xref: /openbmc/linux/block/bio.c (revision d2999e1b)
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  * @bio: the target bio
309  * @parent: the @bio's parent bio
310  *
311  * The caller won't have a bi_end_io called when @bio completes - instead,
312  * @parent's bi_end_io won't be called until both @parent and @bio have
313  * completed; the chained bio will also be freed when it completes.
314  *
315  * The caller must not set bi_private or bi_end_io in @bio.
316  */
317 void bio_chain(struct bio *bio, struct bio *parent)
318 {
319 	BUG_ON(bio->bi_private || bio->bi_end_io);
320 
321 	bio->bi_private = parent;
322 	bio->bi_end_io	= bio_chain_endio;
323 	atomic_inc(&parent->bi_remaining);
324 }
325 EXPORT_SYMBOL(bio_chain);
326 
327 static void bio_alloc_rescue(struct work_struct *work)
328 {
329 	struct bio_set *bs = container_of(work, struct bio_set, rescue_work);
330 	struct bio *bio;
331 
332 	while (1) {
333 		spin_lock(&bs->rescue_lock);
334 		bio = bio_list_pop(&bs->rescue_list);
335 		spin_unlock(&bs->rescue_lock);
336 
337 		if (!bio)
338 			break;
339 
340 		generic_make_request(bio);
341 	}
342 }
343 
344 static void punt_bios_to_rescuer(struct bio_set *bs)
345 {
346 	struct bio_list punt, nopunt;
347 	struct bio *bio;
348 
349 	/*
350 	 * In order to guarantee forward progress we must punt only bios that
351 	 * were allocated from this bio_set; otherwise, if there was a bio on
352 	 * there for a stacking driver higher up in the stack, processing it
353 	 * could require allocating bios from this bio_set, and doing that from
354 	 * our own rescuer would be bad.
355 	 *
356 	 * Since bio lists are singly linked, pop them all instead of trying to
357 	 * remove from the middle of the list:
358 	 */
359 
360 	bio_list_init(&punt);
361 	bio_list_init(&nopunt);
362 
363 	while ((bio = bio_list_pop(current->bio_list)))
364 		bio_list_add(bio->bi_pool == bs ? &punt : &nopunt, bio);
365 
366 	*current->bio_list = nopunt;
367 
368 	spin_lock(&bs->rescue_lock);
369 	bio_list_merge(&bs->rescue_list, &punt);
370 	spin_unlock(&bs->rescue_lock);
371 
372 	queue_work(bs->rescue_workqueue, &bs->rescue_work);
373 }
374 
375 /**
376  * bio_alloc_bioset - allocate a bio for I/O
377  * @gfp_mask:   the GFP_ mask given to the slab allocator
378  * @nr_iovecs:	number of iovecs to pre-allocate
379  * @bs:		the bio_set to allocate from.
380  *
381  * Description:
382  *   If @bs is NULL, uses kmalloc() to allocate the bio; else the allocation is
383  *   backed by the @bs's mempool.
384  *
385  *   When @bs is not NULL, if %__GFP_WAIT is set then bio_alloc will always be
386  *   able to allocate a bio. This is due to the mempool guarantees. To make this
387  *   work, callers must never allocate more than 1 bio at a time from this pool.
388  *   Callers that need to allocate more than 1 bio must always submit the
389  *   previously allocated bio for IO before attempting to allocate a new one.
390  *   Failure to do so can cause deadlocks under memory pressure.
391  *
392  *   Note that when running under generic_make_request() (i.e. any block
393  *   driver), bios are not submitted until after you return - see the code in
394  *   generic_make_request() that converts recursion into iteration, to prevent
395  *   stack overflows.
396  *
397  *   This would normally mean allocating multiple bios under
398  *   generic_make_request() would be susceptible to deadlocks, but we have
399  *   deadlock avoidance code that resubmits any blocked bios from a rescuer
400  *   thread.
401  *
402  *   However, we do not guarantee forward progress for allocations from other
403  *   mempools. Doing multiple allocations from the same mempool under
404  *   generic_make_request() should be avoided - instead, use bio_set's front_pad
405  *   for per bio allocations.
406  *
407  *   RETURNS:
408  *   Pointer to new bio on success, NULL on failure.
409  */
410 struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
411 {
412 	gfp_t saved_gfp = gfp_mask;
413 	unsigned front_pad;
414 	unsigned inline_vecs;
415 	unsigned long idx = BIO_POOL_NONE;
416 	struct bio_vec *bvl = NULL;
417 	struct bio *bio;
418 	void *p;
419 
420 	if (!bs) {
421 		if (nr_iovecs > UIO_MAXIOV)
422 			return NULL;
423 
424 		p = kmalloc(sizeof(struct bio) +
425 			    nr_iovecs * sizeof(struct bio_vec),
426 			    gfp_mask);
427 		front_pad = 0;
428 		inline_vecs = nr_iovecs;
429 	} else {
430 		/*
431 		 * generic_make_request() converts recursion to iteration; this
432 		 * means if we're running beneath it, any bios we allocate and
433 		 * submit will not be submitted (and thus freed) until after we
434 		 * return.
435 		 *
436 		 * This exposes us to a potential deadlock if we allocate
437 		 * multiple bios from the same bio_set() while running
438 		 * underneath generic_make_request(). If we were to allocate
439 		 * multiple bios (say a stacking block driver that was splitting
440 		 * bios), we would deadlock if we exhausted the mempool's
441 		 * reserve.
442 		 *
443 		 * We solve this, and guarantee forward progress, with a rescuer
444 		 * workqueue per bio_set. If we go to allocate and there are
445 		 * bios on current->bio_list, we first try the allocation
446 		 * without __GFP_WAIT; if that fails, we punt those bios we
447 		 * would be blocking to the rescuer workqueue before we retry
448 		 * with the original gfp_flags.
449 		 */
450 
451 		if (current->bio_list && !bio_list_empty(current->bio_list))
452 			gfp_mask &= ~__GFP_WAIT;
453 
454 		p = mempool_alloc(bs->bio_pool, gfp_mask);
455 		if (!p && gfp_mask != saved_gfp) {
456 			punt_bios_to_rescuer(bs);
457 			gfp_mask = saved_gfp;
458 			p = mempool_alloc(bs->bio_pool, gfp_mask);
459 		}
460 
461 		front_pad = bs->front_pad;
462 		inline_vecs = BIO_INLINE_VECS;
463 	}
464 
465 	if (unlikely(!p))
466 		return NULL;
467 
468 	bio = p + front_pad;
469 	bio_init(bio);
470 
471 	if (nr_iovecs > inline_vecs) {
472 		bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx, bs->bvec_pool);
473 		if (!bvl && gfp_mask != saved_gfp) {
474 			punt_bios_to_rescuer(bs);
475 			gfp_mask = saved_gfp;
476 			bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx, bs->bvec_pool);
477 		}
478 
479 		if (unlikely(!bvl))
480 			goto err_free;
481 
482 		bio->bi_flags |= 1 << BIO_OWNS_VEC;
483 	} else if (nr_iovecs) {
484 		bvl = bio->bi_inline_vecs;
485 	}
486 
487 	bio->bi_pool = bs;
488 	bio->bi_flags |= idx << BIO_POOL_OFFSET;
489 	bio->bi_max_vecs = nr_iovecs;
490 	bio->bi_io_vec = bvl;
491 	return bio;
492 
493 err_free:
494 	mempool_free(p, bs->bio_pool);
495 	return NULL;
496 }
497 EXPORT_SYMBOL(bio_alloc_bioset);
498 
499 void zero_fill_bio(struct bio *bio)
500 {
501 	unsigned long flags;
502 	struct bio_vec bv;
503 	struct bvec_iter iter;
504 
505 	bio_for_each_segment(bv, bio, iter) {
506 		char *data = bvec_kmap_irq(&bv, &flags);
507 		memset(data, 0, bv.bv_len);
508 		flush_dcache_page(bv.bv_page);
509 		bvec_kunmap_irq(data, &flags);
510 	}
511 }
512 EXPORT_SYMBOL(zero_fill_bio);
513 
514 /**
515  * bio_put - release a reference to a bio
516  * @bio:   bio to release reference to
517  *
518  * Description:
519  *   Put a reference to a &struct bio, either one you have gotten with
520  *   bio_alloc, bio_get or bio_clone. The last put of a bio will free it.
