~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/fs/direct-io.c

Version: ~ [ linux-5.15-rc6 ] ~ [ linux-5.14.14 ] ~ [ linux-5.13.19 ] ~ [ linux-5.12.19 ] ~ [ linux-5.11.22 ] ~ [ linux-5.10.75 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.155 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.213 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.252 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.287 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.289 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.18.140 ] ~ [ linux-3.16.85 ] ~ [ linux-3.14.79 ] ~ [ linux-3.12.74 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  * fs/direct-io.c
  4  *
  5  * Copyright (C) 2002, Linus Torvalds.
  6  *
  7  * O_DIRECT
  8  *
  9  * 04Jul2002    Andrew Morton
 10  *              Initial version
 11  * 11Sep2002    janetinc@us.ibm.com
 12  *              added readv/writev support.
 13  * 29Oct2002    Andrew Morton
 14  *              rewrote bio_add_page() support.
 15  * 30Oct2002    pbadari@us.ibm.com
 16  *              added support for non-aligned IO.
 17  * 06Nov2002    pbadari@us.ibm.com
 18  *              added asynchronous IO support.
 19  * 21Jul2003    nathans@sgi.com
 20  *              added IO completion notifier.
 21  */
 22 
 23 #include <linux/kernel.h>
 24 #include <linux/module.h>
 25 #include <linux/types.h>
 26 #include <linux/fs.h>
 27 #include <linux/mm.h>
 28 #include <linux/slab.h>
 29 #include <linux/highmem.h>
 30 #include <linux/pagemap.h>
 31 #include <linux/task_io_accounting_ops.h>
 32 #include <linux/bio.h>
 33 #include <linux/wait.h>
 34 #include <linux/err.h>
 35 #include <linux/blkdev.h>
 36 #include <linux/buffer_head.h>
 37 #include <linux/rwsem.h>
 38 #include <linux/uio.h>
 39 #include <linux/atomic.h>
 40 #include <linux/prefetch.h>
 41 
 42 /*
 43  * How many user pages to map in one call to get_user_pages().  This determines
 44  * the size of a structure in the slab cache
 45  */
 46 #define DIO_PAGES       64
 47 
 48 /*
 49  * Flags for dio_complete()
 50  */
 51 #define DIO_COMPLETE_ASYNC              0x01    /* This is async IO */
 52 #define DIO_COMPLETE_INVALIDATE         0x02    /* Can invalidate pages */
 53 
 54 /*
 55  * This code generally works in units of "dio_blocks".  A dio_block is
 56  * somewhere between the hard sector size and the filesystem block size.  it
 57  * is determined on a per-invocation basis.   When talking to the filesystem
 58  * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity
 59  * down by dio->blkfactor.  Similarly, fs-blocksize quantities are converted
 60  * to bio_block quantities by shifting left by blkfactor.
 61  *
 62  * If blkfactor is zero then the user's request was aligned to the filesystem's
 63  * blocksize.
 64  */
 65 
 66 /* dio_state only used in the submission path */
 67 
 68 struct dio_submit {
 69         struct bio *bio;                /* bio under assembly */
 70         unsigned blkbits;               /* doesn't change */
 71         unsigned blkfactor;             /* When we're using an alignment which
 72                                            is finer than the filesystem's soft
 73                                            blocksize, this specifies how much
 74                                            finer.  blkfactor=2 means 1/4-block
 75                                            alignment.  Does not change */
 76         unsigned start_zero_done;       /* flag: sub-blocksize zeroing has
 77                                            been performed at the start of a
 78                                            write */
 79         int pages_in_io;                /* approximate total IO pages */
 80         sector_t block_in_file;         /* Current offset into the underlying
 81                                            file in dio_block units. */
 82         unsigned blocks_available;      /* At block_in_file.  changes */
 83         int reap_counter;               /* rate limit reaping */
 84         sector_t final_block_in_request;/* doesn't change */
 85         int boundary;                   /* prev block is at a boundary */
 86         get_block_t *get_block;         /* block mapping function */
 87         dio_submit_t *submit_io;        /* IO submition function */
 88 
 89         loff_t logical_offset_in_bio;   /* current first logical block in bio */
 90         sector_t final_block_in_bio;    /* current final block in bio + 1 */
 91         sector_t next_block_for_io;     /* next block to be put under IO,
 92                                            in dio_blocks units */
 93 
 94         /*
 95          * Deferred addition of a page to the dio.  These variables are
 96          * private to dio_send_cur_page(), submit_page_section() and
 97          * dio_bio_add_page().
 98          */
 99         struct page *cur_page;          /* The page */
100         unsigned cur_page_offset;       /* Offset into it, in bytes */
101         unsigned cur_page_len;          /* Nr of bytes at cur_page_offset */
102         sector_t cur_page_block;        /* Where it starts */
103         loff_t cur_page_fs_offset;      /* Offset in file */
104 
105         struct iov_iter *iter;
106         /*
107          * Page queue.  These variables belong to dio_refill_pages() and
108          * dio_get_page().
109          */
110         unsigned head;                  /* next page to process */
111         unsigned tail;                  /* last valid page + 1 */
112         size_t from, to;
113 };
114 
115 /* dio_state communicated between submission path and end_io */
116 struct dio {
117         int flags;                      /* doesn't change */
118         int op;
119         int op_flags;
120         blk_qc_t bio_cookie;
121         struct gendisk *bio_disk;
122         struct inode *inode;
123         loff_t i_size;                  /* i_size when submitted */
124         dio_iodone_t *end_io;           /* IO completion function */
125 
126         void *private;                  /* copy from map_bh.b_private */
127 
128         /* BIO completion state */
129         spinlock_t bio_lock;            /* protects BIO fields below */
130         int page_errors;                /* errno from get_user_pages() */
131         int is_async;                   /* is IO async ? */
132         bool defer_completion;          /* defer AIO completion to workqueue? */
133         bool should_dirty;              /* if pages should be dirtied */
134         int io_error;                   /* IO error in completion path */
135         unsigned long refcount;         /* direct_io_worker() and bios */
136         struct bio *bio_list;           /* singly linked via bi_private */
137         struct task_struct *waiter;     /* waiting task (NULL if none) */
138 
139         /* AIO related stuff */
140         struct kiocb *iocb;             /* kiocb */
141         ssize_t result;                 /* IO result */
142 
143         /*
144          * pages[] (and any fields placed after it) are not zeroed out at
145          * allocation time.  Don't add new fields after pages[] unless you
146          * wish that they not be zeroed.
147          */
148         union {
149                 struct page *pages[DIO_PAGES];  /* page buffer */
150                 struct work_struct complete_work;/* deferred AIO completion */
151         };
152 } ____cacheline_aligned_in_smp;
153 
154 static struct kmem_cache *dio_cache __read_mostly;
155 
156 /*
157  * How many pages are in the queue?
