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

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

Version: ~ [ linux-5.2-rc1 ] ~ [ linux-5.1.2 ] ~ [ linux-5.0.16 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.43 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.119 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.176 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.179 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.139 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.67 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ 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 /*
  2  * fs/direct-io.c
  3  *
  4  * Copyright (C) 2002, Linus Torvalds.
  5  *
  6  * O_DIRECT
  7  *
  8  * 04Jul2002    Andrew Morton
  9  *              Initial version
 10  * 11Sep2002    janetinc@us.ibm.com
 11  *              added readv/writev support.
 12  * 29Oct2002    Andrew Morton
 13  *              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>
 30 #include <linux/task_io_accounting_ops.h>
 31 #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 <linux/atomic.h>
 39 #include <linux/prefetch.h>
 40 
 41 /*
 42  * How many user pages to map in one call to get_user_pages().  This determines
 43  * the size of a structure in the slab cache
 44  */
 45 #define DIO_PAGES       64
 46 
 47 /*
 48  * This code generally works in units of "dio_blocks".  A dio_block is
 49  * somewhere between the hard sector size and the filesystem block size.  it
 50  * is determined on a per-invocation basis.   When talking to the filesystem
 51  * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity
 52  * down by dio->blkfactor.  Similarly, fs-blocksize quantities are converted
 53  * to bio_block quantities by shifting left by blkfactor.
 54  *
 55  * If blkfactor is zero then the user's request was aligned to the filesystem's
 56  * blocksize.
 57  */
 58 
 59 /* dio_state only used in the submission path */
 60 
 61 struct dio_submit {
 62         struct bio *bio;                /* bio under assembly */
 63         unsigned blkbits;               /* doesn't change */
 64         unsigned blkfactor;             /* When we're using an alignment which
 65                                            is finer than the filesystem's soft
 66                                            blocksize, this specifies how much
 67                                            finer.  blkfactor=2 means 1/4-block
 68                                            alignment.  Does not change */
 69         unsigned start_zero_done;       /* flag: sub-blocksize zeroing has
 70                                            been performed at the start of a
 71                                            write */
 72         int pages_in_io;                /* approximate total IO pages */
 73         sector_t block_in_file;         /* Current offset into the underlying
 74                                            file in dio_block units. */
 75         unsigned blocks_available;      /* At block_in_file.  changes */
 76         int reap_counter;               /* rate limit reaping */
 77         sector_t final_block_in_request;/* doesn't change */
 78         int boundary;                   /* prev block is at a boundary */
 79         get_block_t *get_block;         /* block mapping function */
 80         dio_submit_t *submit_io;        /* IO submition function */
 81 
 82         loff_t logical_offset_in_bio;   /* current first logical block in bio */
 83         sector_t final_block_in_bio;    /* current final block in bio + 1 */
 84         sector_t next_block_for_io;     /* next block to be put under IO,
 85                                            in dio_blocks units */
 86 
 87         /*
 88          * Deferred addition of a page to the dio.  These variables are
 89          * private to dio_send_cur_page(), submit_page_section() and
 90          * dio_bio_add_page().
 91          */
 92         struct page *cur_page;          /* The page */
 93         unsigned cur_page_offset;       /* Offset into it, in bytes */
 94         unsigned cur_page_len;          /* Nr of bytes at cur_page_offset */
 95         sector_t cur_page_block;        /* Where it starts */
 96         loff_t cur_page_fs_offset;      /* Offset in file */
 97 
 98         struct iov_iter *iter;
 99         /*
100          * Page queue.  These variables belong to dio_refill_pages() and
101          * dio_get_page().
102          */
103         unsigned head;                  /* next page to process */
104         unsigned tail;                  /* last valid page + 1 */
105         size_t from, to;
106 };
107 
108 /* dio_state communicated between submission path and end_io */
109 struct dio {
110         int flags;                      /* doesn't change */
111         int rw;
112         blk_qc_t bio_cookie;
113         struct block_device *bio_bdev;
114         struct inode *inode;
115         loff_t i_size;                  /* i_size when submitted */
116         dio_iodone_t *end_io;           /* IO completion function */
117 
118         void *private;                  /* copy from map_bh.b_private */
119 
120         /* BIO completion state */
121         spinlock_t bio_lock;            /* protects BIO fields below */
122         int page_errors;                /* errno from get_user_pages() */
123         int is_async;                   /* is IO async ? */
124         bool defer_completion;          /* defer AIO completion to workqueue? */
125         bool should_dirty;              /* if pages should be dirtied */
126         int io_error;                   /* IO error in completion path */
127         unsigned long refcount;         /* direct_io_worker() and bios */
128         struct bio *bio_list;           /* singly linked via bi_private */
129         struct task_struct *waiter;     /* waiting task (NULL if none) */
130 
131         /* AIO related stuff */
132         struct kiocb *iocb;             /* kiocb */
133         ssize_t result;                 /* IO result */
134 
135         /*
136          * pages[] (and any fields placed after it) are not zeroed out at
137          * allocation time.  Don't add new fields after pages[] unless you
138          * wish that they not be zeroed.
139          */
140         union {
141                 struct page *pages[DIO_PAGES];  /* page buffer */
142                 struct work_struct complete_work;/* deferred AIO completion */
143         };
144 } ____cacheline_aligned_in_smp;
145 
146 static struct kmem_cache *dio_cache __read_mostly;
147 
148 /*
149  * How many pages are in the queue?
150  */
151 static inline unsigned dio_pages_present(struct dio_submit *sdio)
152 {
153         return sdio->tail - sdio->head;
154 }
155 
156 /*
157  * Go grab and pin some userspace pages.   Typically we'll get 64 at a time.
158  */
159 static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
160 {
161         ssize_t ret;
162 
163         ret = iov_iter_get_pages(sdio->iter, dio->pages, LONG_MAX, DIO_PAGES,
164                                 &sdio->from);
165 
166         if (ret < 0 && sdio->blocks_available && (dio->rw & WRITE)) {
167                 struct page *page = ZERO_PAGE(0);
168                 /*
169                  * A memory fault, but the filesystem has some outstanding
170                  * mapped blocks.  We need to use those blocks up to avoid
171                  * leaking stale data in the file.
172                  */
173                 if (dio->page_errors == 0)
174                         dio->page_errors = ret;
175                 get_page(page);
176                 dio->pages[0] = page;
177                 sdio->head = 0;
178                 sdio->tail = 1;
179                 sdio->from = 0;
180                 sdio->to = PAGE_SIZE;
181                 return 0;
182         }
183 
184         if (ret >= 0) {
185                 iov_iter_advance(sdio->iter, ret);
186                 ret += sdio->from;
187                 sdio->head = 0;
188                 sdio->tail = (ret + PAGE_SIZE - 1) / PAGE_SIZE;
189                 sdio->to = ((ret - 1) & (PAGE_SIZE - 1)) + 1;
190                 return 0;
191         }
192         return ret;     
193 }
194 
195 /*
196  * Get another userspace page.  Returns an ERR_PTR on error.  Pages are
197  * buffered inside the dio so that we can call get_user_pages() against a
198  * decent number of pages, less frequently.  To provide nicer use of the
199  * L1 cache.
200  */
201 static inline struct page *dio_get_page(struct dio *dio,
202                                         struct dio_submit *sdio)
203 {
204         if (dio_pages_present(sdio) == 0) {
205                 int ret;
206 
207                 ret = dio_refill_pages(dio, sdio);
208                 if (ret)
209                         return ERR_PTR(ret);
210                 BUG_ON(dio_pages_present(sdio) == 0);
211         }
212         return dio->pages[sdio->head];
213 }
214 
215 /**
216  * dio_complete() - called when all DIO BIO I/O has been completed
217  * @offset: the byte offset in the file of the completed operation
218  *
219  * This drops i_dio_count, lets interested parties know that a DIO operation
220  * has completed, and calculates the resulting return code for the operation.
221  *
222  * It lets the filesystem know if it registered an interest earlier via
223  * get_block.  Pass the private field of the map buffer_head so that
224  * filesystems can use it to hold additional state between get_block calls and
225  * dio_complete.
226  */
227 static ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret,
228                 bool is_async)
229 {
230         ssize_t transferred = 0;
231 
232         /*
233          * AIO submission can race with bio completion to get here while
234          * expecting to have the last io completed by bio completion.
235          * In that case -EIOCBQUEUED is in fact not an error we want
236          * to preserve through this call.
237          */
238         if (ret == -EIOCBQUEUED)
239                 ret = 0;
240 
241         if (dio->result) {
242                 transferred = dio->result;
243 
244                 /* Check for short read case */
245                 if ((dio->rw == READ) && ((offset + transferred) > dio->i_size))
246                         transferred = dio->i_size - offset;
247         }
248 
249         if (ret == 0)
250                 ret = dio->page_errors;
251         if (ret == 0)
252                 ret = dio->io_error;
253         if (ret == 0)
254                 ret = transferred;
255 
256         if (dio->end_io) {
257                 int err;
258 
259                 err = dio->end_io(dio->iocb, offset, ret, dio->private);
260                 if (err)
261                         ret = err;
262         }
263 
264         if (!(dio->flags & DIO_SKIP_DIO_COUNT))
265                 inode_dio_end(dio->inode);
266 
267         if (is_async) {
268                 if (dio->rw & WRITE) {
269                         int err;
270 
271                         err = generic_write_sync(dio->iocb->ki_filp, offset,
272                                                  transferred);
273                         if (err < 0 && ret > 0)
274                                 ret = err;
275                 }
276 
277                 dio->iocb->ki_complete(dio->iocb, ret, 0);
278         }
279 
280         kmem_cache_free(dio_cache, dio);
281         return ret;
282 }
283 
284 static void dio_aio_complete_work(struct work_struct *work)
285 {
286         struct dio *dio = container_of(work, struct dio, complete_work);
287 
288         dio_complete(dio, dio->iocb->ki_pos, 0, true);
289 }
290 
291 static int dio_bio_complete(struct dio *dio, struct bio *bio);
292 
293 /*
294  * Asynchronous IO callback. 
295  */
296 static void dio_bio_end_aio(struct bio *bio)
297 {
298         struct dio *dio = bio->bi_private;
299         unsigned long remaining;
300         unsigned long flags;
301 
302         /* cleanup the bio */
303         dio_bio_complete(dio, bio);
304 
305         spin_lock_irqsave(&dio->bio_lock, flags);
306         remaining = --dio->refcount;
307         if (remaining == 1 && dio->waiter)
308                 wake_up_process(dio->waiter);
309         spin_unlock_irqrestore(&dio->bio_lock, flags);
310 
311         if (remaining == 0) {
312                 if (dio->result && dio->defer_completion) {
313                         INIT_WORK(&dio->complete_work, dio_aio_complete_work);
314                         queue_work(dio->inode->i_sb->s_dio_done_wq,
315                                    &dio->complete_work);
316                 } else {
317                         dio_complete(dio, dio->iocb->ki_pos, 0, true);
318                 }
319         }
320 }
321 
322 /*
323  * The BIO completion handler simply queues the BIO up for the process-context
324  * handler.
325  *
326  * During I/O bi_private points at the dio.  After I/O, bi_private is used to
327  * implement a singly-linked list of completed BIOs, at dio->bio_list.
328  */
329 static void dio_bio_end_io(struct bio *bio)
330 {
331         struct dio *dio = bio->bi_private;
332         unsigned long flags;
333 
334         spin_lock_irqsave(&dio->bio_lock, flags);
335         bio->bi_private = dio->bio_list;
336         dio->bio_list = bio;
337         if (--dio->refcount == 1 && dio->waiter)
338                 wake_up_process(dio->waiter);
339         spin_unlock_irqrestore(&dio->bio_lock, flags);
340 }
341 
342 /**
343  * dio_end_io - handle the end io action for the given bio
344  * @bio: The direct io bio thats being completed
345  * @error: Error if there was one
346  *
347  * This is meant to be called by any filesystem that uses their own dio_submit_t
348  * so that the DIO specific endio actions are dealt with after the filesystem
349  * has done it's completion work.
350  */
351 void dio_end_io(struct bio *bio, int error)
352 {
353         struct dio *dio = bio->bi_private;
354 
355         if (dio->is_async)
356                 dio_bio_end_aio(bio);
357         else
358                 dio_bio_end_io(bio);
359 }
360 EXPORT_SYMBOL_GPL(dio_end_io);
361 
362 static inline void
363 dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
364               struct block_device *bdev,
365               sector_t first_sector, int nr_vecs)
366 {
367         struct bio *bio;
368 
369         /*
370          * bio_alloc() is guaranteed to return a bio when called with
371          * __GFP_RECLAIM and we request a valid number of vectors.
372          */
373         bio = bio_alloc(GFP_KERNEL, nr_vecs);
374 
375         bio->bi_bdev = bdev;
376         bio->bi_iter.bi_sector = first_sector;
377         if (dio->is_async)
378                 bio->bi_end_io = dio_bio_end_aio;
379         else
380                 bio->bi_end_io = dio_bio_end_io;
381 
382         sdio->bio = bio;
383         sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;
384 }
385 
386 /*
387  * In the AIO read case we speculatively dirty the pages before starting IO.
388  * During IO completion, any of these pages which happen to have been written
389  * back will be redirtied by bio_check_pages_dirty().
390  *
391  * bios hold a dio reference between submit_bio and ->end_io.
392  */
393 static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
394 {
395         struct bio *bio = sdio->bio;
396         unsigned long flags;
397 
398         bio->bi_private = dio;
399 
400         spin_lock_irqsave(&dio->bio_lock, flags);
401         dio->refcount++;
402         spin_unlock_irqrestore(&dio->bio_lock, flags);
403 
404         if (dio->is_async && dio->rw == READ && dio->should_dirty)
405                 bio_set_pages_dirty(bio);
406 
407         dio->bio_bdev = bio->bi_bdev;
408 
409         if (sdio->submit_io) {
410                 sdio->submit_io(dio->rw, bio, dio->inode,
411                                sdio->logical_offset_in_bio);
412                 dio->bio_cookie = BLK_QC_T_NONE;
413         } else
414                 dio->bio_cookie = submit_bio(dio->rw, bio);
415 
416         sdio->bio = NULL;
417         sdio->boundary = 0;
418         sdio->logical_offset_in_bio = 0;
419 }
420 
421 /*
422  * Release any resources in case of a failure
423  */
424 static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
425 {
426         while (sdio->head < sdio->tail)
427                 put_page(dio->pages[sdio->head++]);
428 }
429 
430 /*
431  * Wait for the next BIO to complete.  Remove it and return it.  NULL is
432  * returned once all BIOs have been completed.  This must only be called once
433  * all bios have been issued so that dio->refcount can only decrease.  This
434  * requires that that the caller hold a reference on the dio.
435  */
436 static struct bio *dio_await_one(struct dio *dio)
437 {
438         unsigned long flags;
439         struct bio *bio = NULL;
440 
441         spin_lock_irqsave(&dio->bio_lock, flags);
442 
443         /*
444          * Wait as long as the list is empty and there are bios in flight.  bio
445          * completion drops the count, maybe adds to the list, and wakes while
446          * holding the bio_lock so we don't need set_current_state()'s barrier
447          * and can call it after testing our condition.
448          */
449         while (dio->refcount > 1 && dio->bio_list == NULL) {
450                 __set_current_state(TASK_UNINTERRUPTIBLE);
451                 dio->waiter = current;
452                 spin_unlock_irqrestore(&dio->bio_lock, flags);
453                 if (!(dio->iocb->ki_flags & IOCB_HIPRI) ||
454                     !blk_poll(bdev_get_queue(dio->bio_bdev), dio->bio_cookie))
455                         io_schedule();
456                 /* wake up sets us TASK_RUNNING */
457                 spin_lock_irqsave(&dio->bio_lock, flags);
458                 dio->waiter = NULL;
459         }
460         if (dio->bio_list) {
461                 bio = dio->bio_list;
462                 dio->bio_list = bio->bi_private;
463         }
464         spin_unlock_irqrestore(&dio->bio_lock, flags);
465         return bio;
466 }
467 
468 /*
469  * Process one completed BIO.  No locks are held.
470  */
471 static int dio_bio_complete(struct dio *dio, struct bio *bio)
472 {
473         struct bio_vec *bvec;
474         unsigned i;
475         int err;
476 
477         if (bio->bi_error)
478                 dio->io_error = -EIO;
479 
480         if (dio->is_async && dio->rw == READ && dio->should_dirty) {
481                 err = bio->bi_error;
482                 bio_check_pages_dirty(bio);     /* transfers ownership */
483         } else {
484                 bio_for_each_segment_all(bvec, bio, i) {
485                         struct page *page = bvec->bv_page;
486 
487                         if (dio->rw == READ && !PageCompound(page) &&
488                                         dio->should_dirty)
489                                 set_page_dirty_lock(page);
490                         put_page(page);
491                 }
492                 err = bio->bi_error;
493                 bio_put(bio);
494         }
495         return err;
496 }
497 
498 /*
499  * Wait on and process all in-flight BIOs.  This must only be called once
500  * all bios have been issued so that the refcount can only decrease.
501  * This just waits for all bios to make it through dio_bio_complete.  IO
502  * errors are propagated through dio->io_error and should be propagated via
503  * dio_complete().
504  */
505 static void dio_await_completion(struct dio *dio)
506 {
507         struct bio *bio;
508         do {
509                 bio = dio_await_one(dio);
510                 if (bio)
511                         dio_bio_complete(dio, bio);
512         } while (bio);
513 }
514 
515 /*
516  * A really large O_DIRECT read or write can generate a lot of BIOs.  So
517  * to keep the memory consumption sane we periodically reap any completed BIOs
518  * during the BIO generation phase.
519  *
520  * This also helps to limit the peak amount of pinned userspace memory.
521  */
522 static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
523 {
524         int ret = 0;
525 
526         if (sdio->reap_counter++ >= 64) {
527                 while (dio->bio_list) {
528                         unsigned long flags;
529                         struct bio *bio;
530                         int ret2;
531 
532                         spin_lock_irqsave(&dio->bio_lock, flags);
533                         bio = dio->bio_list;
534                         dio->bio_list = bio->bi_private;
535                         spin_unlock_irqrestore(&dio->bio_lock, flags);
536                         ret2 = dio_bio_complete(dio, bio);
537                         if (ret == 0)
538                                 ret = ret2;
539                 }
540                 sdio->reap_counter = 0;
541         }
542         return ret;
543 }
544 
545 /*
546  * Create workqueue for deferred direct IO completions. We allocate the
547  * workqueue when it's first needed. This avoids creating workqueue for
548  * filesystems that don't need it and also allows us to create the workqueue
549  * late enough so the we can include s_id in the name of the workqueue.
550  */
551 static int sb_init_dio_done_wq(struct super_block *sb)
552 {
553         struct workqueue_struct *old;
554         struct workqueue_struct *wq = alloc_workqueue("dio/%s",
555                                                       WQ_MEM_RECLAIM, 0,
556                                                       sb->s_id);
557         if (!wq)
558                 return -ENOMEM;
559         /*
560          * This has to be atomic as more DIOs can race to create the workqueue
561          */
562         old = cmpxchg(&sb->s_dio_done_wq, NULL, wq);
563         /* Someone created workqueue before us? Free ours... */
564         if (old)
565                 destroy_workqueue(wq);
566         return 0;
567 }
568 
569 static int dio_set_defer_completion(struct dio *dio)
570 {
571         struct super_block *sb = dio->inode->i_sb;
572 
573         if (dio->defer_completion)
574                 return 0;
575         dio->defer_completion = true;
576         if (!sb->s_dio_done_wq)
577                 return sb_init_dio_done_wq(sb);
578         return 0;
579 }
580 
581 /*
582  * Call into the fs to map some more disk blocks.  We record the current number
583  * of available blocks at sdio->blocks_available.  These are in units of the
584  * fs blocksize, (1 << inode->i_blkbits).
585  *
586  * The fs is allowed to map lots of blocks at once.  If it wants to do that,
587  * it uses the passed inode-relative block number as the file offset, as usual.
588  *
589  * get_block() is passed the number of i_blkbits-sized blocks which direct_io
590  * has remaining to do.  The fs should not map more than this number of blocks.
591  *
592  * If the fs has mapped a lot of blocks, it should populate bh->b_size to
593  * indicate how much contiguous disk space has been made available at
594  * bh->b_blocknr.
595  *
596  * If *any* of the mapped blocks are new, then the fs must set buffer_new().
597  * This isn't very efficient...
598  *
599  * In the case of filesystem holes: the fs may return an arbitrarily-large
600  * hole by returning an appropriate value in b_size and by clearing
601  * buffer_mapped().  However the direct-io code will only process holes one
602  * block at a time - it will repeatedly call get_block() as it walks the hole.
603  */
604 static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
605                            struct buffer_head *map_bh)
606 {
607         int ret;
608         sector_t fs_startblk;   /* Into file, in filesystem-sized blocks */
609         sector_t fs_endblk;     /* Into file, in filesystem-sized blocks */
610         unsigned long fs_count; /* Number of filesystem-sized blocks */
611         int create;
612         unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor;
613 
614         /*
615          * If there was a memory error and we've overwritten all the
616          * mapped blocks then we can now return that memory error
617          */
618         ret = dio->page_errors;
619         if (ret == 0) {
620                 BUG_ON(sdio->block_in_file >= sdio->final_block_in_request);
621                 fs_startblk = sdio->block_in_file >> sdio->blkfactor;
622                 fs_endblk = (sdio->final_block_in_request - 1) >>
623                                         sdio->blkfactor;
624                 fs_count = fs_endblk - fs_startblk + 1;
625 
626                 map_bh->b_state = 0;
627                 map_bh->b_size = fs_count << i_blkbits;
628 
629                 /*
630                  * For writes inside i_size on a DIO_SKIP_HOLES filesystem we
631                  * forbid block creations: only overwrites are permitted.
632                  * We will return early to the caller once we see an
633                  * unmapped buffer head returned, and the caller will fall
634                  * back to buffered I/O.
635                  *
636                  * Otherwise the decision is left to the get_blocks method,
637                  * which may decide to handle it or also return an unmapped
638                  * buffer head.
639                  */
640                 create = dio->rw & WRITE;
641                 if (dio->flags & DIO_SKIP_HOLES) {
642                         if (sdio->block_in_file < (i_size_read(dio->inode) >>
643                                                         sdio->blkbits))
644                                 create = 0;
645                 }
646 
647                 ret = (*sdio->get_block)(dio->inode, fs_startblk,
648                                                 map_bh, create);
649 
650                 /* Store for completion */
651                 dio->private = map_bh->b_private;
652 
653                 if (ret == 0 && buffer_defer_completion(map_bh))
654                         ret = dio_set_defer_completion(dio);
655         }
656         return ret;
657 }
658 
659 /*
660  * There is no bio.  Make one now.
661  */
662 static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio,
663                 sector_t start_sector, struct buffer_head *map_bh)
664 {
665         sector_t sector;
666         int ret, nr_pages;
667 
668         ret = dio_bio_reap(dio, sdio);
669         if (ret)
670                 goto out;
671         sector = start_sector << (sdio->blkbits - 9);
672         nr_pages = min(sdio->pages_in_io, BIO_MAX_PAGES);
673         BUG_ON(nr_pages <= 0);
674         dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages);
675         sdio->boundary = 0;
676 out:
677         return ret;
678 }
679 
680 /*
681  * Attempt to put the current chunk of 'cur_page' into the current BIO.  If
682  * that was successful then update final_block_in_bio and take a ref against
683  * the just-added page.
684  *
685  * Return zero on success.  Non-zero means the caller needs to start a new BIO.
686  */
687 static inline int dio_bio_add_page(struct dio_submit *sdio)
688 {
689         int ret;
690 
691         ret = bio_add_page(sdio->bio, sdio->cur_page,
692                         sdio->cur_page_len, sdio->cur_page_offset);
693         if (ret == sdio->cur_page_len) {
694                 /*
695                  * Decrement count only, if we are done with this page
696                  */
697                 if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE)
698                         sdio->pages_in_io--;
699                 get_page(sdio->cur_page);
700                 sdio->final_block_in_bio = sdio->cur_page_block +
701                         (sdio->cur_page_len >> sdio->blkbits);
702                 ret = 0;
703         } else {
704                 ret = 1;
705         }
706         return ret;
707 }
708                 
709 /*
710  * Put cur_page under IO.  The section of cur_page which is described by
711  * cur_page_offset,cur_page_len is put into a BIO.  The section of cur_page
712  * starts on-disk at cur_page_block.
713  *
714  * We take a ref against the page here (on behalf of its presence in the bio).
715  *
716  * The caller of this function is responsible for removing cur_page from the
717  * dio, and for dropping the refcount which came from that presence.
718  */
719 static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
720                 struct buffer_head *map_bh)
721 {
722         int ret = 0;
723 
724         if (sdio->bio) {
725                 loff_t cur_offset = sdio->cur_page_fs_offset;
726                 loff_t bio_next_offset = sdio->logical_offset_in_bio +
727                         sdio->bio->bi_iter.bi_size;
728 
729                 /*
730                  * See whether this new request is contiguous with the old.
731                  *
732                  * Btrfs cannot handle having logically non-contiguous requests
733                  * submitted.  For example if you have
734                  *
735                  * Logical:  [0-4095][HOLE][8192-12287]
736                  * Physical: [0-4095]      [4096-8191]
737                  *
738                  * We cannot submit those pages together as one BIO.  So if our
739                  * current logical offset in the file does not equal what would
740                  * be the next logical offset in the bio, submit the bio we
741                  * have.
742                  */
743                 if (sdio->final_block_in_bio != sdio->cur_page_block ||
744                     cur_offset != bio_next_offset)
745                         dio_bio_submit(dio, sdio);
746         }
747 
748         if (sdio->bio == NULL) {
749                 ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
750                 if (ret)
751                         goto out;
752         }
753 
754         if (dio_bio_add_page(sdio) != 0) {
755                 dio_bio_submit(dio, sdio);
756                 ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
757                 if (ret == 0) {
758                         ret = dio_bio_add_page(sdio);
759                         BUG_ON(ret != 0);
760                 }
761         }
762 out:
763         return ret;
764 }
765 
766 /*
767  * An autonomous function to put a chunk of a page under deferred IO.
768  *
769  * The caller doesn't actually know (or care) whether this piece of page is in
770  * a BIO, or is under IO or whatever.  We just take care of all possible 
771  * situations here.  The separation between the logic of do_direct_IO() and
772  * that of submit_page_section() is important for clarity.  Please don't break.
773  *
774  * The chunk of page starts on-disk at blocknr.
775  *
776  * We perform deferred IO, by recording the last-submitted page inside our
777  * private part of the dio structure.  If possible, we just expand the IO
778  * across that page here.
779  *
780  * If that doesn't work out then we put the old page into the bio and add this
781  * page to the dio instead.
782  */
783 static inline int
784 submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
785                     unsigned offset, unsigned len, sector_t blocknr,
786                     struct buffer_head *map_bh)
787 {
788         int ret = 0;
789 
790         if (dio->rw & WRITE) {
791                 /*
792                  * Read accounting is performed in submit_bio()
793                  */
794                 task_io_account_write(len);
795         }
796 
797         /*
798          * Can we just grow the current page's presence in the dio?
799          */
800         if (sdio->cur_page == page &&
801             sdio->cur_page_offset + sdio->cur_page_len == offset &&
802             sdio->cur_page_block +
803             (sdio->cur_page_len >> sdio->blkbits) == blocknr) {
804                 sdio->cur_page_len += len;
805                 goto out;
806         }
807 
808         /*
809          * If there's a deferred page already there then send it.
810          */
811         if (sdio->cur_page) {
812                 ret = dio_send_cur_page(dio, sdio, map_bh);
813                 put_page(sdio->cur_page);
814                 sdio->cur_page = NULL;
815                 if (ret)
816                         return ret;
817         }
818 
819         get_page(page);         /* It is in dio */
820         sdio->cur_page = page;
821         sdio->cur_page_offset = offset;
822         sdio->cur_page_len = len;
823         sdio->cur_page_block = blocknr;
824         sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits;
825 out:
826         /*
827          * If sdio->boundary then we want to schedule the IO now to
828          * avoid metadata seeks.
829          */
830         if (sdio->boundary) {
831                 ret = dio_send_cur_page(dio, sdio, map_bh);
832                 dio_bio_submit(dio, sdio);
833                 put_page(sdio->cur_page);
834                 sdio->cur_page = NULL;
835         }
836         return ret;
837 }
838 
839 /*
840  * Clean any dirty buffers in the blockdev mapping which alias newly-created
841  * file blocks.  Only called for S_ISREG files - blockdevs do not set
842  * buffer_new
843  */
844 static void clean_blockdev_aliases(struct dio *dio, struct buffer_head *map_bh)
845 {
846         unsigned i;
847         unsigned nblocks;
848 
849         nblocks = map_bh->b_size >> dio->inode->i_blkbits;
850 
851         for (i = 0; i < nblocks; i++) {
852                 unmap_underlying_metadata(map_bh->b_bdev,
853                                           map_bh->b_blocknr + i);
854         }
855 }
856 
857 /*
858  * If we are not writing the entire block and get_block() allocated
859  * the block for us, we need to fill-in the unused portion of the
860  * block with zeros. This happens only if user-buffer, fileoffset or
861  * io length is not filesystem block-size multiple.
862  *
863  * `end' is zero if we're doing the start of the IO, 1 at the end of the
864  * IO.
865  */
866 static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio,
867                 int end, struct buffer_head *map_bh)
868 {
869         unsigned dio_blocks_per_fs_block;
870         unsigned this_chunk_blocks;     /* In dio_blocks */
871         unsigned this_chunk_bytes;
872         struct page *page;
873 
874         sdio->start_zero_done = 1;
875         if (!sdio->blkfactor || !buffer_new(map_bh))
876                 return;
877 
878         dio_blocks_per_fs_block = 1 << sdio->blkfactor;
879         this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1);
880 
881         if (!this_chunk_blocks)
882                 return;
883 
884         /*
885          * We need to zero out part of an fs block.  It is either at the
886          * beginning or the end of the fs block.
887          */
888         if (end) 
889                 this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks;
890 
891         this_chunk_bytes = this_chunk_blocks << sdio->blkbits;
892 
893         page = ZERO_PAGE(0);
894         if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes,
895                                 sdio->next_block_for_io, map_bh))
896                 return;
897 
898         sdio->next_block_for_io += this_chunk_blocks;
899 }
900 
901 /*
902  * Walk the user pages, and the file, mapping blocks to disk and generating
903  * a sequence of (page,offset,len,block) mappings.  These mappings are injected
904  * into submit_page_section(), which takes care of the next stage of submission
905  *
906  * Direct IO against a blockdev is different from a file.  Because we can
907  * happily perform page-sized but 512-byte aligned IOs.  It is important that
908  * blockdev IO be able to have fine alignment and large sizes.
909  *
910  * So what we do is to permit the ->get_block function to populate bh.b_size
911  * with the size of IO which is permitted at this offset and this i_blkbits.
912  *
913  * For best results, the blockdev should be set up with 512-byte i_blkbits and
914  * it should set b_size to PAGE_SIZE or more inside get_block().  This gives
915  * fine alignment but still allows this function to work in PAGE_SIZE units.
916  */
917 static int do_direct_IO(struct dio *dio, struct dio_submit *sdio,
918                         struct buffer_head *map_bh)
919 {
920         const unsigned blkbits = sdio->blkbits;
921         int ret = 0;
922 
923         while (sdio->block_in_file < sdio->final_block_in_request) {
924                 struct page *page;
925                 size_t from, to;
926 
927                 page = dio_get_page(dio, sdio);
928                 if (IS_ERR(page)) {
929                         ret = PTR_ERR(page);
930                         goto out;
931                 }
932                 from = sdio->head ? 0 : sdio->from;
933                 to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE;
934                 sdio->head++;
935 
936                 while (from < to) {
937                         unsigned this_chunk_bytes;      /* # of bytes mapped */
938                         unsigned this_chunk_blocks;     /* # of blocks */
939                         unsigned u;
940 
941                         if (sdio->blocks_available == 0) {
942                                 /*
943                                  * Need to go and map some more disk
944                                  */
945                                 unsigned long blkmask;
946                                 unsigned long dio_remainder;
947 
948                                 ret = get_more_blocks(dio, sdio, map_bh);
949                                 if (ret) {
950                                         put_page(page);
951                                         goto out;
952                                 }
953                                 if (!buffer_mapped(map_bh))
954                                         goto do_holes;
955 
956                                 sdio->blocks_available =
957                                                 map_bh->b_size >> sdio->blkbits;
958                                 sdio->next_block_for_io =
959                                         map_bh->b_blocknr << sdio->blkfactor;
960                                 if (buffer_new(map_bh))
961                                         clean_blockdev_aliases(dio, map_bh);
962 
963                                 if (!sdio->blkfactor)
964                                         goto do_holes;
965 
966                                 blkmask = (1 << sdio->blkfactor) - 1;
967                                 dio_remainder = (sdio->block_in_file & blkmask);
968 
969                                 /*
970                                  * If we are at the start of IO and that IO
971                                  * starts partway into a fs-block,
972                                  * dio_remainder will be non-zero.  If the IO
973                                  * is a read then we can simply advance the IO
974                                  * cursor to the first block which is to be
975                                  * read.  But if the IO is a write and the
976                                  * block was newly allocated we cannot do that;
977                                  * the start of the fs block must be zeroed out
978                                  * on-disk
979                                  */
980                                 if (!buffer_new(map_bh))
981                                         sdio->next_block_for_io += dio_remainder;
982                                 sdio->blocks_available -= dio_remainder;
983                         }
984 do_holes:
985                         /* Handle holes */
986                         if (!buffer_mapped(map_bh)) {
987                                 loff_t i_size_aligned;
988 
989                                 /* AKPM: eargh, -ENOTBLK is a hack */
990                                 if (dio->rw & WRITE) {
991                                         put_page(page);
992                                         return -ENOTBLK;
993                                 }
994 
995                                 /*
996                                  * Be sure to account for a partial block as the
997                                  * last block in the file
998                                  */
999                                 i_size_aligned = ALIGN(i_size_read(dio->inode),
1000                                                         1 << blkbits);
1001                                 if (sdio->block_in_file >=
1002                                                 i_size_aligned >> blkbits) {
1003                                         /* We hit eof */
1004                                         put_page(page);
1005                                         goto out;
1006                                 }
1007                                 zero_user(page, from, 1 << blkbits);
1008                                 sdio->block_in_file++;
1009                                 from += 1 << blkbits;
1010                                 dio->result += 1 << blkbits;
1011                                 goto next_block;
1012                         }
1013 
1014                         /*
1015                          * If we're performing IO which has an alignment which
1016                          * is finer than the underlying fs, go check to see if
1017                          * we must zero out the start of this block.
1018                          */
1019                         if (unlikely(sdio->blkfactor && !sdio->start_zero_done))
1020                                 dio_zero_block(dio, sdio, 0, map_bh);
1021 
1022                         /*
1023                          * Work out, in this_chunk_blocks, how much disk we
1024                          * can add to this page
1025                          */
1026                         this_chunk_blocks = sdio->blocks_available;
1027                         u = (to - from) >> blkbits;
1028                         if (this_chunk_blocks > u)
1029                                 this_chunk_blocks = u;
1030                         u = sdio->final_block_in_request - sdio->block_in_file;
1031                         if (this_chunk_blocks > u)
1032                                 this_chunk_blocks = u;
1033                         this_chunk_bytes = this_chunk_blocks << blkbits;
1034                         BUG_ON(this_chunk_bytes == 0);
1035 
1036                         if (this_chunk_blocks == sdio->blocks_available)
1037                                 sdio->boundary = buffer_boundary(map_bh);
1038                         ret = submit_page_section(dio, sdio, page,
1039                                                   from,
1040                                                   this_chunk_bytes,
1041                                                   sdio->next_block_for_io,
1042                                                   map_bh);
1043                         if (ret) {
1044                                 put_page(page);
1045                                 goto out;
1046                         }
1047                         sdio->next_block_for_io += this_chunk_blocks;
1048 
1049                         sdio->block_in_file += this_chunk_blocks;
1050                         from += this_chunk_bytes;
1051                         dio->result += this_chunk_bytes;
1052                         sdio->blocks_available -= this_chunk_blocks;
1053 next_block:
1054                         BUG_ON(sdio->block_in_file > sdio->final_block_in_request);
1055                         if (sdio->block_in_file == sdio->final_block_in_request)
1056                                 break;
1057                 }
1058 
1059                 /* Drop the ref which was taken in get_user_pages() */
1060                 put_page(page);
1061         }
1062 out:
1063         return ret;
1064 }
1065 
1066 static inline int drop_refcount(struct dio *dio)
1067 {
1068         int ret2;
1069         unsigned long flags;
1070 
1071         /*
1072          * Sync will always be dropping the final ref and completing the
1073          * operation.  AIO can if it was a broken operation described above or
1074          * in fact if all the bios race to complete before we get here.  In
1075          * that case dio_complete() translates the EIOCBQUEUED into the proper
1076          * return code that the caller will hand to ->complete().
1077          *
1078          * This is managed by the bio_lock instead of being an atomic_t so that
1079          * completion paths can drop their ref and use the remaining count to
1080          * decide to wake the submission path atomically.
1081          */
1082         spin_lock_irqsave(&dio->bio_lock, flags);
1083         ret2 = --dio->refcount;
1084         spin_unlock_irqrestore(&dio->bio_lock, flags);
1085         return ret2;
1086 }
1087 
1088 /*
1089  * This is a library function for use by filesystem drivers.
1090  *
1091  * The locking rules are governed by the flags parameter:
1092  *  - if the flags value contains DIO_LOCKING we use a fancy locking
1093  *    scheme for dumb filesystems.
1094  *    For writes this function is called under i_mutex and returns with
1095  *    i_mutex held, for reads, i_mutex is not held on entry, but it is
1096  *    taken and dropped again before returning.
1097  *  - if the flags value does NOT contain DIO_LOCKING we don't use any
1098  *    internal locking but rather rely on the filesystem to synchronize
1099  *    direct I/O reads/writes versus each other and truncate.
1100  *
1101  * To help with locking against truncate we incremented the i_dio_count
1102  * counter before starting direct I/O, and decrement it once we are done.
1103  * Truncate can wait for it to reach zero to provide exclusion.  It is
1104  * expected that filesystem provide exclusion between new direct I/O
1105  * and truncates.  For DIO_LOCKING filesystems this is done by i_mutex,
1106  * but other filesystems need to take care of this on their own.
1107  *
1108  * NOTE: if you pass "sdio" to anything by pointer make sure that function
1109  * is always inlined. Otherwise gcc is unable to split the structure into
1110  * individual fields and will generate much worse code. This is important
1111  * for the whole file.
1112  */
1113 static inline ssize_t
1114 do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
1115                       struct block_device *bdev, struct iov_iter *iter,
1116                       loff_t offset, get_block_t get_block, dio_iodone_t end_io,
1117                       dio_submit_t submit_io, int flags)
1118 {
1119         unsigned i_blkbits = ACCESS_ONCE(inode->i_blkbits);
1120         unsigned blkbits = i_blkbits;
1121         unsigned blocksize_mask = (1 << blkbits) - 1;
1122         ssize_t retval = -EINVAL;
1123         size_t count = iov_iter_count(iter);
1124         loff_t end = offset + count;
1125         struct dio *dio;
1126         struct dio_submit sdio = { 0, };
1127         struct buffer_head map_bh = { 0, };
1128         struct blk_plug plug;
1129         unsigned long align = offset | iov_iter_alignment(iter);
1130 
1131         /*
1132          * Avoid references to bdev if not absolutely needed to give
1133          * the early prefetch in the caller enough time.
1134          */
1135 
1136         if (align & blocksize_mask) {
1137                 if (bdev)
1138                         blkbits = blksize_bits(bdev_logical_block_size(bdev));
1139                 blocksize_mask = (1 << blkbits) - 1;
1140                 if (align & blocksize_mask)
1141                         goto out;
1142         }
1143 
1144         /* watch out for a 0 len io from a tricksy fs */
1145         if (iov_iter_rw(iter) == READ && !iov_iter_count(iter))
1146                 return 0;
1147 
1148         dio = kmem_cache_alloc(dio_cache, GFP_KERNEL);
1149         retval = -ENOMEM;
1150         if (!dio)
1151                 goto out;
1152         /*
1153          * Believe it or not, zeroing out the page array caused a .5%
1154          * performance regression in a database benchmark.  So, we take
1155          * care to only zero out what's needed.
1156          */
1157         memset(dio, 0, offsetof(struct dio, pages));
1158 
1159         dio->flags = flags;
1160         if (dio->flags & DIO_LOCKING) {
1161                 if (iov_iter_rw(iter) == READ) {
1162                         struct address_space *mapping =
1163                                         iocb->ki_filp->f_mapping;
1164 
1165                         /* will be released by direct_io_worker */
1166                         inode_lock(inode);
1167 
1168                         retval = filemap_write_and_wait_range(mapping, offset,
1169                                                               end - 1);
1170                         if (retval) {
1171                                 inode_unlock(inode);
1172                                 kmem_cache_free(dio_cache, dio);
1173                                 goto out;
1174                         }
1175                 }
1176         }
1177 
1178         /* Once we sampled i_size check for reads beyond EOF */
1179         dio->i_size = i_size_read(inode);
1180         if (iov_iter_rw(iter) == READ && offset >= dio->i_size) {
1181                 if (dio->flags & DIO_LOCKING)
1182                         inode_unlock(inode);
1183                 kmem_cache_free(dio_cache, dio);
1184                 retval = 0;
1185                 goto out;
1186         }
1187 
1188         /*
1189          * For file extending writes updating i_size before data writeouts
1190          * complete can expose uninitialized blocks in dumb filesystems.
1191          * In that case we need to wait for I/O completion even if asked
1192          * for an asynchronous write.