521  **/
522 void bio_put(struct bio *bio)
523 {
524 	BIO_BUG_ON(!atomic_read(&bio->bi_cnt));
525 
526 	/*
527 	 * last put frees it
528 	 */
529 	if (atomic_dec_and_test(&bio->bi_cnt))
530 		bio_free(bio);
531 }
532 EXPORT_SYMBOL(bio_put);
533 
534 inline int bio_phys_segments(struct request_queue *q, struct bio *bio)
535 {
536 	if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
537 		blk_recount_segments(q, bio);
538 
539 	return bio->bi_phys_segments;
540 }
541 EXPORT_SYMBOL(bio_phys_segments);
542 
543 /**
544  * 	__bio_clone_fast - clone a bio that shares the original bio's biovec
545  * 	@bio: destination bio
546  * 	@bio_src: bio to clone
547  *
548  *	Clone a &bio. Caller will own the returned bio, but not
549  *	the actual data it points to. Reference count of returned
550  * 	bio will be one.
551  *
552  * 	Caller must ensure that @bio_src is not freed before @bio.
553  */
554 void __bio_clone_fast(struct bio *bio, struct bio *bio_src)
555 {
556 	BUG_ON(bio->bi_pool && BIO_POOL_IDX(bio) != BIO_POOL_NONE);
557 
558 	/*
559 	 * most users will be overriding ->bi_bdev with a new target,
560 	 * so we don't set nor calculate new physical/hw segment counts here
561 	 */
562 	bio->bi_bdev = bio_src->bi_bdev;
563 	bio->bi_flags |= 1 << BIO_CLONED;
564 	bio->bi_rw = bio_src->bi_rw;
565 	bio->bi_iter = bio_src->bi_iter;
566 	bio->bi_io_vec = bio_src->bi_io_vec;
567 }
568 EXPORT_SYMBOL(__bio_clone_fast);
569 
570 /**
571  *	bio_clone_fast - clone a bio that shares the original bio's biovec
572  *	@bio: bio to clone
573  *	@gfp_mask: allocation priority
574  *	@bs: bio_set to allocate from
575  *
576  * 	Like __bio_clone_fast, only also allocates the returned bio
577  */
578 struct bio *bio_clone_fast(struct bio *bio, gfp_t gfp_mask, struct bio_set *bs)
579 {
580 	struct bio *b;
581 
582 	b = bio_alloc_bioset(gfp_mask, 0, bs);
583 	if (!b)
584 		return NULL;
585 
586 	__bio_clone_fast(b, bio);
587 
588 	if (bio_integrity(bio)) {
589 		int ret;
590 
591 		ret = bio_integrity_clone(b, bio, gfp_mask);
592 
593 		if (ret < 0) {
594 			bio_put(b);
595 			return NULL;
596 		}
597 	}
598 
599 	return b;
600 }
601 EXPORT_SYMBOL(bio_clone_fast);
602 
603 /**
604  * 	bio_clone_bioset - clone a bio
605  * 	@bio_src: bio to clone
606  *	@gfp_mask: allocation priority
607  *	@bs: bio_set to allocate from
608  *
609  *	Clone bio. Caller will own the returned bio, but not the actual data it
610  *	points to. Reference count of returned bio will be one.
611  */
612 struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
613 			     struct bio_set *bs)
614 {
615 	struct bvec_iter iter;
616 	struct bio_vec bv;
617 	struct bio *bio;
618 
619 	/*
620 	 * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
621 	 * bio_src->bi_io_vec to bio->bi_io_vec.
622 	 *
623 	 * We can't do that anymore, because:
624 	 *
625 	 *  - The point of cloning the biovec is to produce a bio with a biovec
626 	 *    the caller can modify: bi_idx and bi_bvec_done should be 0.
627 	 *
628 	 *  - The original bio could've had more than BIO_MAX_PAGES biovecs; if
629 	 *    we tried to clone the whole thing bio_alloc_bioset() would fail.
630 	 *    But the clone should succeed as long as the number of biovecs we
631 	 *    actually need to allocate is fewer than BIO_MAX_PAGES.
632 	 *
633 	 *  - Lastly, bi_vcnt should not be looked at or relied upon by code
634 	 *    that does not own the bio - reason being drivers don't use it for
635 	 *    iterating over the biovec anymore, so expecting it to be kept up
636 	 *    to date (i.e. for clones that share the parent biovec) is just
637 	 *    asking for trouble and would force extra work on
638 	 *    __bio_clone_fast() anyways.
639 	 */
640 
641 	bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src), bs);
642 	if (!bio)
643 		return NULL;
644 
645 	bio->bi_bdev		= bio_src->bi_bdev;
646 	bio->bi_rw		= bio_src->bi_rw;
647 	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
648 	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;
649 
650 	if (bio->bi_rw & REQ_DISCARD)
651 		goto integrity_clone;
652 
653 	if (bio->bi_rw & REQ_WRITE_SAME) {
654 		bio->bi_io_vec[bio->bi_vcnt++] = bio_src->bi_io_vec[0];
655 		goto integrity_clone;
656 	}
657 
658 	bio_for_each_segment(bv, bio_src, iter)
659 		bio->bi_io_vec[bio->bi_vcnt++] = bv;
660 
661 integrity_clone:
662 	if (bio_integrity(bio_src)) {
663 		int ret;
664 
665 		ret = bio_integrity_clone(bio, bio_src, gfp_mask);
666 		if (ret < 0) {
667 			bio_put(bio);
668 			return NULL;
669 		}
670 	}
671 
672 	return bio;
673 }
674 EXPORT_SYMBOL(bio_clone_bioset);
675 
676 /**
677  *	bio_get_nr_vecs		- return approx number of vecs
678  *	@bdev:  I/O target
679  *
680  *	Return the approximate number of pages we can send to this target.
681  *	There's no guarantee that you will be able to fit this number of pages
682  *	into a bio, it does not account for dynamic restrictions that vary
683  *	on offset.
684  */
685 int bio_get_nr_vecs(struct block_device *bdev)
686 {
687 	struct request_queue *q = bdev_get_queue(bdev);
688 	int nr_pages;
689 
690 	nr_pages = min_t(unsigned,
691 		     queue_max_segments(q),
692 		     queue_max_sectors(q) / (PAGE_SIZE >> 9) + 1);
693 
694 	return min_t(unsigned, nr_pages, BIO_MAX_PAGES);
695 
696 }
697 EXPORT_SYMBOL(bio_get_nr_vecs);
698 
699 static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
700 			  *page, unsigned int len, unsigned int offset,
701 			  unsigned int max_sectors)
702 {
703 	int retried_segments = 0;
704 	struct bio_vec *bvec;
705 
706 	/*
707 	 * cloned bio must not modify vec list
708 	 */
709 	if (unlikely(bio_flagged(bio, BIO_CLONED)))
710 		return 0;
711 
712 	if (((bio->bi_iter.bi_size + len) >> 9) > max_sectors)
713 		return 0;
714 
715 	/*
716 	 * For filesystems with a blocksize smaller than the pagesize
717 	 * we will often be called with the same page as last time and
718 	 * a consecutive offset.  Optimize this special case.