158  */
159 static inline unsigned dio_pages_present(struct dio_submit *sdio)
160 {
161         return sdio->tail - sdio->head;
162 }
163 
164 /*
165  * Go grab and pin some userspace pages.   Typically we'll get 64 at a time.
166  */
167 static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
168 {
169         ssize_t ret;
170 
171         ret = iov_iter_get_pages(sdio->iter, dio->pages, LONG_MAX, DIO_PAGES,
172                                 &sdio->from);
173 
174         if (ret < 0 && sdio->blocks_available && (dio->op == REQ_OP_WRITE)) {
175                 struct page *page = ZERO_PAGE(0);
176                 /*
177                  * A memory fault, but the filesystem has some outstanding
178                  * mapped blocks.  We need to use those blocks up to avoid
179                  * leaking stale data in the file.
180                  */
181                 if (dio->page_errors == 0)
182                         dio->page_errors = ret;
183                 get_page(page);
184                 dio->pages[0] = page;
185                 sdio->head = 0;
186                 sdio->tail = 1;
187                 sdio->from = 0;
188                 sdio->to = PAGE_SIZE;
189                 return 0;
190         }
191 
192         if (ret >= 0) {
193                 iov_iter_advance(sdio->iter, ret);
194                 ret += sdio->from;
195                 sdio->head = 0;
196                 sdio->tail = (ret + PAGE_SIZE - 1) / PAGE_SIZE;
197                 sdio->to = ((ret - 1) & (PAGE_SIZE - 1)) + 1;
198                 return 0;
199         }
200         return ret;     
201 }
202 
203 /*
204  * Get another userspace page.  Returns an ERR_PTR on error.  Pages are
205  * buffered inside the dio so that we can call get_user_pages() against a
206  * decent number of pages, less frequently.  To provide nicer use of the
207  * L1 cache.
208  */
209 static inline struct page *dio_get_page(struct dio *dio,
210                                         struct dio_submit *sdio)
211 {
212         if (dio_pages_present(sdio) == 0) {
213                 int ret;
214 
215                 ret = dio_refill_pages(dio, sdio);
216                 if (ret)
217                         return ERR_PTR(ret);
218                 BUG_ON(dio_pages_present(sdio) == 0);
219         }
220         return dio->pages[sdio->head];
221 }
222 
223 /*
224  * Warn about a page cache invalidation failure during a direct io write.
225  */
226 void dio_warn_stale_pagecache(struct file *filp)
227 {
228         static DEFINE_RATELIMIT_STATE(_rs, 86400 * HZ, DEFAULT_RATELIMIT_BURST);
229         char pathname[128];
230         struct inode *inode = file_inode(filp);
231         char *path;
232 
233         errseq_set(&inode->i_mapping->wb_err, -EIO);
234         if (__ratelimit(&_rs)) {
235                 path = file_path(filp, pathname, sizeof(pathname));
236                 if (IS_ERR(path))
237                         path = "(unknown)";
238                 pr_crit("Page cache invalidation failure on direct I/O.  Possible data corruption due to collision with buffered I/O!\n");
239                 pr_crit("File: %s PID: %d Comm: %.20s\n", path, current->pid,
240                         current->comm);
241         }
242 }
243 
244 /**
245  * dio_complete() - called when all DIO BIO I/O has been completed
246  * @offset: the byte offset in the file of the completed operation
247  *
248  * This drops i_dio_count, lets interested parties know that a DIO operation
249  * has completed, and calculates the resulting return code for the operation.
250  *
251  * It lets the filesystem know if it registered an interest earlier via
252  * get_block.  Pass the private field of the map buffer_head so that
253  * filesystems can use it to hold additional state between get_block calls and
254  * dio_complete.
255  */
256 static ssize_t dio_complete(struct dio *dio, ssize_t ret, unsigned int flags)
257 {
258         loff_t offset = dio->iocb->ki_pos;
259         ssize_t transferred = 0;
260         int err;
261 
262         /*
263          * AIO submission can race with bio completion to get here while
264          * expecting to have the last io completed by bio completion.
265          * In that case -EIOCBQUEUED is in fact not an error we want
266          * to preserve through this call.
267          */
268         if (ret == -EIOCBQUEUED)
269                 ret = 0;
270 
271         if (dio->result) {
272                 transferred = dio->result;
273 
274                 /* Check for short read case */
275                 if ((dio->op == REQ_OP_READ) &&
276                     ((offset + transferred) > dio->i_size))
277                         transferred = dio->i_size - offset;
278                 /* ignore EFAULT if some IO has been done */
279                 if (unlikely(ret == -EFAULT) && transferred)
280                         ret = 0;
281         }
282 
283         if (ret == 0)
284                 ret = dio->page_errors;
285         if (ret == 0)
286                 ret = dio->io_error;
287         if (ret == 0)
288                 ret = transferred;
289 
290         if (dio->end_io) {
291                 // XXX: ki_pos??
292                 err = dio->end_io(dio->iocb, offset, ret, dio->private);
293                 if (err)
294                         ret = err;
295         }
296 
297         /*
298          * Try again to invalidate clean pages which might have been cached by
299          * non-direct readahead, or faulted in by get_user_pages() if the source
300          * of the write was an mmap'ed region of the file we're writing.  Either
301          * one is a pretty crazy thing to do, so we don't support it 100%.  If
302          * this invalidation fails, tough, the write still worked...
303          *
304          * And this page cache invalidation has to be after dio->end_io(), as
305          * some filesystems convert unwritten extents to real allocations in
306          * end_io() when necessary, otherwise a racing buffer read would cache
307          * zeros from unwritten extents.
308          */
309         if (flags & DIO_COMPLETE_INVALIDATE &&
310             ret > 0 && dio->op == REQ_OP_WRITE &&
311             dio->inode->i_mapping->nrpages) {
312                 err = invalidate_inode_pages2_range(dio->inode->i_mapping,
313                                         offset >> PAGE_SHIFT,
314                                         (offset + ret - 1) >> PAGE_SHIFT);
315                 if (err)
316                         dio_warn_stale_pagecache(dio->iocb->ki_filp);
317         }
318 
319         inode_dio_end(dio->inode);
320 
321         if (flags & DIO_COMPLETE_ASYNC) {
322                 /*
323                  * generic_write_sync expects ki_pos to have been updated
324                  * already, but the submission path only does this for
325                  * synchronous I/O.