1193          */
1194         if (is_sync_kiocb(iocb))
1195                 dio->is_async = false;
1196         else if (!(dio->flags & DIO_ASYNC_EXTEND) &&
1197                  iov_iter_rw(iter) == WRITE && end > i_size_read(inode))
1198                 dio->is_async = false;
1199         else
1200                 dio->is_async = true;
1201 
1202         dio->inode = inode;
1203         dio->rw = iov_iter_rw(iter) == WRITE ? WRITE_ODIRECT : READ;
1204 
1205         /*
1206          * For AIO O_(D)SYNC writes we need to defer completions to a workqueue
1207          * so that we can call ->fsync.
1208          */
1209         if (dio->is_async && iov_iter_rw(iter) == WRITE &&
1210             ((iocb->ki_filp->f_flags & O_DSYNC) ||
1211              IS_SYNC(iocb->ki_filp->f_mapping->host))) {
1212                 retval = dio_set_defer_completion(dio);
1213                 if (retval) {
1214                         /*
1215                          * We grab i_mutex only for reads so we don't have
1216                          * to release it here
1217                          */
1218                         kmem_cache_free(dio_cache, dio);
1219                         goto out;
1220                 }
1221         }
1222 
1223         /*
1224          * Will be decremented at I/O completion time.
1225          */
1226         if (!(dio->flags & DIO_SKIP_DIO_COUNT))
1227                 inode_dio_begin(inode);
1228 
1229         retval = 0;
1230         sdio.blkbits = blkbits;
1231         sdio.blkfactor = i_blkbits - blkbits;
1232         sdio.block_in_file = offset >> blkbits;
1233 
1234         sdio.get_block = get_block;
1235         dio->end_io = end_io;
1236         sdio.submit_io = submit_io;
1237         sdio.final_block_in_bio = -1;
1238         sdio.next_block_for_io = -1;
1239 
1240         dio->iocb = iocb;
1241 
1242         spin_lock_init(&dio->bio_lock);
1243         dio->refcount = 1;
1244 
1245         dio->should_dirty = (iter->type == ITER_IOVEC);
1246         sdio.iter = iter;
1247         sdio.final_block_in_request =
1248                 (offset + iov_iter_count(iter)) >> blkbits;
1249 
1250         /*
1251          * In case of non-aligned buffers, we may need 2 more
1252          * pages since we need to zero out first and last block.
1253          */
1254         if (unlikely(sdio.blkfactor))
1255                 sdio.pages_in_io = 2;
1256 
1257         sdio.pages_in_io += iov_iter_npages(iter, INT_MAX);
1258 
1259         blk_start_plug(&plug);
1260 
1261         retval = do_direct_IO(dio, &sdio, &map_bh);
1262         if (retval)
1263                 dio_cleanup(dio, &sdio);
1264 
1265         if (retval == -ENOTBLK) {
1266                 /*
1267                  * The remaining part of the request will be
1268                  * be handled by buffered I/O when we return
1269                  */
1270                 retval = 0;
1271         }
1272         /*
1273          * There may be some unwritten disk at the end of a part-written
1274          * fs-block-sized block.  Go zero that now.
1275          */
1276         dio_zero_block(dio, &sdio, 1, &map_bh);
1277 
1278         if (sdio.cur_page) {
1279                 ssize_t ret2;
1280 
1281                 ret2 = dio_send_cur_page(dio, &sdio, &map_bh);
1282                 if (retval == 0)
1283                         retval = ret2;
1284                 put_page(sdio.cur_page);
1285                 sdio.cur_page = NULL;
1286         }
1287         if (sdio.bio)
1288                 dio_bio_submit(dio, &sdio);
1289 
1290         blk_finish_plug(&plug);
1291 
1292         /*
1293          * It is possible that, we return short IO due to end of file.
1294          * In that case, we need to release all the pages we got hold on.
1295          */
1296         dio_cleanup(dio, &sdio);
1297 
1298         /*
1299          * All block lookups have been performed. For READ requests
1300          * we can let i_mutex go now that its achieved its purpose
1301          * of protecting us from looking up uninitialized blocks.
1302          */
1303         if (iov_iter_rw(iter) == READ && (dio->flags & DIO_LOCKING))
1304                 inode_unlock(dio->inode);
1305 
1306         /*
1307          * The only time we want to leave bios in flight is when a successful
1308          * partial aio read or full aio write have been setup.  In that case
1309          * bio completion will call aio_complete.  The only time it's safe to
1310          * call aio_complete is when we return -EIOCBQUEUED, so we key on that.
1311          * This had *better* be the only place that raises -EIOCBQUEUED.
1312          */
1313         BUG_ON(retval == -EIOCBQUEUED);
1314         if (dio->is_async && retval == 0 && dio->result &&
1315             (iov_iter_rw(iter) == READ || dio->result == count))
1316                 retval = -EIOCBQUEUED;
1317         else
1318                 dio_await_completion(dio);
1319 
1320         if (drop_refcount(dio) == 0) {
1321                 retval = dio_complete(dio, offset, retval, false);
1322         } else
1323                 BUG_ON(retval != -EIOCBQUEUED);
1324 
1325 out:
1326         return retval;
1327 }
1328 
1329 ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
1330                              struct block_device *bdev, struct iov_iter *iter,
1331                              loff_t offset, get_block_t get_block,
1332                              dio_iodone_t end_io, dio_submit_t submit_io,
1333                              int flags)
1334 {
1335         /*
1336          * The block device state is needed in the end to finally
1337          * submit everything.  Since it's likely to be cache cold
1338          * prefetch it here as first thing to hide some of the
1339          * latency.
1340          *
1341          * Attempt to prefetch the pieces we likely need later.
1342          */
1343         prefetch(&bdev->bd_disk->part_tbl);
1344         prefetch(bdev->bd_queue);
1345         prefetch((char *)bdev->bd_queue + SMP_CACHE_BYTES);
1346 
1347         return do_blockdev_direct_IO(iocb, inode, bdev, iter, offset, get_block,
1348                                      end_io, submit_io, flags);
1349 }
1350 
1351 EXPORT_SYMBOL(__blockdev_direct_IO);
1352 
1353 static __init int dio_init(void)
1354 {
1355         dio_cache = KMEM_CACHE(dio, SLAB_PANIC);
1356         return 0;
1357 }
1358 module_init(dio_init)
1359 

~ [ 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