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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.
Linus Torvalds1da177e2005-04-16 15:20:36 -070056 */
57
58struct dio {
59 /* BIO submission state */
60 struct bio *bio; /* bio under assembly */
61 struct inode *inode;
62 int rw;
Daniel McNeil29504ff2005-04-16 15:25:50 -070063 loff_t i_size; /* i_size when submitted */
Christoph Hellwig5fe878a2009-12-15 16:47:50 -080064 int flags; /* doesn't change */
Linus Torvalds1da177e2005-04-16 15:20:36 -070065 unsigned blkbits; /* doesn't change */
66 unsigned blkfactor; /* When we're using an alignment which
67 is finer than the filesystem's soft
68 blocksize, this specifies how much
69 finer. blkfactor=2 means 1/4-block
70 alignment. Does not change */
71 unsigned start_zero_done; /* flag: sub-blocksize zeroing has
72 been performed at the start of a
73 write */
74 int pages_in_io; /* approximate total IO pages */
75 size_t size; /* total request size (doesn't change)*/
76 sector_t block_in_file; /* Current offset into the underlying
77 file in dio_block units. */
78 unsigned blocks_available; /* At block_in_file. changes */
79 sector_t final_block_in_request;/* doesn't change */
80 unsigned first_block_in_page; /* doesn't change, Used only once */
81 int boundary; /* prev block is at a boundary */
82 int reap_counter; /* rate limit reaping */
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -080083 get_block_t *get_block; /* block mapping function */
Linus Torvalds1da177e2005-04-16 15:20:36 -070084 dio_iodone_t *end_io; /* IO completion function */
Josef Bacikfacd07b2010-05-23 11:00:55 -040085 dio_submit_t *submit_io; /* IO submition function */
86 loff_t logical_offset_in_bio; /* current first logical block in bio */
Linus Torvalds1da177e2005-04-16 15:20:36 -070087 sector_t final_block_in_bio; /* current final block in bio + 1 */
88 sector_t next_block_for_io; /* next block to be put under IO,
89 in dio_blocks units */
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -080090 struct buffer_head map_bh; /* last get_block() result */
Linus Torvalds1da177e2005-04-16 15:20:36 -070091
92 /*
93 * Deferred addition of a page to the dio. These variables are
94 * private to dio_send_cur_page(), submit_page_section() and
95 * dio_bio_add_page().
96 */
97 struct page *cur_page; /* The page */
98 unsigned cur_page_offset; /* Offset into it, in bytes */
99 unsigned cur_page_len; /* Nr of bytes at cur_page_offset */
100 sector_t cur_page_block; /* Where it starts */
Josef Bacikfacd07b2010-05-23 11:00:55 -0400101 loff_t cur_page_fs_offset; /* Offset in file */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103 /* BIO completion state */
104 spinlock_t bio_lock; /* protects BIO fields below */
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800105 unsigned long refcount; /* direct_io_worker() and bios */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106 struct bio *bio_list; /* singly linked via bi_private */
107 struct task_struct *waiter; /* waiting task (NULL if none) */
108
109 /* AIO related stuff */
110 struct kiocb *iocb; /* kiocb */
111 int is_async; /* is IO async ? */
Chen, Kenneth W174e27c2006-03-25 03:08:16 -0800112 int io_error; /* IO error in completion path */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113 ssize_t result; /* IO result */
Jeff Moyer23aee092009-12-15 16:47:49 -0800114
115 /*
116 * Page fetching state. These variables belong to dio_refill_pages().
117 */
118 int curr_page; /* changes */
119 int total_pages; /* doesn't change */
120 unsigned long curr_user_address;/* changes */
121
122 /*
123 * Page queue. These variables belong to dio_refill_pages() and
124 * dio_get_page().
125 */
126 unsigned head; /* next page to process */
127 unsigned tail; /* last valid page + 1 */
128 int page_errors; /* errno from get_user_pages() */
129
130 /*
131 * pages[] (and any fields placed after it) are not zeroed out at
132 * allocation time. Don't add new fields after pages[] unless you
133 * wish that they not be zeroed.
134 */
135 struct page *pages[DIO_PAGES]; /* page buffer */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136};
137
138/*
139 * How many pages are in the queue?
140 */
141static inline unsigned dio_pages_present(struct dio *dio)
142{
143 return dio->tail - dio->head;
144}
145
146/*
147 * Go grab and pin some userspace pages. Typically we'll get 64 at a time.
148 */
149static int dio_refill_pages(struct dio *dio)
150{
151 int ret;
152 int nr_pages;
153
154 nr_pages = min(dio->total_pages - dio->curr_page, DIO_PAGES);
Nick Pigginf5dd33c2008-07-25 19:45:25 -0700155 ret = get_user_pages_fast(
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156 dio->curr_user_address, /* Where from? */
157 nr_pages, /* How many pages? */
158 dio->rw == READ, /* Write to memory? */
Nick Pigginf5dd33c2008-07-25 19:45:25 -0700159 &dio->pages[0]); /* Put results here */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160
Jens Axboeb31dc662006-06-13 08:26:10 +0200161 if (ret < 0 && dio->blocks_available && (dio->rw & WRITE)) {
Nick Piggin557ed1f2007-10-16 01:24:40 -0700162 struct page *page = ZERO_PAGE(0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700163 /*
164 * A memory fault, but the filesystem has some outstanding
165 * mapped blocks. We need to use those blocks up to avoid
166 * leaking stale data in the file.
167 */
168 if (dio->page_errors == 0)
169 dio->page_errors = ret;
Nick Pigginb5810032005-10-29 18:16:12 -0700170 page_cache_get(page);
171 dio->pages[0] = page;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172 dio->head = 0;
173 dio->tail = 1;
174 ret = 0;
175 goto out;
176 }
177
178 if (ret >= 0) {
179 dio->curr_user_address += ret * PAGE_SIZE;
180 dio->curr_page += ret;
181 dio->head = 0;
182 dio->tail = ret;
183 ret = 0;
184 }
185out:
186 return ret;
187}
188
189/*
190 * Get another userspace page. Returns an ERR_PTR on error. Pages are
191 * buffered inside the dio so that we can call get_user_pages() against a
192 * decent number of pages, less frequently. To provide nicer use of the
193 * L1 cache.