326                  */
327                 dio->iocb->ki_pos += transferred;
328 
329                 if (ret > 0 && dio->op == REQ_OP_WRITE)
330                         ret = generic_write_sync(dio->iocb, ret);
331                 dio->iocb->ki_complete(dio->iocb, ret, 0);
332         }
333 
334         kmem_cache_free(dio_cache, dio);
335         return ret;
336 }
337 
338 static void dio_aio_complete_work(struct work_struct *work)
339 {
340         struct dio *dio = container_of(work, struct dio, complete_work);
341 
342         dio_complete(dio, 0, DIO_COMPLETE_ASYNC | DIO_COMPLETE_INVALIDATE);
343 }
344 
345 static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio);
346 
347 /*
348  * Asynchronous IO callback. 
349  */
350 static void dio_bio_end_aio(struct bio *bio)
351 {
352         struct dio *dio = bio->bi_private;
353         unsigned long remaining;
354         unsigned long flags;
355         bool defer_completion = false;
356 
357         /* cleanup the bio */
358         dio_bio_complete(dio, bio);
359 
360         spin_lock_irqsave(&dio->bio_lock, flags);
361         remaining = --dio->refcount;
362         if (remaining == 1 && dio->waiter)
363                 wake_up_process(dio->waiter);
364         spin_unlock_irqrestore(&dio->bio_lock, flags);
365 
366         if (remaining == 0) {
367                 /*
368                  * Defer completion when defer_completion is set or
369                  * when the inode has pages mapped and this is AIO write.
370                  * We need to invalidate those pages because there is a
371                  * chance they contain stale data in the case buffered IO
372                  * went in between AIO submission and completion into the
373                  * same region.
374                  */
375                 if (dio->result)
376                         defer_completion = dio->defer_completion ||
377                                            (dio->op == REQ_OP_WRITE &&
378                                             dio->inode->i_mapping->nrpages);
379                 if (defer_completion) {
380                         INIT_WORK(&dio->complete_work, dio_aio_complete_work);
381                         queue_work(dio->inode->i_sb->s_dio_done_wq,
382                                    &dio->complete_work);
383                 } else {
384                         dio_complete(dio, 0, DIO_COMPLETE_ASYNC);
385                 }
386         }
387 }
388 
389 /*
390  * The BIO completion handler simply queues the BIO up for the process-context
391  * handler.
392  *
393  * During I/O bi_private points at the dio.  After I/O, bi_private is used to
394  * implement a singly-linked list of completed BIOs, at dio->bio_list.
395  */
396 static void dio_bio_end_io(struct bio *bio)
397 {
398         struct dio *dio = bio->bi_private;
399         unsigned long flags;
400 
401         spin_lock_irqsave(&dio->bio_lock, flags);
402         bio->bi_private = dio->bio_list;
403         dio->bio_list = bio;
404         if (--dio->refcount == 1 && dio->waiter)
405                 wake_up_process(dio->waiter);
406         spin_unlock_irqrestore(&dio->bio_lock, flags);
407 }
408 
409 /**
410  * dio_end_io - handle the end io action for the given bio
411  * @bio: The direct io bio thats being completed
412  *
413  * This is meant to be called by any filesystem that uses their own dio_submit_t
414  * so that the DIO specific endio actions are dealt with after the filesystem
415  * has done it's completion work.
416  */
417 void dio_end_io(struct bio *bio)
418 {
419         struct dio *dio = bio->bi_private;
420 
421         if (dio->is_async)
422                 dio_bio_end_aio(bio);
423         else
424                 dio_bio_end_io(bio);
425 }
426 EXPORT_SYMBOL_GPL(dio_end_io);
427 
428 static inline void
429 dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
430               struct block_device *bdev,
431               sector_t first_sector, int nr_vecs)
432 {
433         struct bio *bio;
434 
435         /*
436          * bio_alloc() is guaranteed to return a bio when allowed to sleep and
437          * we request a valid number of vectors.
438          */
439         bio = bio_alloc(GFP_KERNEL, nr_vecs);
440 
441         bio_set_dev(bio, bdev);
442         bio->bi_iter.bi_sector = first_sector;
443         bio_set_op_attrs(bio, dio->op, dio->op_flags);
444         if (dio->is_async)
445                 bio->bi_end_io = dio_bio_end_aio;
446         else
447                 bio->bi_end_io = dio_bio_end_io;
448 
449         bio->bi_write_hint = dio->iocb->ki_hint;
450 
451         sdio->bio = bio;
452         sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;
453 }
454 
455 /*
456  * In the AIO read case we speculatively dirty the pages before starting IO.
457  * During IO completion, any of these pages which happen to have been written
458  * back will be redirtied by bio_check_pages_dirty().
459  *
460  * bios hold a dio reference between submit_bio and ->end_io.
461  */
462 static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
463 {
464         struct bio *bio = sdio->bio;
465         unsigned long flags;
466 
467         bio->bi_private = dio;
468 
469         spin_lock_irqsave(&dio->bio_lock, flags);
470         dio->refcount++;
471         spin_unlock_irqrestore(&dio->bio_lock, flags);
472 
473         if (dio->is_async && dio->op == REQ_OP_READ && dio->should_dirty)
474                 bio_set_pages_dirty(bio);
475 
476         dio->bio_disk = bio->bi_disk;
477 
478         if (sdio->submit_io) {
479                 sdio->submit_io(bio, dio->inode, sdio->logical_offset_in_bio);
480                 dio->bio_cookie = BLK_QC_T_NONE;
481         } else
482                 dio->bio_cookie = submit_bio(bio);
483 
484         sdio->bio = NULL;
485         sdio->boundary = 0;
486         sdio->logical_offset_in_bio = 0;
487 }
488 
489 /*
490  * Release any resources in case of a failure
491  */
492 static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
493 {
494         while (sdio->head < sdio->tail)
495                 put_page(dio->pages[sdio->head++]);
496 }
497 
498 /*
499  * Wait for the next BIO to complete.  Remove it and return it.  NULL is
500  * returned once all BIOs have been completed.  This must only be called once
501  * all bios have been issued so that dio->refcount can only decrease.  This
502  * requires that that the caller hold a reference on the dio.
503  */
504 static struct bio *dio_await_one(struct dio *dio)
505 {
506         unsigned long flags;
507         struct bio *bio = NULL;
508 
509         spin_lock_irqsave(&dio->bio_lock, flags);
510 
511         /*
512          * Wait as long as the list is empty and there are bios in flight.  bio
513          * completion drops the count, maybe adds to the list, and wakes while
514          * holding the bio_lock so we don't need set_current_state()'s barrier
515          * and can call it after testing our condition.
516          */
517         while (dio->refcount > 1 && dio->bio_list == NULL) {
518                 __set_current_state(TASK_UNINTERRUPTIBLE);
519                 dio->waiter = current;
520                 spin_unlock_irqrestore(&dio->bio_lock, flags);
521                 if (!(dio->iocb->ki_flags & IOCB_HIPRI) ||
522                     !blk_poll(dio->bio_disk->queue, dio->bio_cookie, true))
523                         io_schedule();
524                 /* wake up sets us TASK_RUNNING */
525                 spin_lock_irqsave(&dio->bio_lock, flags);
526                 dio->waiter = NULL;
527         }
528         if (dio->bio_list) {
529                 bio = dio->bio_list;
530                 dio->bio_list = bio->bi_private;
531         }
532         spin_unlock_irqrestore(&dio->bio_lock, flags);
533         return bio;
534 }
535 
536 /*
537  * Process one completed BIO.  No locks are held.
