Back to home page

LXR

 
 

    


0001 /*
0002  * Copyright (C) 2001 Jens Axboe <axboe@kernel.dk>
0003  *
0004  * This program is free software; you can redistribute it and/or modify
0005  * it under the terms of the GNU General Public License version 2 as
0006  * published by the Free Software Foundation.
0007  *
0008  * This program is distributed in the hope that it will be useful,
0009  * but WITHOUT ANY WARRANTY; without even the implied warranty of
0010  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
0011  * GNU General Public License for more details.
0012  *
0013  * You should have received a copy of the GNU General Public Licens
0014  * along with this program; if not, write to the Free Software
0015  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
0016  *
0017  */
0018 #include <linux/mm.h>
0019 #include <linux/swap.h>
0020 #include <linux/bio.h>
0021 #include <linux/blkdev.h>
0022 #include <linux/uio.h>
0023 #include <linux/iocontext.h>
0024 #include <linux/slab.h>
0025 #include <linux/init.h>
0026 #include <linux/kernel.h>
0027 #include <linux/export.h>
0028 #include <linux/mempool.h>
0029 #include <linux/workqueue.h>
0030 #include <linux/cgroup.h>
0031 
0032 #include <trace/events/block.h>
0033 
0034 /*
0035  * Test patch to inline a certain number of bi_io_vec's inside the bio
0036  * itself, to shrink a bio data allocation from two mempool calls to one
0037  */
0038 #define BIO_INLINE_VECS     4
0039 
0040 /*
0041  * if you change this list, also change bvec_alloc or things will
0042  * break badly! cannot be bigger than what you can fit into an
0043  * unsigned short
0044  */
0045 #define BV(x) { .nr_vecs = x, .name = "biovec-"__stringify(x) }
0046 static struct biovec_slab bvec_slabs[BVEC_POOL_NR] __read_mostly = {
0047     BV(1), BV(4), BV(16), BV(64), BV(128), BV(BIO_MAX_PAGES),
0048 };
0049 #undef BV
0050 
0051 /*
0052  * fs_bio_set is the bio_set containing bio and iovec memory pools used by
0053  * IO code that does not need private memory pools.
0054  */
0055 struct bio_set *fs_bio_set;
0056 EXPORT_SYMBOL(fs_bio_set);
0057 
0058 /*
0059  * Our slab pool management
0060  */
0061 struct bio_slab {
0062     struct kmem_cache *slab;
0063     unsigned int slab_ref;
0064     unsigned int slab_size;
0065     char name[8];
0066 };
0067 static DEFINE_MUTEX(bio_slab_lock);
0068 static struct bio_slab *bio_slabs;
0069 static unsigned int bio_slab_nr, bio_slab_max;
0070 
0071 static struct kmem_cache *bio_find_or_create_slab(unsigned int extra_size)
0072 {
0073     unsigned int sz = sizeof(struct bio) + extra_size;
0074     struct kmem_cache *slab = NULL;
0075     struct bio_slab *bslab, *new_bio_slabs;
0076     unsigned int new_bio_slab_max;
0077     unsigned int i, entry = -1;
0078 
0079     mutex_lock(&bio_slab_lock);
0080 
0081     i = 0;
0082     while (i < bio_slab_nr) {
0083         bslab = &bio_slabs[i];
0084 
0085         if (!bslab->slab && entry == -1)
0086             entry = i;
0087         else if (bslab->slab_size == sz) {
0088             slab = bslab->slab;
0089             bslab->slab_ref++;
0090             break;
0091         }
0092         i++;
0093     }
0094 
0095     if (slab)
0096         goto out_unlock;
0097 
0098     if (bio_slab_nr == bio_slab_max && entry == -1) {
0099         new_bio_slab_max = bio_slab_max << 1;
0100         new_bio_slabs = krealloc(bio_slabs,
0101                      new_bio_slab_max * sizeof(struct bio_slab),
0102                      GFP_KERNEL);
0103         if (!new_bio_slabs)
0104             goto out_unlock;
0105         bio_slab_max = new_bio_slab_max;
0106         bio_slabs = new_bio_slabs;
0107     }
0108     if (entry == -1)
0109         entry = bio_slab_nr++;
0110 
0111     bslab = &bio_slabs[entry];
0112 
0113     snprintf(bslab->name, sizeof(bslab->name), "bio-%d", entry);
0114     slab = kmem_cache_create(bslab->name, sz, ARCH_KMALLOC_MINALIGN,
0115                  SLAB_HWCACHE_ALIGN, NULL);
0116     if (!slab)
0117         goto out_unlock;
0118 
0119     bslab->slab = slab;
0120     bslab->slab_ref = 1;
0121     bslab->slab_size = sz;
0122 out_unlock:
0123     mutex_unlock(&bio_slab_lock);
0124     return slab;
0125 }
0126 
0127 static void bio_put_slab(struct bio_set *bs)
0128 {
0129     struct bio_slab *bslab = NULL;
0130     unsigned int i;
0131 
0132     mutex_lock(&bio_slab_lock);
0133 
0134     for (i = 0; i < bio_slab_nr; i++) {