194 */
195static struct page *dio_get_page(struct dio *dio)
196{
197 if (dio_pages_present(dio) == 0) {
198 int ret;
199
200 ret = dio_refill_pages(dio);
201 if (ret)
202 return ERR_PTR(ret);
203 BUG_ON(dio_pages_present(dio) == 0);
204 }
205 return dio->pages[dio->head++];
206}
207
Zach Brown6d544bb2006-12-10 02:20:54 -0800208/**
209 * dio_complete() - called when all DIO BIO I/O has been completed
210 * @offset: the byte offset in the file of the completed operation
211 *
212 * This releases locks as dictated by the locking type, lets interested parties
213 * know that a DIO operation has completed, and calculates the resulting return
214 * code for the operation.
215 *
216 * It lets the filesystem know if it registered an interest earlier via
217 * get_block. Pass the private field of the map buffer_head so that
218 * filesystems can use it to hold additional state between get_block calls and
219 * dio_complete.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700220 */
Edward Shishkincd1c5842010-10-26 14:22:28 -0700221static ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret, bool is_async)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700222{
Zach Brown6d544bb2006-12-10 02:20:54 -0800223 ssize_t transferred = 0;
224
Zach Brown8459d862006-12-10 02:21:05 -0800225 /*
226 * AIO submission can race with bio completion to get here while
227 * expecting to have the last io completed by bio completion.
228 * In that case -EIOCBQUEUED is in fact not an error we want
229 * to preserve through this call.
230 */
231 if (ret == -EIOCBQUEUED)
232 ret = 0;
233
Zach Brown6d544bb2006-12-10 02:20:54 -0800234 if (dio->result) {
235 transferred = dio->result;
236
237 /* Check for short read case */
238 if ((dio->rw == READ) && ((offset + transferred) > dio->i_size))
239 transferred = dio->i_size - offset;
240 }
241
Zach Brown6d544bb2006-12-10 02:20:54 -0800242 if (ret == 0)
243 ret = dio->page_errors;
244 if (ret == 0)
245 ret = dio->io_error;
246 if (ret == 0)
247 ret = transferred;
248
Christoph Hellwig40e2e972010-07-18 21:17:09 +0000249 if (dio->end_io && dio->result) {
250 dio->end_io(dio->iocb, offset, transferred,
251 dio->map_bh.b_private, ret, is_async);
252 } else if (is_async) {
253 aio_complete(dio->iocb, ret, 0);
254 }
255
256 if (dio->flags & DIO_LOCKING)
257 /* lockdep: non-owner release */
258 up_read_non_owner(&dio->inode->i_alloc_sem);
259
Zach Brown6d544bb2006-12-10 02:20:54 -0800260 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700261}
262
Linus Torvalds1da177e2005-04-16 15:20:36 -0700263static int dio_bio_complete(struct dio *dio, struct bio *bio);
264/*
265 * Asynchronous IO callback.
266 */
NeilBrown6712ecf2007-09-27 12:47:43 +0200267static void dio_bio_end_aio(struct bio *bio, int error)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700268{
269 struct dio *dio = bio->bi_private;
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800270 unsigned long remaining;
271 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700272
Linus Torvalds1da177e2005-04-16 15:20:36 -0700273 /* cleanup the bio */
274 dio_bio_complete(dio, bio);
Zach Brown02732012006-12-10 02:20:59 -0800275
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800276 spin_lock_irqsave(&dio->bio_lock, flags);
277 remaining = --dio->refcount;
278 if (remaining == 1 && dio->waiter)
Zach Brown20258b22006-12-10 02:21:01 -0800279 wake_up_process(dio->waiter);
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800280 spin_unlock_irqrestore(&dio->bio_lock, flags);
Zach Brown20258b22006-12-10 02:21:01 -0800281
Zach Brown8459d862006-12-10 02:21:05 -0800282 if (remaining == 0) {
Christoph Hellwig40e2e972010-07-18 21:17:09 +0000283 dio_complete(dio, dio->iocb->ki_pos, 0, true);
Zach Brown8459d862006-12-10 02:21:05 -0800284 kfree(dio);
285 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700286}
287
288/*
289 * The BIO completion handler simply queues the BIO up for the process-context
290 * handler.
291 *
292 * During I/O bi_private points at the dio. After I/O, bi_private is used to
293 * implement a singly-linked list of completed BIOs, at dio->bio_list.
294 */
NeilBrown6712ecf2007-09-27 12:47:43 +0200295static void dio_bio_end_io(struct bio *bio, int error)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700296{
297 struct dio *dio = bio->bi_private;
298 unsigned long flags;
299
Linus Torvalds1da177e2005-04-16 15:20:36 -0700300 spin_lock_irqsave(&dio->bio_lock, flags);
301 bio->bi_private = dio->bio_list;
302 dio->bio_list = bio;
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800303 if (--dio->refcount == 1 && dio->waiter)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700304 wake_up_process(dio->waiter);
305 spin_unlock_irqrestore(&dio->bio_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700306}
307
Josef Bacikfacd07b2010-05-23 11:00:55 -0400308/**
309 * dio_end_io - handle the end io action for the given bio
310 * @bio: The direct io bio thats being completed
311 * @error: Error if there was one
312 *
313 * This is meant to be called by any filesystem that uses their own dio_submit_t
314 * so that the DIO specific endio actions are dealt with after the filesystem
315 * has done it's completion work.
316 */
317void dio_end_io(struct bio *bio, int error)
318{
319 struct dio *dio = bio->bi_private;
320
321 if (dio->is_async)
322 dio_bio_end_aio(bio, error);
323 else
324 dio_bio_end_io(bio, error);
325}
326EXPORT_SYMBOL_GPL(dio_end_io);
327
David Dillow20d96002011-01-20 14:44:22 -0800328static void
Linus Torvalds1da177e2005-04-16 15:20:36 -0700329dio_bio_alloc(struct dio *dio, struct block_device *bdev,
330 sector_t first_sector, int nr_vecs)
331{
332 struct bio *bio;
333
David Dillow20d96002011-01-20 14:44:22 -0800334 /*
335 * bio_alloc() is guaranteed to return a bio when called with
336 * __GFP_WAIT and we request a valid number of vectors.