538  */
539 static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio)
540 {
541         struct bio_vec *bvec;
542         blk_status_t err = bio->bi_status;
543 
544         if (err) {
545                 if (err == BLK_STS_AGAIN && (bio->bi_opf & REQ_NOWAIT))
546                         dio->io_error = -EAGAIN;
547                 else
548                         dio->io_error = -EIO;
549         }
550 
551         if (dio->is_async && dio->op == REQ_OP_READ && dio->should_dirty) {
552                 bio_check_pages_dirty(bio);     /* transfers ownership */
553         } else {
554                 struct bvec_iter_all iter_all;
555 
556                 bio_for_each_segment_all(bvec, bio, iter_all) {
557                         struct page *page = bvec->bv_page;
558 
559                         if (dio->op == REQ_OP_READ && !PageCompound(page) &&
560                                         dio->should_dirty)
561                                 set_page_dirty_lock(page);
562                         put_page(page);
563                 }
564                 bio_put(bio);
565         }
566         return err;
567 }
568 
569 /*
570  * Wait on and process all in-flight BIOs.  This must only be called once
571  * all bios have been issued so that the refcount can only decrease.
572  * This just waits for all bios to make it through dio_bio_complete.  IO
573  * errors are propagated through dio->io_error and should be propagated via
574  * dio_complete().
575  */
576 static void dio_await_completion(struct dio *dio)
577 {
578         struct bio *bio;
579         do {
580                 bio = dio_await_one(dio);
581                 if (bio)
582                         dio_bio_complete(dio, bio);
583         } while (bio);
584 }
585 
586 /*
587  * A really large O_DIRECT read or write can generate a lot of BIOs.  So
588  * to keep the memory consumption sane we periodically reap any completed BIOs
589  * during the BIO generation phase.
590  *
591  * This also helps to limit the peak amount of pinned userspace memory.
592  */
593 static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
594 {
595         int ret = 0;
596 
597         if (sdio->reap_counter++ >= 64) {
598                 while (dio->bio_list) {
599                         unsigned long flags;
600                         struct bio *bio;
601                         int ret2;
602 
603                         spin_lock_irqsave(&dio->bio_lock, flags);
604                         bio = dio->bio_list;
605                         dio->bio_list = bio->bi_private;
606                         spin_unlock_irqrestore(&dio->bio_lock, flags);
607                         ret2 = blk_status_to_errno(dio_bio_complete(dio, bio));
608                         if (ret == 0)
609                                 ret = ret2;
610                 }
611                 sdio->reap_counter = 0;
612         }
613         return ret;
614 }
615 
616 /*
617  * Create workqueue for deferred direct IO completions. We allocate the
618  * workqueue when it's first needed. This avoids creating workqueue for
619  * filesystems that don't need it and also allows us to create the workqueue
620  * late enough so the we can include s_id in the name of the workqueue.
621  */
622 int sb_init_dio_done_wq(struct super_block *sb)
623 {
624         struct workqueue_struct *old;
625         struct workqueue_struct *wq = alloc_workqueue("dio/%s",
626                                                       WQ_MEM_RECLAIM, 0,
627                                                       sb->s_id);
628         if (!wq)
629                 return -ENOMEM;
630         /*
631          * This has to be atomic as more DIOs can race to create the workqueue
632          */
633         old = cmpxchg(&sb->s_dio_done_wq, NULL, wq);
634         /* Someone created workqueue before us? Free ours... */
635         if (old)
636                 destroy_workqueue(wq);
637         return 0;
638 }
639 
640 static int dio_set_defer_completion(struct dio *dio)
641 {
642         struct super_block *sb = dio->inode->i_sb;
643 
644         if (dio->defer_completion)
645                 return 0;
646         dio->defer_completion = true;
647         if (!sb->s_dio_done_wq)
648                 return sb_init_dio_done_wq(sb);
649         return 0;
650 }
651 
652 /*
653  * Call into the fs to map some more disk blocks.  We record the current number
654  * of available blocks at sdio->blocks_available.  These are in units of the
655  * fs blocksize, i_blocksize(inode).
656  *
657  * The fs is allowed to map lots of blocks at once.  If it wants to do that,
658  * it uses the passed inode-relative block number as the file offset, as usual.
659  *
660  * get_block() is passed the number of i_blkbits-sized blocks which direct_io
661  * has remaining to do.  The fs should not map more than this number of blocks.
662  *
663  * If the fs has mapped a lot of blocks, it should populate bh->b_size to
664  * indicate how much contiguous disk space has been made available at
665  * bh->b_blocknr.
666  *
667  * If *any* of the mapped blocks are new, then the fs must set buffer_new().
668  * This isn't very efficient...
669  *
670  * In the case of filesystem holes: the fs may return an arbitrarily-large
671  * hole by returning an appropriate value in b_size and by clearing
672  * buffer_mapped().  However the direct-io code will only process holes one
673  * block at a time - it will repeatedly call get_block() as it walks the hole.
674  */
675 static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
676                            struct buffer_head *map_bh)
677 {
678         int ret;
679         sector_t fs_startblk;   /* Into file, in filesystem-sized blocks */
680         sector_t fs_endblk;     /* Into file, in filesystem-sized blocks */
681         unsigned long fs_count; /* Number of filesystem-sized blocks */
682         int create;
683         unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor;
684         loff_t i_size;
685 
686         /*
687          * If there was a memory error and we've overwritten all the
688          * mapped blocks then we can now return that memory error
689          */
690         ret = dio->page_errors;
691         if (ret == 0) {
692                 BUG_ON(sdio->block_in_file >= sdio->final_block_in_request);
693                 fs_startblk = sdio->block_in_file >> sdio->blkfactor;
694                 fs_endblk = (sdio->final_block_in_request - 1) >>
695                                         sdio->blkfactor;
696                 fs_count = fs_endblk - fs_startblk + 1;
697 
698                 map_bh->b_state = 0;
699                 map_bh->b_size = fs_count << i_blkbits;
700 
701                 /*
702                  * For writes that could fill holes inside i_size on a
703                  * DIO_SKIP_HOLES filesystem we forbid block creations: only
704                  * overwrites are permitted. We will return early to the caller
705                  * once we see an unmapped buffer head returned, and the caller
706                  * will fall back to buffered I/O.
707                  *
708                  * Otherwise the decision is left to the get_blocks method,
709                  * which may decide to handle it or also return an unmapped
710                  * buffer head.