719 	 */
720 	if (bio->bi_vcnt > 0) {
721 		struct bio_vec *prev = &bio->bi_io_vec[bio->bi_vcnt - 1];
722 
723 		if (page == prev->bv_page &&
724 		    offset == prev->bv_offset + prev->bv_len) {
725 			unsigned int prev_bv_len = prev->bv_len;
726 			prev->bv_len += len;
727 
728 			if (q->merge_bvec_fn) {
729 				struct bvec_merge_data bvm = {
730 					/* prev_bvec is already charged in
731 					   bi_size, discharge it in order to
732 					   simulate merging updated prev_bvec
733 					   as new bvec. */
734 					.bi_bdev = bio->bi_bdev,
735 					.bi_sector = bio->bi_iter.bi_sector,
736 					.bi_size = bio->bi_iter.bi_size -
737 						prev_bv_len,
738 					.bi_rw = bio->bi_rw,
739 				};
740 
741 				if (q->merge_bvec_fn(q, &bvm, prev) < prev->bv_len) {
742 					prev->bv_len -= len;
743 					return 0;
744 				}
745 			}
746 
747 			goto done;
748 		}
749 
750 		/*
751 		 * If the queue doesn't support SG gaps and adding this
752 		 * offset would create a gap, disallow it.
753 		 */
754 		if (q->queue_flags & (1 << QUEUE_FLAG_SG_GAPS) &&
755 		    bvec_gap_to_prev(prev, offset))
756 			return 0;
757 	}
758 
759 	if (bio->bi_vcnt >= bio->bi_max_vecs)
760 		return 0;
761 
762 	/*
763 	 * we might lose a segment or two here, but rather that than
764 	 * make this too complex.
765 	 */
766 
767 	while (bio->bi_phys_segments >= queue_max_segments(q)) {
768 
769 		if (retried_segments)
770 			return 0;
771 
772 		retried_segments = 1;
773 		blk_recount_segments(q, bio);
774 	}
775 
776 	/*
777 	 * setup the new entry, we might clear it again later if we
778 	 * cannot add the page
779 	 */
780 	bvec = &bio->bi_io_vec[bio->bi_vcnt];
781 	bvec->bv_page = page;
782 	bvec->bv_len = len;
783 	bvec->bv_offset = offset;
784 
785 	/*
786 	 * if queue has other restrictions (eg varying max sector size
787 	 * depending on offset), it can specify a merge_bvec_fn in the
788 	 * queue to get further control
789 	 */
790 	if (q->merge_bvec_fn) {
791 		struct bvec_merge_data bvm = {
792 			.bi_bdev = bio->bi_bdev,
793 			.bi_sector = bio->bi_iter.bi_sector,
794 			.bi_size = bio->bi_iter.bi_size,
795 			.bi_rw = bio->bi_rw,
796 		};
797 
798 		/*
799 		 * merge_bvec_fn() returns number of bytes it can accept
800 		 * at this offset
801 		 */
802 		if (q->merge_bvec_fn(q, &bvm, bvec) < bvec->bv_len) {
803 			bvec->bv_page = NULL;
804 			bvec->bv_len = 0;
805 			bvec->bv_offset = 0;
806 			return 0;
807 		}
808 	}
809 
810 	/* If we may be able to merge these biovecs, force a recount */
811 	if (bio->bi_vcnt && (BIOVEC_PHYS_MERGEABLE(bvec-1, bvec)))
812 		bio->bi_flags &= ~(1 << BIO_SEG_VALID);
813 
814 	bio->bi_vcnt++;
815 	bio->bi_phys_segments++;
816  done:
817 	bio->bi_iter.bi_size += len;
818 	return len;
819 }
820 
821 /**
822  *	bio_add_pc_page	-	attempt to add page to bio
823  *	@q: the target queue
824  *	@bio: destination bio
825  *	@page: page to add
826  *	@len: vec entry length
827  *	@offset: vec entry offset
828  *
829  *	Attempt to add a page to the bio_vec maplist. This can fail for a
830  *	number of reasons, such as the bio being full or target block device
831  *	limitations. The target block device must allow bio's up to PAGE_SIZE,
832  *	so it is always possible to add a single page to an empty bio.
833  *
834  *	This should only be used by REQ_PC bios.
835  */
836 int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page *page,
837 		    unsigned int len, unsigned int offset)
838 {
839 	return __bio_add_page(q, bio, page, len, offset,
840 			      queue_max_hw_sectors(q));
841 }
842 EXPORT_SYMBOL(bio_add_pc_page);
843 
844 /**
845  *	bio_add_page	-	attempt to add page to bio
846  *	@bio: destination bio
847  *	@page: page to add
848  *	@len: vec entry length
849  *	@offset: vec entry offset
850  *
851  *	Attempt to add a page to the bio_vec maplist. This can fail for a
852  *	number of reasons, such as the bio being full or target block device
853  *	limitations. The target block device must allow bio's up to PAGE_SIZE,
854  *	so it is always possible to add a single page to an empty bio.
855  */
856 int bio_add_page(struct bio *bio, struct page *page, unsigned int len,
857 		 unsigned int offset)
858 {
859 	struct request_queue *q = bdev_get_queue(bio->bi_bdev);
860 	unsigned int max_sectors;
861 
862 	max_sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
863 	if ((max_sectors < (len >> 9)) && !bio->bi_iter.bi_size)
864 		max_sectors = len >> 9;
865 
866 	return __bio_add_page(q, bio, page, len, offset, max_sectors);
867 }
868 EXPORT_SYMBOL(bio_add_page);
869 
870 struct submit_bio_ret {
871 	struct completion event;
872 	int error;
873 };
874 
875 static void submit_bio_wait_endio(struct bio *bio, int error)
876 {
877 	struct submit_bio_ret *ret = bio->bi_private;
878 
879 	ret->error = error;
880 	complete(&ret->event);
881 }
882 
883 /**
884  * submit_bio_wait - submit a bio, and wait until it completes
885  * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
886  * @bio: The &struct bio which describes the I/O
887  *
888  * Simple wrapper around submit_bio(). Returns 0 on success, or the error from
889  * bio_endio() on failure.
890  */
891 int submit_bio_wait(int rw, struct bio *bio)
892 {
893 	struct submit_bio_ret ret;
894 
895 	rw |= REQ_SYNC;
896 	init_completion(&ret.event);
897 	bio->bi_private = &ret;
898 	bio->bi_end_io = submit_bio_wait_endio;
899 	submit_bio(rw, bio);
900 	wait_for_completion(&ret.event);
901 
902 	return ret.error;
903 }
904 EXPORT_SYMBOL(submit_bio_wait);
905 
906 /**
907  * bio_advance - increment/complete a bio by some number of bytes
908  * @bio:	bio to advance
909  * @bytes:	number of bytes to complete
910  *
911  * This updates bi_sector, bi_size and bi_idx; if the number of bytes to
912  * complete doesn't align with a bvec boundary, then bv_len and bv_offset will
913  * be updated on the last bvec as well.
914  *
915  * @bio will then represent the remaining, uncompleted portion of the io.
916  */
917 void bio_advance(struct bio *bio, unsigned bytes)
918 {
919 	if (bio_integrity(bio))
920 		bio_integrity_advance(bio, bytes);
921 
922 	bio_advance_iter(bio, &bio->bi_iter, bytes);
923 }
924 EXPORT_SYMBOL(bio_advance);
925 
926 /**
927  * bio_alloc_pages - allocates a single page for each bvec in a bio
928  * @bio: bio to allocate pages for
929  * @gfp_mask: flags for allocation
930  *
931  * Allocates pages up to @bio->bi_vcnt.
932  *
933  * Returns 0 on success, -ENOMEM on failure. On failure, any allocated pages are
934  * freed.
935  */
936 int bio_alloc_pages(struct bio *bio, gfp_t gfp_mask)
937 {
938 	int i;
939 	struct bio_vec *bv;
940 
941 	bio_for_each_segment_all(bv, bio, i) {
942 		bv->bv_page = alloc_page(gfp_mask);
943 		if (!bv->bv_page) {
944 			while (--bv >= bio->bi_io_vec)
945 				__free_page(bv->bv_page);
946 			return -ENOMEM;
947 		}
948 	}
949 
950 	return 0;
951 }
952 EXPORT_SYMBOL(bio_alloc_pages);
953 
954 /**
955  * bio_copy_data - copy contents of data buffers from one chain of bios to
956  * another
957  * @src: source bio list
958  * @dst: destination bio list
959  *
960  * If @src and @dst are single bios, bi_next must be NULL - otherwise, treats
961  * @src and @dst as linked lists of bios.