337 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700338 bio = bio_alloc(GFP_KERNEL, nr_vecs);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700339
340 bio->bi_bdev = bdev;
341 bio->bi_sector = first_sector;
342 if (dio->is_async)
343 bio->bi_end_io = dio_bio_end_aio;
344 else
345 bio->bi_end_io = dio_bio_end_io;
346
347 dio->bio = bio;
Josef Bacikfacd07b2010-05-23 11:00:55 -0400348 dio->logical_offset_in_bio = dio->cur_page_fs_offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349}
350
351/*
352 * In the AIO read case we speculatively dirty the pages before starting IO.
353 * During IO completion, any of these pages which happen to have been written
354 * back will be redirtied by bio_check_pages_dirty().
Zach Brown02732012006-12-10 02:20:59 -0800355 *
356 * bios hold a dio reference between submit_bio and ->end_io.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700357 */
358static void dio_bio_submit(struct dio *dio)
359{
360 struct bio *bio = dio->bio;
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800361 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700362
363 bio->bi_private = dio;
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800364
365 spin_lock_irqsave(&dio->bio_lock, flags);
366 dio->refcount++;
367 spin_unlock_irqrestore(&dio->bio_lock, flags);
368
Linus Torvalds1da177e2005-04-16 15:20:36 -0700369 if (dio->is_async && dio->rw == READ)
370 bio_set_pages_dirty(bio);
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800371
Josef Bacikfacd07b2010-05-23 11:00:55 -0400372 if (dio->submit_io)
373 dio->submit_io(dio->rw, bio, dio->inode,
374 dio->logical_offset_in_bio);
375 else
376 submit_bio(dio->rw, bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700377
378 dio->bio = NULL;
379 dio->boundary = 0;
Josef Bacikfacd07b2010-05-23 11:00:55 -0400380 dio->logical_offset_in_bio = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700381}
382
383/*
384 * Release any resources in case of a failure
385 */
386static void dio_cleanup(struct dio *dio)
387{
388 while (dio_pages_present(dio))
389 page_cache_release(dio_get_page(dio));
390}
391
392/*
Zach Brown02732012006-12-10 02:20:59 -0800393 * Wait for the next BIO to complete. Remove it and return it. NULL is
394 * returned once all BIOs have been completed. This must only be called once
395 * all bios have been issued so that dio->refcount can only decrease. This
396 * requires that that the caller hold a reference on the dio.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700397 */
398static struct bio *dio_await_one(struct dio *dio)
399{
400 unsigned long flags;
Zach Brown02732012006-12-10 02:20:59 -0800401 struct bio *bio = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700402
403 spin_lock_irqsave(&dio->bio_lock, flags);
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800404
405 /*
406 * Wait as long as the list is empty and there are bios in flight. bio
407 * completion drops the count, maybe adds to the list, and wakes while
408 * holding the bio_lock so we don't need set_current_state()'s barrier
409 * and can call it after testing our condition.
410 */
411 while (dio->refcount > 1 && dio->bio_list == NULL) {
412 __set_current_state(TASK_UNINTERRUPTIBLE);
413 dio->waiter = current;
414 spin_unlock_irqrestore(&dio->bio_lock, flags);
415 io_schedule();
416 /* wake up sets us TASK_RUNNING */
417 spin_lock_irqsave(&dio->bio_lock, flags);
418 dio->waiter = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700419 }
Zach Brown02732012006-12-10 02:20:59 -0800420 if (dio->bio_list) {
421 bio = dio->bio_list;
422 dio->bio_list = bio->bi_private;
423 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700424 spin_unlock_irqrestore(&dio->bio_lock, flags);
425 return bio;
426}
427
428/*
429 * Process one completed BIO. No locks are held.
430 */
431static int dio_bio_complete(struct dio *dio, struct bio *bio)
432{
433 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
434 struct bio_vec *bvec = bio->bi_io_vec;
435 int page_no;
436
437 if (!uptodate)
Chen, Kenneth W174e27c2006-03-25 03:08:16 -0800438 dio->io_error = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700439
440 if (dio->is_async && dio->rw == READ) {
441 bio_check_pages_dirty(bio); /* transfers ownership */
442 } else {
443 for (page_no = 0; page_no < bio->bi_vcnt; page_no++) {
444 struct page *page = bvec[page_no].bv_page;
445
446 if (dio->rw == READ && !PageCompound(page))
447 set_page_dirty_lock(page);
448 page_cache_release(page);
449 }
450 bio_put(bio);
451 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700452 return uptodate ? 0 : -EIO;
453}
454
455/*
Zach Brown02732012006-12-10 02:20:59 -0800456 * Wait on and process all in-flight BIOs. This must only be called once
457 * all bios have been issued so that the refcount can only decrease.
458 * This just waits for all bios to make it through dio_bio_complete. IO
Robert P. J. Daybeb7dd82007-05-09 07:14:03 +0200459 * errors are propagated through dio->io_error and should be propagated via
Zach Brown02732012006-12-10 02:20:59 -0800460 * dio_complete().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700461 */
Zach Brown6d544bb2006-12-10 02:20:54 -0800462static void dio_await_completion(struct dio *dio)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700463{
Zach Brown02732012006-12-10 02:20:59 -0800464 struct bio *bio;
465 do {
466 bio = dio_await_one(dio);
467 if (bio)
468 dio_bio_complete(dio, bio);
469 } while (bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700470}
471
472/*
473 * A really large O_DIRECT read or write can generate a lot of BIOs. So
474 * to keep the memory consumption sane we periodically reap any completed BIOs
475 * during the BIO generation phase.
476 *
477 * This also helps to limit the peak amount of pinned userspace memory.
478 */
479static int dio_bio_reap(struct dio *dio)
480{
481 int ret = 0;
482
483 if (dio->reap_counter++ >= 64) {
484 while (dio->bio_list) {
485 unsigned long flags;
486 struct bio *bio;
487 int ret2;
488
489 spin_lock_irqsave(&dio->bio_lock, flags);
490 bio = dio->bio_list;
491 dio->bio_list = bio->bi_private;
492 spin_unlock_irqrestore(&dio->bio_lock, flags);
493 ret2 = dio_bio_complete(dio, bio);
494 if (ret == 0)
495 ret = ret2;
496 }
497 dio->reap_counter = 0;
498 }
499 return ret;
500}
501
502/*
503 * Call into the fs to map some more disk blocks. We record the current number
504 * of available blocks at dio->blocks_available. These are in units of the
505 * fs blocksize, (1 << inode->i_blkbits).
