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TOMOYO Linux Cross Reference
Linux/block/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 
 32 #include <trace/events/block.h>
 33 
 34 /*
 35  * Test patch to inline a certain number of bi_io_vec's inside the bio
 36  * itself, to shrink a bio data allocation from two mempool calls to one
 37  */
 38 #define BIO_INLINE_VECS         4
 39 
 40 /*
 41  * if you change this list, also change bvec_alloc or things will
 42  * break badly! cannot be bigger than what you can fit into an
 43  * unsigned short
 44  */
 45 #define BV(x) { .nr_vecs = x, .name = "biovec-"__stringify(x) }
 46 static struct biovec_slab bvec_slabs[BIOVEC_NR_POOLS] __read_mostly = {
 47         BV(1), BV(4), BV(16), BV(64), BV(128), BV(BIO_MAX_PAGES),
 48 };
 49 #undef BV
 50 
 51 /*
 52  * fs_bio_set is the bio_set containing bio and iovec memory pools used by
 53  * IO code that does not need private memory pools.
 54  */
 55 struct bio_set *fs_bio_set;
 56 EXPORT_SYMBOL(fs_bio_set);
 57 
 58 /*
 59  * Our slab pool management
 60  */
 61 struct bio_slab {
 62         struct kmem_cache *slab;
 63         unsigned int slab_ref;
 64         unsigned int slab_size;
 65         char name[8];
 66 };
 67 static DEFINE_MUTEX(bio_slab_lock);
 68 static struct bio_slab *bio_slabs;
 69 static unsigned int bio_slab_nr, bio_slab_max;
 70 
 71 static struct kmem_cache *bio_find_or_create_slab(unsigned int extra_size)
 72 {
 73         unsigned int sz = sizeof(struct bio) + extra_size;
 74         struct kmem_cache *slab = NULL;
 75         struct bio_slab *bslab, *new_bio_slabs;
 76         unsigned int new_bio_slab_max;
 77         unsigned int i, entry = -1;
 78 
 79         mutex_lock(&bio_slab_lock);
 80 
 81         i = 0;
 82         while (i < bio_slab_nr) {
 83                 bslab = &bio_slabs[i];
 84 
 85                 if (!bslab->slab && entry == -1)
 86                         entry = i;
 87                 else if (bslab->slab_size == sz) {
 88                         slab = bslab->slab;
 89                         bslab->slab_ref++;
 90                         break;
 91                 }
 92                 i++;
 93         }
 94 
 95         if (slab)
 96                 goto out_unlock;
 97 
 98         if (bio_slab_nr == bio_slab_max && entry == -1) {
 99                 new_bio_slab_max = bio_slab_max << 1;
100                 new_bio_slabs = krealloc(bio_slabs,
101                                          new_bio_slab_max * sizeof(struct bio_slab),
102                                          GFP_KERNEL);
103                 if (!new_bio_slabs)
104                         goto out_unlock;
105                 bio_slab_max = new_bio_slab_max;
106                 bio_slabs = new_bio_slabs;
107         }
108         if (entry == -1)
109                 entry = bio_slab_nr++;
110 
111         bslab = &bio_slabs[entry];
112 
113         snprintf(bslab->name, sizeof(bslab->name), "bio-%d", entry);
114         slab = kmem_cache_create(bslab->name, sz, ARCH_KMALLOC_MINALIGN,
115                                  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_DIRECT_RECLAIM | __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_DIRECT_RECLAIM
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_DIRECT_RECLAIM))) {
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         atomic_set(&bio->__bi_remaining, 1);
273         atomic_set(&bio->__bi_cnt, 1);
274 }
275 EXPORT_SYMBOL(bio_init);
276 
277 /**
278  * bio_reset - reinitialize a bio
279  * @bio:        bio to reset
280  *
281  * Description:
282  *   After calling bio_reset(), @bio will be in the same state as a freshly
283  *   allocated bio returned bio bio_alloc_bioset() - the only fields that are
284  *   preserved are the ones that are initialized by bio_alloc_bioset(). See
285  *   comment in struct bio.
286  */
287 void bio_reset(struct bio *bio)
288 {
289         unsigned long flags = bio->bi_flags & (~0UL << BIO_RESET_BITS);
290 
291         __bio_free(bio);
292 
293         memset(bio, 0, BIO_RESET_BYTES);
294         bio->bi_flags = flags;
295         atomic_set(&bio->__bi_remaining, 1);
296 }
297 EXPORT_SYMBOL(bio_reset);
298 
299 static void bio_chain_endio(struct bio *bio)
300 {
301         struct bio *parent = bio->bi_private;
302 
303         parent->bi_error = bio->bi_error;
304         bio_endio(parent);
305         bio_put(bio);
306 }
307 
308 /*
309  * Increment chain count for the bio. Make sure the CHAIN flag update
310  * is visible before the raised count.
311  */
312 static inline void bio_inc_remaining(struct bio *bio)
313 {
314         bio_set_flag(bio, BIO_CHAIN);
315         smp_mb__before_atomic();
316         atomic_inc(&bio->__bi_remaining);
317 }
318 
319 /**
320  * bio_chain - chain bio completions
321  * @bio: the target bio
322  * @parent: the @bio's parent bio
323  *
324  * The caller won't have a bi_end_io called when @bio completes - instead,
325  * @parent's bi_end_io won't be called until both @parent and @bio have
326  * completed; the chained bio will also be freed when it completes.
327  *
328  * The caller must not set bi_private or bi_end_io in @bio.
329  */
330 void bio_chain(struct bio *bio, struct bio *parent)
331 {
332         BUG_ON(bio->bi_private || bio->bi_end_io);
333 
334         bio->bi_private = parent;
335         bio->bi_end_io  = bio_chain_endio;
336         bio_inc_remaining(parent);
337 }
338 EXPORT_SYMBOL(bio_chain);
339 
340 static void bio_alloc_rescue(struct work_struct *work)
341 {
342         struct bio_set *bs = container_of(work, struct bio_set, rescue_work);
343         struct bio *bio;
344 
345         while (1) {
346                 spin_lock(&bs->rescue_lock);
347                 bio = bio_list_pop(&bs->rescue_list);
348                 spin_unlock(&bs->rescue_lock);
349 
350                 if (!bio)
351                         break;
352 
353                 generic_make_request(bio);
354         }
355 }
356 
357 static void punt_bios_to_rescuer(struct bio_set *bs)
358 {
359         struct bio_list punt, nopunt;
360         struct bio *bio;
361 
362         /*
363          * In order to guarantee forward progress we must punt only bios that
364          * were allocated from this bio_set; otherwise, if there was a bio on
365          * there for a stacking driver higher up in the stack, processing it
366          * could require allocating bios from this bio_set, and doing that from
367          * our own rescuer would be bad.
368          *
369          * Since bio lists are singly linked, pop them all instead of trying to
370          * remove from the middle of the list:
371          */
372 
373         bio_list_init(&punt);
374         bio_list_init(&nopunt);
375 
376         while ((bio = bio_list_pop(current->bio_list)))
377                 bio_list_add(bio->bi_pool == bs ? &punt : &nopunt, bio);
378 
379         *current->bio_list = nopunt;
380 
381         spin_lock(&bs->rescue_lock);
382         bio_list_merge(&bs->rescue_list, &punt);
383         spin_unlock(&bs->rescue_lock);
384 
385         queue_work(bs->rescue_workqueue, &bs->rescue_work);
386 }
387 
388 /**
389  * bio_alloc_bioset - allocate a bio for I/O
390  * @gfp_mask:   the GFP_ mask given to the slab allocator
391  * @nr_iovecs:  number of iovecs to pre-allocate
392  * @bs:         the bio_set to allocate from.
393  *
394  * Description:
395  *   If @bs is NULL, uses kmalloc() to allocate the bio; else the allocation is
396  *   backed by the @bs's mempool.
397  *
398  *   When @bs is not NULL, if %__GFP_DIRECT_RECLAIM is set then bio_alloc will
399  *   always be able to allocate a bio. This is due to the mempool guarantees.
400  *   To make this work, callers must never allocate more than 1 bio at a time
401  *   from this pool. Callers that need to allocate more than 1 bio must always
402  *   submit the previously allocated bio for IO before attempting to allocate
403  *   a new one. Failure to do so can cause deadlocks under memory pressure.
404  *
405  *   Note that when running under generic_make_request() (i.e. any block
406  *   driver), bios are not submitted until after you return - see the code in
407  *   generic_make_request() that converts recursion into iteration, to prevent
408  *   stack overflows.
409  *
410  *   This would normally mean allocating multiple bios under
411  *   generic_make_request() would be susceptible to deadlocks, but we have
412  *   deadlock avoidance code that resubmits any blocked bios from a rescuer
413  *   thread.
414  *
415  *   However, we do not guarantee forward progress for allocations from other
416  *   mempools. Doing multiple allocations from the same mempool under
417  *   generic_make_request() should be avoided - instead, use bio_set's front_pad
418  *   for per bio allocations.
419  *
420  *   RETURNS:
421  *   Pointer to new bio on success, NULL on failure.
422  */
423 struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
424 {
425         gfp_t saved_gfp = gfp_mask;
426         unsigned front_pad;
427         unsigned inline_vecs;
428         unsigned long idx = BIO_POOL_NONE;
429         struct bio_vec *bvl = NULL;
430         struct bio *bio;
431         void *p;
432 
433         if (!bs) {
434                 if (nr_iovecs > UIO_MAXIOV)
435                         return NULL;
436 
437                 p = kmalloc(sizeof(struct bio) +
438                             nr_iovecs * sizeof(struct bio_vec),
439                             gfp_mask);
440                 front_pad = 0;
441                 inline_vecs = nr_iovecs;
442         } else {
443                 /* should not use nobvec bioset for nr_iovecs > 0 */
444                 if (WARN_ON_ONCE(!bs->bvec_pool && nr_iovecs > 0))
445                         return NULL;
446                 /*
447                  * generic_make_request() converts recursion to iteration; this
448                  * means if we're running beneath it, any bios we allocate and
449                  * submit will not be submitted (and thus freed) until after we
450                  * return.
451                  *
452                  * This exposes us to a potential deadlock if we allocate
453                  * multiple bios from the same bio_set() while running
454                  * underneath generic_make_request(). If we were to allocate
455                  * multiple bios (say a stacking block driver that was splitting
456                  * bios), we would deadlock if we exhausted the mempool's
457                  * reserve.
458                  *
459                  * We solve this, and guarantee forward progress, with a rescuer
460                  * workqueue per bio_set. If we go to allocate and there are
461                  * bios on current->bio_list, we first try the allocation
462                  * without __GFP_DIRECT_RECLAIM; if that fails, we punt those
463                  * bios we would be blocking to the rescuer workqueue before
464                  * we retry with the original gfp_flags.
465                  */
466 
467                 if (current->bio_list && !bio_list_empty(current->bio_list))
468                         gfp_mask &= ~__GFP_DIRECT_RECLAIM;
469 
470                 p = mempool_alloc(bs->bio_pool, gfp_mask);
471                 if (!p && gfp_mask != saved_gfp) {
472                         punt_bios_to_rescuer(bs);
473                         gfp_mask = saved_gfp;
474                         p = mempool_alloc(bs->bio_pool, gfp_mask);
475                 }
476 
477                 front_pad = bs->front_pad;
478                 inline_vecs = BIO_INLINE_VECS;
479         }
480 
481         if (unlikely(!p))
482                 return NULL;
483 
484         bio = p + front_pad;
485         bio_init(bio);
486 
487         if (nr_iovecs > inline_vecs) {
488                 bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx, bs->bvec_pool);
489                 if (!bvl && gfp_mask != saved_gfp) {
490                         punt_bios_to_rescuer(bs);
491                         gfp_mask = saved_gfp;
492                         bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx, bs->bvec_pool);
493                 }
494 
495                 if (unlikely(!bvl))
496                         goto err_free;
497 
498                 bio_set_flag(bio, BIO_OWNS_VEC);
499         } else if (nr_iovecs) {
500                 bvl = bio->bi_inline_vecs;
501         }
502 
503         bio->bi_pool = bs;
504         bio->bi_flags |= idx << BIO_POOL_OFFSET;
505         bio->bi_max_vecs = nr_iovecs;
506         bio->bi_io_vec = bvl;
507         return bio;
508 
509 err_free:
510         mempool_free(p, bs->bio_pool);
511         return NULL;
512 }
513 EXPORT_SYMBOL(bio_alloc_bioset);
514 
515 void zero_fill_bio(struct bio *bio)
516 {
517         unsigned long flags;
518         struct bio_vec bv;
519         struct bvec_iter iter;
520 
521         bio_for_each_segment(bv, bio, iter) {
522                 char *data = bvec_kmap_irq(&bv, &flags);
523                 memset(data, 0, bv.bv_len);
524                 flush_dcache_page(bv.bv_page);
525                 bvec_kunmap_irq(data, &flags);
526         }
527 }
528 EXPORT_SYMBOL(zero_fill_bio);
529 
530 /**
531  * bio_put - release a reference to a bio
532  * @bio:   bio to release reference to
533  *
534  * Description:
535  *   Put a reference to a &struct bio, either one you have gotten with
536  *   bio_alloc, bio_get or bio_clone. The last put of a bio will free it.
537  **/
538 void bio_put(struct bio *bio)
539 {
540         if (!bio_flagged(bio, BIO_REFFED))
541                 bio_free(bio);
542         else {
543                 BIO_BUG_ON(!atomic_read(&bio->__bi_cnt));
544 
545                 /*
546                  * last put frees it
547                  */
548                 if (atomic_dec_and_test(&bio->__bi_cnt))
549                         bio_free(bio);
550         }
551 }
552 EXPORT_SYMBOL(bio_put);
553 
554 inline int bio_phys_segments(struct request_queue *q, struct bio *bio)
555 {
556         if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
557                 blk_recount_segments(q, bio);
558 
559         return bio->bi_phys_segments;
560 }
561 EXPORT_SYMBOL(bio_phys_segments);
562 
563 /**
564  *      __bio_clone_fast - clone a bio that shares the original bio's biovec
565  *      @bio: destination bio
566  *      @bio_src: bio to clone
567  *
568  *      Clone a &bio. Caller will own the returned bio, but not
569  *      the actual data it points to. Reference count of returned
570  *      bio will be one.
571  *
572  *      Caller must ensure that @bio_src is not freed before @bio.
573  */
574 void __bio_clone_fast(struct bio *bio, struct bio *bio_src)
575 {
576         BUG_ON(bio->bi_pool && BIO_POOL_IDX(bio) != BIO_POOL_NONE);
577 
578         /*
579          * most users will be overriding ->bi_bdev with a new target,
580          * so we don't set nor calculate new physical/hw segment counts here
581          */
582         bio->bi_bdev = bio_src->bi_bdev;
583         bio_set_flag(bio, BIO_CLONED);
584         bio->bi_rw = bio_src->bi_rw;
585         bio->bi_iter = bio_src->bi_iter;
586         bio->bi_io_vec = bio_src->bi_io_vec;
587 }
588 EXPORT_SYMBOL(__bio_clone_fast);
589 
590 /**
591  *      bio_clone_fast - clone a bio that shares the original bio's biovec
592  *      @bio: bio to clone
593  *      @gfp_mask: allocation priority
594  *      @bs: bio_set to allocate from
595  *
596  *      Like __bio_clone_fast, only also allocates the returned bio
597  */
598 struct bio *bio_clone_fast(struct bio *bio, gfp_t gfp_mask, struct bio_set *bs)
599 {
600         struct bio *b;
601 
602         b = bio_alloc_bioset(gfp_mask, 0, bs);
603         if (!b)
604                 return NULL;
605 
606         __bio_clone_fast(b, bio);
607 
608         if (bio_integrity(bio)) {
609                 int ret;
610 
611                 ret = bio_integrity_clone(b, bio, gfp_mask);
612 
613                 if (ret < 0) {
614                         bio_put(b);
615                         return NULL;
616                 }
617         }
618 
619         return b;
620 }
621 EXPORT_SYMBOL(bio_clone_fast);
622 
623 /**
624  *      bio_clone_bioset - clone a bio
625  *      @bio_src: bio to clone
626  *      @gfp_mask: allocation priority
627  *      @bs: bio_set to allocate from
628  *
629  *      Clone bio. Caller will own the returned bio, but not the actual data it
630  *      points to. Reference count of returned bio will be one.
631  */
632 struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
633                              struct bio_set *bs)
634 {
635         struct bvec_iter iter;
636         struct bio_vec bv;
637         struct bio *bio;
638 
639         /*
640          * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
641          * bio_src->bi_io_vec to bio->bi_io_vec.
642          *
643          * We can't do that anymore, because:
644          *
645          *  - The point of cloning the biovec is to produce a bio with a biovec
646          *    the caller can modify: bi_idx and bi_bvec_done should be 0.
647          *
648          *  - The original bio could've had more than BIO_MAX_PAGES biovecs; if
649          *    we tried to clone the whole thing bio_alloc_bioset() would fail.
650          *    But the clone should succeed as long as the number of biovecs we
651          *    actually need to allocate is fewer than BIO_MAX_PAGES.
652          *
653          *  - Lastly, bi_vcnt should not be looked at or relied upon by code
654          *    that does not own the bio - reason being drivers don't use it for
655          *    iterating over the biovec anymore, so expecting it to be kept up
656          *    to date (i.e. for clones that share the parent biovec) is just
657          *    asking for trouble and would force extra work on
658          *    __bio_clone_fast() anyways.
659          */
660 
661         bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src), bs);
662         if (!bio)
663                 return NULL;
664 
665         bio->bi_bdev            = bio_src->bi_bdev;
666         bio->bi_rw              = bio_src->bi_rw;
667         bio->bi_iter.bi_sector  = bio_src->bi_iter.bi_sector;
668         bio->bi_iter.bi_size    = bio_src->bi_iter.bi_size;
669 
670         if (bio->bi_rw & REQ_DISCARD)
671                 goto integrity_clone;
672 
673         if (bio->bi_rw & REQ_WRITE_SAME) {
674                 bio->bi_io_vec[bio->bi_vcnt++] = bio_src->bi_io_vec[0];
675                 goto integrity_clone;
676         }
677 
678         bio_for_each_segment(bv, bio_src, iter)
679                 bio->bi_io_vec[bio->bi_vcnt++] = bv;
680 
681 integrity_clone:
682         if (bio_integrity(bio_src)) {
683                 int ret;
684 
685                 ret = bio_integrity_clone(bio, bio_src, gfp_mask);
686                 if (ret < 0) {
687                         bio_put(bio);
688                         return NULL;
689                 }
690         }
691 
692         return bio;
693 }
694 EXPORT_SYMBOL(bio_clone_bioset);
695 
696 /**
697  *      bio_add_pc_page -       attempt to add page to bio
698  *      @q: the target queue
699  *      @bio: destination bio
700  *      @page: page to add
701  *      @len: vec entry length
702  *      @offset: vec entry offset
703  *
704  *      Attempt to add a page to the bio_vec maplist. This can fail for a
705  *      number of reasons, such as the bio being full or target block device
706  *      limitations. The target block device must allow bio's up to PAGE_SIZE,
707  *      so it is always possible to add a single page to an empty bio.
708  *
709  *      This should only be used by REQ_PC bios.
710  */
711 int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page
712                     *page, unsigned int len, unsigned int offset)
713 {
714         int retried_segments = 0;
715         struct bio_vec *bvec;
716 
717         /*
718          * cloned bio must not modify vec list
719          */
720         if (unlikely(bio_flagged(bio, BIO_CLONED)))
721                 return 0;
722 
723         if (((bio->bi_iter.bi_size + len) >> 9) > queue_max_hw_sectors(q))
724                 return 0;
725 
726         /*
727          * For filesystems with a blocksize smaller than the pagesize
728          * we will often be called with the same page as last time and
729          * a consecutive offset.  Optimize this special case.
730          */
731         if (bio->bi_vcnt > 0) {
732                 struct bio_vec *prev = &bio->bi_io_vec[bio->bi_vcnt - 1];
733 
734                 if (page == prev->bv_page &&
735                     offset == prev->bv_offset + prev->bv_len) {
736                         prev->bv_len += len;
737                         bio->bi_iter.bi_size += len;
738                         goto done;
739                 }
740 
741                 /*
742                  * If the queue doesn't support SG gaps and adding this
743                  * offset would create a gap, disallow it.
744                  */
745                 if (bvec_gap_to_prev(q, prev, offset))
746                         return 0;
747         }
748 
749         if (bio->bi_vcnt >= bio->bi_max_vecs)
750                 return 0;
751 
752         /*
753          * setup the new entry, we might clear it again later if we
754          * cannot add the page
755          */
756         bvec = &bio->bi_io_vec[bio->bi_vcnt];
757         bvec->bv_page = page;
758         bvec->bv_len = len;
759         bvec->bv_offset = offset;
760         bio->bi_vcnt++;
761         bio->bi_phys_segments++;
762         bio->bi_iter.bi_size += len;
763 
764         /*
765          * Perform a recount if the number of segments is greater
766          * than queue_max_segments(q).
767          */
768 
769         while (bio->bi_phys_segments > queue_max_segments(q)) {
770 
771                 if (retried_segments)
772                         goto failed;
773 
774                 retried_segments = 1;
775                 blk_recount_segments(q, bio);
776         }
777 
778         /* If we may be able to merge these biovecs, force a recount */
779         if (bio->bi_vcnt > 1 && (BIOVEC_PHYS_MERGEABLE(bvec-1, bvec)))
780                 bio_clear_flag(bio, BIO_SEG_VALID);
781 
782  done:
783         return len;
784 
785  failed:
786         bvec->bv_page = NULL;
787         bvec->bv_len = 0;
788         bvec->bv_offset = 0;
789         bio->bi_vcnt--;
790         bio->bi_iter.bi_size -= len;
791         blk_recount_segments(q, bio);
792         return 0;
793 }
794 EXPORT_SYMBOL(bio_add_pc_page);
795 
796 /**
797  *      bio_add_page    -       attempt to add page to bio
798  *      @bio: destination bio
799  *      @page: page to add
800  *      @len: vec entry length
801  *      @offset: vec entry offset
802  *
803  *      Attempt to add a page to the bio_vec maplist. This will only fail
804  *      if either bio->bi_vcnt == bio->bi_max_vecs or it's a cloned bio.
805  */
806 int bio_add_page(struct bio *bio, struct page *page,
807                  unsigned int len, unsigned int offset)
808 {
809         struct bio_vec *bv;
810 
811         /*
812          * cloned bio must not modify vec list
813          */
814         if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
815                 return 0;
816 
817         /*
818          * For filesystems with a blocksize smaller than the pagesize
819          * we will often be called with the same page as last time and
820          * a consecutive offset.  Optimize this special case.
821          */
822         if (bio->bi_vcnt > 0) {
823                 bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
824 
825                 if (page == bv->bv_page &&
826                     offset == bv->bv_offset + bv->bv_len) {
827                         bv->bv_len += len;
828                         goto done;
829                 }
830         }
831 
832         if (bio->bi_vcnt >= bio->bi_max_vecs)
833                 return 0;
834 
835         bv              = &bio->bi_io_vec[bio->bi_vcnt];
836         bv->bv_page     = page;
837         bv->bv_len      = len;
838         bv->bv_offset   = offset;
839 
840         bio->bi_vcnt++;
841 done:
842         bio->bi_iter.bi_size += len;
843         return len;
844 }
845 EXPORT_SYMBOL(bio_add_page);
846 
847 struct submit_bio_ret {
848         struct completion event;
849         int error;
850 };
851 
852 static void submit_bio_wait_endio(struct bio *bio)
853 {
854         struct submit_bio_ret *ret = bio->bi_private;
855 
856         ret->error = bio->bi_error;
857         complete(&ret->event);
858 }
859 
860 /**
861  * submit_bio_wait - submit a bio, and wait until it completes
862  * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
863  * @bio: The &struct bio which describes the I/O
864  *
865  * Simple wrapper around submit_bio(). Returns 0 on success, or the error from
866  * bio_endio() on failure.
867  */
868 int submit_bio_wait(int rw, struct bio *bio)
869 {
870         struct submit_bio_ret ret;
871 
872         rw |= REQ_SYNC;
873         init_completion(&ret.event);
874         bio->bi_private = &ret;
875         bio->bi_end_io = submit_bio_wait_endio;
876         submit_bio(rw, bio);
877         wait_for_completion_io(&ret.event);
878 
879         return ret.error;
880 }
881 EXPORT_SYMBOL(submit_bio_wait);
882 
883 /**
884  * bio_advance - increment/complete a bio by some number of bytes
885  * @bio:        bio to advance
886  * @bytes:      number of bytes to complete
887  *
888  * This updates bi_sector, bi_size and bi_idx; if the number of bytes to
889  * complete doesn't align with a bvec boundary, then bv_len and bv_offset will
890  * be updated on the last bvec as well.
891  *
892  * @bio will then represent the remaining, uncompleted portion of the io.
893  */
894 void bio_advance(struct bio *bio, unsigned bytes)
895 {
896         if (bio_integrity(bio))
897                 bio_integrity_advance(bio, bytes);
898 
899         bio_advance_iter(bio, &bio->bi_iter, bytes);
900 }
901 EXPORT_SYMBOL(bio_advance);
902 
903 /**
904  * bio_alloc_pages - allocates a single page for each bvec in a bio
905  * @bio: bio to allocate pages for
906  * @gfp_mask: flags for allocation
907  *
908  * Allocates pages up to @bio->bi_vcnt.
909  *
910  * Returns 0 on success, -ENOMEM on failure. On failure, any allocated pages are
911  * freed.
912  */
913 int bio_alloc_pages(struct bio *bio, gfp_t gfp_mask)
914 {
915         int i;
916         struct bio_vec *bv;
917 
918         bio_for_each_segment_all(bv, bio, i) {
919                 bv->bv_page = alloc_page(gfp_mask);
920                 if (!bv->bv_page) {
921                         while (--bv >= bio->bi_io_vec)
922                                 __free_page(bv->bv_page);
923                         return -ENOMEM;
924                 }
925         }
926 
927         return 0;
928 }
929 EXPORT_SYMBOL(bio_alloc_pages);
930 
931 /**
932  * bio_copy_data - copy contents of data buffers from one chain of bios to
933  * another
934  * @src: source bio list
935  * @dst: destination bio list
936  *
937  * If @src and @dst are single bios, bi_next must be NULL - otherwise, treats
938  * @src and @dst as linked lists of bios.
939  *
940  * Stops when it reaches the end of either @src or @dst - that is, copies
941  * min(src->bi_size, dst->bi_size) bytes (or the equivalent for lists of bios).
942  */
943 void bio_copy_data(struct bio *dst, struct bio *src)
944 {
945         struct bvec_iter src_iter, dst_iter;
946         struct bio_vec src_bv, dst_bv;
947         void *src_p, *dst_p;
948         unsigned bytes;
949 
950         src_iter = src->bi_iter;
951         dst_iter = dst->bi_iter;
952 
953         while (1) {
954                 if (!src_iter.bi_size) {
955                         src = src->bi_next;
956                         if (!src)
957                                 break;
958 
959                         src_iter = src->bi_iter;
960                 }
961 
962                 if (!dst_iter.bi_size) {
963                         dst = dst->bi_next;
964                         if (!dst)
965                                 break;
966 
967                         dst_iter = dst->bi_iter;
968                 }
969 
970                 src_bv = bio_iter_iovec(src, src_iter);
971                 dst_bv = bio_iter_iovec(dst, dst_iter);
972 
973                 bytes = min(src_bv.bv_len, dst_bv.bv_len);
974 
975                 src_p = kmap_atomic(src_bv.bv_page);
976                 dst_p = kmap_atomic(dst_bv.bv_page);
977 
978                 memcpy(dst_p + dst_bv.bv_offset,
979                        src_p + src_bv.bv_offset,
980                        bytes);
981 
982                 kunmap_atomic(dst_p);
983                 kunmap_atomic(src_p);
984 
985                 bio_advance_iter(src, &src_iter, bytes);
986                 bio_advance_iter(dst, &dst_iter, bytes);
987         }
988 }
989 EXPORT_SYMBOL(bio_copy_data);
990 
991 struct bio_map_data {
992         int is_our_pages;
993         struct iov_iter iter;
994         struct iovec iov[];
995 };
996 
997 static struct bio_map_data *bio_alloc_map_data(unsigned int iov_count,
998                                                gfp_t gfp_mask)
999 {
1000         if (iov_count > UIO_MAXIOV)
1001                 return NULL;
1002 
1003         return kmalloc(sizeof(struct bio_map_data) +
1004                        sizeof(struct iovec) * iov_count, gfp_mask);
1005 }
1006 
1007 /**
1008  * bio_copy_from_iter - copy all pages from iov_iter to bio
1009  * @bio: The &struct bio which describes the I/O as destination
1010  * @iter: iov_iter as source
1011  *
1012  * Copy all pages from iov_iter to bio.
1013  * Returns 0 on success, or error on failure.
1014  */
1015 static int bio_copy_from_iter(struct bio *bio, struct iov_iter iter)
1016 {
1017         int i;
1018         struct bio_vec *bvec;
1019 
1020         bio_for_each_segment_all(bvec, bio, i) {
1021                 ssize_t ret;
1022 
1023                 ret = copy_page_from_iter(bvec->bv_page,
1024                                           bvec->bv_offset,
1025                                           bvec->bv_len,
1026                                           &iter);
1027 
1028                 if (!iov_iter_count(&iter))
1029                         break;
1030 
1031                 if (ret < bvec->bv_len)
1032                         return -EFAULT;
1033         }
1034 
1035         return 0;
1036 }
1037 
1038 /**
1039  * bio_copy_to_iter - copy all pages from bio to iov_iter
1040  * @bio: The &struct bio which describes the I/O as source
1041  * @iter: iov_iter as destination
1042  *
1043  * Copy all pages from bio to iov_iter.
1044  * Returns 0 on success, or error on failure.
1045  */
1046 static int bio_copy_to_iter(struct bio *bio, struct iov_iter iter)
1047 {
1048         int i;
1049         struct bio_vec *bvec;
1050 
1051         bio_for_each_segment_all(bvec, bio, i) {
1052                 ssize_t ret;
1053 
1054                 ret = copy_page_to_iter(bvec->bv_page,
1055                                         bvec->bv_offset,
1056                                         bvec->bv_len,
1057                                         &iter);
1058 
1059                 if (!iov_iter_count(&iter))
1060                         break;
1061 
1062                 if (ret < bvec->bv_len)
1063                         return -EFAULT;
1064         }
1065 
1066         return 0;
1067 }
1068 
1069 static void bio_free_pages(struct bio *bio)
1070 {
1071         struct bio_vec *bvec;
1072         int i;
1073 
1074         bio_for_each_segment_all(bvec, bio, i)
1075                 __free_page(bvec->bv_page);
1076 }
1077 
1078 /**
1079  *      bio_uncopy_user -       finish previously mapped bio
1080  *      @bio: bio being terminated
1081  *
1082  *      Free pages allocated from bio_copy_user_iov() and write back data
1083  *      to user space in case of a read.
1084  */
1085 int bio_uncopy_user(struct bio *bio)
1086 {
1087         struct bio_map_data *bmd = bio->bi_private;
1088         int ret = 0;
1089 
1090         if (!bio_flagged(bio, BIO_NULL_MAPPED)) {
1091                 /*
1092                  * if we're in a workqueue, the request is orphaned, so
1093                  * don't copy into a random user address space, just free
1094                  * and return -EINTR so user space doesn't expect any data.
1095                  */
1096                 if (!current->mm)
1097                         ret = -EINTR;
1098                 else if (bio_data_dir(bio) == READ)
1099                         ret = bio_copy_to_iter(bio, bmd->iter);
1100                 if (bmd->is_our_pages)
1101                         bio_free_pages(bio);
1102         }
1103         kfree(bmd);
1104         bio_put(bio);
1105         return ret;
1106 }
1107 EXPORT_SYMBOL(bio_uncopy_user);
1108 
1109 /**
1110  *      bio_copy_user_iov       -       copy user data to bio
1111  *      @q:             destination block queue
1112  *      @map_data:      pointer to the rq_map_data holding pages (if necessary)
1113  *      @iter:          iovec iterator
1114  *      @gfp_mask:      memory allocation flags
1115  *
1116  *      Prepares and returns a bio for indirect user io, bouncing data
1117  *      to/from kernel pages as necessary. Must be paired with
1118  *      call bio_uncopy_user() on io completion.
1119  */
1120 struct bio *bio_copy_user_iov(struct request_queue *q,
1121                               struct rq_map_data *map_data,
1122                               const struct iov_iter *iter,
1123                               gfp_t gfp_mask)
1124 {
1125         struct bio_map_data *bmd;
1126         struct page *page;
1127         struct bio *bio;
1128         int i, ret;
1129         int nr_pages = 0;
1130         unsigned int len = iter->count;
1131         unsigned int offset = map_data ? offset_in_page(map_data->offset) : 0;
1132 
1133         for (i = 0; i < iter->nr_segs; i++) {
1134                 unsigned long uaddr;
1135                 unsigned long end;
1136                 unsigned long start;
1137 
1138                 uaddr = (unsigned long) iter->iov[i].iov_base;
1139                 end = (uaddr + iter->iov[i].iov_len + PAGE_SIZE - 1)
1140                         >> PAGE_SHIFT;
1141                 start = uaddr >> PAGE_SHIFT;
1142 
1143                 /*
1144                  * Overflow, abort
1145                  */
1146                 if (end < start)
1147                         return ERR_PTR(-EINVAL);
1148 
1149                 nr_pages += end - start;
1150         }
1151 
1152         if (offset)
1153                 nr_pages++;
1154 
1155         bmd = bio_alloc_map_data(iter->nr_segs, gfp_mask);
1156         if (!bmd)
1157                 return ERR_PTR(-ENOMEM);
1158 
1159         /*
1160          * We need to do a deep copy of the iov_iter including the iovecs.
1161          * The caller provided iov might point to an on-stack or otherwise
1162          * shortlived one.
1163          */
1164         bmd->is_our_pages = map_data ? 0 : 1;
1165         memcpy(bmd->iov, iter->iov, sizeof(struct iovec) * iter->nr_segs);
1166         iov_iter_init(&bmd->iter, iter->type, bmd->iov,
1167                         iter->nr_segs, iter->count);
1168 
1169         ret = -ENOMEM;
1170         bio = bio_kmalloc(gfp_mask, nr_pages);
1171         if (!bio)
1172                 goto out_bmd;
1173 
1174         if (iter->type & WRITE)
1175                 bio->bi_rw |= REQ_WRITE;
1176 
1177         ret = 0;
1178 
1179         if (map_data) {
1180                 nr_pages = 1 << map_data->page_order;
1181                 i = map_data->offset / PAGE_SIZE;
1182         }
1183         while (len) {
1184                 unsigned int bytes = PAGE_SIZE;
1185 
1186                 bytes -= offset;
1187 
1188                 if (bytes > len)
1189                         bytes = len;
1190 
1191                 if (map_data) {
1192                         if (i == map_data->nr_entries * nr_pages) {
1193                                 ret = -ENOMEM;
1194                                 break;
1195                         }
1196 
1197                         page = map_data->pages[i / nr_pages];
1198                         page += (i % nr_pages);
1199 
1200                         i++;
1201                 } else {
1202                         page = alloc_page(q->bounce_gfp | gfp_mask);
1203                         if (!page) {
1204                                 ret = -ENOMEM;
1205                                 break;
1206                         }
1207                 }
1208 
1209                 if (bio_add_pc_page(q, bio, page, bytes, offset) < bytes)
1210                         break;
1211 
1212                 len -= bytes;
1213                 offset = 0;
1214         }
1215 
1216         if (ret)
1217                 goto cleanup;
1218 
1219         /*
1220          * success
1221          */
1222         if (((iter->type & WRITE) && (!map_data || !map_data->null_mapped)) ||
1223             (map_data && map_data->from_user)) {
1224                 ret = bio_copy_from_iter(bio, *iter);
1225                 if (ret)
1226                         goto cleanup;
1227         }
1228 
1229         bio->bi_private = bmd;
1230         return bio;
1231 cleanup:
1232         if (!map_data)
1233                 bio_free_pages(bio);
1234         bio_put(bio);
1235 out_bmd:
1236         kfree(bmd);
1237         return ERR_PTR(ret);
1238 }
1239 
1240 /**
1241  *      bio_map_user_iov - map user iovec into bio
1242  *      @q:             the struct request_queue for the bio
1243  *      @iter:          iovec iterator
1244  *      @gfp_mask:      memory allocation flags
1245  *
1246  *      Map the user space address into a bio suitable for io to a block
1247  *      device. Returns an error pointer in case of error.
1248  */
1249 struct bio *bio_map_user_iov(struct request_queue *q,
1250                              const struct iov_iter *iter,
1251                              gfp_t gfp_mask)
1252 {
1253         int j;
1254         int nr_pages = 0;
1255         struct page **pages;
1256         struct bio *bio;
1257         int cur_page = 0;
1258         int ret, offset;
1259         struct iov_iter i;
1260         struct iovec iov;
1261 
1262         iov_for_each(iov, i, *iter) {
1263                 unsigned long uaddr = (unsigned long) iov.iov_base;
1264                 unsigned long len = iov.iov_len;
1265                 unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1266                 unsigned long start = uaddr >> PAGE_SHIFT;
1267 
1268                 /*
1269                  * Overflow, abort
1270                  */
1271                 if (end < start)
1272                         return ERR_PTR(-EINVAL);
1273 
1274                 nr_pages += end - start;
1275                 /*
1276                  * buffer must be aligned to at least hardsector size for now
1277                  */
1278                 if (uaddr & queue_dma_alignment(q))
1279                         return ERR_PTR(-EINVAL);
1280         }
1281 
1282         if (!nr_pages)
1283                 return ERR_PTR(-EINVAL);
1284 
1285         bio = bio_kmalloc(gfp_mask, nr_pages);
1286         if (!bio)
1287                 return ERR_PTR(-ENOMEM);
1288 
1289         ret = -ENOMEM;
1290         pages = kcalloc(nr_pages, sizeof(struct page *), gfp_mask);
1291         if (!pages)
1292                 goto out;
1293 
1294         iov_for_each(iov, i, *iter) {
1295                 unsigned long uaddr = (unsigned long) iov.iov_base;
1296                 unsigned long len = iov.iov_len;
1297                 unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1298                 unsigned long start = uaddr >> PAGE_SHIFT;
1299                 const int local_nr_pages = end - start;
1300                 const int page_limit = cur_page + local_nr_pages;
1301 
1302                 ret = get_user_pages_fast(uaddr, local_nr_pages,
1303                                 (iter->type & WRITE) != WRITE,
1304                                 &pages[cur_page]);
1305                 if (ret < local_nr_pages) {
1306                         ret = -EFAULT;
1307                         goto out_unmap;
1308                 }
1309 
1310                 offset = offset_in_page(uaddr);
1311                 for (j = cur_page; j < page_limit; j++) {
1312                         unsigned int bytes = PAGE_SIZE - offset;
1313 
1314                         if (len <= 0)
1315                                 break;
1316                         
1317                         if (bytes > len)
1318                                 bytes = len;
1319 
1320                         /*
1321                          * sorry...
1322                          */
1323                         if (bio_add_pc_page(q, bio, pages[j], bytes, offset) <
1324                                             bytes)
1325                                 break;
1326 
1327                         len -= bytes;
1328                         offset = 0;
1329                 }
1330 
1331                 cur_page = j;
1332                 /*
1333                  * release the pages we didn't map into the bio, if any
1334                  */
1335                 while (j < page_limit)
1336                         page_cache_release(pages[j++]);
1337         }
1338 
1339         kfree(pages);
1340 
1341         /*
1342          * set data direction, and check if mapped pages need bouncing
1343          */
1344         if (iter->type & WRITE)
1345                 bio->bi_rw |= REQ_WRITE;
1346 
1347         bio_set_flag(bio, BIO_USER_MAPPED);
1348 
1349         /*
1350          * subtle -- if __bio_map_user() ended up bouncing a bio,
1351          * it would normally disappear when its bi_end_io is run.
1352          * however, we need it for the unmap, so grab an extra
1353          * reference to it
1354          */
1355         bio_get(bio);
1356         return bio;
1357 
1358  out_unmap:
1359         for (j = 0; j < nr_pages; j++) {
1360                 if (!pages[j])
1361                         break;
1362                 page_cache_release(pages[j]);
1363         }
1364  out:
1365         kfree(pages);
1366         bio_put(bio);
1367         return ERR_PTR(ret);
1368 }
1369 
1370 static void __bio_unmap_user(struct bio *bio)
1371 {
1372         struct bio_vec *bvec;
1373         int i;
1374 
1375         /*
1376          * make sure we dirty pages we wrote to
1377          */
1378         bio_for_each_segment_all(bvec, bio, i) {
1379                 if (bio_data_dir(bio) == READ)
1380                         set_page_dirty_lock(bvec->bv_page);
1381 
1382                 page_cache_release(bvec->bv_page);
1383         }
1384 
1385         bio_put(bio);
1386 }
1387 
1388 /**
1389  *      bio_unmap_user  -       unmap a bio
1390  *      @bio:           the bio being unmapped
1391  *
1392  *      Unmap a bio previously mapped by bio_map_user(). Must be called with
1393  *      a process context.
1394  *
1395  *      bio_unmap_user() may sleep.
1396  */
1397 void bio_unmap_user(struct bio *bio)
1398 {
1399         __bio_unmap_user(bio);
1400         bio_put(bio);
1401 }
1402 EXPORT_SYMBOL(bio_unmap_user);
1403 
1404 static void bio_map_kern_endio(struct bio *bio)
1405 {
1406         bio_put(bio);
1407 }
1408 
1409 /**
1410  *      bio_map_kern    -       map kernel address into bio
1411  *      @q: the struct request_queue for the bio
1412  *      @data: pointer to buffer to map
1413  *      @len: length in bytes
1414  *      @gfp_mask: allocation flags for bio allocation
1415  *
1416  *      Map the kernel address into a bio suitable for io to a block
1417  *      device. Returns an error pointer in case of error.
1418  */
1419 struct bio *bio_map_kern(struct request_queue *q, void *data, unsigned int len,
1420                          gfp_t gfp_mask)
1421 {
1422         unsigned long kaddr = (unsigned long)data;
1423         unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1424         unsigned long start = kaddr >> PAGE_SHIFT;
1425         const int nr_pages = end - start;
1426         int offset, i;
1427         struct bio *bio;
1428 
1429         bio = bio_kmalloc(gfp_mask, nr_pages);
1430         if (!bio)
1431                 return ERR_PTR(-ENOMEM);
1432 
1433         offset = offset_in_page(kaddr);
1434         for (i = 0; i < nr_pages; i++) {
1435                 unsigned int bytes = PAGE_SIZE - offset;
1436 
1437                 if (len <= 0)
1438                         break;
1439 
1440                 if (bytes > len)
1441                         bytes = len;
1442 
1443                 if (bio_add_pc_page(q, bio, virt_to_page(data), bytes,
1444                                     offset) < bytes) {
1445                         /* we don't support partial mappings */
1446                         bio_put(bio);
1447                         return ERR_PTR(-EINVAL);
1448                 }
1449 
1450                 data += bytes;
1451                 len -= bytes;
1452                 offset = 0;
1453         }
1454 
1455         bio->bi_end_io = bio_map_kern_endio;
1456         return bio;
1457 }
1458 EXPORT_SYMBOL(bio_map_kern);
1459 
1460 static void bio_copy_kern_endio(struct bio *bio)
1461 {
1462         bio_free_pages(bio);
1463         bio_put(bio);
1464 }
1465 
1466 static void bio_copy_kern_endio_read(struct bio *bio)
1467 {
1468         char *p = bio->bi_private;
1469         struct bio_vec *bvec;
1470         int i;
1471 
1472         bio_for_each_segment_all(bvec, bio, i) {
1473                 memcpy(p, page_address(bvec->bv_page), bvec->bv_len);
1474                 p += bvec->bv_len;
1475         }
1476 
1477         bio_copy_kern_endio(bio);
1478 }
1479 
1480 /**
1481  *      bio_copy_kern   -       copy kernel address into bio
1482  *      @q: the struct request_queue for the bio
1483  *      @data: pointer to buffer to copy
1484  *      @len: length in bytes
1485  *      @gfp_mask: allocation flags for bio and page allocation
1486  *      @reading: data direction is READ
1487  *
1488  *      copy the kernel address into a bio suitable for io to a block
1489  *      device. Returns an error pointer in case of error.
1490  */
1491 struct bio *bio_copy_kern(struct request_queue *q, void *data, unsigned int len,
1492                           gfp_t gfp_mask, int reading)
1493 {
1494         unsigned long kaddr = (unsigned long)data;
1495         unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1496         unsigned long start = kaddr >> PAGE_SHIFT;
1497         struct bio *bio;
1498         void *p = data;
1499         int nr_pages = 0;
1500 
1501         /*
1502          * Overflow, abort
1503          */
1504         if (end < start)
1505                 return ERR_PTR(-EINVAL);
1506 
1507         nr_pages = end - start;
1508         bio = bio_kmalloc(gfp_mask, nr_pages);
1509         if (!bio)
1510                 return ERR_PTR(-ENOMEM);
1511 
1512         while (len) {
1513                 struct page *page;
1514                 unsigned int bytes = PAGE_SIZE;
1515 
1516                 if (bytes > len)
1517                         bytes = len;
1518 
1519                 page = alloc_page(q->bounce_gfp | gfp_mask);
1520                 if (!page)
1521                         goto cleanup;
1522 
1523                 if (!reading)
1524                         memcpy(page_address(page), p, bytes);
1525 
1526                 if (bio_add_pc_page(q, bio, page, bytes, 0) < bytes)
1527                         break;
1528 
1529                 len -= bytes;
1530                 p += bytes;
1531         }
1532 
1533         if (reading) {
1534                 bio->bi_end_io = bio_copy_kern_endio_read;
1535                 bio->bi_private = data;
1536         } else {
1537                 bio->bi_end_io = bio_copy_kern_endio;
1538                 bio->bi_rw |= REQ_WRITE;
1539         }
1540 
1541         return bio;
1542 
1543 cleanup:
1544         bio_free_pages(bio);
1545         bio_put(bio);
1546         return ERR_PTR(-ENOMEM);
1547 }
1548 EXPORT_SYMBOL(bio_copy_kern);
1549 
1550 /*
1551  * bio_set_pages_dirty() and bio_check_pages_dirty() are support functions
1552  * for performing direct-IO in BIOs.
1553  *
1554  * The problem is that we cannot run set_page_dirty() from interrupt context
1555  * because the required locks are not interrupt-safe.  So what we can do is to
1556  * mark the pages dirty _before_ performing IO.  And in interrupt context,
1557  * check that the pages are still dirty.   If so, fine.  If not, redirty them
1558  * in process context.
1559  *
1560  * We special-case compound pages here: normally this means reads into hugetlb
1561  * pages.  The logic in here doesn't really work right for compound pages
1562  * because the VM does not uniformly chase down the head page in all cases.
1563  * But dirtiness of compound pages is pretty meaningless anyway: the VM doesn't
1564  * handle them at all.  So we skip compound pages here at an early stage.
1565  *
1566  * Note that this code is very hard to test under normal circumstances because
1567  * direct-io pins the pages with get_user_pages().  This makes
1568  * is_page_cache_freeable return false, and the VM will not clean the pages.
1569  * But other code (eg, flusher threads) could clean the pages if they are mapped
1570  * pagecache.
1571  *
1572  * Simply disabling the call to bio_set_pages_dirty() is a good way to test the
1573  * deferred bio dirtying paths.
1574  */
1575 
1576 /*
1577  * bio_set_pages_dirty() will mark all the bio's pages as dirty.
1578  */
1579 void bio_set_pages_dirty(struct bio *bio)
1580 {
1581         struct bio_vec *bvec;
1582         int i;
1583 
1584         bio_for_each_segment_all(bvec, bio, i) {
1585                 struct page *page = bvec->bv_page;
1586 
1587                 if (page && !PageCompound(page))
1588                         set_page_dirty_lock(page);
1589         }
1590 }
1591 
1592 static void bio_release_pages(struct bio *bio)
1593 {
1594         struct bio_vec *bvec;
1595         int i;
1596 
1597         bio_for_each_segment_all(bvec, bio, i) {
1598                 struct page *page = bvec->bv_page;
1599 
1600                 if (page)
1601                         put_page(page);
1602         }
1603 }
1604 
1605 /*
1606  * bio_check_pages_dirty() will check that all the BIO's pages are still dirty.
1607  * If they are, then fine.  If, however, some pages are clean then they must
1608  * have been written out during the direct-IO read.  So we take another ref on
1609  * the BIO and the offending pages and re-dirty the pages in process context.
1610  *
1611  * It is expected that bio_check_pages_dirty() will wholly own the BIO from
1612  * here on.  It will run one page_cache_release() against each page and will
1613  * run one bio_put() against the BIO.
1614  */
1615 
1616 static void bio_dirty_fn(struct work_struct *work);
1617 
1618 static DECLARE_WORK(bio_dirty_work, bio_dirty_fn);
1619 static DEFINE_SPINLOCK(bio_dirty_lock);
1620 static struct bio *bio_dirty_list;
1621 
1622 /*
1623  * This runs in process context
1624  */
1625 static void bio_dirty_fn(struct work_struct *work)
1626 {
1627         unsigned long flags;
1628         struct bio *bio;
1629 
1630         spin_lock_irqsave(&bio_dirty_lock, flags);
1631         bio = bio_dirty_list;
1632         bio_dirty_list = NULL;
1633         spin_unlock_irqrestore(&bio_dirty_lock, flags);
1634 
1635         while (bio) {
1636                 struct bio *next = bio->bi_private;
1637 
1638                 bio_set_pages_dirty(bio);
1639                 bio_release_pages(bio);
1640                 bio_put(bio);
1641                 bio = next;
1642         }
1643 }
1644 
1645 void bio_check_pages_dirty(struct bio *bio)
1646 {
1647         struct bio_vec *bvec;
1648         int nr_clean_pages = 0;
1649         int i;
1650 
1651         bio_for_each_segment_all(bvec, bio, i) {
1652                 struct page *page = bvec->bv_page;
1653 
1654                 if (PageDirty(page) || PageCompound(page)) {
1655                         page_cache_release(page);
1656                         bvec->bv_page = NULL;
1657                 } else {
1658                         nr_clean_pages++;
1659                 }
1660         }
1661 
1662         if (nr_clean_pages) {
1663                 unsigned long flags;
1664 
1665                 spin_lock_irqsave(&bio_dirty_lock, flags);
1666                 bio->bi_private = bio_dirty_list;
1667                 bio_dirty_list = bio;
1668                 spin_unlock_irqrestore(&bio_dirty_lock, flags);
1669                 schedule_work(&bio_dirty_work);
1670         } else {
1671                 bio_put(bio);
1672         }
1673 }
1674 
1675 void generic_start_io_acct(int rw, unsigned long sectors,
1676                            struct hd_struct *part)
1677 {
1678         int cpu = part_stat_lock();
1679 
1680         part_round_stats(cpu, part);
1681         part_stat_inc(cpu, part, ios[rw]);
1682         part_stat_add(cpu, part, sectors[rw], sectors);
1683         part_inc_in_flight(part, rw);
1684 
1685         part_stat_unlock();
1686 }
1687 EXPORT_SYMBOL(generic_start_io_acct);
1688 
1689 void generic_end_io_acct(int rw, struct hd_struct *part,
1690                          unsigned long start_time)
1691 {
1692         unsigned long duration = jiffies - start_time;
1693         int cpu = part_stat_lock();
1694 
1695         part_stat_add(cpu, part, ticks[rw], duration);
1696         part_round_stats(cpu, part);
1697         part_dec_in_flight(part, rw);
1698 
1699         part_stat_unlock();
1700 }
1701 EXPORT_SYMBOL(generic_end_io_acct);
1702 
1703 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
1704 void bio_flush_dcache_pages(struct bio *bi)
1705 {
1706         struct bio_vec bvec;
1707         struct bvec_iter iter;
1708 
1709         bio_for_each_segment(bvec, bi, iter)
1710                 flush_dcache_page(bvec.bv_page);
1711 }
1712 EXPORT_SYMBOL(bio_flush_dcache_pages);
1713 #endif
1714 
1715 static inline bool bio_remaining_done(struct bio *bio)
1716 {
1717         /*
1718          * If we're not chaining, then ->__bi_remaining is always 1 and
1719          * we always end io on the first invocation.
1720          */
1721         if (!bio_flagged(bio, BIO_CHAIN))
1722                 return true;
1723 
1724         BUG_ON(atomic_read(&bio->__bi_remaining) <= 0);
1725 
1726         if (atomic_dec_and_test(&bio->__bi_remaining)) {
1727                 bio_clear_flag(bio, BIO_CHAIN);
1728                 return true;
1729         }
1730 
1731         return false;
1732 }
1733 
1734 /**
1735  * bio_endio - end I/O on a bio
1736  * @bio:        bio
1737  *
1738  * Description:
1739  *   bio_endio() will end I/O on the whole bio. bio_endio() is the preferred
1740  *   way to end I/O on a bio. No one should call bi_end_io() directly on a
1741  *   bio unless they own it and thus know that it has an end_io function.
1742  **/
1743 void bio_endio(struct bio *bio)
1744 {
1745         while (bio) {
1746                 if (unlikely(!bio_remaining_done(bio)))
1747                         break;
1748 
1749                 /*
1750                  * Need to have a real endio function for chained bios,
1751                  * otherwise various corner cases will break (like stacking
1752                  * block devices that save/restore bi_end_io) - however, we want
1753                  * to avoid unbounded recursion and blowing the stack. Tail call
1754                  * optimization would handle this, but compiling with frame
1755                  * pointers also disables gcc's sibling call optimization.
1756                  */
1757                 if (bio->bi_end_io == bio_chain_endio) {
1758                         struct bio *parent = bio->bi_private;
1759                         parent->bi_error = bio->bi_error;
1760                         bio_put(bio);
1761                         bio = parent;
1762                 } else {
1763                         if (bio->bi_end_io)
1764                                 bio->bi_end_io(bio);
1765                         bio = NULL;
1766                 }
1767         }
1768 }
1769 EXPORT_SYMBOL(bio_endio);
1770 
1771 /**
1772  * bio_split - split a bio
1773  * @bio:        bio to split
1774  * @sectors:    number of sectors to split from the front of @bio
1775  * @gfp:        gfp mask
1776  * @bs:         bio set to allocate from
1777  *
1778  * Allocates and returns a new bio which represents @sectors from the start of
1779  * @bio, and updates @bio to represent the remaining sectors.
1780  *
1781  * Unless this is a discard request the newly allocated bio will point
1782  * to @bio's bi_io_vec; it is the caller's responsibility to ensure that
1783  * @bio is not freed before the split.
1784  */
1785 struct bio *bio_split(struct bio *bio, int sectors,
1786                       gfp_t gfp, struct bio_set *bs)
1787 {
1788         struct bio *split = NULL;
1789 
1790         BUG_ON(sectors <= 0);
1791         BUG_ON(sectors >= bio_sectors(bio));
1792 
1793         /*
1794          * Discards need a mutable bio_vec to accommodate the payload
1795          * required by the DSM TRIM and UNMAP commands.
1796          */
1797         if (bio->bi_rw & REQ_DISCARD)
1798                 split = bio_clone_bioset(bio, gfp, bs);
1799         else
1800                 split = bio_clone_fast(bio, gfp, bs);
1801 
1802         if (!split)
1803                 return NULL;
1804 
1805         split->bi_iter.bi_size = sectors << 9;
1806 
1807         if (bio_integrity(split))
1808                 bio_integrity_trim(split, 0, sectors);
1809 
1810         bio_advance(bio, split->bi_iter.bi_size);
1811 
1812         return split;
1813 }
1814 EXPORT_SYMBOL(bio_split);
1815 
1816 /**
1817  * bio_trim - trim a bio
1818  * @bio:        bio to trim
1819  * @offset:     number of sectors to trim from the front of @bio
1820  * @size:       size we want to trim @bio to, in sectors
1821  */
1822 void bio_trim(struct bio *bio, int offset, int size)
1823 {
1824         /* 'bio' is a cloned bio which we need to trim to match
1825          * the given offset and size.
1826          */
1827 
1828         size <<= 9;
1829         if (offset == 0 && size == bio->bi_iter.bi_size)
1830                 return;
1831 
1832         bio_clear_flag(bio, BIO_SEG_VALID);
1833 
1834         bio_advance(bio, offset << 9);
1835 
1836         bio->bi_iter.bi_size = size;
1837 }
1838 EXPORT_SYMBOL_GPL(bio_trim);
1839 
1840 /*
1841  * create memory pools for biovec's in a bio_set.
1842  * use the global biovec slabs created for general use.
1843  */
1844 mempool_t *biovec_create_pool(int pool_entries)
1845 {
1846         struct biovec_slab *bp = bvec_slabs + BIOVEC_MAX_IDX;
1847 
1848         return mempool_create_slab_pool(pool_entries, bp->slab);
1849 }
1850 
1851 void bioset_free(struct bio_set *bs)
1852 {
1853         if (bs->rescue_workqueue)
1854                 destroy_workqueue(bs->rescue_workqueue);
1855 
1856         if (bs->bio_pool)
1857                 mempool_destroy(bs->bio_pool);
1858 
1859         if (bs->bvec_pool)
1860                 mempool_destroy(bs->bvec_pool);
1861 
1862         bioset_integrity_free(bs);
1863         bio_put_slab(bs);
1864 
1865         kfree(bs);
1866 }
1867 EXPORT_SYMBOL(bioset_free);
1868 
1869 static struct bio_set *__bioset_create(unsigned int pool_size,
1870                                        unsigned int front_pad,
1871                                        bool create_bvec_pool)
1872 {
1873         unsigned int back_pad = BIO_INLINE_VECS * sizeof(struct bio_vec);
1874         struct bio_set *bs;
1875 
1876         bs = kzalloc(sizeof(*bs), GFP_KERNEL);
1877         if (!bs)
1878                 return NULL;
1879 
1880         bs->front_pad = front_pad;
1881 
1882         spin_lock_init(&bs->rescue_lock);
1883         bio_list_init(&bs->rescue_list);
1884         INIT_WORK(&bs->rescue_work, bio_alloc_rescue);
1885 
1886         bs->bio_slab = bio_find_or_create_slab(front_pad + back_pad);
1887         if (!bs->bio_slab) {
1888                 kfree(bs);
1889                 return NULL;
1890         }
1891 
1892         bs->bio_pool = mempool_create_slab_pool(pool_size, bs->bio_slab);
1893         if (!bs->bio_pool)
1894                 goto bad;
1895 
1896         if (create_bvec_pool) {
1897                 bs->bvec_pool = biovec_create_pool(pool_size);
1898                 if (!bs->bvec_pool)
1899                         goto bad;
1900         }
1901 
1902         bs->rescue_workqueue = alloc_workqueue("bioset", WQ_MEM_RECLAIM, 0);
1903         if (!bs->rescue_workqueue)
1904                 goto bad;
1905 
1906         return bs;
1907 bad:
1908         bioset_free(bs);
1909         return NULL;
1910 }
1911 
1912 /**
1913  * bioset_create  - Create a bio_set
1914  * @pool_size:  Number of bio and bio_vecs to cache in the mempool
1915  * @front_pad:  Number of bytes to allocate in front of the returned bio
1916  *
1917  * Description:
1918  *    Set up a bio_set to be used with @bio_alloc_bioset. Allows the caller
1919  *    to ask for a number of bytes to be allocated in front of the bio.
1920  *    Front pad allocation is useful for embedding the bio inside
1921  *    another structure, to avoid allocating extra data to go with the bio.
1922  *    Note that the bio must be embedded at the END of that structure always,
1923  *    or things will break badly.
1924  */
1925 struct bio_set *bioset_create(unsigned int pool_size, unsigned int front_pad)
1926 {
1927         return __bioset_create(pool_size, front_pad, true);
1928 }
1929 EXPORT_SYMBOL(bioset_create);
1930 
1931 /**
1932  * bioset_create_nobvec  - Create a bio_set without bio_vec mempool
1933  * @pool_size:  Number of bio to cache in the mempool
1934  * @front_pad:  Number of bytes to allocate in front of the returned bio
1935  *
1936  * Description:
1937  *    Same functionality as bioset_create() except that mempool is not
1938  *    created for bio_vecs. Saving some memory for bio_clone_fast() users.
1939  */
1940 struct bio_set *bioset_create_nobvec(unsigned int pool_size, unsigned int front_pad)
1941 {
1942         return __bioset_create(pool_size, front_pad, false);
1943 }
1944 EXPORT_SYMBOL(bioset_create_nobvec);
1945 
1946 #ifdef CONFIG_BLK_CGROUP
1947 
1948 /**
1949  * bio_associate_blkcg - associate a bio with the specified blkcg
1950  * @bio: target bio
1951  * @blkcg_css: css of the blkcg to associate
1952  *
1953  * Associate @bio with the blkcg specified by @blkcg_css.  Block layer will
1954  * treat @bio as if it were issued by a task which belongs to the blkcg.
1955  *
1956  * This function takes an extra reference of @blkcg_css which will be put
1957  * when @bio is released.  The caller must own @bio and is responsible for
1958  * synchronizing calls to this function.
1959  */
1960 int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css)
1961 {
1962         if (unlikely(bio->bi_css))
1963                 return -EBUSY;
1964         css_get(blkcg_css);
1965         bio->bi_css = blkcg_css;
1966         return 0;
1967 }
1968 EXPORT_SYMBOL_GPL(bio_associate_blkcg);
1969 
1970 /**
1971  * bio_associate_current - associate a bio with %current
1972  * @bio: target bio
1973  *
1974  * Associate @bio with %current if it hasn't been associated yet.  Block
1975  * layer will treat @bio as if it were issued by %current no matter which
1976  * task actually issues it.
1977  *
1978  * This function takes an extra reference of @task's io_context and blkcg
1979  * which will be put when @bio is released.  The caller must own @bio,
1980  * ensure %current->io_context exists, and is responsible for synchronizing
1981  * calls to this function.
1982  */
1983 int bio_associate_current(struct bio *bio)
1984 {
1985         struct io_context *ioc;
1986 
1987         if (bio->bi_css)
1988                 return -EBUSY;
1989 
1990         ioc = current->io_context;
1991         if (!ioc)
1992                 return -ENOENT;
1993 
1994         get_io_context_active(ioc);
1995         bio->bi_ioc = ioc;
1996         bio->bi_css = task_get_css(current, io_cgrp_id);
1997         return 0;
1998 }
1999 EXPORT_SYMBOL_GPL(bio_associate_current);
2000 
2001 /**
2002  * bio_disassociate_task - undo bio_associate_current()
2003  * @bio: target bio
2004  */
2005 void bio_disassociate_task(struct bio *bio)
2006 {
2007         if (bio->bi_ioc) {
2008                 put_io_context(bio->bi_ioc);
2009                 bio->bi_ioc = NULL;
2010         }
2011         if (bio->bi_css) {
2012                 css_put(bio->bi_css);
2013                 bio->bi_css = NULL;
2014         }
2015 }
2016 
2017 #endif /* CONFIG_BLK_CGROUP */
2018 
2019 static void __init biovec_init_slabs(void)
2020 {
2021         int i;
2022 
2023         for (i = 0; i < BIOVEC_NR_POOLS; i++) {
2024                 int size;
2025                 struct biovec_slab *bvs = bvec_slabs + i;
2026 
2027                 if (bvs->nr_vecs <= BIO_INLINE_VECS) {
2028                         bvs->slab = NULL;
2029                         continue;
2030                 }
2031 
2032                 size = bvs->nr_vecs * sizeof(struct bio_vec);
2033                 bvs->slab = kmem_cache_create(bvs->name, size, 0,
2034                                 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
2035         }
2036 }
2037 
2038 static int __init init_bio(void)
2039 {
2040         bio_slab_max = 2;
2041         bio_slab_nr = 0;
2042         bio_slabs = kzalloc(bio_slab_max * sizeof(struct bio_slab), GFP_KERNEL);
2043         if (!bio_slabs)
2044                 panic("bio: can't allocate bios\n");
2045 
2046         bio_integrity_init();
2047         biovec_init_slabs();
2048 
2049         fs_bio_set = bioset_create(BIO_POOL_SIZE, 0);
2050         if (!fs_bio_set)
2051                 panic("bio: can't allocate bios\n");
2052 
2053         if (bioset_integrity_create(fs_bio_set, BIO_POOL_SIZE))
2054                 panic("bio: can't create integrity pool\n");
2055 
2056         return 0;
2057 }
2058 subsys_initcall(init_bio);
2059 

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