711                  */
712                 create = dio->op == REQ_OP_WRITE;
713                 if (dio->flags & DIO_SKIP_HOLES) {
714                         i_size = i_size_read(dio->inode);
715                         if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits)
716                                 create = 0;
717                 }
718 
719                 ret = (*sdio->get_block)(dio->inode, fs_startblk,
720                                                 map_bh, create);
721 
722                 /* Store for completion */
723                 dio->private = map_bh->b_private;
724 
725                 if (ret == 0 && buffer_defer_completion(map_bh))
726                         ret = dio_set_defer_completion(dio);
727         }
728         return ret;
729 }
730 
731 /*
732  * There is no bio.  Make one now.
733  */
734 static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio,
735                 sector_t start_sector, struct buffer_head *map_bh)
736 {
737         sector_t sector;
738         int ret, nr_pages;
739 
740         ret = dio_bio_reap(dio, sdio);
741         if (ret)
742                 goto out;
743         sector = start_sector << (sdio->blkbits - 9);
744         nr_pages = min(sdio->pages_in_io, BIO_MAX_PAGES);
745         BUG_ON(nr_pages <= 0);
746         dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages);
747         sdio->boundary = 0;
748 out:
749         return ret;
750 }
751 
752 /*
753  * Attempt to put the current chunk of 'cur_page' into the current BIO.  If
754  * that was successful then update final_block_in_bio and take a ref against
755  * the just-added page.
756  *
757  * Return zero on success.  Non-zero means the caller needs to start a new BIO.
758  */
759 static inline int dio_bio_add_page(struct dio_submit *sdio)
760 {
761         int ret;
762 
763         ret = bio_add_page(sdio->bio, sdio->cur_page,
764                         sdio->cur_page_len, sdio->cur_page_offset);
765         if (ret == sdio->cur_page_len) {
766                 /*
767                  * Decrement count only, if we are done with this page
768                  */
769                 if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE)
770                         sdio->pages_in_io--;
771                 get_page(sdio->cur_page);
772                 sdio->final_block_in_bio = sdio->cur_page_block +
773                         (sdio->cur_page_len >> sdio->blkbits);
774                 ret = 0;
775         } else {
776                 ret = 1;
777         }
778         return ret;
779 }
780                 
781 /*
782  * Put cur_page under IO.  The section of cur_page which is described by
783  * cur_page_offset,cur_page_len is put into a BIO.  The section of cur_page
784  * starts on-disk at cur_page_block.
785  *
786  * We take a ref against the page here (on behalf of its presence in the bio).
787  *
788  * The caller of this function is responsible for removing cur_page from the
789  * dio, and for dropping the refcount which came from that presence.
790  */
791 static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
792                 struct buffer_head *map_bh)
793 {
794         int ret = 0;
795 
796         if (sdio->bio) {
797                 loff_t cur_offset = sdio->cur_page_fs_offset;
798                 loff_t bio_next_offset = sdio->logical_offset_in_bio +
799                         sdio->bio->bi_iter.bi_size;
800 
801                 /*
802                  * See whether this new request is contiguous with the old.
803                  *
804                  * Btrfs cannot handle having logically non-contiguous requests
805                  * submitted.  For example if you have
806                  *
807                  * Logical:  [0-4095][HOLE][8192-12287]
808                  * Physical: [0-4095]      [4096-8191]
809                  *
810                  * We cannot submit those pages together as one BIO.  So if our
811                  * current logical offset in the file does not equal what would
812                  * be the next logical offset in the bio, submit the bio we
813                  * have.
814                  */
815                 if (sdio->final_block_in_bio != sdio->cur_page_block ||
816                     cur_offset != bio_next_offset)
817                         dio_bio_submit(dio, sdio);
818         }
819 
820         if (sdio->bio == NULL) {
821                 ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
822                 if (ret)
823                         goto out;
824         }
825 
826         if (dio_bio_add_page(sdio) != 0) {
827                 dio_bio_submit(dio, sdio);
828                 ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
829                 if (ret == 0) {
830                         ret = dio_bio_add_page(sdio);
831                         BUG_ON(ret != 0);
832                 }
833         }
834 out:
835         return ret;
836 }
837 
838 /*
839  * An autonomous function to put a chunk of a page under deferred IO.
840  *
841  * The caller doesn't actually know (or care) whether this piece of page is in
842  * a BIO, or is under IO or whatever.  We just take care of all possible 
843  * situations here.  The separation between the logic of do_direct_IO() and
844  * that of submit_page_section() is important for clarity.  Please don't break.
845  *
846  * The chunk of page starts on-disk at blocknr.
847  *
848  * We perform deferred IO, by recording the last-submitted page inside our
849  * private part of the dio structure.  If possible, we just expand the IO
850  * across that page here.
851  *
852  * If that doesn't work out then we put the old page into the bio and add this
853  * page to the dio instead.
854  */
855 static inline int
856 submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
857                     unsigned offset, unsigned len, sector_t blocknr,
858                     struct buffer_head *map_bh)
859 {
860         int ret = 0;
861 
862         if (dio->op == REQ_OP_WRITE) {
863                 /*
864                  * Read accounting is performed in submit_bio()
865                  */
866                 task_io_account_write(len);
867         }
868 
869         /*
870          * Can we just grow the current page's presence in the dio?
871          */
872         if (sdio->cur_page == page &&
873             sdio->cur_page_offset + sdio->cur_page_len == offset &&
874             sdio->cur_page_block +
875             (sdio->cur_page_len >> sdio->blkbits) == blocknr) {
876                 sdio->cur_page_len += len;
877                 goto out;
878         }
879 
880         /*
881          * If there's a deferred page already there then send it.
882          */
883         if (sdio->cur_page) {
884                 ret = dio_send_cur_page(dio, sdio, map_bh);
885                 put_page(sdio->cur_page);
886                 sdio->cur_page = NULL;
887                 if (ret)
888                         return ret;
889         }
890 
891         get_page(page);         /* It is in dio */
892         sdio->cur_page = page;
893         sdio->cur_page_offset = offset;
894         sdio->cur_page_len = len;
895         sdio->cur_page_block = blocknr;
896         sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits;
897 out:
898         /*
899          * If sdio->boundary then we want to schedule the IO now to
900          * avoid metadata seeks.
901          */
902         if (sdio->boundary) {
903                 ret = dio_send_cur_page(dio, sdio, map_bh);
904                 if (sdio->bio)
905                         dio_bio_submit(dio, sdio);
906                 put_page(sdio->cur_page);
907                 sdio->cur_page = NULL;
908         }
909         return ret;
910 }
911 
912 /*
913  * If we are not writing the entire block and get_block() allocated
914  * the block for us, we need to fill-in the unused portion of the
915  * block with zeros. This happens only if user-buffer, fileoffset or
916  * io length is not filesystem block-size multiple.