962  *
963  * Stops when it reaches the end of either @src or @dst - that is, copies
964  * min(src->bi_size, dst->bi_size) bytes (or the equivalent for lists of bios).
965  */
966 void bio_copy_data(struct bio *dst, struct bio *src)
967 {
968 	struct bvec_iter src_iter, dst_iter;
969 	struct bio_vec src_bv, dst_bv;
970 	void *src_p, *dst_p;
971 	unsigned bytes;
972 
973 	src_iter = src->bi_iter;
974 	dst_iter = dst->bi_iter;
975 
976 	while (1) {
977 		if (!src_iter.bi_size) {
978 			src = src->bi_next;
979 			if (!src)
980 				break;
981 
982 			src_iter = src->bi_iter;
983 		}
984 
985 		if (!dst_iter.bi_size) {
986 			dst = dst->bi_next;
987 			if (!dst)
988 				break;
989 
990 			dst_iter = dst->bi_iter;
991 		}
992 
993 		src_bv = bio_iter_iovec(src, src_iter);
994 		dst_bv = bio_iter_iovec(dst, dst_iter);
995 
996 		bytes = min(src_bv.bv_len, dst_bv.bv_len);
997 
998 		src_p = kmap_atomic(src_bv.bv_page);
999 		dst_p = kmap_atomic(dst_bv.bv_page);
1000 
1001 		memcpy(dst_p + dst_bv.bv_offset,
1002 		       src_p + src_bv.bv_offset,
1003 		       bytes);
1004 
1005 		kunmap_atomic(dst_p);
1006 		kunmap_atomic(src_p);
1007 
1008 		bio_advance_iter(src, &src_iter, bytes);
1009 		bio_advance_iter(dst, &dst_iter, bytes);
1010 	}
1011 }
1012 EXPORT_SYMBOL(bio_copy_data);
1013 
1014 struct bio_map_data {
1015 	int nr_sgvecs;
1016 	int is_our_pages;
1017 	struct sg_iovec sgvecs[];
1018 };
1019 
1020 static void bio_set_map_data(struct bio_map_data *bmd, struct bio *bio,
1021 			     const struct sg_iovec *iov, int iov_count,
1022 			     int is_our_pages)
1023 {
1024 	memcpy(bmd->sgvecs, iov, sizeof(struct sg_iovec) * iov_count);
1025 	bmd->nr_sgvecs = iov_count;
1026 	bmd->is_our_pages = is_our_pages;
1027 	bio->bi_private = bmd;
1028 }
1029 
1030 static struct bio_map_data *bio_alloc_map_data(unsigned int iov_count,
1031 					       gfp_t gfp_mask)
1032 {
1033 	if (iov_count > UIO_MAXIOV)
1034 		return NULL;
1035 
1036 	return kmalloc(sizeof(struct bio_map_data) +
1037 		       sizeof(struct sg_iovec) * iov_count, gfp_mask);
1038 }
1039 
1040 static int __bio_copy_iov(struct bio *bio, const struct sg_iovec *iov, int iov_count,
1041 			  int to_user, int from_user, int do_free_page)
1042 {
1043 	int ret = 0, i;
1044 	struct bio_vec *bvec;
1045 	int iov_idx = 0;
1046 	unsigned int iov_off = 0;
1047 
1048 	bio_for_each_segment_all(bvec, bio, i) {
1049 		char *bv_addr = page_address(bvec->bv_page);
1050 		unsigned int bv_len = bvec->bv_len;
1051 
1052 		while (bv_len && iov_idx < iov_count) {
1053 			unsigned int bytes;
1054 			char __user *iov_addr;
1055 
1056 			bytes = min_t(unsigned int,
1057 				      iov[iov_idx].iov_len - iov_off, bv_len);
1058 			iov_addr = iov[iov_idx].iov_base + iov_off;
1059 
1060 			if (!ret) {
1061 				if (to_user)
1062 					ret = copy_to_user(iov_addr, bv_addr,
1063 							   bytes);
1064 
1065 				if (from_user)
1066 					ret = copy_from_user(bv_addr, iov_addr,
1067 							     bytes);
1068 
1069 				if (ret)
1070 					ret = -EFAULT;
1071 			}
1072 
1073 			bv_len -= bytes;
1074 			bv_addr += bytes;
1075 			iov_addr += bytes;
1076 			iov_off += bytes;
1077 
1078 			if (iov[iov_idx].iov_len == iov_off) {
1079 				iov_idx++;
1080 				iov_off = 0;
1081 			}
1082 		}
1083 
1084 		if (do_free_page)
1085 			__free_page(bvec->bv_page);
1086 	}
1087 
1088 	return ret;
1089 }
1090 
1091 /**
1092  *	bio_uncopy_user	-	finish previously mapped bio
1093  *	@bio: bio being terminated
1094  *
1095  *	Free pages allocated from bio_copy_user() and write back data
1096  *	to user space in case of a read.
1097  */
1098 int bio_uncopy_user(struct bio *bio)
1099 {
1100 	struct bio_map_data *bmd = bio->bi_private;
1101 	struct bio_vec *bvec;
1102 	int ret = 0, i;
1103 
1104 	if (!bio_flagged(bio, BIO_NULL_MAPPED)) {
1105 		/*
1106 		 * if we're in a workqueue, the request is orphaned, so
1107 		 * don't copy into a random user address space, just free.
1108 		 */
1109 		if (current->mm)
1110 			ret = __bio_copy_iov(bio, bmd->sgvecs, bmd->nr_sgvecs,
1111 					     bio_data_dir(bio) == READ,
1112 					     0, bmd->is_our_pages);
1113 		else if (bmd->is_our_pages)
1114 			bio_for_each_segment_all(bvec, bio, i)
1115 				__free_page(bvec->bv_page);
1116 	}
1117 	kfree(bmd);
1118 	bio_put(bio);
1119 	return ret;
1120 }
1121 EXPORT_SYMBOL(bio_uncopy_user);
1122 
1123 /**
1124  *	bio_copy_user_iov	-	copy user data to bio
1125  *	@q: destination block queue
1126  *	@map_data: pointer to the rq_map_data holding pages (if necessary)
1127  *	@iov:	the iovec.
1128  *	@iov_count: number of elements in the iovec
1129  *	@write_to_vm: bool indicating writing to pages or not
1130  *	@gfp_mask: memory allocation flags
1131  *
1132  *	Prepares and returns a bio for indirect user io, bouncing data
1133  *	to/from kernel pages as necessary. Must be paired with
1134  *	call bio_uncopy_user() on io completion.