0135         if (bs->bio_slab == bio_slabs[i].slab) {
0136             bslab = &bio_slabs[i];
0137             break;
0138         }
0139     }
0140 
0141     if (WARN(!bslab, KERN_ERR "bio: unable to find slab!\n"))
0142         goto out;
0143 
0144     WARN_ON(!bslab->slab_ref);
0145 
0146     if (--bslab->slab_ref)
0147         goto out;
0148 
0149     kmem_cache_destroy(bslab->slab);
0150     bslab->slab = NULL;
0151 
0152 out:
0153     mutex_unlock(&bio_slab_lock);
0154 }
0155 
0156 unsigned int bvec_nr_vecs(unsigned short idx)
0157 {
0158     return bvec_slabs[idx].nr_vecs;
0159 }
0160 
0161 void bvec_free(mempool_t *pool, struct bio_vec *bv, unsigned int idx)
0162 {
0163     if (!idx)
0164         return;
0165     idx--;
0166 
0167     BIO_BUG_ON(idx >= BVEC_POOL_NR);
0168 
0169     if (idx == BVEC_POOL_MAX) {
0170         mempool_free(bv, pool);
0171     } else {
0172         struct biovec_slab *bvs = bvec_slabs + idx;
0173 
0174         kmem_cache_free(bvs->slab, bv);
0175     }
0176 }
0177 
0178 struct bio_vec *bvec_alloc(gfp_t gfp_mask, int nr, unsigned long *idx,
0179                mempool_t *pool)
0180 {
0181     struct bio_vec *bvl;
0182 
0183     /*
0184      * see comment near bvec_array define!
0185      */
0186     switch (nr) {
0187     case 1:
0188         *idx = 0;
0189         break;
0190     case 2 ... 4:
0191         *idx = 1;
0192         break;
0193     case 5 ... 16:
0194         *idx = 2;
0195         break;
0196     case 17 ... 64:
0197         *idx = 3;
0198         break;
0199     case 65 ... 128:
0200         *idx = 4;
0201         break;
0202     case 129 ... BIO_MAX_PAGES:
0203         *idx = 5;
0204         break;
0205     default:
0206         return NULL;
0207     }
0208 
0209     /*
0210      * idx now points to the pool we want to allocate from. only the
0211      * 1-vec entry pool is mempool backed.
0212      */
0213     if (*idx == BVEC_POOL_MAX) {
0214 fallback:
0215         bvl = mempool_alloc(pool, gfp_mask);
0216     } else {
0217         struct biovec_slab *bvs = bvec_slabs + *idx;
0218         gfp_t __gfp_mask = gfp_mask & ~(__GFP_DIRECT_RECLAIM | __GFP_IO);
0219 
0220         /*
0221          * Make this allocation restricted and don't dump info on
0222          * allocation failures, since we'll fallback to the mempool
0223          * in case of failure.
0224          */
0225         __gfp_mask |= __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
0226 
0227         /*
0228          * Try a slab allocation. If this fails and __GFP_DIRECT_RECLAIM
0229          * is set, retry with the 1-entry mempool
0230          */
0231         bvl = kmem_cache_alloc(bvs->slab, __gfp_mask);
0232         if (unlikely(!bvl && (gfp_mask & __GFP_DIRECT_RECLAIM))) {
0233             *idx = BVEC_POOL_MAX;
0234             goto fallback;
0235         }
0236     }
0237 
0238     (*idx)++;
0239     return bvl;
0240 }
0241 
0242 static void __bio_free(struct bio *bio)
0243 {
0244     bio_disassociate_task(bio);
0245 
0246     if (bio_integrity(bio))
0247         bio_integrity_free(bio);
0248 }
0249 
0250 static void bio_free(struct bio *bio)
0251 {
0252     struct bio_set *bs = bio->bi_pool;
0253     void *p;
0254 
0255     __bio_free(bio);
0256 
0257     if (bs) {
0258         bvec_free(bs->bvec_pool, bio->bi_io_vec, BVEC_POOL_IDX(bio));
0259 
0260         /*
0261          * If we have front padding, adjust the bio pointer before freeing
0262          */
0263         p = bio;
0264         p -= bs->front_pad;
0265 
0266         mempool_free(p, bs->bio_pool);
0267     } else {
0268         /* Bio was allocated by bio_kmalloc() */
0269         kfree(bio);
0270     }
0271 }
0272 
0273 void bio_init(struct bio *bio, struct bio_vec *table,
0274           unsigned short max_vecs)
0275 {
0276     memset(bio, 0, sizeof(*bio));
0277     atomic_set(&bio->__bi_remaining, 1);
0278     atomic_set(&bio->__bi_cnt, 1);
0279 
0280     bio->bi_io_vec = table;
0281     bio->bi_max_vecs = max_vecs;
0282 }
0283 EXPORT_SYMBOL(bio_init);
0284 
0285 /**
0286  * bio_reset - reinitialize a bio
0287  * @bio:    bio to reset
0288  *
0289  * Description:
0290  *   After calling bio_reset(), @bio will be in the same state as a freshly
0291  *   allocated bio returned bio bio_alloc_bioset() - the only fields that are
0292  *   preserved are the ones that are initialized by bio_alloc_bioset(). See
0293  *   comment in struct bio.