506 *
507 * The fs is allowed to map lots of blocks at once. If it wants to do that,
508 * it uses the passed inode-relative block number as the file offset, as usual.
509 *
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -0800510 * get_block() is passed the number of i_blkbits-sized blocks which direct_io
Linus Torvalds1da177e2005-04-16 15:20:36 -0700511 * has remaining to do. The fs should not map more than this number of blocks.
512 *
513 * If the fs has mapped a lot of blocks, it should populate bh->b_size to
514 * indicate how much contiguous disk space has been made available at
515 * bh->b_blocknr.
516 *
517 * If *any* of the mapped blocks are new, then the fs must set buffer_new().
518 * This isn't very efficient...
519 *
520 * In the case of filesystem holes: the fs may return an arbitrarily-large
521 * hole by returning an appropriate value in b_size and by clearing
522 * buffer_mapped(). However the direct-io code will only process holes one
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -0800523 * block at a time - it will repeatedly call get_block() as it walks the hole.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700524 */
525static int get_more_blocks(struct dio *dio)
526{
527 int ret;
528 struct buffer_head *map_bh = &dio->map_bh;
529 sector_t fs_startblk; /* Into file, in filesystem-sized blocks */
530 unsigned long fs_count; /* Number of filesystem-sized blocks */
531 unsigned long dio_count;/* Number of dio_block-sized blocks */
532 unsigned long blkmask;
533 int create;
534
535 /*
536 * If there was a memory error and we've overwritten all the
537 * mapped blocks then we can now return that memory error
538 */
539 ret = dio->page_errors;
540 if (ret == 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700541 BUG_ON(dio->block_in_file >= dio->final_block_in_request);
542 fs_startblk = dio->block_in_file >> dio->blkfactor;
543 dio_count = dio->final_block_in_request - dio->block_in_file;
544 fs_count = dio_count >> dio->blkfactor;
545 blkmask = (1 << dio->blkfactor) - 1;
546 if (dio_count & blkmask)
547 fs_count++;
548
Nathan Scott3c674e72006-03-29 09:26:15 +1000549 map_bh->b_state = 0;
550 map_bh->b_size = fs_count << dio->inode->i_blkbits;
551
Christoph Hellwig5fe878a2009-12-15 16:47:50 -0800552 /*
553 * For writes inside i_size on a DIO_SKIP_HOLES filesystem we
554 * forbid block creations: only overwrites are permitted.
555 * We will return early to the caller once we see an
556 * unmapped buffer head returned, and the caller will fall
557 * back to buffered I/O.
558 *
559 * Otherwise the decision is left to the get_blocks method,
560 * which may decide to handle it or also return an unmapped
561 * buffer head.
562 */
Jens Axboeb31dc662006-06-13 08:26:10 +0200563 create = dio->rw & WRITE;
Christoph Hellwig5fe878a2009-12-15 16:47:50 -0800564 if (dio->flags & DIO_SKIP_HOLES) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700565 if (dio->block_in_file < (i_size_read(dio->inode) >>
566 dio->blkbits))
567 create = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700568 }
Nathan Scott3c674e72006-03-29 09:26:15 +1000569
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -0800570 ret = (*dio->get_block)(dio->inode, fs_startblk,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700571 map_bh, create);
572 }
573 return ret;
574}
575
576/*
577 * There is no bio. Make one now.
578 */
579static int dio_new_bio(struct dio *dio, sector_t start_sector)
580{
581 sector_t sector;
582 int ret, nr_pages;
583
584 ret = dio_bio_reap(dio);
585 if (ret)
586 goto out;
587 sector = start_sector << (dio->blkbits - 9);
588 nr_pages = min(dio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev));
David Dillow20d96002011-01-20 14:44:22 -0800589 nr_pages = min(nr_pages, BIO_MAX_PAGES);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700590 BUG_ON(nr_pages <= 0);
David Dillow20d96002011-01-20 14:44:22 -0800591 dio_bio_alloc(dio, dio->map_bh.b_bdev, sector, nr_pages);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700592 dio->boundary = 0;
593out:
594 return ret;
595}
596
597/*
598 * Attempt to put the current chunk of 'cur_page' into the current BIO. If
599 * that was successful then update final_block_in_bio and take a ref against
600 * the just-added page.
601 *
602 * Return zero on success. Non-zero means the caller needs to start a new BIO.
603 */
604static int dio_bio_add_page(struct dio *dio)
605{
606 int ret;
607
608 ret = bio_add_page(dio->bio, dio->cur_page,
609 dio->cur_page_len, dio->cur_page_offset);
610 if (ret == dio->cur_page_len) {
611 /*
612 * Decrement count only, if we are done with this page
613 */
614 if ((dio->cur_page_len + dio->cur_page_offset) == PAGE_SIZE)
615 dio->pages_in_io--;
616 page_cache_get(dio->cur_page);
617 dio->final_block_in_bio = dio->cur_page_block +
618 (dio->cur_page_len >> dio->blkbits);
619 ret = 0;
620 } else {
621 ret = 1;
622 }
623 return ret;
624}
625
626/*
627 * Put cur_page under IO. The section of cur_page which is described by
628 * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page
629 * starts on-disk at cur_page_block.
630 *
631 * We take a ref against the page here (on behalf of its presence in the bio).
632 *
633 * The caller of this function is responsible for removing cur_page from the
634 * dio, and for dropping the refcount which came from that presence.
635 */
636static int dio_send_cur_page(struct dio *dio)
637{
638 int ret = 0;
639
640 if (dio->bio) {
Jeff Moyer7a801ac2010-09-09 16:37:33 -0700641 loff_t cur_offset = dio->cur_page_fs_offset;
Josef Bacikc2c6ca42010-05-23 11:00:55 -0400642 loff_t bio_next_offset = dio->logical_offset_in_bio +
643 dio->bio->bi_size;
644
Linus Torvalds1da177e2005-04-16 15:20:36 -0700645 /*
Josef Bacikc2c6ca42010-05-23 11:00:55 -0400646 * See whether this new request is contiguous with the old.