917  *
918  * `end' is zero if we're doing the start of the IO, 1 at the end of the
919  * IO.
920  */
921 static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio,
922                 int end, struct buffer_head *map_bh)
923 {
924         unsigned dio_blocks_per_fs_block;
925         unsigned this_chunk_blocks;     /* In dio_blocks */
926         unsigned this_chunk_bytes;
927         struct page *page;
928 
929         sdio->start_zero_done = 1;
930         if (!sdio->blkfactor || !buffer_new(map_bh))
931                 return;
932 
933         dio_blocks_per_fs_block = 1 << sdio->blkfactor;
934         this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1);
935 
936         if (!this_chunk_blocks)
937                 return;
938 
939         /*
940          * We need to zero out part of an fs block.  It is either at the
941          * beginning or the end of the fs block.
942          */
943         if (end) 
944                 this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks;
945 
946         this_chunk_bytes = this_chunk_blocks << sdio->blkbits;
947 
948         page = ZERO_PAGE(0);
949         if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes,
950                                 sdio->next_block_for_io, map_bh))
951                 return;
952 
953         sdio->next_block_for_io += this_chunk_blocks;
954 }
955 
956 /*
957  * Walk the user pages, and the file, mapping blocks to disk and generating
958  * a sequence of (page,offset,len,block) mappings.  These mappings are injected
959  * into submit_page_section(), which takes care of the next stage of submission
960  *
961  * Direct IO against a blockdev is different from a file.  Because we can
962  * happily perform page-sized but 512-byte aligned IOs.  It is important that
963  * blockdev IO be able to have fine alignment and large sizes.
964  *
965  * So what we do is to permit the ->get_block function to populate bh.b_size
966  * with the size of IO which is permitted at this offset and this i_blkbits.
967  *
968  * For best results, the blockdev should be set up with 512-byte i_blkbits and
969  * it should set b_size to PAGE_SIZE or more inside get_block().  This gives
970  * fine alignment but still allows this function to work in PAGE_SIZE units.
971  */
972 static int do_direct_IO(struct dio *dio, struct dio_submit *sdio,
973                         struct buffer_head *map_bh)
974 {
975         const unsigned blkbits = sdio->blkbits;
976         const unsigned i_blkbits = blkbits + sdio->blkfactor;
977         int ret = 0;
978 
979         while (sdio->block_in_file < sdio->final_block_in_request) {
980                 struct page *page;
981                 size_t from, to;
982 
983                 page = dio_get_page(dio, sdio);
984                 if (IS_ERR(page)) {
985                         ret = PTR_ERR(page);
986                         goto out;
987                 }
988                 from = sdio->head ? 0 : sdio->from;
989                 to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE;
990                 sdio->head++;
991 
992                 while (from < to) {
993                         unsigned this_chunk_bytes;      /* # of bytes mapped */
994                         unsigned this_chunk_blocks;     /* # of blocks */
995                         unsigned u;
996 
997                         if (sdio->blocks_available == 0) {
998                                 /*
999                                  * Need to go and map some more disk
1000                                  */
1001                                 unsigned long blkmask;
1002                                 unsigned long dio_remainder;
1003 
1004                                 ret = get_more_blocks(dio, sdio, map_bh);
1005                                 if (ret) {
1006                                         put_page(page);
1007                                         goto out;
1008                                 }
1009                                 if (!buffer_mapped(map_bh))
1010                                         goto do_holes;
1011 
1012                                 sdio->blocks_available =
1013                                                 map_bh->b_size >> blkbits;
1014                                 sdio->next_block_for_io =
1015                                         map_bh->b_blocknr << sdio->blkfactor;
1016                                 if (buffer_new(map_bh)) {
1017                                         clean_bdev_aliases(
1018                                                 map_bh->b_bdev,
1019                                                 map_bh->b_blocknr,
1020                                                 map_bh->b_size >> i_blkbits);
1021                                 }
1022 
1023                                 if (!sdio->blkfactor)
1024                                         goto do_holes;
1025 
1026                                 blkmask = (1 << sdio->blkfactor) - 1;
1027                                 dio_remainder = (sdio->block_in_file & blkmask);
1028 
1029                                 /*
1030                                  * If we are at the start of IO and that IO
1031                                  * starts partway into a fs-block,
1032                                  * dio_remainder will be non-zero.  If the IO
1033                                  * is a read then we can simply advance the IO
1034                                  * cursor to the first block which is to be
1035                                  * read.  But if the IO is a write and the
1036                                  * block was newly allocated we cannot do that;
1037                                  * the start of the fs block must be zeroed out
1038                                  * on-disk
1039                                  */
1040                                 if (!buffer_new(map_bh))
1041                                         sdio->next_block_for_io += dio_remainder;
1042                                 sdio->blocks_available -= dio_remainder;
1043                         }
1044 do_holes:
1045                         /* Handle holes */
1046                         if (!buffer_mapped(map_bh)) {
1047                                 loff_t i_size_aligned;
1048 
1049                                 /* AKPM: eargh, -ENOTBLK is a hack */
1050                                 if (dio->op == REQ_OP_WRITE) {
1051                                         put_page(page);
1052                                         return -ENOTBLK;
1053                                 }
1054 
1055                                 /*
1056                                  * Be sure to account for a partial block as the
1057                                  * last block in the file
1058                                  */
1059                                 i_size_aligned = ALIGN(i_size_read(dio->inode),
1060                                                         1 << blkbits);
1061                                 if (sdio->block_in_file >=
1062                                                 i_size_aligned >> blkbits) {
1063                                         /* We hit eof */
1064                                         put_page(page);
1065                                         goto out;
1066                                 }
1067                                 zero_user(page, from, 1 << blkbits);
1068                                 sdio->block_in_file++;
1069                                 from += 1 << blkbits;
1070                                 dio->result += 1 << blkbits;
1071                                 goto next_block;
1072                         }
1073 
1074                         /*
1075                          * If we're performing IO which has an alignment which
1076                          * is finer than the underlying fs, go check to see if
1077                          * we must zero out the start of this block.