0294  */
0295 void bio_reset(struct bio *bio)
0296 {
0297     unsigned long flags = bio->bi_flags & (~0UL << BIO_RESET_BITS);
0298 
0299     __bio_free(bio);
0300 
0301     memset(bio, 0, BIO_RESET_BYTES);
0302     bio->bi_flags = flags;
0303     atomic_set(&bio->__bi_remaining, 1);
0304 }
0305 EXPORT_SYMBOL(bio_reset);
0306 
0307 static struct bio *__bio_chain_endio(struct bio *bio)
0308 {
0309     struct bio *parent = bio->bi_private;
0310 
0311     if (!parent->bi_error)
0312         parent->bi_error = bio->bi_error;
0313     bio_put(bio);
0314     return parent;
0315 }
0316 
0317 static void bio_chain_endio(struct bio *bio)
0318 {
0319     bio_endio(__bio_chain_endio(bio));
0320 }
0321 
0322 /**
0323  * bio_chain - chain bio completions
0324  * @bio: the target bio
0325  * @parent: the @bio's parent bio
0326  *
0327  * The caller won't have a bi_end_io called when @bio completes - instead,
0328  * @parent's bi_end_io won't be called until both @parent and @bio have
0329  * completed; the chained bio will also be freed when it completes.
0330  *
0331  * The caller must not set bi_private or bi_end_io in @bio.
0332  */
0333 void bio_chain(struct bio *bio, struct bio *parent)
0334 {
0335     BUG_ON(bio->bi_private || bio->bi_end_io);
0336 
0337     bio->bi_private = parent;
0338     bio->bi_end_io  = bio_chain_endio;
0339     bio_inc_remaining(parent);
0340 }
0341 EXPORT_SYMBOL(bio_chain);
0342 
0343 static void bio_alloc_rescue(struct work_struct *work)
0344 {
0345     struct bio_set *bs = container_of(work, struct bio_set, rescue_work);
0346     struct bio *bio;
0347 
0348     while (1) {
0349         spin_lock(&bs->rescue_lock);
0350         bio = bio_list_pop(&bs->rescue_list);
0351         spin_unlock(&bs->rescue_lock);
0352 
0353         if (!bio)
0354             break;
0355 
0356         generic_make_request(bio);
0357     }
0358 }
0359 
0360 static void punt_bios_to_rescuer(struct bio_set *bs)
0361 {
0362     struct bio_list punt, nopunt;
0363     struct bio *bio;
0364 
0365     /*
0366      * In order to guarantee forward progress we must punt only bios that
0367      * were allocated from this bio_set; otherwise, if there was a bio on
0368      * there for a stacking driver higher up in the stack, processing it
0369      * could require allocating bios from this bio_set, and doing that from
0370      * our own rescuer would be bad.
0371      *
0372      * Since bio lists are singly linked, pop them all instead of trying to
0373      * remove from the middle of the list:
0374      */
0375 
0376     bio_list_init(&punt);
0377     bio_list_init(&nopunt);
0378 
0379     while ((bio = bio_list_pop(current->bio_list)))
0380         bio_list_add(bio->bi_pool == bs ? &punt : &nopunt, bio);
0381 
0382     *current->bio_list = nopunt;
0383 
0384     spin_lock(&bs->rescue_lock);
0385     bio_list_merge(&bs->rescue_list, &punt);
0386     spin_unlock(&bs->rescue_lock);
0387 
0388     queue_work(bs->rescue_workqueue, &bs->rescue_work);
0389 }
0390 
0391 /**
0392  * bio_alloc_bioset - allocate a bio for I/O
0393  * @gfp_mask:   the GFP_ mask given to the slab allocator
0394  * @nr_iovecs:  number of iovecs to pre-allocate
0395  * @bs:     the bio_set to allocate from.
0396  *
0397  * Description:
0398  *   If @bs is NULL, uses kmalloc() to allocate the bio; else the allocation is
0399  *   backed by the @bs's mempool.
0400  *
0401  *   When @bs is not NULL, if %__GFP_DIRECT_RECLAIM is set then bio_alloc will
0402  *   always be able to allocate a bio. This is due to the mempool guarantees.
0403  *   To make this work, callers must never allocate more than 1 bio at a time
0404  *   from this pool. Callers that need to allocate more than 1 bio must always
0405  *   submit the previously allocated bio for IO before attempting to allocate
0406  *   a new one. Failure to do so can cause deadlocks under memory pressure.
0407  *
0408  *   Note that when running under generic_make_request() (i.e. any block
0409  *   driver), bios are not submitted until after you return - see the code in
0410  *   generic_make_request() that converts recursion into iteration, to prevent
0411  *   stack overflows.
