size_read(inode)));
1208
1209 retval = direct_io_worker(rw, iocb, inode, iov, offset,
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -08001210 nr_segs, blkbits, get_block, end_io, dio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001211
Dmitri Monakhov0f644152009-01-06 14:40:04 -08001212 /*
1213 * In case of error extending write may have instantiated a few
1214 * blocks outside i_size. Trim these off again for DIO_LOCKING.
1215 * NOTE: DIO_NO_LOCK/DIO_OWN_LOCK callers have to handle this by
1216 * it's own meaner.
1217 */
1218 if (unlikely(retval < 0 && (rw & WRITE))) {
1219 loff_t isize = i_size_read(inode);
1220
1221 if (end > isize && dio_lock_type == DIO_LOCKING)
1222 vmtruncate(inode, isize);
1223 }
1224
Linus Torvalds1da177e2005-04-16 15:20:36 -07001225 if (rw == READ && dio_lock_type == DIO_LOCKING)
Nathan Scott3fb962b2006-03-15 15:14:45 +11001226 release_i_mutex = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001227
1228out:
Nathan Scott3fb962b2006-03-15 15:14:45 +11001229 if (release_i_mutex)
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001230 mutex_unlock(&inode->i_mutex);
Nathan Scott3fb962b2006-03-15 15:14:45 +11001231 else if (acquire_i_mutex)
1232 mutex_lock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001233 return retval;
1234}
1235EXPORT_SYMBOL(__blockdev_direct_IO);