1135  */
1136 struct bio *bio_copy_user_iov(struct request_queue *q,
1137 			      struct rq_map_data *map_data,
1138 			      const struct sg_iovec *iov, int iov_count,
1139 			      int write_to_vm, gfp_t gfp_mask)
1140 {
1141 	struct bio_map_data *bmd;
1142 	struct bio_vec *bvec;
1143 	struct page *page;
1144 	struct bio *bio;
1145 	int i, ret;
1146 	int nr_pages = 0;
1147 	unsigned int len = 0;
1148 	unsigned int offset = map_data ? map_data->offset & ~PAGE_MASK : 0;
1149 
1150 	for (i = 0; i < iov_count; i++) {
1151 		unsigned long uaddr;
1152 		unsigned long end;
1153 		unsigned long start;
1154 
1155 		uaddr = (unsigned long)iov[i].iov_base;
1156 		end = (uaddr + iov[i].iov_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1157 		start = uaddr >> PAGE_SHIFT;
1158 
1159 		/*
1160 		 * Overflow, abort
1161 		 */
1162 		if (end < start)
1163 			return ERR_PTR(-EINVAL);
1164 
1165 		nr_pages += end - start;
1166 		len += iov[i].iov_len;
1167 	}
1168 
1169 	if (offset)
1170 		nr_pages++;
1171 
1172 	bmd = bio_alloc_map_data(iov_count, gfp_mask);
1173 	if (!bmd)
1174 		return ERR_PTR(-ENOMEM);
1175 
1176 	ret = -ENOMEM;
1177 	bio = bio_kmalloc(gfp_mask, nr_pages);
1178 	if (!bio)
1179 		goto out_bmd;
1180 
1181 	if (!write_to_vm)
1182 		bio->bi_rw |= REQ_WRITE;
1183 
1184 	ret = 0;
1185 
1186 	if (map_data) {
1187 		nr_pages = 1 << map_data->page_order;
1188 		i = map_data->offset / PAGE_SIZE;
1189 	}
1190 	while (len) {
1191 		unsigned int bytes = PAGE_SIZE;
1192 
1193 		bytes -= offset;
1194 
1195 		if (bytes > len)
1196 			bytes = len;
1197 
1198 		if (map_data) {
1199 			if (i == map_data->nr_entries * nr_pages) {
1200 				ret = -ENOMEM;
1201 				break;
1202 			}
1203 
1204 			page = map_data->pages[i / nr_pages];
1205 			page += (i % nr_pages);
1206 
1207 			i++;
1208 		} else {
1209 			page = alloc_page(q->bounce_gfp | gfp_mask);
1210 			if (!page) {
1211 				ret = -ENOMEM;
1212 				break;
1213 			}
1214 		}
1215 
1216 		if (bio_add_pc_page(q, bio, page, bytes, offset) < bytes)
1217 			break;
1218 
1219 		len -= bytes;
1220 		offset = 0;
1221 	}
1222 
1223 	if (ret)
1224 		goto cleanup;
1225 
1226 	/*
1227 	 * success
1228 	 */
1229 	if ((!write_to_vm && (!map_data || !map_data->null_mapped)) ||
1230 	    (map_data && map_data->from_user)) {
1231 		ret = __bio_copy_iov(bio, iov, iov_count, 0, 1, 0);
1232 		if (ret)
1233 			goto cleanup;
1234 	}
1235 
1236 	bio_set_map_data(bmd, bio, iov, iov_count, map_data ? 0 : 1);
1237 	return bio;
1238 cleanup:
1239 	if (!map_data)
1240 		bio_for_each_segment_all(bvec, bio, i)
1241 			__free_page(bvec->bv_page);
1242 
1243 	bio_put(bio);
1244 out_bmd:
1245 	kfree(bmd);
1246 	return ERR_PTR(ret);
1247 }
1248 
1249 /**
1250  *	bio_copy_user	-	copy user data to bio
1251  *	@q: destination block queue
1252  *	@map_data: pointer to the rq_map_data holding pages (if necessary)
1253  *	@uaddr: start of user address
1254  *	@len: length in bytes
1255  *	@write_to_vm: bool indicating writing to pages or not
1256  *	@gfp_mask: memory allocation flags
1257  *
1258  *	Prepares and returns a bio for indirect user io, bouncing data
1259  *	to/from kernel pages as necessary. Must be paired with
1260  *	call bio_uncopy_user() on io completion.
1261  */
1262 struct bio *bio_copy_user(struct request_queue *q, struct rq_map_data *map_data,
1263 			  unsigned long uaddr, unsigned int len,
1264 			  int write_to_vm, gfp_t gfp_mask)
1265 {
1266 	struct sg_iovec iov;
1267 
1268 	iov.iov_base = (void __user *)uaddr;
1269 	iov.iov_len = len;
1270 
1271 	return bio_copy_user_iov(q, map_data, &iov, 1, write_to_vm, gfp_mask);
1272 }
1273 EXPORT_SYMBOL(bio_copy_user);
1274 
1275 static struct bio *__bio_map_user_iov(struct request_queue *q,
1276 				      struct block_device *bdev,
1277 				      const struct sg_iovec *iov, int iov_count,
1278 				      int write_to_vm, gfp_t gfp_mask)
1279 {
1280 	int i, j;
1281 	int nr_pages = 0;
1282 	struct page **pages;
1283 	struct bio *bio;
1284 	int cur_page = 0;
1285 	int ret, offset;
1286 
1287 	for (i = 0; i < iov_count; i++) {
1288 		unsigned long uaddr = (unsigned long)iov[i].iov_base;
1289 		unsigned long len = iov[i].iov_len;
1290 		unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1291 		unsigned long start = uaddr >> PAGE_SHIFT;
1292 
1293 		/*
1294 		 * Overflow, abort
1295 		 */
1296 		if (end < start)
1297 			return ERR_PTR(-EINVAL);
1298 
1299 		nr_pages += end - start;
1300 		/*
1301 		 * buffer must be aligned to at least hardsector size for now
1302 		 */
1303 		if (uaddr & queue_dma_alignment(q))
1304 			return ERR_PTR(-EINVAL);
1305 	}
1306 
1307 	if (!nr_pages)
1308 		return ERR_PTR(-EINVAL);
1309 
1310 	bio = bio_kmalloc(gfp_mask, nr_pages);
1311 	if (!bio)
1312 		return ERR_PTR(-ENOMEM);
1313 
1314 	ret = -ENOMEM;
1315 	pages = kcalloc(nr_pages, sizeof(struct page *), gfp_mask);
1316 	if (!pages)
1317 		goto out;
1318 
1319 	for (i = 0; i < iov_count; i++) {
1320 		unsigned long uaddr = (unsigned long)iov[i].iov_base;
1321 		unsigned long len = iov[i].iov_len;
1322 		unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1323 		unsigned long start = uaddr >> PAGE_SHIFT;
1324 		const int local_nr_pages = end - start;
1325 		const int page_limit = cur_page + local_nr_pages;
1326 
1327 		ret = get_user_pages_fast(uaddr, local_nr_pages,
1328 				write_to_vm, &pages[cur_page]);
1329 		if (ret < local_nr_pages) {
1330 			ret = -EFAULT;
1331 			goto out_unmap;
1332 		}
1333 
1334 		offset = uaddr & ~PAGE_MASK;
1335 		for (j = cur_page; j < page_limit; j++) {
1336 			unsigned int bytes = PAGE_SIZE - offset;
1337 
1338 			if (len <= 0)
1339 				break;
1340 
1341 			if (bytes > len)
1342 				bytes = len;
1343 
1344 			/*
1345 			 * sorry...
1346 			 */
1347 			if (bio_add_pc_page(q, bio, pages[j], bytes, offset) <
1348 					    bytes)
1349 				break;
1350 
1351 			len -= bytes;
1352 			offset = 0;
1353 		}
1354 
1355 		cur_page = j;
1356 		/*
1357 		 * release the pages we didn't map into the bio, if any
1358 		 */
1359 		while (j < page_limit)
1360 			page_cache_release(pages[j++]);
1361 	}
1362 
1363 	kfree(pages);
1364 
1365 	/*
1366 	 * set data direction, and check if mapped pages need bouncing
1367 	 */
1368 	if (!write_to_vm)
1369 		bio->bi_rw |= REQ_WRITE;
1370 
1371 	bio->bi_bdev = bdev;
1372 	bio->bi_flags |= (1 << BIO_USER_MAPPED);
1373 	return bio;
1374 
1375  out_unmap:
1376 	for (i = 0; i < nr_pages; i++) {
1377 		if(!pages[i])
1378 			break;
1379 		page_cache_release(pages[i]);
1380 	}
1381  out:
1382 	kfree(pages);
1383 	bio_put(bio);
1384 	return ERR_PTR(ret);
1385 }
1386 
1387 /**
1388  *	bio_map_user	-	map user address into bio
1389  *	@q: the struct request_queue for the bio
1390  *	@bdev: destination block device
1391  *	@uaddr: start of user address
1392  *	@len: length in bytes
1393  *	@write_to_vm: bool indicating writing to pages or not
1394  *	@gfp_mask: memory allocation flags
1395  *
1396  *	Map the user space address into a bio suitable for io to a block
1397  *	device. Returns an error pointer in case of error.