0412  *
0413  *   This would normally mean allocating multiple bios under
0414  *   generic_make_request() would be susceptible to deadlocks, but we have
0415  *   deadlock avoidance code that resubmits any blocked bios from a rescuer
0416  *   thread.
0417  *
0418  *   However, we do not guarantee forward progress for allocations from other
0419  *   mempools. Doing multiple allocations from the same mempool under
0420  *   generic_make_request() should be avoided - instead, use bio_set's front_pad
0421  *   for per bio allocations.
0422  *
0423  *   RETURNS:
0424  *   Pointer to new bio on success, NULL on failure.
0425  */
0426 struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
0427 {
0428     gfp_t saved_gfp = gfp_mask;
0429     unsigned front_pad;
0430     unsigned inline_vecs;
0431     struct bio_vec *bvl = NULL;
0432     struct bio *bio;
0433     void *p;
0434 
0435     if (!bs) {
0436         if (nr_iovecs > UIO_MAXIOV)
0437             return NULL;
0438 
0439         p = kmalloc(sizeof(struct bio) +
0440                 nr_iovecs * sizeof(struct bio_vec),
0441                 gfp_mask);
0442         front_pad = 0;
0443         inline_vecs = nr_iovecs;
0444     } else {
0445         /* should not use nobvec bioset for nr_iovecs > 0 */
0446         if (WARN_ON_ONCE(!bs->bvec_pool && nr_iovecs > 0))
0447             return NULL;
0448         /*
0449          * generic_make_request() converts recursion to iteration; this
0450          * means if we're running beneath it, any bios we allocate and
0451          * submit will not be submitted (and thus freed) until after we
0452          * return.
0453          *
0454          * This exposes us to a potential deadlock if we allocate
0455          * multiple bios from the same bio_set() while running
0456          * underneath generic_make_request(). If we were to allocate
0457          * multiple bios (say a stacking block driver that was splitting
0458          * bios), we would deadlock if we exhausted the mempool's
0459          * reserve.
0460          *
0461          * We solve this, and guarantee forward progress, with a rescuer
0462          * workqueue per bio_set. If we go to allocate and there are
0463          * bios on current->bio_list, we first try the allocation
0464          * without __GFP_DIRECT_RECLAIM; if that fails, we punt those
0465          * bios we would be blocking to the rescuer workqueue before
0466          * we retry with the original gfp_flags.
0467          */
0468 
0469         if (current->bio_list && !bio_list_empty(current->bio_list))
0470             gfp_mask &= ~__GFP_DIRECT_RECLAIM;
0471 
0472         p = mempool_alloc(bs->bio_pool, gfp_mask);
0473         if (!p && gfp_mask != saved_gfp) {
0474             punt_bios_to_rescuer(bs);
0475             gfp_mask = saved_gfp;
0476             p = mempool_alloc(bs->bio_pool, gfp_mask);
0477         }
0478 
0479         front_pad = bs->front_pad;
0480         inline_vecs = BIO_INLINE_VECS;
0481     }
0482 
0483     if (unlikely(!p))
0484         return NULL;
0485 
0486     bio = p + front_pad;
0487     bio_init(bio, NULL, 0);
0488 
0489     if (nr_iovecs > inline_vecs) {
0490         unsigned long idx = 0;
0491 
0492         bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx, bs->bvec_pool);
0493         if (!bvl && gfp_mask != saved_gfp) {
0494             punt_bios_to_rescuer(bs);
0495             gfp_mask = saved_gfp;
0496             bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx, bs->bvec_pool);
0497         }
0498 
0499         if (unlikely(!bvl))
0500             goto err_free;
0501 
0502         bio->bi_flags |= idx << BVEC_POOL_OFFSET;
0503     } else if (nr_iovecs) {
0504         bvl = bio->bi_inline_vecs;
0505     }
0506 
0507     bio->bi_pool = bs;
0508     bio->bi_max_vecs = nr_iovecs;
0509     bio->bi_io_vec = bvl;
0510     return bio;
0511 
0512 err_free:
0513     mempool_free(p, bs->bio_pool);
0514     return NULL;
0515 }
0516 EXPORT_SYMBOL(bio_alloc_bioset);
0517 
0518 void zero_fill_bio(struct bio *bio)
0519 {
0520     unsigned long flags;
0521     struct bio_vec bv;
0522     struct bvec_iter iter;
0523 
0524     bio_for_each_segment(bv, bio, iter) {
0525         char *data = bvec_kmap_irq(&bv, &flags);
0526         memset(data, 0, bv.bv_len);
0527         flush_dcache_page(bv.bv_page);
0528         bvec_kunmap_irq(data, &flags);
0529     }
0530 }
0531 EXPORT_SYMBOL(zero_fill_bio);
0532 
0533 /**
0534  * bio_put - release a reference to a bio
0535  * @bio:   bio to release reference to
0536  *
0537  * Description:
0538  *   Put a reference to a &struct bio, either one you have gotten with
0539  *   bio_alloc, bio_get or bio_clone. The last put of a bio will free it.