647 *
Namhyung Kimf0940ce2011-01-11 21:15:03 +0900648 * Btrfs cannot handle having logically non-contiguous requests
649 * submitted. For example if you have
Josef Bacikc2c6ca42010-05-23 11:00:55 -0400650 *
651 * Logical: [0-4095][HOLE][8192-12287]
Namhyung Kimf0940ce2011-01-11 21:15:03 +0900652 * Physical: [0-4095] [4096-8191]
Josef Bacikc2c6ca42010-05-23 11:00:55 -0400653 *
654 * We cannot submit those pages together as one BIO. So if our
655 * current logical offset in the file does not equal what would
656 * be the next logical offset in the bio, submit the bio we
657 * have.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700658 */
Josef Bacikc2c6ca42010-05-23 11:00:55 -0400659 if (dio->final_block_in_bio != dio->cur_page_block ||
660 cur_offset != bio_next_offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700661 dio_bio_submit(dio);
662 /*
663 * Submit now if the underlying fs is about to perform a
664 * metadata read
665 */
Jeff Moyer7a801ac2010-09-09 16:37:33 -0700666 else if (dio->boundary)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700667 dio_bio_submit(dio);
668 }
669
670 if (dio->bio == NULL) {
671 ret = dio_new_bio(dio, dio->cur_page_block);
672 if (ret)
673 goto out;
674 }
675
676 if (dio_bio_add_page(dio) != 0) {
677 dio_bio_submit(dio);
678 ret = dio_new_bio(dio, dio->cur_page_block);
679 if (ret == 0) {
680 ret = dio_bio_add_page(dio);
681 BUG_ON(ret != 0);
682 }
683 }
684out:
685 return ret;
686}
687
688/*
689 * An autonomous function to put a chunk of a page under deferred IO.
690 *
691 * The caller doesn't actually know (or care) whether this piece of page is in
692 * a BIO, or is under IO or whatever. We just take care of all possible
693 * situations here. The separation between the logic of do_direct_IO() and
694 * that of submit_page_section() is important for clarity. Please don't break.
695 *
696 * The chunk of page starts on-disk at blocknr.
697 *
698 * We perform deferred IO, by recording the last-submitted page inside our
699 * private part of the dio structure. If possible, we just expand the IO
700 * across that page here.
701 *
702 * If that doesn't work out then we put the old page into the bio and add this
703 * page to the dio instead.
704 */
705static int
706submit_page_section(struct dio *dio, struct page *page,
707 unsigned offset, unsigned len, sector_t blocknr)
708{
709 int ret = 0;
710
Andrew Morton98c4d572006-12-10 02:19:47 -0800711 if (dio->rw & WRITE) {
712 /*
713 * Read accounting is performed in submit_bio()
714 */
715 task_io_account_write(len);
716 }
717
Linus Torvalds1da177e2005-04-16 15:20:36 -0700718 /*
719 * Can we just grow the current page's presence in the dio?
720 */
721 if ( (dio->cur_page == page) &&
722 (dio->cur_page_offset + dio->cur_page_len == offset) &&
723 (dio->cur_page_block +
724 (dio->cur_page_len >> dio->blkbits) == blocknr)) {
725 dio->cur_page_len += len;
726
727 /*
728 * If dio->boundary then we want to schedule the IO now to
729 * avoid metadata seeks.
730 */
731 if (dio->boundary) {
732 ret = dio_send_cur_page(dio);
733 page_cache_release(dio->cur_page);
734 dio->cur_page = NULL;
735 }
736 goto out;
737 }
738
739 /*
740 * If there's a deferred page already there then send it.
741 */
742 if (dio->cur_page) {
743 ret = dio_send_cur_page(dio);
744 page_cache_release(dio->cur_page);
745 dio->cur_page = NULL;
746 if (ret)
747 goto out;
748 }
749
750 page_cache_get(page); /* It is in dio */
751 dio->cur_page = page;
752 dio->cur_page_offset = offset;
753 dio->cur_page_len = len;
754 dio->cur_page_block = blocknr;
Josef Bacikfacd07b2010-05-23 11:00:55 -0400755 dio->cur_page_fs_offset = dio->block_in_file << dio->blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700756out:
757 return ret;
758}
759
760/*
761 * Clean any dirty buffers in the blockdev mapping which alias newly-created
762 * file blocks. Only called for S_ISREG files - blockdevs do not set
763 * buffer_new
764 */
765static void clean_blockdev_aliases(struct dio *dio)
766{
767 unsigned i;
768 unsigned nblocks;
769
770 nblocks = dio->map_bh.b_size >> dio->inode->i_blkbits;
771
772 for (i = 0; i < nblocks; i++) {
773 unmap_underlying_metadata(dio->map_bh.b_bdev,
774 dio->map_bh.b_blocknr + i);
775 }
776}
777
778/*
779 * If we are not writing the entire block and get_block() allocated
780 * the block for us, we need to fill-in the unused portion of the
781 * block with zeros. This happens only if user-buffer, fileoffset or
782 * io length is not filesystem block-size multiple.
783 *
784 * `end' is zero if we're doing the start of the IO, 1 at the end of the
785 * IO.
786 */
787static void dio_zero_block(struct dio *dio, int end)
788{
789 unsigned dio_blocks_per_fs_block;
790 unsigned this_chunk_blocks; /* In dio_blocks */
791 unsigned this_chunk_bytes;
792 struct page *page;
793
794 dio->start_zero_done = 1;
795 if (!dio->blkfactor || !buffer_new(&dio->map_bh))
796 return;
797
798 dio_blocks_per_fs_block = 1 << dio->blkfactor;
799 this_chunk_blocks = dio->block_in_file & (dio_blocks_per_fs_block - 1);
800
801 if (!this_chunk_blocks)
802 return;
803
804 /*
805 * We need to zero out part of an fs block. It is either at the
806 * beginning or the end of the fs block.
807 */
808 if (end)
809 this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks;
810
811 this_chunk_bytes = this_chunk_blocks << dio->blkbits;
812
Nick Piggin557ed1f2007-10-16 01:24:40 -0700813 page = ZERO_PAGE(0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700814 if (submit_page_section(dio, page, 0, this_chunk_bytes,
815 dio->next_block_for_io))
816 return;
817
818 dio->next_block_for_io += this_chunk_blocks;
819}
820
821/*
822 * Walk the user pages, and the file, mapping blocks to disk and generating
823 * a sequence of (page,offset,len,block) mappings. These mappings are injected
824 * into submit_page_section(), which takes care of the next stage of submission
825 *
826 * Direct IO against a blockdev is different from a file. Because we can
827 * happily perform page-sized but 512-byte aligned IOs. It is important that
828 * blockdev IO be able to have fine alignment and large sizes.