1398  */
1399 struct bio *bio_map_user(struct request_queue *q, struct block_device *bdev,
1400 			 unsigned long uaddr, unsigned int len, int write_to_vm,
1401 			 gfp_t gfp_mask)
1402 {
1403 	struct sg_iovec iov;
1404 
1405 	iov.iov_base = (void __user *)uaddr;
1406 	iov.iov_len = len;
1407 
1408 	return bio_map_user_iov(q, bdev, &iov, 1, write_to_vm, gfp_mask);
1409 }
1410 EXPORT_SYMBOL(bio_map_user);
1411 
1412 /**
1413  *	bio_map_user_iov - map user sg_iovec table into bio
1414  *	@q: the struct request_queue for the bio
1415  *	@bdev: destination block device
1416  *	@iov:	the iovec.
1417  *	@iov_count: number of elements in the iovec
1418  *	@write_to_vm: bool indicating writing to pages or not
1419  *	@gfp_mask: memory allocation flags
1420  *
1421  *	Map the user space address into a bio suitable for io to a block
1422  *	device. Returns an error pointer in case of error.
1423  */
1424 struct bio *bio_map_user_iov(struct request_queue *q, struct block_device *bdev,
1425 			     const struct sg_iovec *iov, int iov_count,
1426 			     int write_to_vm, gfp_t gfp_mask)
1427 {
1428 	struct bio *bio;
1429 
1430 	bio = __bio_map_user_iov(q, bdev, iov, iov_count, write_to_vm,
1431 				 gfp_mask);
1432 	if (IS_ERR(bio))
1433 		return bio;
1434 
1435 	/*
1436 	 * subtle -- if __bio_map_user() ended up bouncing a bio,
1437 	 * it would normally disappear when its bi_end_io is run.
1438 	 * however, we need it for the unmap, so grab an extra
1439 	 * reference to it
1440 	 */
1441 	bio_get(bio);
1442 
1443 	return bio;
1444 }
1445 
1446 static void __bio_unmap_user(struct bio *bio)
1447 {
1448 	struct bio_vec *bvec;
1449 	int i;
1450 
1451 	/*
1452 	 * make sure we dirty pages we wrote to
1453 	 */
1454 	bio_for_each_segment_all(bvec, bio, i) {
1455 		if (bio_data_dir(bio) == READ)
1456 			set_page_dirty_lock(bvec->bv_page);
1457 
1458 		page_cache_release(bvec->bv_page);
1459 	}
1460 
1461 	bio_put(bio);
1462 }
1463 
1464 /**
1465  *	bio_unmap_user	-	unmap a bio
1466  *	@bio:		the bio being unmapped
1467  *
1468  *	Unmap a bio previously mapped by bio_map_user(). Must be called with
1469  *	a process context.
1470  *
1471  *	bio_unmap_user() may sleep.
1472  */
1473 void bio_unmap_user(struct bio *bio)
1474 {
1475 	__bio_unmap_user(bio);
1476 	bio_put(bio);
1477 }
1478 EXPORT_SYMBOL(bio_unmap_user);
1479 
1480 static void bio_map_kern_endio(struct bio *bio, int err)
1481 {
1482 	bio_put(bio);
1483 }
1484 
1485 static struct bio *__bio_map_kern(struct request_queue *q, void *data,
1486 				  unsigned int len, gfp_t gfp_mask)
1487 {
1488 	unsigned long kaddr = (unsigned long)data;
1489 	unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1490 	unsigned long start = kaddr >> PAGE_SHIFT;
1491 	const int nr_pages = end - start;
1492 	int offset, i;
1493 	struct bio *bio;
1494 
1495 	bio = bio_kmalloc(gfp_mask, nr_pages);
1496 	if (!bio)
1497 		return ERR_PTR(-ENOMEM);
1498 
1499 	offset = offset_in_page(kaddr);
1500 	for (i = 0; i < nr_pages; i++) {
1501 		unsigned int bytes = PAGE_SIZE - offset;
1502 
1503 		if (len <= 0)
1504 			break;
1505 
1506 		if (bytes > len)
1507 			bytes = len;
1508 
1509 		if (bio_add_pc_page(q, bio, virt_to_page(data), bytes,
1510 				    offset) < bytes)
1511 			break;
1512 
1513 		data += bytes;
1514 		len -= bytes;
1515 		offset = 0;
1516 	}
1517 
1518 	bio->bi_end_io = bio_map_kern_endio;
1519 	return bio;
1520 }
1521 
1522 /**
1523  *	bio_map_kern	-	map kernel address into bio
1524  *	@q: the struct request_queue for the bio
1525  *	@data: pointer to buffer to map
1526  *	@len: length in bytes
1527  *	@gfp_mask: allocation flags for bio allocation
1528  *
1529  *	Map the kernel address into a bio suitable for io to a block
1530  *	device. Returns an error pointer in case of error.
1531  */
1532 struct bio *bio_map_kern(struct request_queue *q, void *data, unsigned int len,
1533 			 gfp_t gfp_mask)
1534 {
1535 	struct bio *bio;
1536 
1537 	bio = __bio_map_kern(q, data, len, gfp_mask);
1538 	if (IS_ERR(bio))
1539 		return bio;
1540 
1541 	if (bio->bi_iter.bi_size == len)
1542 		return bio;
1543 
1544 	/*
1545 	 * Don't support partial mappings.
1546 	 */
1547 	bio_put(bio);
1548 	return ERR_PTR(-EINVAL);
1549 }
1550 EXPORT_SYMBOL(bio_map_kern);
1551 
1552 static void bio_copy_kern_endio(struct bio *bio, int err)
1553 {
1554 	struct bio_vec *bvec;
1555 	const int read = bio_data_dir(bio) == READ;
1556 	struct bio_map_data *bmd = bio->bi_private;
1557 	int i;
1558 	char *p = bmd->sgvecs[0].iov_base;
1559 
1560 	bio_for_each_segment_all(bvec, bio, i) {
1561 		char *addr = page_address(bvec->bv_page);
1562 
1563 		if (read)
1564 			memcpy(p, addr, bvec->bv_len);
1565 
1566 		__free_page(bvec->bv_page);
1567 		p += bvec->bv_len;
1568 	}
1569 
1570 	kfree(bmd);
1571 	bio_put(bio);
1572 }
1573 
1574 /**
1575  *	bio_copy_kern	-	copy kernel address into bio
1576  *	@q: the struct request_queue for the bio
1577  *	@data: pointer to buffer to copy
1578  *	@len: length in bytes
1579  *	@gfp_mask: allocation flags for bio and page allocation
1580  *	@reading: data direction is READ
1581  *
1582  *	copy the kernel address into a bio suitable for io to a block
1583  *	device. Returns an error pointer in case of error.
1584  */
1585 struct bio *bio_copy_kern(struct request_queue *q, void *data, unsigned int len,
1586 			  gfp_t gfp_mask, int reading)
1587 {
1588 	struct bio *bio;
1589 	struct bio_vec *bvec;
1590 	int i;
1591 
1592 	bio = bio_copy_user(q, NULL, (unsigned long)data, len, 1, gfp_mask);
1593 	if (IS_ERR(bio))
1594 		return bio;
1595 
1596 	if (!reading) {
1597 		void *p = data;
1598 
1599 		bio_for_each_segment_all(bvec, bio, i) {
1600 			char *addr = page_address(bvec->bv_page);
1601 
1602 			memcpy(addr, p, bvec->bv_len);
1603 			p += bvec->bv_len;
1604 		}
1605 	}
1606 
1607 	bio->bi_end_io = bio_copy_kern_endio;
1608 
1609 	return bio;
1610 }
1611 EXPORT_SYMBOL(bio_copy_kern);
1612 
1613 /*
1614  * bio_set_pages_dirty() and bio_check_pages_dirty() are support functions
1615  * for performing direct-IO in BIOs.
1616  *
1617  * The problem is that we cannot run set_page_dirty() from interrupt context
1618  * because the required locks are not interrupt-safe.  So what we can do is to
1619  * mark the pages dirty _before_ performing IO.  And in interrupt context,
1620  * check that the pages are still dirty.   If so, fine.  If not, redirty them
1621  * in process context.
1622  *
1623  * We special-case compound pages here: normally this means reads into hugetlb
1624  * pages.  The logic in here doesn't really work right for compound pages
1625  * because the VM does not uniformly chase down the head page in all cases.
1626  * But dirtiness of compound pages is pretty meaningless anyway: the VM doesn't
1627  * handle them at all.  So we skip compound pages here at an early stage.
1628  *
1629  * Note that this code is very hard to test under normal circumstances because
1630  * direct-io pins the pages with get_user_pages().  This makes
1631  * is_page_cache_freeable return false, and the VM will not clean the pages.
1632  * But other code (eg, flusher threads) could clean the pages if they are mapped
1633  * pagecache.
1634  *
1635  * Simply disabling the call to bio_set_pages_dirty() is a good way to test the
1636  * deferred bio dirtying paths.
1637  */
1638 
1639 /*
1640  * bio_set_pages_dirty() will mark all the bio's pages as dirty.
1641  */
1642 void bio_set_pages_dirty(struct bio *bio)
1643 {
1644 	struct bio_vec *bvec;
1645 	int i;
1646 
1647 	bio_for_each_segment_all(bvec, bio, i) {
1648 		struct page *page = bvec->bv_page;
1649 
1650 		if (page && !PageCompound(page))
1651 			set_page_dirty_lock(page);
1652 	}
1653 }
1654 
1655 static void bio_release_pages(struct bio *bio)
1656 {
1657 	struct bio_vec *bvec;
1658 	int i;
1659 
1660 	bio_for_each_segment_all(bvec, bio, i) {
1661 		struct page *page = bvec->bv_page;
1662 
1663 		if (page)
1664 			put_page(page);
1665 	}
1666 }
1667 
1668 /*
1669  * bio_check_pages_dirty() will check that all the BIO's pages are still dirty.
1670  * If they are, then fine.  If, however, some pages are clean then they must
1671  * have been written out during the direct-IO read.  So we take another ref on
1672  * the BIO and the offending pages and re-dirty the pages in process context.
1673  *
1674  * It is expected that bio_check_pages_dirty() will wholly own the BIO from
1675  * here on.  It will run one page_cache_release() against each page and will
1676  * run one bio_put() against the BIO.
1677  */
1678 
1679 static void bio_dirty_fn(struct work_struct *work);
1680 
1681 static DECLARE_WORK(bio_dirty_work, bio_dirty_fn);
1682 static DEFINE_SPINLOCK(bio_dirty_lock);
1683 static struct bio *bio_dirty_list;
1684 
1685 /*
1686  * This runs in process context
1687  */
1688 static void bio_dirty_fn(struct work_struct *work)
1689 {
1690 	unsigned long flags;
1691 	struct bio *bio;
1692 
1693 	spin_lock_irqsave(&bio_dirty_lock, flags);
1694 	bio = bio_dirty_list;
1695 	bio_dirty_list = NULL;
1696 	spin_unlock_irqrestore(&bio_dirty_lock, flags);
1697 
1698 	while (bio) {
1699 		struct bio *next = bio->bi_private;
1700 
1701 		bio_set_pages_dirty(bio);
1702 		bio_release_pages(bio);
1703 		bio_put(bio);
1704 		bio = next;
1705 	}
1706 }
1707 
1708 void bio_check_pages_dirty(struct bio *bio)
1709 {
1710 	struct bio_vec *bvec;
1711 	int nr_clean_pages = 0;
1712 	int i;
1713 
1714 	bio_for_each_segment_all(bvec, bio, i) {
1715 		struct page *page = bvec->bv_page;
1716 
1717 		if (PageDirty(page) || PageCompound(page)) {
1718 			page_cache_release(page);
1719 			bvec->bv_page = NULL;
1720 		} else {
1721 			nr_clean_pages++;
1722 		}
1723 	}
1724 
1725 	if (nr_clean_pages) {
1726 		unsigned long flags;
1727 
1728 		spin_lock_irqsave(&bio_dirty_lock, flags);
1729 		bio->bi_private = bio_dirty_list;
1730 		bio_dirty_list = bio;
1731 		spin_unlock_irqrestore(&bio_dirty_lock, flags);
1732 		schedule_work(&bio_dirty_work);
1733 	} else {
1734 		bio_put(bio);
1735 	}
1736 }
1737 
1738 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
1739 void bio_flush_dcache_pages(struct bio *bi)
1740 {
1741 	struct bio_vec bvec;
1742 	struct bvec_iter iter;
1743 
1744 	bio_for_each_segment(bvec, bi, iter)
1745 		flush_dcache_page(bvec.bv_page);
1746 }
1747 EXPORT_SYMBOL(bio_flush_dcache_pages);
1748 #endif
1749 
1750 /**
1751  * bio_endio - end I/O on a bio
1752  * @bio:	bio
1753  * @error:	error, if any
1754  *
1755  * Description:
1756  *   bio_endio() will end I/O on the whole bio. bio_endio() is the
1757  *   preferred way to end I/O on a bio, it takes care of clearing
1758  *   BIO_UPTODATE on error. @error is 0 on success, and and one of the
1759  *   established -Exxxx (-EIO, for instance) error values in case
1760  *   something went wrong. No one should call bi_end_io() directly on a
1761  *   bio unless they own it and thus know that it has an end_io
1762  *   function.
1763  **/
1764 void bio_endio(struct bio *bio, int error)
1765 {
1766 	while (bio) {
1767 		BUG_ON(atomic_read(&bio->bi_remaining) <= 0);
1768 
1769 		if (error)
1770 			clear_bit(BIO_UPTODATE, &bio->bi_flags);
1771 		else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
1772 			error = -EIO;
1773 
1774 		if (!atomic_dec_and_test(&bio->bi_remaining))
1775 			return;
1776 
1777 		/*
1778 		 * Need to have a real endio function for chained bios,
1779 		 * otherwise various corner cases will break (like stacking
1780 		 * block devices that save/restore bi_end_io) - however, we want
1781 		 * to avoid unbounded recursion and blowing the stack. Tail call
1782 		 * optimization would handle this, but compiling with frame
1783 		 * pointers also disables gcc's sibling call optimization.
1784 		 */
1785 		if (bio->bi_end_io == bio_chain_endio) {
1786 			struct bio *parent = bio->bi_private;
1787 			bio_put(bio);
1788 			bio = parent;
1789 		} else {
1790 			if (bio->bi_end_io)
1791 				bio->bi_end_io(bio, error);
1792 			bio = NULL;
1793 		}
1794 	}
1795 }
1796 EXPORT_SYMBOL(bio_endio);
1797 
1798 /**
1799  * bio_endio_nodec - end I/O on a bio, without decrementing bi_remaining
1800  * @bio:	bio
1801  * @error:	error, if any
1802  *
1803  * For code that has saved and restored bi_end_io; thing hard before using this
1804  * function, probably you should've cloned the entire bio.
1805  **/
1806 void bio_endio_nodec(struct bio *bio, int error)
1807 {
1808 	atomic_inc(&bio->bi_remaining);
1809 	bio_endio(bio, error);
1810 }
1811 EXPORT_SYMBOL(bio_endio_nodec);
1812 
1813 /**
1814  * bio_split - split a bio
1815  * @bio:	bio to split
1816  * @sectors:	number of sectors to split from the front of @bio
1817  * @gfp:	gfp mask
1818  * @bs:		bio set to allocate from
1819  *
1820  * Allocates and returns a new bio which represents @sectors from the start of
1821  * @bio, and updates @bio to represent the remaining sectors.
1822  *
1823  * The newly allocated bio will point to @bio's bi_io_vec; it is the caller's
1824  * responsibility to ensure that @bio is not freed before the split.
1825  */
1826 struct bio *bio_split(struct bio *bio, int sectors,
1827 		      gfp_t gfp, struct bio_set *bs)
1828 {
1829 	struct bio *split = NULL;
1830 
1831 	BUG_ON(sectors <= 0);
1832 	BUG_ON(sectors >= bio_sectors(bio));
1833 
1834 	split = bio_clone_fast(bio, gfp, bs);
1835 	if (!split)
1836 		return NULL;
1837 
1838 	split->bi_iter.bi_size = sectors << 9;
1839 
1840 	if (bio_integrity(split))
1841 		bio_integrity_trim(split, 0, sectors);
1842 
1843 	bio_advance(bio, split->bi_iter.bi_size);
1844 
1845 	return split;
1846 }
1847 EXPORT_SYMBOL(bio_split);
1848 
1849 /**
1850  * bio_trim - trim a bio
1851  * @bio:	bio to trim
1852  * @offset:	number of sectors to trim from the front of @bio
1853  * @size:	size we want to trim @bio to, in sectors
1854  */
1855 void bio_trim(struct bio *bio, int offset, int size)
1856 {
1857 	/* 'bio' is a cloned bio which we need to trim to match
1858 	 * the given offset and size.
1859 	 */
1860 
1861 	size <<= 9;
1862 	if (offset == 0 && size == bio->bi_iter.bi_size)
1863 		return;
1864 
1865 	clear_bit(BIO_SEG_VALID, &bio->bi_flags);
1866 
1867 	bio_advance(bio, offset << 9);
1868 
1869 	bio->bi_iter.bi_size = size;
1870 }
1871 EXPORT_SYMBOL_GPL(bio_trim);
1872 
1873 /*
1874  * create memory pools for biovec's in a bio_set.
1875  * use the global biovec slabs created for general use.
1876  */
1877 mempool_t *biovec_create_pool(int pool_entries)
1878 {
1879 	struct biovec_slab *bp = bvec_slabs + BIOVEC_MAX_IDX;
1880 
1881 	return mempool_create_slab_pool(pool_entries, bp->slab);
1882 }
1883 
1884 void bioset_free(struct bio_set *bs)
1885 {
1886 	if (bs->rescue_workqueue)
1887 		destroy_workqueue(bs->rescue_workqueue);
1888 
1889 	if (bs->bio_pool)
1890 		mempool_destroy(bs->bio_pool);
1891 
1892 	if (bs->bvec_pool)
1893 		mempool_destroy(bs->bvec_pool);
1894 
1895 	bioset_integrity_free(bs);
1896 	bio_put_slab(bs);
1897 
1898 	kfree(bs);
1899 }
1900 EXPORT_SYMBOL(bioset_free);
1901 
1902 /**
1903  * bioset_create  - Create a bio_set
1904  * @pool_size:	Number of bio and bio_vecs to cache in the mempool
1905  * @front_pad:	Number of bytes to allocate in front of the returned bio
1906  *
1907  * Description:
1908  *    Set up a bio_set to be used with @bio_alloc_bioset. Allows the caller
1909  *    to ask for a number of bytes to be allocated in front of the bio.
1910  *    Front pad allocation is useful for embedding the bio inside
1911  *    another structure, to avoid allocating extra data to go with the bio.
1912  *    Note that the bio must be embedded at the END of that structure always,
1913  *    or things will break badly.
1914  */
1915 struct bio_set *bioset_create(unsigned int pool_size, unsigned int front_pad)
1916 {
1917 	unsigned int back_pad = BIO_INLINE_VECS * sizeof(struct bio_vec);
1918 	struct bio_set *bs;
1919 
1920 	bs = kzalloc(sizeof(*bs), GFP_KERNEL);
1921 	if (!bs)
1922 		return NULL;
1923 
1924 	bs->front_pad = front_pad;
1925 
1926 	spin_lock_init(&bs->rescue_lock);
1927 	bio_list_init(&bs->rescue_list);
1928 	INIT_WORK(&bs->rescue_work, bio_alloc_rescue);
1929 
1930 	bs->bio_slab = bio_find_or_create_slab(front_pad + back_pad);
1931 	if (!bs->bio_slab) {
1932 		kfree(bs);
1933 		return NULL;
1934 	}
1935 
1936 	bs->bio_pool = mempool_create_slab_pool(pool_size, bs->bio_slab);
1937 	if (!bs->bio_pool)
1938 		goto bad;
1939 
1940 	bs->bvec_pool = biovec_create_pool(pool_size);
1941 	if (!bs->bvec_pool)
1942 		goto bad;
1943 
1944 	bs->rescue_workqueue = alloc_workqueue("bioset", WQ_MEM_RECLAIM, 0);
1945 	if (!bs->rescue_workqueue)
1946 		goto bad;
1947 
1948 	return bs;
1949 bad:
1950 	bioset_free(bs);
1951 	return NULL;
1952 }
1953 EXPORT_SYMBOL(bioset_create);
1954 
1955 #ifdef CONFIG_BLK_CGROUP
1956 /**
1957  * bio_associate_current - associate a bio with %current
1958  * @bio: target bio
1959  *
1960  * Associate @bio with %current if it hasn't been associated yet.  Block
1961  * layer will treat @bio as if it were issued by %current no matter which
1962  * task actually issues it.
1963  *
1964  * This function takes an extra reference of @task's io_context and blkcg
1965  * which will be put when @bio is released.  The caller must own @bio,
1966  * ensure %current->io_context exists, and is responsible for synchronizing
1967  * calls to this function.
1968  */
1969 int bio_associate_current(struct bio *bio)
1970 {
1971 	struct io_context *ioc;
1972 	struct cgroup_subsys_state *css;
1973 
1974 	if (bio->bi_ioc)
1975 		return -EBUSY;
1976 
1977 	ioc = current->io_context;
1978 	if (!ioc)
1979 		return -ENOENT;
1980 
1981 	/* acquire active ref on @ioc and associate */
1982 	get_io_context_active(ioc);
1983 	bio->bi_ioc = ioc;
1984 
1985 	/* associate blkcg if exists */
1986 	rcu_read_lock();
1987 	css = task_css(current, blkio_cgrp_id);
1988 	if (css && css_tryget_online(css))
1989 		bio->bi_css = css;
1990 	rcu_read_unlock();
1991 
1992 	return 0;
1993 }
1994 
1995 /**
1996  * bio_disassociate_task - undo bio_associate_current()
1997  * @bio: target bio
1998  */
1999 void bio_disassociate_task(struct bio *bio)
2000 {
2001 	if (bio->bi_ioc) {
2002 		put_io_context(bio->bi_ioc);
2003 		bio->bi_ioc = NULL;
2004 	}
2005 	if (bio->bi_css) {
2006 		css_put(bio->bi_css);
2007 		bio->bi_css = NULL;
2008 	}
2009 }
2010 
2011 #endif /* CONFIG_BLK_CGROUP */
2012 
2013 static void __init biovec_init_slabs(void)
2014 {
2015 	int i;
2016 
2017 	for (i = 0; i < BIOVEC_NR_POOLS; i++) {
2018 		int size;
2019 		struct biovec_slab *bvs = bvec_slabs + i;
2020 
2021 		if (bvs->nr_vecs <= BIO_INLINE_VECS) {
2022 			bvs->slab = NULL;
2023 			continue;
2024 		}
2025 
2026 		size = bvs->nr_vecs * sizeof(struct bio_vec);
2027 		bvs->slab = kmem_cache_create(bvs->name, size, 0,
2028                                 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
2029 	}
2030 }
2031 
2032 static int __init init_bio(void)
2033 {
2034 	bio_slab_max = 2;
2035 	bio_slab_nr = 0;
2036 	bio_slabs = kzalloc(bio_slab_max * sizeof(struct bio_slab), GFP_KERNEL);
2037 	if (!bio_slabs)
2038 		panic("bio: can't allocate bios\n");
2039 
2040 	bio_integrity_init();
2041 	biovec_init_slabs();
2042 
2043 	fs_bio_set = bioset_create(BIO_POOL_SIZE, 0);
2044 	if (!fs_bio_set)
2045 		panic("bio: can't allocate bios\n");
2046 
2047 	if (bioset_integrity_create(fs_bio_set, BIO_POOL_SIZE))
2048 		panic("bio: can't create integrity pool\n");
2049 
2050 	return 0;
2051 }
2052 subsys_initcall(init_bio);
2053