0540  **/
0541 void bio_put(struct bio *bio)
0542 {
0543     if (!bio_flagged(bio, BIO_REFFED))
0544         bio_free(bio);
0545     else {
0546         BIO_BUG_ON(!atomic_read(&bio->__bi_cnt));
0547 
0548         /*
0549          * last put frees it
0550          */
0551         if (atomic_dec_and_test(&bio->__bi_cnt))
0552             bio_free(bio);
0553     }
0554 }
0555 EXPORT_SYMBOL(bio_put);
0556 
0557 inline int bio_phys_segments(struct request_queue *q, struct bio *bio)
0558 {
0559     if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
0560         blk_recount_segments(q, bio);
0561 
0562     return bio->bi_phys_segments;
0563 }
0564 EXPORT_SYMBOL(bio_phys_segments);
0565 
0566 /**
0567  *  __bio_clone_fast - clone a bio that shares the original bio's biovec
0568  *  @bio: destination bio
0569  *  @bio_src: bio to clone
0570  *
0571  *  Clone a &bio. Caller will own the returned bio, but not
0572  *  the actual data it points to. Reference count of returned
0573  *  bio will be one.
0574  *
0575  *  Caller must ensure that @bio_src is not freed before @bio.
0576  */
0577 void __bio_clone_fast(struct bio *bio, struct bio *bio_src)
0578 {
0579     BUG_ON(bio->bi_pool && BVEC_POOL_IDX(bio));
0580 
0581     /*
0582      * most users will be overriding ->bi_bdev with a new target,
0583      * so we don't set nor calculate new physical/hw segment counts here
0584      */
0585     bio->bi_bdev = bio_src->bi_bdev;
0586     bio_set_flag(bio, BIO_CLONED);
0587     bio->bi_opf = bio_src->bi_opf;
0588     bio->bi_iter = bio_src->bi_iter;
0589     bio->bi_io_vec = bio_src->bi_io_vec;
0590 
0591     bio_clone_blkcg_association(bio, bio_src);
0592 }
0593 EXPORT_SYMBOL(__bio_clone_fast);
0594 
0595 /**
0596  *  bio_clone_fast - clone a bio that shares the original bio's biovec
0597  *  @bio: bio to clone
0598  *  @gfp_mask: allocation priority
0599  *  @bs: bio_set to allocate from
0600  *
0601  *  Like __bio_clone_fast, only also allocates the returned bio
0602  */
0603 struct bio *bio_clone_fast(struct bio *bio, gfp_t gfp_mask, struct bio_set *bs)
0604 {
0605     struct bio *b;
0606 
0607     b = bio_alloc_bioset(gfp_mask, 0, bs);
0608     if (!b)
0609         return NULL;
0610 
0611     __bio_clone_fast(b, bio);
0612 
0613     if (bio_integrity(bio)) {
0614         int ret;
0615 
0616         ret = bio_integrity_clone(b, bio, gfp_mask);
0617 
0618         if (ret < 0) {
0619             bio_put(b);
0620             return NULL;
0621         }
0622     }
0623 
0624     return b;
0625 }
0626 EXPORT_SYMBOL(bio_clone_fast);
0627 
0628 /**
0629  *  bio_clone_bioset - clone a bio
0630  *  @bio_src: bio to clone
0631  *  @gfp_mask: allocation priority
0632  *  @bs: bio_set to allocate from
0633  *
0634  *  Clone bio. Caller will own the returned bio, but not the actual data it
0635  *  points to. Reference count of returned bio will be one.
0636  */
0637 struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
0638                  struct bio_set *bs)
0639 {
0640     struct bvec_iter iter;
0641     struct bio_vec bv;
0642     struct bio *bio;
0643 
0644     /*
0645      * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
0646      * bio_src->bi_io_vec to bio->bi_io_vec.
0647      *
0648      * We can't do that anymore, because:
0649      *
0650      *  - The point of cloning the biovec is to produce a bio with a biovec
0651      *    the caller can modify: bi_idx and bi_bvec_done should be 0.
0652      *
0653      *  - The original bio could've had more than BIO_MAX_PAGES biovecs; if
0654      *    we tried to clone the whole thing bio_alloc_bioset() would fail.
0655      *    But the clone should succeed as long as the number of biovecs we
0656      *    actually need to allocate is fewer than BIO_MAX_PAGES.
0657      *
0658      *  - Lastly, bi_vcnt should not be looked at or relied upon by code
0659      *    that does not own the bio - reason being drivers don't use it for
0660      *    iterating over the biovec anymore, so expecting it to be kept up
0661      *    to date (i.e. for clones that share the parent biovec) is just
0662      *    asking for trouble and would force extra work on
0663      *    __bio_clone_fast() anyways.