1078                          */
1079                         if (unlikely(sdio->blkfactor && !sdio->start_zero_done))
1080                                 dio_zero_block(dio, sdio, 0, map_bh);
1081 
1082                         /*
1083                          * Work out, in this_chunk_blocks, how much disk we
1084                          * can add to this page
1085                          */
1086                         this_chunk_blocks = sdio->blocks_available;
1087                         u = (to - from) >> blkbits;
1088                         if (this_chunk_blocks > u)
1089                                 this_chunk_blocks = u;
1090                         u = sdio->final_block_in_request - sdio->block_in_file;
1091                         if (this_chunk_blocks > u)
1092                                 this_chunk_blocks = u;
1093                         this_chunk_bytes = this_chunk_blocks << blkbits;
1094                         BUG_ON(this_chunk_bytes == 0);
1095 
1096                         if (this_chunk_blocks == sdio->blocks_available)
1097                                 sdio->boundary = buffer_boundary(map_bh);
1098                         ret = submit_page_section(dio, sdio, page,
1099                                                   from,
1100                                                   this_chunk_bytes,
1101                                                   sdio->next_block_for_io,
1102                                                   map_bh);
1103                         if (ret) {
1104                                 put_page(page);
1105                                 goto out;
1106                         }
1107                         sdio->next_block_for_io += this_chunk_blocks;
1108 
1109                         sdio->block_in_file += this_chunk_blocks;
1110                         from += this_chunk_bytes;
1111                         dio->result += this_chunk_bytes;
1112                         sdio->blocks_available -= this_chunk_blocks;
1113 next_block:
1114                         BUG_ON(sdio->block_in_file > sdio->final_block_in_request);
1115                         if (sdio->block_in_file == sdio->final_block_in_request)
1116                                 break;
1117                 }
1118 
1119                 /* Drop the ref which was taken in get_user_pages() */
1120                 put_page(page);
1121         }
1122 out:
1123         return ret;
1124 }
1125 
1126 static inline int drop_refcount(struct dio *dio)
1127 {
1128         int ret2;
1129         unsigned long flags;
1130 
1131         /*
1132          * Sync will always be dropping the final ref and completing the
1133          * operation.  AIO can if it was a broken operation described above or
1134          * in fact if all the bios race to complete before we get here.  In
1135          * that case dio_complete() translates the EIOCBQUEUED into the proper
1136          * return code that the caller will hand to ->complete().
1137          *
1138          * This is managed by the bio_lock instead of being an atomic_t so that
1139          * completion paths can drop their ref and use the remaining count to
1140          * decide to wake the submission path atomically.
1141          */
1142         spin_lock_irqsave(&dio->bio_lock, flags);
1143         ret2 = --dio->refcount;
1144         spin_unlock_irqrestore(&dio->bio_lock, flags);
1145         return ret2;
1146 }
1147 
1148 /*
1149  * This is a library function for use by filesystem drivers.
1150  *
1151  * The locking rules are governed by the flags parameter:
1152  *  - if the flags value contains DIO_LOCKING we use a fancy locking
1153  *    scheme for dumb filesystems.
1154  *    For writes this function is called under i_mutex and returns with
1155  *    i_mutex held, for reads, i_mutex is not held on entry, but it is
1156  *    taken and dropped again before returning.
1157  *  - if the flags value does NOT contain DIO_LOCKING we don't use any
1158  *    internal locking but rather rely on the filesystem to synchronize
1159  *    direct I/O reads/writes versus each other and truncate.
1160  *
1161  * To help with locking against truncate we incremented the i_dio_count
1162  * counter before starting direct I/O, and decrement it once we are done.
1163  * Truncate can wait for it to reach zero to provide exclusion.  It is
1164  * expected that filesystem provide exclusion between new direct I/O
1165  * and truncates.  For DIO_LOCKING filesystems this is done by i_mutex,
1166  * but other filesystems need to take care of this on their own.
1167  *
1168  * NOTE: if you pass "sdio" to anything by pointer make sure that function
1169  * is always inlined. Otherwise gcc is unable to split the structure into
1170  * individual fields and will generate much worse code. This is important
1171  * for the whole file.
1172  */
1173 static inline ssize_t
1174 do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
1175                       struct block_device *bdev, struct iov_iter *iter,
1176                       get_block_t get_block, dio_iodone_t end_io,
1177                       dio_submit_t submit_io, int flags)
1178 {
1179         unsigned i_blkbits = READ_ONCE(inode->i_blkbits);
1180         unsigned blkbits = i_blkbits;
1181         unsigned blocksize_mask = (1 << blkbits) - 1;
1182         ssize_t retval = -EINVAL;
1183         const size_t count = iov_iter_count(iter);
1184         loff_t offset = iocb->ki_pos;
1185         const loff_t end = offset + count;
1186         struct dio *dio;
1187         struct dio_submit sdio = { 0, };
1188         struct buffer_head map_bh = { 0, };
1189         struct blk_plug plug;
1190         unsigned long align = offset | iov_iter_alignment(iter);
1191 
1192         /*
1193          * Avoid references to bdev if not absolutely needed to give
1194          * the early prefetch in the caller enough time.
1195          */
1196 
1197         if (align & blocksize_mask) {
1198                 if (bdev)
1199                         blkbits = blksize_bits(bdev_logical_block_size(bdev));
1200                 blocksize_mask = (1 << blkbits) - 1;
1201                 if (align & blocksize_mask)
1202                         goto out;
1203         }
1204 
1205         /* watch out for a 0 len io from a tricksy fs */
1206         if (iov_iter_rw(iter) == READ && !count)
1207                 return 0;
1208 
1209         dio = kmem_cache_alloc(dio_cache, GFP_KERNEL);
1210         retval = -ENOMEM;
1211         if (!dio)
1212                 goto out;
1213         /*
1214          * Believe it or not, zeroing out the page array caused a .5%
1215          * performance regression in a database benchmark.  So, we take
1216          * care to only zero out what's needed.
1217          */
1218         memset(dio, 0, offsetof(struct dio, pages));
1219 
1220         dio->flags = flags;
1221         if (dio->flags & DIO_LOCKING) {
1222                 if (iov_iter_rw(iter) == READ) {
1223                         struct address_space *mapping =
1224                                         iocb->ki_filp->f_mapping;
1225 
1226                         /* will be released by direct_io_worker */
1227                         inode_lock(inode);
1228 
1229                         retval = filemap_write_and_wait_range(mapping, offset,
1230                                                               end - 1);
1231                         if (retval) {
1232                                 inode_unlock(inode);
1233                                 kmem_cache_free(dio_cache, dio);
1234                                 goto out;
1235                         }
1236                 }
1237         }
1238 
1239         /* Once we sampled i_size check for reads beyond EOF */
1240         dio->i_size = i_size_read(inode);
1241         if (iov_iter_rw(iter) == READ && offset >= dio->i_size) {
1242                 if (dio->flags & DIO_LOCKING)
1243                         inode_unlock(inode);
1244                 kmem_cache_free(dio_cache, dio);
1245                 retval = 0;
1246                 goto out;
1247         }
1248 
1249         /*
1250          * For file extending writes updating i_size before data writeouts
1251          * complete can expose uninitialized blocks in dumb filesystems.
1252          * In that case we need to wait for I/O completion even if asked
1253          * for an asynchronous write.