829 *
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -0800830 * So what we do is to permit the ->get_block function to populate bh.b_size
Linus Torvalds1da177e2005-04-16 15:20:36 -0700831 * with the size of IO which is permitted at this offset and this i_blkbits.
832 *
833 * For best results, the blockdev should be set up with 512-byte i_blkbits and
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -0800834 * it should set b_size to PAGE_SIZE or more inside get_block(). This gives
Linus Torvalds1da177e2005-04-16 15:20:36 -0700835 * fine alignment but still allows this function to work in PAGE_SIZE units.
836 */
837static int do_direct_IO(struct dio *dio)
838{
839 const unsigned blkbits = dio->blkbits;
840 const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
841 struct page *page;
842 unsigned block_in_page;
843 struct buffer_head *map_bh = &dio->map_bh;
844 int ret = 0;
845
846 /* The I/O can start at any block offset within the first page */
847 block_in_page = dio->first_block_in_page;
848
849 while (dio->block_in_file < dio->final_block_in_request) {
850 page = dio_get_page(dio);
851 if (IS_ERR(page)) {
852 ret = PTR_ERR(page);
853 goto out;
854 }
855
856 while (block_in_page < blocks_per_page) {
857 unsigned offset_in_page = block_in_page << blkbits;
858 unsigned this_chunk_bytes; /* # of bytes mapped */
859 unsigned this_chunk_blocks; /* # of blocks */
860 unsigned u;
861
862 if (dio->blocks_available == 0) {
863 /*
864 * Need to go and map some more disk
865 */
866 unsigned long blkmask;
867 unsigned long dio_remainder;
868
869 ret = get_more_blocks(dio);
870 if (ret) {
871 page_cache_release(page);
872 goto out;
873 }
874 if (!buffer_mapped(map_bh))
875 goto do_holes;
876
877 dio->blocks_available =
878 map_bh->b_size >> dio->blkbits;
879 dio->next_block_for_io =
880 map_bh->b_blocknr << dio->blkfactor;
881 if (buffer_new(map_bh))
882 clean_blockdev_aliases(dio);
883
884 if (!dio->blkfactor)
885 goto do_holes;
886
887 blkmask = (1 << dio->blkfactor) - 1;
888 dio_remainder = (dio->block_in_file & blkmask);
889
890 /*
891 * If we are at the start of IO and that IO
892 * starts partway into a fs-block,
893 * dio_remainder will be non-zero. If the IO
894 * is a read then we can simply advance the IO
895 * cursor to the first block which is to be
896 * read. But if the IO is a write and the
897 * block was newly allocated we cannot do that;
898 * the start of the fs block must be zeroed out
899 * on-disk
900 */
901 if (!buffer_new(map_bh))
902 dio->next_block_for_io += dio_remainder;
903 dio->blocks_available -= dio_remainder;
904 }
905do_holes:
906 /* Handle holes */
907 if (!buffer_mapped(map_bh)) {
Jeff Moyer35dc8162006-02-03 03:04:27 -0800908 loff_t i_size_aligned;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700909
910 /* AKPM: eargh, -ENOTBLK is a hack */
Jens Axboeb31dc662006-06-13 08:26:10 +0200911 if (dio->rw & WRITE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700912 page_cache_release(page);
913 return -ENOTBLK;
914 }
915
Jeff Moyer35dc8162006-02-03 03:04:27 -0800916 /*
917 * Be sure to account for a partial block as the
918 * last block in the file
919 */
920 i_size_aligned = ALIGN(i_size_read(dio->inode),
921 1 << blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700922 if (dio->block_in_file >=
Jeff Moyer35dc8162006-02-03 03:04:27 -0800923 i_size_aligned >> blkbits) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700924 /* We hit eof */
925 page_cache_release(page);
926 goto out;
927 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -0800928 zero_user(page, block_in_page << blkbits,
929 1 << blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700930 dio->block_in_file++;
931 block_in_page++;
932 goto next_block;
933 }
934
935 /*
936 * If we're performing IO which has an alignment which
937 * is finer than the underlying fs, go check to see if
938 * we must zero out the start of this block.
939 */
940 if (unlikely(dio->blkfactor && !dio->start_zero_done))
941 dio_zero_block(dio, 0);
942
943 /*
944 * Work out, in this_chunk_blocks, how much disk we
945 * can add to this page
946 */
947 this_chunk_blocks = dio->blocks_available;
948 u = (PAGE_SIZE - offset_in_page) >> blkbits;
949 if (this_chunk_blocks > u)
950 this_chunk_blocks = u;
951 u = dio->final_block_in_request - dio->block_in_file;
952 if (this_chunk_blocks > u)
953 this_chunk_blocks = u;
954 this_chunk_bytes = this_chunk_blocks << blkbits;
955 BUG_ON(this_chunk_bytes == 0);
956
957 dio->boundary = buffer_boundary(map_bh);
958 ret = submit_page_section(dio, page, offset_in_page,
959 this_chunk_bytes, dio->next_block_for_io);
960 if (ret) {
961 page_cache_release(page);
962 goto out;
963 }
964 dio->next_block_for_io += this_chunk_blocks;
965
966 dio->block_in_file += this_chunk_blocks;
967 block_in_page += this_chunk_blocks;
968 dio->blocks_available -= this_chunk_blocks;
969next_block:
Eric Sesterhennd4569d22006-04-01 01:10:13 +0200970 BUG_ON(dio->block_in_file > dio->final_block_in_request);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700971 if (dio->block_in_file == dio->final_block_in_request)
972 break;
973 }
974
975 /* Drop the ref which was taken in get_user_pages() */
976 page_cache_release(page);
977 block_in_page = 0;
978 }
979out:
980 return ret;
981}
982
983/*
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800984 * Releases both i_mutex and i_alloc_sem
Linus Torvalds1da177e2005-04-16 15:20:36 -0700985 */
986static ssize_t
987direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
988 const struct iovec *iov, loff_t offset, unsigned long nr_segs,
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -0800989 unsigned blkbits, get_block_t get_block, dio_iodone_t end_io,
Josef Bacikfacd07b2010-05-23 11:00:55 -0400990 dio_submit_t submit_io, struct dio *dio)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700991{
992 unsigned long user_addr;
Zach Brown5eb6c7a2006-12-10 02:21:07 -0800993 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700994 int seg;
995 ssize_t ret = 0;
996 ssize_t ret2;
997 size_t bytes;
998
Linus Torvalds1da177e2005-04-16 15:20:36 -0700999 dio->inode = inode;
1000 dio->rw = rw;
1001 dio->blkbits = blkbits;
1002 dio->blkfactor = inode->i_blkbits - blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001003 dio->block_in_file = offset >> blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001004
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -08001005 dio->get_block = get_block;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001006 dio->end_io = end_io;
Josef Bacikfacd07b2010-05-23 11:00:55 -04001007 dio->submit_io = submit_io;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001008 dio->final_block_in_bio = -1;
1009 dio->next_block_for_io = -1;
1010
Linus Torvalds1da177e2005-04-16 15:20:36 -07001011 dio->iocb = iocb;
Daniel McNeil29504ff2005-04-16 15:25:50 -07001012 dio->i_size = i_size_read(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001013
Linus Torvalds1da177e2005-04-16 15:20:36 -07001014 spin_lock_init(&dio->bio_lock);
Zach Brown5eb6c7a2006-12-10 02:21:07 -08001015 dio->refcount = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001016
1017 /*
1018 * In case of non-aligned buffers, we may need 2 more
1019 * pages since we need to zero out first and last block.