0664      */
0665 
0666     bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src), bs);
0667     if (!bio)
0668         return NULL;
0669     bio->bi_bdev        = bio_src->bi_bdev;
0670     bio->bi_opf     = bio_src->bi_opf;
0671     bio->bi_iter.bi_sector  = bio_src->bi_iter.bi_sector;
0672     bio->bi_iter.bi_size    = bio_src->bi_iter.bi_size;
0673 
0674     switch (bio_op(bio)) {
0675     case REQ_OP_DISCARD:
0676     case REQ_OP_SECURE_ERASE:
0677     case REQ_OP_WRITE_ZEROES:
0678         break;
0679     case REQ_OP_WRITE_SAME:
0680         bio->bi_io_vec[bio->bi_vcnt++] = bio_src->bi_io_vec[0];
0681         break;
0682     default:
0683         bio_for_each_segment(bv, bio_src, iter)
0684             bio->bi_io_vec[bio->bi_vcnt++] = bv;
0685         break;
0686     }
0687 
0688     if (bio_integrity(bio_src)) {
0689         int ret;
0690 
0691         ret = bio_integrity_clone(bio, bio_src, gfp_mask);
0692         if (ret < 0) {
0693             bio_put(bio);
0694             return NULL;
0695         }
0696     }
0697 
0698     bio_clone_blkcg_association(bio, bio_src);
0699 
0700     return bio;
0701 }
0702 EXPORT_SYMBOL(bio_clone_bioset);
0703 
0704 /**
0705  *  bio_add_pc_page -   attempt to add page to bio
0706  *  @q: the target queue
0707  *  @bio: destination bio
0708  *  @page: page to add
0709  *  @len: vec entry length
0710  *  @offset: vec entry offset
0711  *
0712  *  Attempt to add a page to the bio_vec maplist. This can fail for a
0713  *  number of reasons, such as the bio being full or target block device
0714  *  limitations. The target block device must allow bio's up to PAGE_SIZE,
0715  *  so it is always possible to add a single page to an empty bio.
0716  *
0717  *  This should only be used by REQ_PC bios.
0718  */
0719 int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page
0720             *page, unsigned int len, unsigned int offset)
0721 {
0722     int retried_segments = 0;
0723     struct bio_vec *bvec;
0724 
0725     /*
0726      * cloned bio must not modify vec list
0727      */
0728     if (unlikely(bio_flagged(bio, BIO_CLONED)))
0729         return 0;
0730 
0731     if (((bio->bi_iter.bi_size + len) >> 9) > queue_max_hw_sectors(q))
0732         return 0;
0733 
0734     /*
0735      * For filesystems with a blocksize smaller than the pagesize
0736      * we will often be called with the same page as last time and
0737      * a consecutive offset.  Optimize this special case.
0738      */
0739     if (bio->bi_vcnt > 0) {
0740         struct bio_vec *prev = &bio->bi_io_vec[bio->bi_vcnt - 1];
0741 
0742         if (page == prev->bv_page &&
0743             offset == prev->bv_offset + prev->bv_len) {
0744             prev->bv_len += len;
0745             bio->bi_iter.bi_size += len;
0746             goto done;
0747         }
0748 
0749         /*
0750          * If the queue doesn't support SG gaps and adding this
0751          * offset would create a gap, disallow it.
0752          */
0753         if (bvec_gap_to_prev(q, prev, offset))
0754             return 0;
0755     }
0756 
0757     if (bio->bi_vcnt >= bio->bi_max_vecs)
0758         return 0;
0759 
0760     /*
0761      * setup the new entry, we might clear it again later if we
0762      * cannot add the page
0763      */
0764     bvec = &bio->bi_io_vec[bio->bi_vcnt];
0765     bvec->bv_page = page;
0766     bvec->bv_len = len;
0767     bvec->bv_offset = offset;
0768     bio->bi_vcnt++;
0769     bio->bi_phys_segments++;
0770     bio->bi_iter.bi_size += len;
0771 
0772     /*
0773      * Perform a recount if the number of segments is greater
0774      * than queue_max_segments(q).
0775      */
0776 
0777     while (bio->bi_phys_segments > queue_max_segments(q)) {
0778 
0779         if (retried_segments)
0780             goto failed;
0781 
0782         retried_segments = 1;
0783         blk_recount_segments(q, bio);
0784     }
0785 
0786     /* If we may be able to merge these biovecs, force a recount */
0787     if (bio->bi_vcnt > 1 && (BIOVEC_PHYS_MERGEABLE(bvec-1, bvec)))
0788         bio_clear_flag(bio, BIO_SEG_VALID);
0789 
0790  done:
0791     return len;
0792 
0793  failed:
0794     bvec->bv_page = NULL;
0795     bvec->bv_len = 0;
0796     bvec->bv_offset = 0;
0797     bio->bi_vcnt--;
0798     bio->bi_iter.bi_size -= len;
0799     blk_recount_segments(q, bio);
0800     return 0;
0801 }
0802 EXPORT_SYMBOL(bio_add_pc_page);
0803 
0804 /**
0805  *  bio_add_page    -   attempt to add page to bio
0806  *  @bio: destination bio
0807  *  @page: page to add
0808  *  @len: vec entry length
0809  *  @offset: vec entry offset
0810  *
0811  *  Attempt to add a page to the bio_vec maplist. This will only fail
0812  *  if either bio->bi_vcnt == bio->bi_max_vecs or it's a cloned bio.