1254          */
1255         if (is_sync_kiocb(iocb))
1256                 dio->is_async = false;
1257         else if (iov_iter_rw(iter) == WRITE && end > i_size_read(inode))
1258                 dio->is_async = false;
1259         else
1260                 dio->is_async = true;
1261 
1262         dio->inode = inode;
1263         if (iov_iter_rw(iter) == WRITE) {
1264                 dio->op = REQ_OP_WRITE;
1265                 dio->op_flags = REQ_SYNC | REQ_IDLE;
1266                 if (iocb->ki_flags & IOCB_NOWAIT)
1267                         dio->op_flags |= REQ_NOWAIT;
1268         } else {
1269                 dio->op = REQ_OP_READ;
1270         }
1271         if (iocb->ki_flags & IOCB_HIPRI)
1272                 dio->op_flags |= REQ_HIPRI;
1273 
1274         /*
1275          * For AIO O_(D)SYNC writes we need to defer completions to a workqueue
1276          * so that we can call ->fsync.
1277          */
1278         if (dio->is_async && iov_iter_rw(iter) == WRITE) {
1279                 retval = 0;
1280                 if (iocb->ki_flags & IOCB_DSYNC)
1281                         retval = dio_set_defer_completion(dio);
1282                 else if (!dio->inode->i_sb->s_dio_done_wq) {
1283                         /*
1284                          * In case of AIO write racing with buffered read we
1285                          * need to defer completion. We can't decide this now,
1286                          * however the workqueue needs to be initialized here.
1287                          */
1288                         retval = sb_init_dio_done_wq(dio->inode->i_sb);
1289                 }
1290                 if (retval) {
1291                         /*
1292                          * We grab i_mutex only for reads so we don't have
1293                          * to release it here
1294                          */
1295                         kmem_cache_free(dio_cache, dio);
1296                         goto out;
1297                 }
1298         }
1299 
1300         /*
1301          * Will be decremented at I/O completion time.
1302          */
1303         inode_dio_begin(inode);
1304 
1305         retval = 0;
1306         sdio.blkbits = blkbits;
1307         sdio.blkfactor = i_blkbits - blkbits;
1308         sdio.block_in_file = offset >> blkbits;
1309 
1310         sdio.get_block = get_block;
1311         dio->end_io = end_io;
1312         sdio.submit_io = submit_io;
1313         sdio.final_block_in_bio = -1;
1314         sdio.next_block_for_io = -1;
1315 
1316         dio->iocb = iocb;
1317 
1318         spin_lock_init(&dio->bio_lock);
1319         dio->refcount = 1;
1320 
1321         dio->should_dirty = iter_is_iovec(iter) && iov_iter_rw(iter) == READ;
1322         sdio.iter = iter;
1323         sdio.final_block_in_request = end >> blkbits;
1324 
1325         /*
1326          * In case of non-aligned buffers, we may need 2 more
1327          * pages since we need to zero out first and last block.
1328          */
1329         if (unlikely(sdio.blkfactor))
1330                 sdio.pages_in_io = 2;
1331 
1332         sdio.pages_in_io += iov_iter_npages(iter, INT_MAX);
1333 
1334         blk_start_plug(&plug);
1335 
1336         retval = do_direct_IO(dio, &sdio, &map_bh);
1337         if (retval)
1338                 dio_cleanup(dio, &sdio);
1339 
1340         if (retval == -ENOTBLK) {
1341                 /*
1342                  * The remaining part of the request will be
1343                  * be handled by buffered I/O when we return
1344                  */
1345                 retval = 0;
1346         }
1347         /*
1348          * There may be some unwritten disk at the end of a part-written
1349          * fs-block-sized block.  Go zero that now.
1350          */
1351         dio_zero_block(dio, &sdio, 1, &map_bh);
1352 
1353         if (sdio.cur_page) {
1354                 ssize_t ret2;
1355 
1356                 ret2 = dio_send_cur_page(dio, &sdio, &map_bh);
1357                 if (retval == 0)
1358                         retval = ret2;
1359                 put_page(sdio.cur_page);
1360                 sdio.cur_page = NULL;
1361         }
1362         if (sdio.bio)
1363                 dio_bio_submit(dio, &sdio);
1364 
1365         blk_finish_plug(&plug);
1366 
1367         /*
1368          * It is possible that, we return short IO due to end of file.
1369          * In that case, we need to release all the pages we got hold on.
1370          */
1371         dio_cleanup(dio, &sdio);
1372 
1373         /*
1374          * All block lookups have been performed. For READ requests
1375          * we can let i_mutex go now that its achieved its purpose
1376          * of protecting us from looking up uninitialized blocks.
1377          */
1378         if (iov_iter_rw(iter) == READ && (dio->flags & DIO_LOCKING))
1379                 inode_unlock(dio->inode);
1380 
1381         /*
1382          * The only time we want to leave bios in flight is when a successful
1383          * partial aio read or full aio write have been setup.  In that case
1384          * bio completion will call aio_complete.  The only time it's safe to
1385          * call aio_complete is when we return -EIOCBQUEUED, so we key on that.
1386          * This had *better* be the only place that raises -EIOCBQUEUED.
1387          */
1388         BUG_ON(retval == -EIOCBQUEUED);
1389         if (dio->is_async && retval == 0 && dio->result &&
1390             (iov_iter_rw(iter) == READ || dio->result == count))
1391                 retval = -EIOCBQUEUED;
1392         else
1393                 dio_await_completion(dio);
1394 
1395         if (drop_refcount(dio) == 0) {
1396                 retval = dio_complete(dio, retval, DIO_COMPLETE_INVALIDATE);
1397         } else
1398                 BUG_ON(retval != -EIOCBQUEUED);
1399 
1400 out:
1401         return retval;
1402 }
1403 
1404 ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
1405                              struct block_device *bdev, struct iov_iter *iter,
1406                              get_block_t get_block,
1407                              dio_iodone_t end_io, dio_submit_t submit_io,
1408                              int flags)
1409 {
1410         /*
1411          * The block device state is needed in the end to finally
1412          * submit everything.  Since it's likely to be cache cold
1413          * prefetch it here as first thing to hide some of the
1414          * latency.
1415          *
1416          * Attempt to prefetch the pieces we likely need later.
1417          */
1418         prefetch(&bdev->bd_disk->part_tbl);
1419         prefetch(bdev->bd_queue);
1420         prefetch((char *)bdev->bd_queue + SMP_CACHE_BYTES);
1421 
1422         return do_blockdev_direct_IO(iocb, inode, bdev, iter, get_block,
1423                                      end_io, submit_io, flags);
1424 }
1425 
1426 EXPORT_SYMBOL(__blockdev_direct_IO);
1427 
1428 static __init int dio_init(void)
1429 {
1430         dio_cache = KMEM_CACHE(dio, SLAB_PANIC);
1431         return 0;
1432 }
1433 module_init(dio_init)
1434 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp