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TOMOYO Linux Cross Reference
Linux/fs/bio.c

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  1 /*
  2  * Copyright (C) 2001 Jens Axboe <axboe@kernel.dk>
  3  *
  4  * This program is free software; you can redistribute it and/or modify
  5  * it under the terms of the GNU General Public License version 2 as
  6  * published by the Free Software Foundation.
  7  *
  8  * This program is distributed in the hope that it will be useful,
  9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 11  * GNU General Public License for more details.
 12  *
 13  * You should have received a copy of the GNU General Public Licens
 14  * along with this program; if not, write to the Free Software
 15  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
 16  *
 17  */
 18 #include <linux/mm.h>
 19 #include <linux/swap.h>
 20 #include <linux/bio.h>
 21 #include <linux/blkdev.h>
 22 #include <linux/uio.h>
 23 #include <linux/iocontext.h>
 24 #include <linux/slab.h>
 25 #include <linux/init.h>
 26 #include <linux/kernel.h>
 27 #include <linux/export.h>
 28 #include <linux/mempool.h>
 29 #include <linux/workqueue.h>
 30 #include <linux/cgroup.h>
 31 #include <scsi/sg.h>            /* for struct sg_iovec */
 32 
 33 #include <trace/events/block.h>
 34 
 35 /*
 36  * Test patch to inline a certain number of bi_io_vec's inside the bio
 37  * itself, to shrink a bio data allocation from two mempool calls to one
 38  */
 39 #define BIO_INLINE_VECS         4
 40 
 41 /*
 42  * if you change this list, also change bvec_alloc or things will
 43  * break badly! cannot be bigger than what you can fit into an
 44  * unsigned short
 45  */
 46 #define BV(x) { .nr_vecs = x, .name = "biovec-"__stringify(x) }
 47 static struct biovec_slab bvec_slabs[BIOVEC_NR_POOLS] __read_mostly = {
 48         BV(1), BV(4), BV(16), BV(64), BV(128), BV(BIO_MAX_PAGES),
 49 };
 50 #undef BV
 51 
 52 /*
 53  * fs_bio_set is the bio_set containing bio and iovec memory pools used by
 54  * IO code that does not need private memory pools.
 55  */
 56 struct bio_set *fs_bio_set;
 57 EXPORT_SYMBOL(fs_bio_set);
 58 
 59 /*
 60  * Our slab pool management
 61  */
 62 struct bio_slab {
 63         struct kmem_cache *slab;
 64         unsigned int slab_ref;
 65         unsigned int slab_size;
 66         char name[8];
 67 };
 68 static DEFINE_MUTEX(bio_slab_lock);
 69 static struct bio_slab *bio_slabs;
 70 static unsigned int bio_slab_nr, bio_slab_max;
 71 
 72 static struct kmem_cache *bio_find_or_create_slab(unsigned int extra_size)
 73 {
 74         unsigned int sz = sizeof(struct bio) + extra_size;
 75         struct kmem_cache *slab = NULL;
 76         struct bio_slab *bslab, *new_bio_slabs;
 77         unsigned int new_bio_slab_max;
 78         unsigned int i, entry = -1;
 79 
 80         mutex_lock(&bio_slab_lock);
 81 
 82         i = 0;
 83         while (i < bio_slab_nr) {
 84                 bslab = &bio_slabs[i];
 85 
 86                 if (!bslab->slab && entry == -1)
 87                         entry = i;
 88                 else if (bslab->slab_size == sz) {
 89                         slab = bslab->slab;
 90                         bslab->slab_ref++;
 91                         break;
 92                 }
 93                 i++;
 94         }
 95 
 96         if (slab)
 97                 goto out_unlock;
 98 
 99         if (bio_slab_nr == bio_slab_max && entry == -1) {
100                 new_bio_slab_max = bio_slab_max << 1;
101                 new_bio_slabs = krealloc(bio_slabs,
102                                          new_bio_slab_max * sizeof(struct bio_slab),
103                                          GFP_KERNEL);
104                 if (!new_bio_slabs)
105                         goto out_unlock;
106                 bio_slab_max = new_bio_slab_max;
107                 bio_slabs = new_bio_slabs;
108         }
109         if (entry == -1)
110                 entry = bio_slab_nr++;
111 
112         bslab = &bio_slabs[entry];
113 
114         snprintf(bslab->name, sizeof(bslab->name), "bio-%d", entry);
115         slab = kmem_cache_create(bslab->name, sz, 0, SLAB_HWCACHE_ALIGN, NULL);
116         if (!slab)
117                 goto out_unlock;
118 
119         bslab->slab = slab;
120         bslab->slab_ref = 1;
121         bslab->slab_size = sz;
122 out_unlock:
123         mutex_unlock(&bio_slab_lock);
124         return slab;
125 }
126 
127 static void bio_put_slab(struct bio_set *bs)
128 {
129         struct bio_slab *bslab = NULL;
130         unsigned int i;
131 
132         mutex_lock(&bio_slab_lock);
133 
134         for (i = 0; i < bio_slab_nr; i++) {
135                 if (bs->bio_slab == bio_slabs[i].slab) {
136                         bslab = &bio_slabs[i];
137                         break;
138                 }
139         }
140 
141         if (WARN(!bslab, KERN_ERR "bio: unable to find slab!\n"))
142                 goto out;
143 
144         WARN_ON(!bslab->slab_ref);
145 
146         if (--bslab->slab_ref)
147                 goto out;
148 
149         kmem_cache_destroy(bslab->slab);
150         bslab->slab = NULL;
151 
152 out:
153         mutex_unlock(&bio_slab_lock);
154 }
155 
156 unsigned int bvec_nr_vecs(unsigned short idx)
157 {
158         return bvec_slabs[idx].nr_vecs;
159 }
160 
161 void bvec_free(mempool_t *pool, struct bio_vec *bv, unsigned int idx)
162 {
163         BIO_BUG_ON(idx >= BIOVEC_NR_POOLS);
164 
165         if (idx == BIOVEC_MAX_IDX)
166                 mempool_free(bv, pool);
167         else {
168                 struct biovec_slab *bvs = bvec_slabs + idx;
169 
170                 kmem_cache_free(bvs->slab, bv);
171         }
172 }
173 
174 struct bio_vec *bvec_alloc(gfp_t gfp_mask, int nr, unsigned long *idx,
175                            mempool_t *pool)
176 {
177         struct bio_vec *bvl;
178 
179         /*
180          * see comment near bvec_array define!
181          */
182         switch (nr) {
183         case 1:
184                 *idx = 0;
185                 break;
186         case 2 ... 4:
187                 *idx = 1;
188                 break;
189         case 5 ... 16:
190                 *idx = 2;
191                 break;
192         case 17 ... 64:
193                 *idx = 3;
194                 break;
195         case 65 ... 128:
196                 *idx = 4;
197                 break;
198         case 129 ... BIO_MAX_PAGES:
199                 *idx = 5;
200                 break;
201         default:
202                 return NULL;
203         }
204 
205         /*
206          * idx now points to the pool we want to allocate from. only the
207          * 1-vec entry pool is mempool backed.
208          */
209         if (*idx == BIOVEC_MAX_IDX) {
210 fallback:
211                 bvl = mempool_alloc(pool, gfp_mask);
212         } else {
213                 struct biovec_slab *bvs = bvec_slabs + *idx;
214                 gfp_t __gfp_mask = gfp_mask & ~(__GFP_WAIT | __GFP_IO);
215 
216                 /*
217                  * Make this allocation restricted and don't dump info on
218                  * allocation failures, since we'll fallback to the mempool
219                  * in case of failure.
220                  */
221                 __gfp_mask |= __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
222 
223                 /*
224                  * Try a slab allocation. If this fails and __GFP_WAIT
225                  * is set, retry with the 1-entry mempool
226                  */
227                 bvl = kmem_cache_alloc(bvs->slab, __gfp_mask);
228                 if (unlikely(!bvl && (gfp_mask & __GFP_WAIT))) {
229                         *idx = BIOVEC_MAX_IDX;
230                         goto fallback;
231                 }
232         }
233 
234         return bvl;
235 }
236 
237 static void __bio_free(struct bio *bio)
238 {
239         bio_disassociate_task(bio);
240 
241         if (bio_integrity(bio))
242                 bio_integrity_free(bio);
243 }
244 
245 static void bio_free(struct bio *bio)
246 {
247         struct bio_set *bs = bio->bi_pool;
248         void *p;
249 
250         __bio_free(bio);
251 
252         if (bs) {
253                 if (bio_flagged(bio, BIO_OWNS_VEC))
254                         bvec_free(bs->bvec_pool, bio->bi_io_vec, BIO_POOL_IDX(bio));
255 
256                 /*
257                  * If we have front padding, adjust the bio pointer before freeing
258                  */
259                 p = bio;
260                 p -= bs->front_pad;
261 
262                 mempool_free(p, bs->bio_pool);
263         } else {
264                 /* Bio was allocated by bio_kmalloc() */
265                 kfree(bio);
266         }
267 }
268 
269 void bio_init(struct bio *bio)
270 {
271         memset(bio, 0, sizeof(*bio));
272         bio->bi_flags = 1 << BIO_UPTODATE;
273         atomic_set(&bio->bi_remaining, 1);
274         atomic_set(&bio->bi_cnt, 1);
275 }
276 EXPORT_SYMBOL(bio_init);
277 
278 /**
279  * bio_reset - reinitialize a bio
280  * @bio:        bio to reset
281  *
282  * Description:
283  *   After calling bio_reset(), @bio will be in the same state as a freshly
284  *   allocated bio returned bio bio_alloc_bioset() - the only fields that are
285  *   preserved are the ones that are initialized by bio_alloc_bioset(). See
286  *   comment in struct bio.