0813  */
0814 int bio_add_page(struct bio *bio, struct page *page,
0815          unsigned int len, unsigned int offset)
0816 {
0817     struct bio_vec *bv;
0818 
0819     /*
0820      * cloned bio must not modify vec list
0821      */
0822     if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
0823         return 0;
0824 
0825     /*
0826      * For filesystems with a blocksize smaller than the pagesize
0827      * we will often be called with the same page as last time and
0828      * a consecutive offset.  Optimize this special case.
0829      */
0830     if (bio->bi_vcnt > 0) {
0831         bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
0832 
0833         if (page == bv->bv_page &&
0834             offset == bv->bv_offset + bv->bv_len) {
0835             bv->bv_len += len;
0836             goto done;
0837         }
0838     }
0839 
0840     if (bio->bi_vcnt >= bio->bi_max_vecs)
0841         return 0;
0842 
0843     bv      = &bio->bi_io_vec[bio->bi_vcnt];
0844     bv->bv_page = page;
0845     bv->bv_len  = len;
0846     bv->bv_offset   = offset;
0847 
0848     bio->bi_vcnt++;
0849 done:
0850     bio->bi_iter.bi_size += len;
0851     return len;
0852 }
0853 EXPORT_SYMBOL(bio_add_page);
0854 
0855 /**
0856  * bio_iov_iter_get_pages - pin user or kernel pages and add them to a bio
0857  * @bio: bio to add pages to
0858  * @iter: iov iterator describing the region to be mapped
0859  *
0860  * Pins as many pages from *iter and appends them to @bio's bvec array. The
0861  * pages will have to be released using put_page() when done.
0862  */
0863 int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
0864 {
0865     unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt;
0866     struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt;
0867     struct page **pages = (struct page **)bv;
0868     size_t offset, diff;
0869     ssize_t size;
0870 
0871     size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
0872     if (unlikely(size <= 0))
0873         return size ? size : -EFAULT;
0874     nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE;
0875 
0876     /*
0877      * Deep magic below:  We need to walk the pinned pages backwards
0878      * because we are abusing the space allocated for the bio_vecs
0879      * for the page array.  Because the bio_vecs are larger than the
0880      * page pointers by definition this will always work.  But it also
0881      * means we can't use bio_add_page, so any changes to it's semantics
0882      * need to be reflected here as well.
0883      */
0884     bio->bi_iter.bi_size += size;
0885     bio->bi_vcnt += nr_pages;
0886 
0887     diff = (nr_pages * PAGE_SIZE - offset) - size;
0888     while (nr_pages--) {
0889         bv[nr_pages].bv_page = pages[nr_pages];
0890         bv[nr_pages].bv_len = PAGE_SIZE;
0891         bv[nr_pages].bv_offset = 0;
0892     }
0893 
0894     bv[0].bv_offset += offset;
0895     bv[0].bv_len -= offset;
0896     if (diff)
0897         bv[bio->bi_vcnt - 1].bv_len -= diff;
0898 
0899     iov_iter_advance(iter, size);
0900     return 0;
0901 }
0902 EXPORT_SYMBOL_GPL(bio_iov_iter_get_pages);
0903 
0904 struct submit_bio_ret {
0905     struct completion event;
0906     int error;
0907 };
0908 
0909 static void submit_bio_wait_endio(struct bio *bio)
0910 {
0911     struct submit_bio_ret *ret = bio->bi_private;
0912 
0913     ret->error = bio->bi_error;
0914     complete(&ret->event);
0915 }
0916 
0917 /**
0918  * submit_bio_wait - submit a bio, and wait until it completes
0919  * @bio: The &struct bio which describes the I/O
0920  *
0921  * Simple wrapper around submit_bio(). Returns 0 on success, or the error from
0922  * bio_endio() on failure.
0923  */
0924 int submit_bio_wait(struct bio *bio)
0925 {
0926     struct submit_bio_ret ret;
0927 
0928     init_completion(&ret.event);
0929     bio->bi_private = &ret;
0930     bio->bi_end_io = submit_bio_wait_endio;
0931     bio->bi_opf |= REQ_SYNC;
0932     submit_bio(bio);
0933     wait_for_completion_io(&ret.event);
0934 
0935     return ret.error;
0936 }
0937 EXPORT_SYMBOL(submit_bio_wait);
0938 
0939 /**
0940  * bio_advance - increment/complete a bio by some number of bytes
0941  * @bio:    bio to advance
0942  * @bytes:  number of bytes to complete
0943  *
0944  * This updates bi_sector, bi_size and bi_idx; if the number of bytes to
0945  * complete doesn't align with a bvec boundary, then bv_len and bv_offset will
0946  * be updated on the last bvec as well.
0947  *
0948  * @bio will then represent the remaining, uncompleted portion of the io.