1020 */
1021 if (unlikely(dio->blkfactor))
1022 dio->pages_in_io = 2;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001023
1024 for (seg = 0; seg < nr_segs; seg++) {
1025 user_addr = (unsigned long)iov[seg].iov_base;
1026 dio->pages_in_io +=
1027 ((user_addr+iov[seg].iov_len +PAGE_SIZE-1)/PAGE_SIZE
1028 - user_addr/PAGE_SIZE);
1029 }
1030
1031 for (seg = 0; seg < nr_segs; seg++) {
1032 user_addr = (unsigned long)iov[seg].iov_base;
1033 dio->size += bytes = iov[seg].iov_len;
1034
1035 /* Index into the first page of the first block */
1036 dio->first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits;
1037 dio->final_block_in_request = dio->block_in_file +
1038 (bytes >> blkbits);
1039 /* Page fetching state */
1040 dio->head = 0;
1041 dio->tail = 0;
1042 dio->curr_page = 0;
1043
1044 dio->total_pages = 0;
1045 if (user_addr & (PAGE_SIZE-1)) {
1046 dio->total_pages++;
1047 bytes -= PAGE_SIZE - (user_addr & (PAGE_SIZE - 1));
1048 }
1049 dio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
1050 dio->curr_user_address = user_addr;
1051
1052 ret = do_direct_IO(dio);
1053
1054 dio->result += iov[seg].iov_len -
1055 ((dio->final_block_in_request - dio->block_in_file) <<
1056 blkbits);
1057
1058 if (ret) {
1059 dio_cleanup(dio);
1060 break;
1061 }
1062 } /* end iovec loop */
1063
Josef Bacikfacd07b2010-05-23 11:00:55 -04001064 if (ret == -ENOTBLK) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001065 /*
1066 * The remaining part of the request will be
1067 * be handled by buffered I/O when we return
1068 */
1069 ret = 0;
1070 }
1071 /*
1072 * There may be some unwritten disk at the end of a part-written
1073 * fs-block-sized block. Go zero that now.
1074 */
1075 dio_zero_block(dio, 1);
1076
1077 if (dio->cur_page) {
1078 ret2 = dio_send_cur_page(dio);
1079 if (ret == 0)
1080 ret = ret2;
1081 page_cache_release(dio->cur_page);
1082 dio->cur_page = NULL;
1083 }
1084 if (dio->bio)
1085 dio_bio_submit(dio);
1086
1087 /*
1088 * It is possible that, we return short IO due to end of file.
1089 * In that case, we need to release all the pages we got hold on.
1090 */
1091 dio_cleanup(dio);
1092
1093 /*
1094 * All block lookups have been performed. For READ requests
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001095 * we can let i_mutex go now that its achieved its purpose
Linus Torvalds1da177e2005-04-16 15:20:36 -07001096 * of protecting us from looking up uninitialized blocks.
1097 */
Christoph Hellwig5fe878a2009-12-15 16:47:50 -08001098 if (rw == READ && (dio->flags & DIO_LOCKING))
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08001099 mutex_unlock(&dio->inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001100
1101 /*
Zach Brown8459d862006-12-10 02:21:05 -08001102 * The only time we want to leave bios in flight is when a successful
1103 * partial aio read or full aio write have been setup. In that case
1104 * bio completion will call aio_complete. The only time it's safe to
1105 * call aio_complete is when we return -EIOCBQUEUED, so we key on that.
1106 * This had *better* be the only place that raises -EIOCBQUEUED.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001107 */
Zach Brown8459d862006-12-10 02:21:05 -08001108 BUG_ON(ret == -EIOCBQUEUED);
1109 if (dio->is_async && ret == 0 && dio->result &&
1110 ((rw & READ) || (dio->result == dio->size)))
1111 ret = -EIOCBQUEUED;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001112
Jens Axboe7eaceac2011-03-10 08:52:07 +01001113 if (ret != -EIOCBQUEUED)
Zach Brown6d544bb2006-12-10 02:20:54 -08001114 dio_await_completion(dio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001115
Zach Brown8459d862006-12-10 02:21:05 -08001116 /*
1117 * Sync will always be dropping the final ref and completing the
Zach Brown5eb6c7a2006-12-10 02:21:07 -08001118 * operation. AIO can if it was a broken operation described above or
1119 * in fact if all the bios race to complete before we get here. In
1120 * that case dio_complete() translates the EIOCBQUEUED into the proper
1121 * return code that the caller will hand to aio_complete().
1122 *
1123 * This is managed by the bio_lock instead of being an atomic_t so that
1124 * completion paths can drop their ref and use the remaining count to
1125 * decide to wake the submission path atomically.
Zach Brown8459d862006-12-10 02:21:05 -08001126 */
Zach Brown5eb6c7a2006-12-10 02:21:07 -08001127 spin_lock_irqsave(&dio->bio_lock, flags);
1128 ret2 = --dio->refcount;
1129 spin_unlock_irqrestore(&dio->bio_lock, flags);
Zach Brownfcb82f82007-07-03 15:28:55 -07001130
Zach Brown5eb6c7a2006-12-10 02:21:07 -08001131 if (ret2 == 0) {
Christoph Hellwig40e2e972010-07-18 21:17:09 +00001132 ret = dio_complete(dio, offset, ret, false);
Zach Brown8459d862006-12-10 02:21:05 -08001133 kfree(dio);
1134 } else
1135 BUG_ON(ret != -EIOCBQUEUED);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001136
Linus Torvalds1da177e2005-04-16 15:20:36 -07001137 return ret;
1138}
1139
Christoph Hellwigeafdc7d2010-06-04 11:29:53 +02001140/*
1141 * This is a library function for use by filesystem drivers.
1142 *
1143 * The locking rules are governed by the flags parameter:
1144 * - if the flags value contains DIO_LOCKING we use a fancy locking
1145 * scheme for dumb filesystems.
1146 * For writes this function is called under i_mutex and returns with
1147 * i_mutex held, for reads, i_mutex is not held on entry, but it is
1148 * taken and dropped again before returning.
1149 * For reads and writes i_alloc_sem is taken in shared mode and released
1150 * on I/O completion (which may happen asynchronously after returning to
1151 * the caller).
1152 *
1153 * - if the flags value does NOT contain DIO_LOCKING we don't use any
1154 * internal locking but rather rely on the filesystem to synchronize
1155 * direct I/O reads/writes versus each other and truncate.
1156 * For reads and writes both i_mutex and i_alloc_sem are not held on
1157 * entry and are never taken.
1158 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001159ssize_t
Christoph Hellwigeafdc7d2010-06-04 11:29:53 +02001160__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001161 struct block_device *bdev, const struct iovec *iov, loff_t offset,
Badari Pulavarty1d8fa7a2006-03-26 01:38:02 -08001162 unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
Josef Bacikfacd07b2010-05-23 11:00:55 -04001163 dio_submit_t submit_io, int flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001164{
1165 int seg;
1166 size_t size;
1167 unsigned long addr;
1168 unsigned blkbits = inode->i_blkbits;
1169 unsigned bdev_blkbits = 0;
1170 unsigned blocksize_mask = (1 << blkbits) - 1;
1171 ssize_t retval = -EINVAL;
1172 loff_t end = offset;
1173 struct dio *dio;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001174
1175 if (rw & WRITE)
Jens Axboe721a9602011-03-09 11:56:30 +01001176 rw = WRITE_ODIRECT;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001177
1178 if (bdev)
Martin K. Petersene1defc42009-05-22 17:17:49 -04001179 bdev_blkbits = blksize_bits(bdev_logical_block_size(bdev));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001180
1181 if (offset & blocksize_mask) {
1182 if (bdev)
1183 blkbits = bdev_blkbits;
1184 blocksize_mask = (1 << blkbits) - 1;
1185 if (offset & blocksize_mask)
1186 goto out;
1187 }
1188
1189 /* Check the memory alignment. Blocks cannot straddle pages */
1190 for (seg = 0; seg < nr_segs; seg++) {
1191 addr = (unsigned long)iov[seg].iov_base;
1192 size = iov[seg].iov_len;
1193 end += size;
1194 if ((addr & blocksize_mask) || (size & blocksize_mask)) {
1195 if (bdev)
1196 blkbits = bdev_blkbits;
1197 blocksize_mask = (1 << blkbits) - 1;
1198 if ((addr & blocksize_mask) || (size & blocksize_mask))
1199 goto out;
1200 }
1201 }
1202
Jeff Moyer23aee092009-12-15 16:47:49 -08001203 dio = kmalloc(sizeof(*dio), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001204 retval = -ENOMEM;
1205 if (!dio)
1206 goto out;
Jeff Moyer23aee092009-12-15 16:47:49 -08001207 /*
1208 * Believe it or not, zeroing out the page array caused a .5%
1209 * performance regression in a database benchmark. So, we take
1210 * care to only zero out what's needed.
1211 */
1212 memset(dio, 0, offsetof(struct dio, pages));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001213
Christoph Hellwig5fe878a2009-12-15 16:47:50 -08001214 dio->flags = flags;
1215 if (dio->flags & DIO_LOCKING) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001216 /* watch out for a 0 len io from a tricksy fs */
1217 if (rw == READ && end > offset) {
Christoph Hellwig5fe878a2009-12-15 16:47:50 -08001218 struct address_space *mapping =
1219 iocb->ki_filp->f_mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001220
Christoph Hellwig5fe878a2009-12-15 16:47:50 -08001221 /* will be released by direct_io_worker */
1222 mutex_lock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001223
1224 retval = filemap_write_and_wait_range(mapping, offset,
1225 end - 1);
1226 if (retval) {
Christoph Hellwig5fe878a2009-12-15 16:47:50 -08001227 mutex_unlock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001228 kfree(dio);
1229 goto out;
1230 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001231 }
1232
Christoph Hellwig5fe878a2009-12-15 16:47:50 -08001233 /*
1234 * Will be released at I/O completion, possibly in a
1235 * different thread.
1236 */
1237 down_read_non_owner(&inode->i_alloc_sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001238 }
1239
1240 /*
1241 * For file extending writes updating i_size before data
1242 * writeouts complete can expose uninitialized blocks. So
1243 * even for AIO, we need to wait for i/o to complete before
1244 * returning in this case.
1245 */
Jens Axboeb31dc662006-06-13 08:26:10 +02001246 dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001247 (end > i_size_read(inode)));
1248
1249 retval = direct_io_worker(rw, iocb, inode, iov, offset,
Josef Bacikfacd07b2010-05-23 11:00:55 -04001250 nr_segs, blkbits, get_block, end_io,
1251 submit_io, dio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001252
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10001253out:
1254 return retval;
1255}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001256EXPORT_SYMBOL(__blockdev_direct_IO);