287  */
288 void bio_reset(struct bio *bio)
289 {
290         unsigned long flags = bio->bi_flags & (~0UL << BIO_RESET_BITS);
291 
292         __bio_free(bio);
293 
294         memset(bio, 0, BIO_RESET_BYTES);
295         bio->bi_flags = flags|(1 << BIO_UPTODATE);
296         atomic_set(&bio->bi_remaining, 1);
297 }
298 EXPORT_SYMBOL(bio_reset);
299 
300 static void bio_chain_endio(struct bio *bio, int error)
301 {
302         bio_endio(bio->bi_private, error);
303         bio_put(bio);
304 }
305 
306 /**
307  * bio_chain - chain bio completions
308  *
309  * The caller won't have a bi_end_io called when @bio completes - instead,
310  * @parent's bi_end_io won't be called until both @parent and @bio have
311  * completed; the chained bio will also be freed when it completes.
312  *
313  * The caller must not set bi_private or bi_end_io in @bio.
314  */
315 void bio_chain(struct bio *bio, struct bio *parent)
316 {
317         BUG_ON(bio->bi_private || bio->bi_end_io);
318 
319         bio->bi_private = parent;
320         bio->bi_end_io  = bio_chain_endio;
321         atomic_inc(&parent->bi_remaining);
322 }
323 EXPORT_SYMBOL(bio_chain);
324 
325 static void bio_alloc_rescue(struct work_struct *work)
326 {
327         struct bio_set *bs = container_of(work, struct bio_set, rescue_work);
328         struct bio *bio;
329 
330         while (1) {
331                 spin_lock(&bs->rescue_lock);
332                 bio = bio_list_pop(&bs->rescue_list);
333                 spin_unlock(&bs->rescue_lock);
334 
335                 if (!bio)
336                         break;
337 
338                 generic_make_request(bio);
339         }
340 }
341 
342 static void punt_bios_to_rescuer(struct bio_set *bs)
343 {
344         struct bio_list punt, nopunt;
345         struct bio *bio;
346 
347         /*
348          * In order to guarantee forward progress we must punt only bios that
349          * were allocated from this bio_set; otherwise, if there was a bio on
350          * there for a stacking driver higher up in the stack, processing it
351          * could require allocating bios from this bio_set, and doing that from
352          * our own rescuer would be bad.
353          *
354          * Since bio lists are singly linked, pop them all instead of trying to
355          * remove from the middle of the list:
356          */
357 
358         bio_list_init(&punt);
359         bio_list_init(&nopunt);
360 
361         while ((bio = bio_list_pop(current->bio_list)))
362                 bio_list_add(bio->bi_pool == bs ? &punt : &nopunt, bio);
363 
364         *current->bio_list = nopunt;
365 
366         spin_lock(&bs->rescue_lock);
367         bio_list_merge(&bs->rescue_list, &punt);
368         spin_unlock(&bs->rescue_lock);
369 
370         queue_work(bs->rescue_workqueue, &bs->rescue_work);
371 }
372 
373 /**
374  * bio_alloc_bioset - allocate a bio for I/O
375  * @gfp_mask:   the GFP_ mask given to the slab allocator
376  * @nr_iovecs:  number of iovecs to pre-allocate
377  * @bs:         the bio_set to allocate from.
378  *
379  * Description:
380  *   If @bs is NULL, uses kmalloc() to allocate the bio; else the allocation is
381  *   backed by the @bs's mempool.
382  *
383  *   When @bs is not NULL, if %__GFP_WAIT is set then bio_alloc will always be
384  *   able to allocate a bio. This is due to the mempool guarantees. To make this
385  *   work, callers must never allocate more than 1 bio at a time from this pool.
386  *   Callers that need to allocate more than 1 bio must always submit the
387  *   previously allocated bio for IO before attempting to allocate a new one.
388  *   Failure to do so can cause deadlocks under memory pressure.
389  *
390  *   Note that when running under generic_make_request() (i.e. any block
391  *   driver), bios are not submitted until after you return - see the code in
392  *   generic_make_request() that converts recursion into iteration, to prevent
393  *   stack overflows.
394  *
395  *   This would normally mean allocating multiple bios under
396  *   generic_make_request() would be susceptible to deadlocks, but we have
397  *   deadlock avoidance code that resubmits any blocked bios from a rescuer
398  *   thread.
399  *
400  *   However, we do not guarantee forward progress for allocations from other
401  *   mempools. Doing multiple allocations from the same mempool under
402  *   generic_make_request() should be avoided - instead, use bio_set's front_pad
403  *   for per bio allocations.
404  *
405  *   RETURNS:
406  *   Pointer to new bio on success, NULL on failure.
407  */
408 struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
409 {
410         gfp_t saved_gfp = gfp_mask;
411         unsigned front_pad;
412         unsigned inline_vecs;
413         unsigned long idx = BIO_POOL_NONE;
414         struct bio_vec *bvl = NULL;
415         struct bio *bio;
416         void *p;
417 
418         if (!bs) {
419                 if (nr_iovecs > UIO_MAXIOV)
420                         return NULL;
421 
422                 p = kmalloc(sizeof(struct bio) +
423                             nr_iovecs * sizeof(struct bio_vec),
424                             gfp_mask);
425                 front_pad = 0;
426                 inline_vecs = nr_iovecs;
427         } else {
428                 /*
429                  * generic_make_request() converts recursion to iteration; this
430                  * means if we're running beneath it, any bios we allocate and
431                  * submit will not be submitted (and thus freed) until after we
432                  * return.
433                  *
434                  * This exposes us to a potential deadlock if we allocate
435                  * multiple bios from the same bio_set() while running
436                  * underneath generic_make_request(). If we were to allocate
437                  * multiple bios (say a stacking block driver that was splitting
438                  * bios), we would deadlock if we exhausted the mempool's
439                  * reserve.
440                  *
441                  * We solve this, and guarantee forward progress, with a rescuer
442                  * workqueue per bio_set. If we go to allocate and there are
443                  * bios on current->bio_list, we first try the allocation
444                  * without __GFP_WAIT; if that fails, we punt those bios we
445                  * would be blocking to the rescuer workqueue before we retry
446                  * with the original gfp_flags.
447                  */
448 
449                 if (current->bio_list && !bio_list_empty(current->bio_list))
450                         gfp_mask &= ~__GFP_WAIT;
451 
452                 p = mempool_alloc(bs->bio_pool, gfp_mask);
453                 if (!p && gfp_mask != saved_gfp) {
454                         punt_bios_to_rescuer(bs);
455                         gfp_mask = saved_gfp;
456                         p = mempool_alloc(bs->bio_pool, gfp_mask);
457                 }
458 
459                 front_pad = bs->front_pad;
460                 inline_vecs = BIO_INLINE_VECS;
461         }
462 
463         if (unlikely(!p))
464                 return NULL;
465 
466         bio = p + front_pad;
467         bio_init(bio);
468 
469         if (nr_iovecs > inline_vecs) {
470                 bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx, bs->bvec_pool);
471                 if (!bvl && gfp_mask != saved_gfp) {
472                         punt_bios_to_rescuer(bs);
473                         gfp_mask = saved_gfp;
474                         bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx, bs->bvec_pool);
475                 }
476 
477                 if (unlikely(!bvl))
478                         goto err_free;
479 
480                 bio->bi_flags |= 1 << BIO_OWNS_VEC;
481         } else if (nr_iovecs) {
482                 bvl = bio->bi_inline_vecs;
483         }
484 
485         bio->bi_pool = bs;
486         bio->bi_flags |= idx << BIO_POOL_OFFSET;
487         bio->bi_max_vecs = nr_iovecs;
488         bio->bi_io_vec = bvl;
489         return bio;
490 
491 err_free:
492         mempool_free(p, bs->bio_pool);
493         return NULL;
494 }
495 EXPORT_SYMBOL(bio_alloc_bioset);
496 
497 void zero_fill_bio(struct bio *bio)
498 {
499         unsigned long flags;
500         struct bio_vec bv;
501         struct bvec_iter iter;
502 
503         bio_for_each_segment(bv, bio, iter) {
504                 char *data = bvec_kmap_irq(&bv, &flags);
505                 memset(data, 0, bv.bv_len);
506                 flush_dcache_page(bv.bv_page);
507                 bvec_kunmap_irq(data, &flags);
508         }
509 }
510 EXPORT_SYMBOL(zero_fill_bio);
511 
512 /**
513  * bio_put - release a reference to a bio
514  * @bio:   bio to release reference to
515  *
516  * Description:
517  *   Put a reference to a &struct bio, either one you have gotten with
518  *   bio_alloc, bio_get or bio_clone. The last put of a bio will free it.
519  **/
520 void bio_put(struct bio *bio)
521 {
522         BIO_BUG_ON(!atomic_read(&bio->bi_cnt));
523 
524         /*
525          * last put frees it
526          */
527         if (atomic_dec_and_test(&bio->bi_cnt))
528                 bio_free(bio);
529 }
530 EXPORT_SYMBOL(bio_put);
531 
532 inline int bio_phys_segments(struct request_queue *q, struct bio *bio)
533 {
534         if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
535                 blk_recount_segments(q, bio);
536 
537         return bio->bi_phys_segments;
538 }
539 EXPORT_SYMBOL(bio_phys_segments);
540 
541 /**
542  *      __bio_clone_fast - clone a bio that shares the original bio's biovec
543  *      @bio: destination bio
544  *      @bio_src: bio to clone
545  *
546  *      Clone a &bio. Caller will own the returned bio, but not
547  *      the actual data it points to. Reference count of returned
548  *      bio will be one.
549  *
550  *      Caller must ensure that @bio_src is not freed before @bio.
551  */
552 void __bio_clone_fast(struct bio *bio, struct bio *bio_src)
553 {
554         BUG_ON(bio->bi_pool && BIO_POOL_IDX(bio) != BIO_POOL_NONE);
555 
556         /*
557          * most users will be overriding ->bi_bdev with a new target,
558          * so we don't set nor calculate new physical/hw segment counts here
559          */
560         bio->bi_bdev = bio_src->bi_bdev;
561         bio->bi_flags |= 1 << BIO_CLONED;
562         bio->bi_rw = bio_src->bi_rw;
563         bio->bi_iter = bio_src->bi_iter;
564         bio->bi_io_vec = bio_src->bi_io_vec;
565 }
566 EXPORT_SYMBOL(__bio_clone_fast);
567 
568 /**
569  *      bio_clone_fast - clone a bio that shares the original bio's biovec
570  *      @bio: bio to clone
571  *      @gfp_mask: allocation priority
572  *      @bs: bio_set to allocate from
573  *
574  *      Like __bio_clone_fast, only also allocates the returned bio
575  */
576 struct bio *bio_clone_fast(struct bio *bio, gfp_t gfp_mask, struct bio_set *bs)
577 {
578         struct bio *b;
579 
580         b = bio_alloc_bioset(gfp_mask, 0, bs);
581         if (!b)
582                 return NULL;
583 
584         __bio_clone_fast(b, bio);
585 
586         if (bio_integrity(bio)) {
587                 int ret;
588 
589                 ret = bio_integrity_clone(b, bio, gfp_mask);
590 
591                 if (ret < 0) {
592                         bio_put(b);
593                         return NULL;
594                 }
595         }
596 
597         return b;
598 }
599 EXPORT_SYMBOL(bio_clone_fast);
600 
601 /**
602  *      bio_clone_bioset - clone a bio
603  *      @bio_src: bio to clone
604  *      @gfp_mask: allocation priority
605  *      @bs: bio_set to allocate from
606  *
607  *      Clone bio. Caller will own the returned bio, but not the actual data it
608  *      points to. Reference count of returned bio will be one.
609  */
610 struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
611                              struct bio_set *bs)
612 {
613         struct bvec_iter iter;
614         struct bio_vec bv;
615         struct bio *bio;
616 
617         /*
618          * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
619          * bio_src->bi_io_vec to bio->bi_io_vec.
620          *
621          * We can't do that anymore, because:
622          *
623          *  - The point of cloning the biovec is to produce a bio with a biovec
624          *    the caller can modify: bi_idx and bi_bvec_done should be 0.
625          *
626          *  - The original bio could've had more than BIO_MAX_PAGES biovecs; if
627          *    we tried to clone the whole thing bio_alloc_bioset() would fail.
628          *    But the clone should succeed as long as the number of biovecs we
629          *    actually need to allocate is fewer than BIO_MAX_PAGES.
630          *
631          *  - Lastly, bi_vcnt should not be looked at or relied upon by code
632          *    that does not own the bio - reason being drivers don't use it for
633          *    iterating over the biovec anymore, so expecting it to be kept up
634          *    to date (i.e. for clones that share the parent biovec) is just
635          *    asking for trouble and would force extra work on
636          *    __bio_clone_fast() anyways.
637          */
638 
639         bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src), bs);
640         if (!bio)
641                 return NULL;
642 
643         bio->bi_bdev            = bio_src->bi_bdev;
644         bio->bi_rw              = bio_src->bi_rw;
645         bio->bi_iter.bi_sector  = bio_src->bi_iter.bi_sector;
646         bio->bi_iter.bi_size    = bio_src->bi_iter.bi_size;
647 
648         if (bio->bi_rw & REQ_DISCARD)
649                 goto integrity_clone;
650 
651         if (bio->bi_rw & REQ_WRITE_SAME) {
652                 bio->bi_io_vec[bio->bi_vcnt++] = bio_src->bi_io_vec[0];
653                 goto integrity_clone;
654         }
655 
656         bio_for_each_segment(bv, bio_src, iter)
657                 bio->bi_io_vec[bio->bi_vcnt++] = bv;
658 
659 integrity_clone:
660         if (bio_integrity(bio_src)) {
661                 int ret;
662 
663                 ret = bio_integrity_clone(bio, bio_src, gfp_mask);
664                 if (ret < 0) {
665                         bio_put(bio);
666                         return NULL;
667                 }
668         }
669 
670         return bio;
671 }
672 EXPORT_SYMBOL(bio_clone_bioset);
673 
674 /**
675  *      bio_get_nr_vecs         - return approx number of vecs
676  *      @bdev:  I/O target
677  *
678  *      Return the approximate number of pages we can send to this target.
679  *      There's no guarantee that you will be able to fit this number of pages
680  *      into a bio, it does not account for dynamic restrictions that vary
681  *      on offset.
682  */
683 int bio_get_nr_vecs(struct block_device *bdev)
684 {
685         struct request_queue *q = bdev_get_queue(bdev);
686         int nr_pages;
687 
688         nr_pages = min_t(unsigned,
689                      queue_max_segments(q),
690                      queue_max_sectors(q) / (PAGE_SIZE >> 9) + 1);
691 
692         return min_t(unsigned, nr_pages, BIO_MAX_PAGES);
693 
694 }
695 EXPORT_SYMBOL(bio_get_nr_vecs);
696 
697 static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
698                           *page, unsigned int len, unsigned int offset,
699                           unsigned int max_sectors)
700 {
701         int retried_segments = 0;
702         struct bio_vec *bvec;
703 
704         /*
705          * cloned bio must not modify vec list
706          */
707         if (unlikely(bio_flagged(bio, BIO_CLONED)))
708                 return 0;
709 
710         if (((bio->bi_iter.bi_size + len) >> 9) > max_sectors)
711                 return 0;
712 
713         /*
714          * For filesystems with a blocksize smaller than the pagesize
715          * we will often be called with the same page as last time and
716          * a consecutive offset.  Optimize this special case.
717          */
718         if (bio->bi_vcnt > 0) {
719                 struct bio_vec *prev = &bio->bi_io_vec[bio->bi_vcnt - 1];
720 
721                 if (page == prev->bv_page &&
722                     offset == prev->bv_offset + prev->bv_len) {
723                         unsigned int prev_bv_len = prev->bv_len;
724                         prev->bv_len += len;
725 
726                         if (q->merge_bvec_fn) {
727                                 struct bvec_merge_data bvm = {
728                                         /* prev_bvec is already charged in
729                                            bi_size, discharge it in order to
730                                            simulate merging updated prev_bvec
731                                            as new bvec. */
732                                         .bi_bdev = bio->bi_bdev,
733                                         .bi_sector = bio->bi_iter.bi_sector,
734                                         .bi_size = bio->bi_iter.bi_size -
735                                                 prev_bv_len,
736                                         .bi_rw = bio->bi_rw,
737                                 };
738 
739                                 if (q->merge_bvec_fn(q, &bvm, prev) < prev->bv_len) {
740                                         prev->bv_len -= len;
741                                         return 0;
742                                 }
743                         }
744 
745                         goto done;
746                 }
747         }
748 
749         if (bio->bi_vcnt >= bio->bi_max_vecs)
750                 return 0;
751 
752         /*
753          * we might lose a segment or two here, but rather that than
754          * make this too complex.
755          */
756 
757         while (bio->bi_phys_segments >= queue_max_segments(q)) {
758 
759                 if (retried_segments)
760                         return 0;
761 
762                 retried_segments = 1;
763                 blk_recount_segments(q, bio);
764         }
765 
766         /*
767          * setup the new entry, we might clear it again later if we
768          * cannot add the page
769          */
770         bvec = &bio->bi_io_vec[bio->bi_vcnt];
771         bvec->bv_page = page;
772         bvec->bv_len = len;
773         bvec->bv_offset = offset;
774 
775         /*
776          * if queue has other restrictions (eg varying max sector size
777          * depending on offset), it can specify a merge_bvec_fn in the
778          * queue to get further control
779          */
780         if (q->merge_bvec_fn) {
781                 struct bvec_merge_data bvm = {
782                         .bi_bdev = bio->bi_bdev,
783                         .bi_sector = bio->bi_iter.bi_sector,
784                         .bi_size = bio->bi_iter.bi_size,
785                         .bi_rw = bio->bi_rw,
786                 };
787 
788                 /*
789                  * merge_bvec_fn() returns number of bytes it can accept
790                  * at this offset
791                  */
792                 if (q->merge_bvec_fn(q, &bvm, bvec) < bvec->bv_len) {
793                         bvec->bv_page = NULL;
794                         bvec->bv_len = 0;
795                         bvec->bv_offset = 0;
796                         return 0;
797                 }
798         }
799 
800         /* If we may be able to merge these biovecs, force a recount */
801         if (bio->bi_vcnt && (BIOVEC_PHYS_MERGEABLE(bvec-1, bvec)))
802                 bio->bi_flags &= ~(1 << BIO_SEG_VALID);
803 
804         bio->bi_vcnt++;
805         bio->bi_phys_segments++;
806  done:
807         bio->bi_iter.bi_size += len;
808         return len;
809 }
810 
811 /**
812  *      bio_add_pc_page -       attempt to add page to bio
813  *      @q: the target queue
814  *      @bio: destination bio
815  *      @page: page to add
816  *      @len: vec entry length
817  *      @offset: vec entry offset
818  *
819  *      Attempt to add a page to the bio_vec maplist. This can fail for a
820  *      number of reasons, such as the bio being full or target block device
821  *      limitations. The target block device must allow bio's up to PAGE_SIZE,
822  *      so it is always possible to add a single page to an empty bio.
823  *
824  *      This should only be used by REQ_PC bios.
825  */
826 int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page *page,
827                     unsigned int len, unsigned int offset)
828 {
829         return __bio_add_page(q, bio, page, len, offset,
830                               queue_max_hw_sectors(q));
831 }
832 EXPORT_SYMBOL(bio_add_pc_page);
833 
834 /**
835  *      bio_add_page    -       attempt to add page to bio
836  *      @bio: destination bio
837  *      @page: page to add
838  *      @len: vec entry length
839  *      @offset: vec entry offset
840  *
841  *      Attempt to add a page to the bio_vec maplist. This can fail for a
842  *      number of reasons, such as the bio being full or target block device
843  *      limitations. The target block device must allow bio's up to PAGE_SIZE,
844  *      so it is always possible to add a single page to an empty bio.
845  */
846 int bio_add_page(struct bio *bio, struct page *page, unsigned int len,
847                  unsigned int offset)
848 {
849         struct request_queue *q = bdev_get_queue(bio->bi_bdev);
850         return __bio_add_page(q, bio, page, len, offset, queue_max_sectors(q));
851 }
852 EXPORT_SYMBOL(bio_add_page);
853 
854 struct submit_bio_ret {
855         struct completion event;
856         int error;
857 };
858 
859 static void submit_bio_wait_endio(struct bio *bio, int error)
860 {
861         struct submit_bio_ret *ret = bio->bi_private;
862 
863         ret->error = error;
864         complete(&ret->event);
865 }
866 
867 /**
868  * submit_bio_wait - submit a bio, and wait until it completes
869  * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
870  * @bio: The &struct bio which describes the I/O
871  *
872  * Simple wrapper around submit_bio(). Returns 0 on success, or the error from
873  * bio_endio() on failure.
874  */
875 int submit_bio_wait(int rw, struct bio *bio)
876 {
877         struct submit_bio_ret ret;
878 
879         rw |= REQ_SYNC;
880         init_completion(&ret.event);
881         bio->bi_private = &ret;
882         bio->bi_end_io = submit_bio_wait_endio;
883         submit_bio(rw, bio);
884         wait_for_completion(&ret.event);
885 
886         return ret.error;
887 }
888 EXPORT_SYMBOL(submit_bio_wait);
889 
890 /**
891  * bio_advance - increment/complete a bio by some number of bytes
892  * @bio:        bio to advance
893  * @bytes:      number of bytes to complete
894  *
895  * This updates bi_sector, bi_size and bi_idx; if the number of bytes to
896  * complete doesn't align with a bvec boundary, then bv_len and bv_offset will
897  * be updated on the last bvec as well.
898  *
899  * @bio will then represent the remaining, uncompleted portion of the io.
900  */
901 void bio_advance(struct bio *bio, unsigned bytes)
902 {
903         if (bio_integrity(bio))
904                 bio_integrity_advance(bio, bytes);
905 
906         bio_advance_iter(bio, &bio->bi_iter, bytes);
907 }
908 EXPORT_SYMBOL(bio_advance);
909 
910 /**
911  * bio_alloc_pages - allocates a single page for each bvec in a bio
912  * @bio: bio to allocate pages for
913  * @gfp_mask: flags for allocation
914  *
915  * Allocates pages up to @bio->bi_vcnt.
916  *
917  * Returns 0 on success, -ENOMEM on failure. On failure, any allocated pages are
918  * freed.
919  */
920 int bio_alloc_pages(struct bio *bio, gfp_t gfp_mask)
921 {
922         int i;
923         struct bio_vec *bv;
924 
925         bio_for_each_segment_all(bv, bio, i) {
926                 bv->bv_page = alloc_page(gfp_mask);
927                 if (!bv->bv_page) {
928                         while (--bv >= bio->bi_io_vec)
929                                 __free_page(bv->bv_page);
930                         return -ENOMEM;
931                 }
932         }
933 
934         return 0;
935 }
936 EXPORT_SYMBOL(bio_alloc_pages);
937 
938 /**
939  * bio_copy_data - copy contents of data buffers from one chain of bios to
940  * another
941  * @src: source bio list
942  * @dst: destination bio list
943  *
944  * If @src and @dst are single bios, bi_next must be NULL - otherwise, treats
945  * @src and @dst as linked lists of bios.
946  *
947  * Stops when it reaches the end of either @src or @dst - that is, copies
948  * min(src->bi_size, dst->bi_size) bytes (or the equivalent for lists of bios).
949  */
950 void bio_copy_data(struct bio *dst, struct bio *src)
951 {
952         struct bvec_iter src_iter, dst_iter;
953         struct bio_vec src_bv, dst_bv;
954         void *src_p, *dst_p;
955         unsigned bytes;
956 
957         src_iter = src->bi_iter;
958         dst_iter = dst->bi_iter;
959 
960         while (1) {
961                 if (!src_iter.bi_size) {
962                         src = src->bi_next;
963                         if (!src)
964                                 break;
965 
966                         src_iter = src->bi_iter;
967                 }
968 
969                 if (!dst_iter.bi_size) {
970                         dst = dst->bi_next;
971                         if (!dst)
972                                 break;
973 
974                         dst_iter = dst->bi_iter;
975                 }
976 
977                 src_bv = bio_iter_iovec(src, src_iter);
978                 dst_bv = bio_iter_iovec(dst, dst_iter);
979 
980                 bytes = min(src_bv.bv_len, dst_bv.bv_len);
981 
982                 src_p = kmap_atomic(src_bv.bv_page);
983                 dst_p = kmap_atomic(dst_bv.bv_page);
984 
985                 memcpy(dst_p + dst_bv.bv_offset,
986                        src_p + src_bv.bv_offset,
987                        bytes);
988 
989                 kunmap_atomic(dst_p);
990                 kunmap_atomic(src_p);
991 
992                 bio_advance_iter(src, &src_iter, bytes);
993                 bio_advance_iter(dst, &dst_iter, bytes);
994         }
995 }
996 EXPORT_SYMBOL(bio_copy_data);
997 
998 struct bio_map_data {
999         int nr_sgvecs;
1000         int is_our_pages;
1001         struct sg_iovec sgvecs[];
1002 };
1003 
1004 static void bio_set_map_data(struct bio_map_data *bmd, struct bio *bio,
1005                              const struct sg_iovec *iov, int iov_count,
1006                              int is_our_pages)
1007 {
1008         memcpy(bmd->sgvecs, iov, sizeof(struct sg_iovec) * iov_count);
1009         bmd->nr_sgvecs = iov_count;
1010         bmd->is_our_pages = is_our_pages;
1011         bio->bi_private = bmd;
1012 }
1013 
1014 static struct bio_map_data *bio_alloc_map_data(int nr_segs,
1015                                                unsigned int iov_count,
1016                                                gfp_t gfp_mask)
1017 {
1018         if (iov_count > UIO_MAXIOV)
1019                 return NULL;
1020 
1021         return kmalloc(sizeof(struct bio_map_data) +
1022                        sizeof(struct sg_iovec) * iov_count, gfp_mask);
1023 }
1024 
1025 static int __bio_copy_iov(struct bio *bio, const struct sg_iovec *iov, int iov_count,
1026                           int to_user, int from_user, int do_free_page)
1027 {
1028         int ret = 0, i;
1029         struct bio_vec *bvec;
1030         int iov_idx = 0;
1031         unsigned int iov_off = 0;
1032 
1033         bio_for_each_segment_all(bvec, bio, i) {
1034                 char *bv_addr = page_address(bvec->bv_page);
1035                 unsigned int bv_len = bvec->bv_len;
1036 
1037                 while (bv_len && iov_idx < iov_count) {
1038                         unsigned int bytes;
1039                         char __user *iov_addr;
1040 
1041                         bytes = min_t(unsigned int,
1042                                       iov[iov_idx].iov_len - iov_off, bv_len);
1043                         iov_addr = iov[iov_idx].iov_base + iov_off;
1044 
1045                         if (!ret) {
1046                                 if (to_user)
1047                                         ret = copy_to_user(iov_addr, bv_addr,
1048                                                            bytes);
1049 
1050                                 if (from_user)
1051                                         ret = copy_from_user(bv_addr, iov_addr,
1052                                                              bytes);
1053 
1054                                 if (ret)
1055                                         ret = -EFAULT;
1056                         }
1057 
1058                         bv_len -= bytes;
1059                         bv_addr += bytes;
1060                         iov_addr += bytes;
1061                         iov_off += bytes;
1062 
1063                         if (iov[iov_idx].iov_len == iov_off) {
1064                                 iov_idx++;
1065                                 iov_off = 0;
1066                         }
1067                 }
1068 
1069                 if (do_free_page)
1070                         __free_page(bvec->bv_page);
1071         }
1072 
1073         return ret;
1074 }
1075 
1076 /**
1077  *      bio_uncopy_user -       finish previously mapped bio
1078  *      @bio: bio being terminated
1079  *
1080  *      Free pages allocated from bio_copy_user() and write back data
1081  *      to user space in case of a read.
1082  */
1083 int bio_uncopy_user(struct bio *bio)
1084 {
1085         struct bio_map_data *bmd = bio->bi_private;
1086         struct bio_vec *bvec;
1087         int ret = 0, i;
1088 
1089         if (!bio_flagged(bio, BIO_NULL_MAPPED)) {
1090                 /*
1091                  * if we're in a workqueue, the request is orphaned, so
1092                  * don't copy into a random user address space, just free.
1093                  */
1094                 if (current->mm)
1095                         ret = __bio_copy_iov(bio, bmd->sgvecs, bmd->nr_sgvecs,
1096                                              bio_data_dir(bio) == READ,
1097                                              0, bmd->is_our_pages);
1098                 else if (bmd->is_our_pages)
1099                         bio_for_each_segment_all(bvec, bio, i)
1100                                 __free_page(bvec->bv_page);
1101         }
1102         kfree(bmd);
1103         bio_put(bio);
1104         return ret;
1105 }
1106 EXPORT_SYMBOL(bio_uncopy_user);
1107 
1108 /**
1109  *      bio_copy_user_iov       -       copy user data to bio
1110  *      @q: destination block queue
1111  *      @map_data: pointer to the rq_map_data holding pages (if necessary)
1112  *      @iov:   the iovec.
1113  *      @iov_count: number of elements in the iovec
1114  *      @write_to_vm: bool indicating writing to pages or not
1115  *      @gfp_mask: memory allocation flags
1116  *
1117  *      Prepares and returns a bio for indirect user io, bouncing data
1118  *      to/from kernel pages as necessary. Must be paired with
1119  *      call bio_uncopy_user() on io completion.
1120  */
1121 struct bio *bio_copy_user_iov(struct request_queue *q,
1122                               struct rq_map_data *map_data,
1123                               const struct sg_iovec *iov, int iov_count,
1124                               int write_to_vm, gfp_t gfp_mask)
1125 {
1126         struct bio_map_data *bmd;
1127         struct bio_vec *bvec;
1128         struct page *page;
1129         struct bio *bio;
1130         int i, ret;
1131         int nr_pages = 0;
1132         unsigned int len = 0;
1133         unsigned int offset = map_data ? map_data->offset & ~PAGE_MASK : 0;
1134 
1135         for (i = 0; i < iov_count; i++) {
1136                 unsigned long uaddr;
1137                 unsigned long end;
1138                 unsigned long start;
1139 
1140                 uaddr = (unsigned long)iov[i].iov_base;
1141                 end = (uaddr + iov[i].iov_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1142                 start = uaddr >> PAGE_SHIFT;
1143 
1144                 /*
1145                  * Overflow, abort
1146                  */
1147                 if (end < start)
1148                         return ERR_PTR(-EINVAL);
1149 
1150                 nr_pages += end - start;
1151                 len += iov[i].iov_len;
1152         }
1153 
1154         if (offset)
1155                 nr_pages++;
1156 
1157         bmd = bio_alloc_map_data(nr_pages, iov_count, gfp_mask);
1158         if (!bmd)
1159                 return ERR_PTR(-ENOMEM);
1160 
1161         ret = -ENOMEM;
1162         bio = bio_kmalloc(gfp_mask, nr_pages);
1163         if (!bio)
1164                 goto out_bmd;
1165 
1166         if (!write_to_vm)
1167                 bio->bi_rw |= REQ_WRITE;
1168 
1169         ret = 0;
1170 
1171         if (map_data) {
1172                 nr_pages = 1 << map_data->page_order;
1173                 i = map_data->offset / PAGE_SIZE;
1174         }
1175         while (len) {
1176                 unsigned int bytes = PAGE_SIZE;
1177 
1178                 bytes -= offset;
1179 
1180                 if (bytes > len)
1181                         bytes = len;
1182 
1183                 if (map_data) {
1184                         if (i == map_data->nr_entries * nr_pages) {
1185                                 ret = -ENOMEM;
1186                                 break;
1187                         }
1188 
1189                         page = map_data->pages[i / nr_pages];
1190                         page += (i % nr_pages);
1191 
1192                         i++;
1193                 } else {
1194                         page = alloc_page(q->bounce_gfp | gfp_mask);
1195                         if (!page) {
1196                                 ret = -ENOMEM;
1197                                 break;
1198                         }
1199                 }
1200 
1201                 if (bio_add_pc_page(q, bio, page, bytes, offset) < bytes)
1202                         break;
1203 
1204                 len -= bytes;
1205                 offset = 0;
1206         }
1207 
1208         if (ret)
1209                 goto cleanup;
1210 
1211         /*
1212          * success
1213          */
1214         if ((!write_to_vm && (!map_data || !map_data->null_mapped)) ||
1215             (map_data && map_data->from_user)) {
1216                 ret = __bio_copy_iov(bio, iov, iov_count, 0, 1, 0);
1217                 if (ret)
1218                         goto cleanup;
1219         }
1220 
1221         bio_set_map_data(bmd, bio, iov, iov_count, map_data ? 0 : 1);
1222         return bio;
1223 cleanup:
1224         if (!map_data)
1225                 bio_for_each_segment_all(bvec, bio, i)
1226                         __free_page(bvec->bv_page);
1227 
1228         bio_put(bio);
1229 out_bmd:
1230         kfree(bmd);
1231         return ERR_PTR(ret);
1232 }
1233 
1234 /**
1235  *      bio_copy_user   -       copy user data to bio
1236  *      @q: destination block queue
1237  *      @map_data: pointer to the rq_map_data holding pages (if necessary)
1238  *      @uaddr: start of user address
1239  *      @len: length in bytes
1240  *      @write_to_vm: bool indicating writing to pages or not
1241  *      @gfp_mask: memory allocation flags
1242  *
1243  *      Prepares and returns a bio for indirect user io, bouncing data
1244  *      to/from kernel pages as necessary. Must be paired with
1245  *      call bio_uncopy_user() on io completion.
1246  */
1247 struct bio *bio_copy_user(struct request_queue *q, struct rq_map_data *map_data,
1248                           unsigned long uaddr, unsigned int len,
1249                           int write_to_vm, gfp_t gfp_mask)
1250 {
1251         struct sg_iovec iov;
1252 
1253         iov.iov_base = (void __user *)uaddr;
1254         iov.iov_len = len;
1255 
1256         return bio_copy_user_iov(q, map_data, &iov, 1, write_to_vm, gfp_mask);
1257 }
1258 EXPORT_SYMBOL(bio_copy_user);
1259 
1260 static struct bio *__bio_map_user_iov(struct request_queue *q,
1261                                       struct block_device *bdev,
1262                                       const struct sg_iovec *iov, int iov_count,
1263                                       int write_to_vm, gfp_t gfp_mask)
1264 {
1265         int i, j;
1266         int nr_pages = 0;
1267         struct page **pages;
1268         struct bio *bio;
1269         int cur_page = 0;
1270         int ret, offset;
1271 
1272         for (i = 0; i < iov_count; i++) {
1273                 unsigned long uaddr = (unsigned long)iov[i].iov_base;
1274                 unsigned long len = iov[i].iov_len;
1275                 unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1276                 unsigned long start = uaddr >> PAGE_SHIFT;
1277 
1278                 /*
1279                  * Overflow, abort
1280                  */
1281                 if (end < start)
1282                         return ERR_PTR(-EINVAL);
1283 
1284                 nr_pages += end - start;
1285                 /*
1286                  * buffer must be aligned to at least hardsector size for now
1287                  */
1288                 if (uaddr & queue_dma_alignment(q))
1289                         return ERR_PTR(-EINVAL);
1290         }
1291 
1292         if (!nr_pages)
1293                 return ERR_PTR(-EINVAL);
1294 
1295         bio = bio_kmalloc(gfp_mask, nr_pages);
1296         if (!bio)
1297                 return ERR_PTR(-ENOMEM);
1298 
1299         ret = -ENOMEM;
1300         pages = kcalloc(nr_pages, sizeof(struct page *), gfp_mask);
1301         if (!pages)
1302                 goto out;
1303 
1304         for (i = 0; i < iov_count; i++) {
1305                 unsigned long uaddr = (unsigned long)iov[i].iov_base;
1306                 unsigned long len = iov[i].iov_len;
1307                 unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1308                 unsigned long start = uaddr >> PAGE_SHIFT;
1309                 const int local_nr_pages = end - start;
1310                 const int page_limit = cur_page + local_nr_pages;
1311 
1312                 ret = get_user_pages_fast(uaddr, local_nr_pages,
1313                                 write_to_vm, &pages[cur_page]);
1314                 if (ret < local_nr_pages) {
1315                         ret = -EFAULT;
1316                         goto out_unmap;
1317                 }
1318 
1319                 offset = uaddr & ~PAGE_MASK;
1320                 for (j = cur_page; j < page_limit; j++) {
1321                         unsigned int bytes = PAGE_SIZE - offset;
1322 
1323                         if (len <= 0)
1324                                 break;
1325                         
1326                         if (bytes > len)
1327                                 bytes = len;
1328 
1329                         /*
1330                          * sorry...
1331                          */
1332                         if (bio_add_pc_page(q, bio, pages[j], bytes, offset) <
1333                                             bytes)
1334                                 break;
1335 
1336                         len -= bytes;
1337                         offset = 0;
1338                 }
1339 
1340                 cur_page = j;
1341                 /*
1342                  * release the pages we didn't map into the bio, if any
1343                  */
1344                 while (j < page_limit)
1345                         page_cache_release(pages[j++]);
1346         }
1347 
1348         kfree(pages);
1349 
1350         /*
1351          * set data direction, and check if mapped pages need bouncing
1352          */
1353         if (!write_to_vm)
1354                 bio->bi_rw |= REQ_WRITE;
1355 
1356         bio->bi_bdev = bdev;
1357         bio->bi_flags |= (1 << BIO_USER_MAPPED);
1358         return bio;
1359 
1360  out_unmap:
1361         for (i = 0; i < nr_pages; i++) {
1362                 if(!pages[i])
1363                         break;
1364                 page_cache_release(pages[i]);
1365         }
1366  out:
1367         kfree(pages);
1368         bio_put(bio);
1369         return ERR_PTR(ret);
1370 }
1371 
1372 /**
1373  *      bio_map_user    -       map user address into bio
1374  *      @q: the struct request_queue for the bio
1375  *      @bdev: destination block device
1376  *      @uaddr: start of user address
1377  *      @len: length in bytes
1378  *      @write_to_vm: bool indicating writing to pages or not
1379  *      @gfp_mask: memory allocation flags
1380  *
1381  *      Map the user space address into a bio suitable for io to a block
1382  *      device. Returns an error pointer in case of error.
1383  */
1384 struct bio *bio_map_user(struct request_queue *q, struct block_device *bdev,
1385                          unsigned long uaddr, unsigned int len, int write_to_vm,
1386                          gfp_t gfp_mask)
1387 {
1388         struct sg_iovec iov;
1389 
1390         iov.iov_base = (void __user *)uaddr;
1391         iov.iov_len = len;
1392 
1393         return bio_map_user_iov(q, bdev, &iov, 1, write_to_vm, gfp_mask);
1394 }
1395 EXPORT_SYMBOL(bio_map_user);
1396 
1397 /**
1398  *      bio_map_user_iov - map user sg_iovec table into bio
1399  *      @q: the struct request_queue for the bio
1400  *      @bdev: destination block device
1401  *      @iov:   the iovec.
1402  *      @iov_count: number of elements in the iovec
1403  *      @write_to_vm: bool indicating writing to pages or not
1404  *      @gfp_mask: memory allocation flags
1405  *
1406  *      Map the user space address into a bio suitable for io to a block
1407  *      device. Returns an error pointer in case of error.
1408  */
1409 struct bio *bio_map_user_iov(struct request_queue *q, struct block_device *bdev,
1410                              const struct sg_iovec *iov, int iov_count,
1411                              int write_to_vm, gfp_t gfp_mask)
1412 {
1413         struct bio *bio;
1414 
1415         bio = __bio_map_user_iov(q, bdev, iov, iov_count, write_to_vm,
1416                                  gfp_mask);
1417         if (IS_ERR(bio))
1418                 return bio;
1419 
1420         /*
1421          * subtle -- if __bio_map_user() ended up bouncing a bio,
1422          * it would normally disappear when its bi_end_io is run.
1423          * however, we need it for the unmap, so grab an extra
1424          * reference to it
1425          */
1426         bio_get(bio);
1427 
1428         return bio;
1429 }
1430 
1431 static void __bio_unmap_user(struct bio *bio)
1432 {
1433         struct bio_vec *bvec;
1434         int i;
1435 
1436         /*
1437          * make sure we dirty pages we wrote to
1438          */
1439         bio_for_each_segment_all(bvec, bio, i) {
1440                 if (bio_data_dir(bio) == READ)
1441                         set_page_dirty_lock(bvec->bv_page);
1442 
1443                 page_cache_release(bvec->bv_page);
1444         }
1445 
1446         bio_put(bio);
1447 }
1448 
1449 /**
1450  *      bio_unmap_user  -       unmap a bio
1451  *      @bio:           the bio being unmapped
1452  *
1453  *      Unmap a bio previously mapped by bio_map_user(). Must be called with
1454  *      a process context.
1455  *
1456  *      bio_unmap_user() may sleep.
1457  */
1458 void bio_unmap_user(struct bio *bio)
1459 {
1460         __bio_unmap_user(bio);
1461         bio_put(bio);
1462 }
1463 EXPORT_SYMBOL(bio_unmap_user);
1464 
1465 static void bio_map_kern_endio(struct bio *bio, int err)
1466 {
1467         bio_put(bio);
1468 }
1469 
1470 static struct bio *__bio_map_kern(struct request_queue *q, void *data,
1471                                   unsigned int len, gfp_t gfp_mask)
1472 {
1473         unsigned long kaddr = (unsigned long)data;
1474         unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1475         unsigned long start = kaddr >> PAGE_SHIFT;
1476         const int nr_pages = end - start;
1477         int offset, i;
1478         struct bio *bio;
1479 
1480         bio = bio_kmalloc(gfp_mask, nr_pages);
1481         if (!bio)
1482                 return ERR_PTR(-ENOMEM);
1483 
1484         offset = offset_in_page(kaddr);
1485         for (i = 0; i < nr_pages; i++) {
1486                 unsigned int bytes = PAGE_SIZE - offset;
1487 
1488                 if (len <= 0)
1489                         break;
1490 
1491                 if (bytes > len)
1492                         bytes = len;
1493 
1494                 if (bio_add_pc_page(q, bio, virt_to_page(data), bytes,
1495                                     offset) < bytes)
1496                         break;
1497 
1498                 data += bytes;
1499                 len -= bytes;
1500                 offset = 0;
1501         }
1502 
1503         bio->bi_end_io = bio_map_kern_endio;
1504         return bio;
1505 }
1506 
1507 /**
1508  *      bio_map_kern    -       map kernel address into bio
1509  *      @q: the struct request_queue for the bio
1510  *      @data: pointer to buffer to map
1511  *      @len: length in bytes
1512  *      @gfp_mask: allocation flags for bio allocation
1513  *
1514  *      Map the kernel address into a bio suitable for io to a block
1515  *      device. Returns an error pointer in case of error.
1516  */
1517 struct bio *bio_map_kern(struct request_queue *q, void *data, unsigned int len,
1518                          gfp_t gfp_mask)
1519 {
1520         struct bio *bio;
1521 
1522         bio = __bio_map_kern(q, data, len, gfp_mask);
1523         if (IS_ERR(bio))
1524                 return bio;
1525 
1526         if (bio->bi_iter.bi_size == len)
1527                 return bio;
1528 
1529         /*
1530          * Don't support partial mappings.
1531          */
1532         bio_put(bio);
1533         return ERR_PTR(-EINVAL);
1534 }
1535 EXPORT_SYMBOL(bio_map_kern);
1536 
1537 static void bio_copy_kern_endio(struct bio *bio, int err)
1538 {
1539         struct bio_vec *bvec;
1540         const int read = bio_data_dir(bio) == READ;
1541         struct bio_map_data *bmd = bio->bi_private;
1542         int i;
1543         char *p = bmd->sgvecs[0].iov_base;
1544 
1545         bio_for_each_segment_all(bvec, bio, i) {
1546                 char *addr = page_address(bvec->bv_page);
1547 
1548                 if (read)
1549                         memcpy(p, addr, bvec->bv_len);
1550 
1551                 __free_page(bvec->bv_page);
1552                 p += bvec->bv_len;
1553         }
1554 
1555         kfree(bmd);
1556         bio_put(bio);
1557 }
1558 
1559 /**
1560  *      bio_copy_kern   -       copy kernel address into bio
1561  *      @q: the struct request_queue for the bio
1562  *      @data: pointer to buffer to copy
1563  *      @len: length in bytes
1564  *      @gfp_mask: allocation flags for bio and page allocation
1565  *      @reading: data direction is READ
1566  *
1567  *      copy the kernel address into a bio suitable for io to a block
1568  *      device. Returns an error pointer in case of error.
1569  */
1570 struct bio *bio_copy_kern(struct request_queue *q, void *data, unsigned int len,
1571                           gfp_t gfp_mask, int reading)
1572 {
1573         struct bio *bio;
1574         struct bio_vec *bvec;
1575         int i;
1576 
1577         bio = bio_copy_user(q, NULL, (unsigned long)data, len, 1, gfp_mask);
1578         if (IS_ERR(bio))
1579                 return bio;
1580 
1581         if (!reading) {
1582                 void *p = data;
1583 
1584                 bio_for_each_segment_all(bvec, bio, i) {
1585                         char *addr = page_address(bvec->bv_page);
1586 
1587                         memcpy(addr, p, bvec->bv_len);
1588                         p += bvec->bv_len;
1589                 }
1590         }
1591 
1592         bio->bi_end_io = bio_copy_kern_endio;
1593 
1594         return bio;
1595 }
1596 EXPORT_SYMBOL(bio_copy_kern);
1597 
1598 /*
1599  * bio_set_pages_dirty() and bio_check_pages_dirty() are support functions
1600  * for performing direct-IO in BIOs.
1601  *
1602  * The problem is that we cannot run set_page_dirty() from interrupt context
1603  * because the required locks are not interrupt-safe.  So what we can do is to
1604  * mark the pages dirty _before_ performing IO.  And in interrupt context,
1605  * check that the pages are still dirty.   If so, fine.  If not, redirty them
1606  * in process context.
1607  *
1608  * We special-case compound pages here: normally this means reads into hugetlb
1609  * pages.  The logic in here doesn't really work right for compound pages
1610  * because the VM does not uniformly chase down the head page in all cases.
1611  * But dirtiness of compound pages is pretty meaningless anyway: the VM doesn't
1612  * handle them at all.  So we skip compound pages here at an early stage.
1613  *
1614  * Note that this code is very hard to test under normal circumstances because
1615  * direct-io pins the pages with get_user_pages().  This makes
1616  * is_page_cache_freeable return false, and the VM will not clean the pages.
1617  * But other code (eg, flusher threads) could clean the pages if they are mapped
1618  * pagecache.
1619  *
1620  * Simply disabling the call to bio_set_pages_dirty() is a good way to test the
1621  * deferred bio dirtying paths.
1622  */
1623 
1624 /*
1625  * bio_set_pages_dirty() will mark all the bio's pages as dirty.
1626  */
1627 void bio_set_pages_dirty(struct bio *bio)
1628 {
1629         struct bio_vec *bvec;
1630         int i;
1631 
1632         bio_for_each_segment_all(bvec, bio, i) {
1633                 struct page *page = bvec->bv_page;
1634 
1635                 if (page && !PageCompound(page))
1636                         set_page_dirty_lock(page);
1637         }
1638 }
1639 
1640 static void bio_release_pages(struct bio *bio)
1641 {
1642         struct bio_vec *bvec;
1643         int i;
1644 
1645         bio_for_each_segment_all(bvec, bio, i) {
1646                 struct page *page = bvec->bv_page;
1647 
1648                 if (page)
1649                         put_page(page);
1650         }
1651 }
1652 
1653 /*
1654  * bio_check_pages_dirty() will check that all the BIO's pages are still dirty.
1655  * If they are, then fine.  If, however, some pages are clean then they must
1656  * have been written out during the direct-IO read.  So we take another ref on
1657  * the BIO and the offending pages and re-dirty the pages in process context.
1658  *
1659  * It is expected that bio_check_pages_dirty() will wholly own the BIO from
1660  * here on.  It will run one page_cache_release() against each page and will
1661  * run one bio_put() against the BIO.
1662  */
1663 
1664 static void bio_dirty_fn(struct work_struct *work);
1665 
1666 static DECLARE_WORK(bio_dirty_work, bio_dirty_fn);
1667 static DEFINE_SPINLOCK(bio_dirty_lock);
1668 static struct bio *bio_dirty_list;
1669 
1670 /*
1671  * This runs in process context
1672  */
1673 static void bio_dirty_fn(struct work_struct *work)
1674 {
1675         unsigned long flags;
1676         struct bio *bio;
1677 
1678         spin_lock_irqsave(&bio_dirty_lock, flags);
1679         bio = bio_dirty_list;
1680         bio_dirty_list = NULL;
1681         spin_unlock_irqrestore(&bio_dirty_lock, flags);
1682 
1683         while (bio) {
1684                 struct bio *next = bio->bi_private;
1685 
1686                 bio_set_pages_dirty(bio);
1687                 bio_release_pages(bio);
1688                 bio_put(bio);
1689                 bio = next;
1690         }
1691 }
1692 
1693 void bio_check_pages_dirty(struct bio *bio)
1694 {
1695         struct bio_vec *bvec;
1696         int nr_clean_pages = 0;
1697         int i;
1698 
1699         bio_for_each_segment_all(bvec, bio, i) {
1700                 struct page *page = bvec->bv_page;
1701 
1702                 if (PageDirty(page) || PageCompound(page)) {
1703                         page_cache_release(page);
1704                         bvec->bv_page = NULL;
1705                 } else {
1706                         nr_clean_pages++;
1707                 }
1708         }
1709 
1710         if (nr_clean_pages) {
1711                 unsigned long flags;
1712 
1713                 spin_lock_irqsave(&bio_dirty_lock, flags);
1714                 bio->bi_private = bio_dirty_list;
1715                 bio_dirty_list = bio;
1716                 spin_unlock_irqrestore(&bio_dirty_lock, flags);
1717                 schedule_work(&bio_dirty_work);
1718         } else {
1719                 bio_put(bio);
1720         }
1721 }
1722 
1723 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
1724 void bio_flush_dcache_pages(struct bio *bi)
1725 {
1726         struct bio_vec bvec;
1727         struct bvec_iter iter;
1728 
1729         bio_for_each_segment(bvec, bi, iter)
1730                 flush_dcache_page(bvec.bv_page);
1731 }
1732 EXPORT_SYMBOL(bio_flush_dcache_pages);
1733 #endif
1734 
1735 /**
1736  * bio_endio - end I/O on a bio
1737  * @bio:        bio
1738  * @error:      error, if any
1739  *
1740  * Description:
1741  *   bio_endio() will end I/O on the whole bio. bio_endio() is the
1742  *   preferred way to end I/O on a bio, it takes care of clearing
1743  *   BIO_UPTODATE on error. @error is 0 on success, and and one of the
1744  *   established -Exxxx (-EIO, for instance) error values in case
1745  *   something went wrong. No one should call bi_end_io() directly on a
1746  *   bio unless they own it and thus know that it has an end_io
1747  *   function.
1748  **/
1749 void bio_endio(struct bio *bio, int error)
1750 {
1751         while (bio) {
1752                 BUG_ON(atomic_read(&bio->bi_remaining) <= 0);
1753 
1754                 if (error)
1755                         clear_bit(BIO_UPTODATE, &bio->bi_flags);
1756                 else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
1757                         error = -EIO;
1758 
1759                 if (!atomic_dec_and_test(&bio->bi_remaining))
1760                         return;
1761 
1762                 /*
1763                  * Need to have a real endio function for chained bios,
1764                  * otherwise various corner cases will break (like stacking
1765                  * block devices that save/restore bi_end_io) - however, we want
1766                  * to avoid unbounded recursion and blowing the stack. Tail call
1767                  * optimization would handle this, but compiling with frame
1768                  * pointers also disables gcc's sibling call optimization.
1769                  */
1770                 if (bio->bi_end_io == bio_chain_endio) {
1771                         struct bio *parent = bio->bi_private;
1772                         bio_put(bio);
1773                         bio = parent;
1774                 } else {
1775                         if (bio->bi_end_io)
1776                                 bio->bi_end_io(bio, error);
1777                         bio = NULL;
1778                 }
1779         }
1780 }
1781 EXPORT_SYMBOL(bio_endio);
1782 
1783 /**
1784  * bio_endio_nodec - end I/O on a bio, without decrementing bi_remaining
1785  * @bio:        bio
1786  * @error:      error, if any
1787  *
1788  * For code that has saved and restored bi_end_io; thing hard before using this
1789  * function, probably you should've cloned the entire bio.
1790  **/
1791 void bio_endio_nodec(struct bio *bio, int error)
1792 {
1793         atomic_inc(&bio->bi_remaining);
1794         bio_endio(bio, error);
1795 }
1796 EXPORT_SYMBOL(bio_endio_nodec);
1797 
1798 /**
1799  * bio_split - split a bio
1800  * @bio:        bio to split
1801  * @sectors:    number of sectors to split from the front of @bio
1802  * @gfp:        gfp mask
1803  * @bs:         bio set to allocate from
1804  *
1805  * Allocates and returns a new bio which represents @sectors from the start of
1806  * @bio, and updates @bio to represent the remaining sectors.
1807  *
1808  * The newly allocated bio will point to @bio's bi_io_vec; it is the caller's
1809  * responsibility to ensure that @bio is not freed before the split.
1810  */
1811 struct bio *bio_split(struct bio *bio, int sectors,
1812                       gfp_t gfp, struct bio_set *bs)
1813 {
1814         struct bio *split = NULL;
1815 
1816         BUG_ON(sectors <= 0);
1817         BUG_ON(sectors >= bio_sectors(bio));
1818 
1819         split = bio_clone_fast(bio, gfp, bs);
1820         if (!split)
1821                 return NULL;
1822 
1823         split->bi_iter.bi_size = sectors << 9;
1824 
1825         if (bio_integrity(split))
1826                 bio_integrity_trim(split, 0, sectors);
1827 
1828         bio_advance(bio, split->bi_iter.bi_size);
1829 
1830         return split;
1831 }
1832 EXPORT_SYMBOL(bio_split);
1833 
1834 /**
1835  * bio_trim - trim a bio
1836  * @bio:        bio to trim
1837  * @offset:     number of sectors to trim from the front of @bio
1838  * @size:       size we want to trim @bio to, in sectors
1839  */
1840 void bio_trim(struct bio *bio, int offset, int size)
1841 {
1842         /* 'bio' is a cloned bio which we need to trim to match
1843          * the given offset and size.
1844          */
1845 
1846         size <<= 9;
1847         if (offset == 0 && size == bio->bi_iter.bi_size)
1848                 return;
1849 
1850         clear_bit(BIO_SEG_VALID, &bio->bi_flags);
1851 
1852         bio_advance(bio, offset << 9);
1853 
1854         bio->bi_iter.bi_size = size;
1855 }
1856 EXPORT_SYMBOL_GPL(bio_trim);
1857 
1858 /*
1859  * create memory pools for biovec's in a bio_set.
1860  * use the global biovec slabs created for general use.
1861  */
1862 mempool_t *biovec_create_pool(struct bio_set *bs, int pool_entries)
1863 {
1864         struct biovec_slab *bp = bvec_slabs + BIOVEC_MAX_IDX;
1865 
1866         return mempool_create_slab_pool(pool_entries, bp->slab);
1867 }
1868 
1869 void bioset_free(struct bio_set *bs)
1870 {
1871         if (bs->rescue_workqueue)
1872                 destroy_workqueue(bs->rescue_workqueue);
1873 
1874         if (bs->bio_pool)
1875                 mempool_destroy(bs->bio_pool);
1876 
1877         if (bs->bvec_pool)
1878                 mempool_destroy(bs->bvec_pool);
1879 
1880         bioset_integrity_free(bs);
1881         bio_put_slab(bs);
1882 
1883         kfree(bs);
1884 }
1885 EXPORT_SYMBOL(bioset_free);
1886 
1887 /**
1888  * bioset_create  - Create a bio_set
1889  * @pool_size:  Number of bio and bio_vecs to cache in the mempool
1890  * @front_pad:  Number of bytes to allocate in front of the returned bio
1891  *
1892  * Description:
1893  *    Set up a bio_set to be used with @bio_alloc_bioset. Allows the caller
1894  *    to ask for a number of bytes to be allocated in front of the bio.
1895  *    Front pad allocation is useful for embedding the bio inside
1896  *    another structure, to avoid allocating extra data to go with the bio.
1897  *    Note that the bio must be embedded at the END of that structure always,
1898  *    or things will break badly.
1899  */
1900 struct bio_set *bioset_create(unsigned int pool_size, unsigned int front_pad)
1901 {
1902         unsigned int back_pad = BIO_INLINE_VECS * sizeof(struct bio_vec);
1903         struct bio_set *bs;
1904 
1905         bs = kzalloc(sizeof(*bs), GFP_KERNEL);
1906         if (!bs)
1907                 return NULL;
1908 
1909         bs->front_pad = front_pad;
1910 
1911         spin_lock_init(&bs->rescue_lock);
1912         bio_list_init(&bs->rescue_list);
1913         INIT_WORK(&bs->rescue_work, bio_alloc_rescue);
1914 
1915         bs->bio_slab = bio_find_or_create_slab(front_pad + back_pad);
1916         if (!bs->bio_slab) {
1917                 kfree(bs);
1918                 return NULL;
1919         }
1920 
1921         bs->bio_pool = mempool_create_slab_pool(pool_size, bs->bio_slab);
1922         if (!bs->bio_pool)
1923                 goto bad;
1924 
1925         bs->bvec_pool = biovec_create_pool(bs, pool_size);
1926         if (!bs->bvec_pool)
1927                 goto bad;
1928 
1929         bs->rescue_workqueue = alloc_workqueue("bioset", WQ_MEM_RECLAIM, 0);
1930         if (!bs->rescue_workqueue)
1931                 goto bad;
1932 
1933         return bs;
1934 bad:
1935         bioset_free(bs);
1936         return NULL;
1937 }
1938 EXPORT_SYMBOL(bioset_create);
1939 
1940 #ifdef CONFIG_BLK_CGROUP
1941 /**
1942  * bio_associate_current - associate a bio with %current
1943  * @bio: target bio
1944  *
1945  * Associate @bio with %current if it hasn't been associated yet.  Block
1946  * layer will treat @bio as if it were issued by %current no matter which
1947  * task actually issues it.
1948  *
1949  * This function takes an extra reference of @task's io_context and blkcg
1950  * which will be put when @bio is released.  The caller must own @bio,
1951  * ensure %current->io_context exists, and is responsible for synchronizing
1952  * calls to this function.
1953  */
1954 int bio_associate_current(struct bio *bio)
1955 {
1956         struct io_context *ioc;
1957         struct cgroup_subsys_state *css;
1958 
1959         if (bio->bi_ioc)
1960                 return -EBUSY;
1961 
1962         ioc = current->io_context;
1963         if (!ioc)
1964                 return -ENOENT;
1965 
1966         /* acquire active ref on @ioc and associate */
1967         get_io_context_active(ioc);
1968         bio->bi_ioc = ioc;
1969 
1970         /* associate blkcg if exists */
1971         rcu_read_lock();
1972         css = task_css(current, blkio_cgrp_id);
1973         if (css && css_tryget(css))
1974                 bio->bi_css = css;
1975         rcu_read_unlock();
1976 
1977         return 0;
1978 }
1979 
1980 /**
1981  * bio_disassociate_task - undo bio_associate_current()
1982  * @bio: target bio
1983  */
1984 void bio_disassociate_task(struct bio *bio)
1985 {
1986         if (bio->bi_ioc) {
1987                 put_io_context(bio->bi_ioc);
1988                 bio->bi_ioc = NULL;
1989         }
1990         if (bio->bi_css) {
1991                 css_put(bio->bi_css);
1992                 bio->bi_css = NULL;
1993         }
1994 }
1995 
1996 #endif /* CONFIG_BLK_CGROUP */
1997 
1998 static void __init biovec_init_slabs(void)
1999 {
2000         int i;
2001 
2002         for (i = 0; i < BIOVEC_NR_POOLS; i++) {
2003                 int size;
2004                 struct biovec_slab *bvs = bvec_slabs + i;
2005 
2006                 if (bvs->nr_vecs <= BIO_INLINE_VECS) {
2007                         bvs->slab = NULL;
2008                         continue;
2009                 }
2010 
2011                 size = bvs->nr_vecs * sizeof(struct bio_vec);
2012                 bvs->slab = kmem_cache_create(bvs->name, size, 0,
2013                                 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
2014         }
2015 }
2016 
2017 static int __init init_bio(void)
2018 {
2019         bio_slab_max = 2;
2020         bio_slab_nr = 0;
2021         bio_slabs = kzalloc(bio_slab_max * sizeof(struct bio_slab), GFP_KERNEL);
2022         if (!bio_slabs)
2023                 panic("bio: can't allocate bios\n");
2024 
2025         bio_integrity_init();
2026         biovec_init_slabs();
2027 
2028         fs_bio_set = bioset_create(BIO_POOL_SIZE, 0);
2029         if (!fs_bio_set)
2030                 panic("bio: can't allocate bios\n");
2031 
2032         if (bioset_integrity_create(fs_bio_set, BIO_POOL_SIZE))
2033                 panic("bio: can't create integrity pool\n");
2034 
2035         return 0;
2036 }
2037 subsys_initcall(init_bio);
2038 

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