0949  */
0950 void bio_advance(struct bio *bio, unsigned bytes)
0951 {
0952     if (bio_integrity(bio))
0953         bio_integrity_advance(bio, bytes);
0954 
0955     bio_advance_iter(bio, &bio->bi_iter, bytes);
0956 }
0957 EXPORT_SYMBOL(bio_advance);
0958 
0959 /**
0960  * bio_alloc_pages - allocates a single page for each bvec in a bio
0961  * @bio: bio to allocate pages for
0962  * @gfp_mask: flags for allocation
0963  *
0964  * Allocates pages up to @bio->bi_vcnt.
0965  *
0966  * Returns 0 on success, -ENOMEM on failure. On failure, any allocated pages are
0967  * freed.
0968  */
0969 int bio_alloc_pages(struct bio *bio, gfp_t gfp_mask)
0970 {
0971     int i;
0972     struct bio_vec *bv;
0973 
0974     bio_for_each_segment_all(bv, bio, i) {
0975         bv->bv_page = alloc_page(gfp_mask);
0976         if (!bv->bv_page) {
0977             while (--bv >= bio->bi_io_vec)
0978                 __free_page(bv->bv_page);
0979             return -ENOMEM;
0980         }
0981     }
0982 
0983     return 0;
0984 }
0985 EXPORT_SYMBOL(bio_alloc_pages);
0986 
0987 /**
0988  * bio_copy_data - copy contents of data buffers from one chain of bios to
0989  * another
0990  * @src: source bio list
0991  * @dst: destination bio list
0992  *
0993  * If @src and @dst are single bios, bi_next must be NULL - otherwise, treats
0994  * @src and @dst as linked lists of bios.
0995  *
0996  * Stops when it reaches the end of either @src or @dst - that is, copies
0997  * min(src->bi_size, dst->bi_size) bytes (or the equivalent for lists of bios).
0998  */
0999 void bio_copy_data(struct bio *dst, struct bio *src)
1000 {
1001     struct bvec_iter src_iter, dst_iter;
1002     struct bio_vec src_bv, dst_bv;
1003     void *src_p, *dst_p;
1004     unsigned bytes;
1005 
1006     src_iter = src->bi_iter;
1007     dst_iter = dst->bi_iter;
1008 
1009     while (1) {
1010         if (!src_iter.bi_size) {
1011             src = src->bi_next;
1012             if (!src)
1013                 break;
1014 
1015             src_iter = src->bi_iter;
1016         }
1017 
1018         if (!dst_iter.bi_size) {
1019             dst = dst->bi_next;
1020             if (!dst)
1021                 break;
1022 
1023             dst_iter = dst->bi_iter;
1024         }
1025 
1026         src_bv = bio_iter_iovec(src, src_iter);
1027         dst_bv = bio_iter_iovec(dst, dst_iter);
1028 
1029         bytes = min(src_bv.bv_len, dst_bv.bv_len);
1030 
1031         src_p = kmap_atomic(src_bv.bv_page);
1032         dst_p = kmap_atomic(dst_bv.bv_page);
1033 
1034         memcpy(dst_p + dst_bv.bv_offset,
1035                src_p + src_bv.bv_offset,
1036                bytes);
1037 
1038         kunmap_atomic(dst_p);
1039         kunmap_atomic(src_p);
1040 
1041         bio_advance_iter(src, &src_iter, bytes);
1042         bio_advance_iter(dst, &dst_iter, bytes);
1043     }
1044 }
1045 EXPORT_SYMBOL(bio_copy_data);
1046 
1047 struct bio_map_data {
1048     int is_our_pages;
1049     struct iov_iter iter;
1050     struct iovec iov[];
1051 };
1052 
1053 static struct bio_map_data *bio_alloc_map_data(unsigned int iov_count,
1054                            gfp_t gfp_mask)
1055 {
1056     if (iov_count > UIO_MAXIOV)
1057         return NULL;
1058 
1059     return kmalloc(sizeof(struct bio_map_data) +
1060                sizeof(struct iovec) * iov_count, gfp_mask);
1061 }
1062 
1063 /**
1064  * bio_copy_from_iter - copy all pages from iov_iter to bio
1065  * @bio: The &struct bio which describes the I/O as destination
1066  * @iter: iov_iter as source
1067  *
1068  * Copy all pages from iov_iter to bio.
1069  * Returns 0 on success, or error on failure.
1070  */
1071 static int bio_copy_from_iter(struct bio *bio, struct iov_iter iter)
1072 {
1073     int i;
1074     struct bio_vec *bvec;
1075 
1076     bio_for_each_segment_all(bvec, bio, i) {
1077         ssize_t ret;
1078 
1079         ret = copy_page_from_iter(bvec->bv_page,
1080                       bvec->bv_offset,
1081                       bvec->bv_len,
1082                       &iter);
1083 
1084         if (!iov_iter_count(&iter))
1085             break;
1086 
1087         if (ret < bvec->bv_len)
1088             return -EFAULT;
1089     }
1090 
1091     return 0;
1092 }
1093 
1094 /**
1095  * bio_copy_to_iter - copy all pages from bio to iov_iter
1096  * @bio: The &struct bio which describes the I/O as source
1097  * @iter: iov_iter as destination
1098  *
1099  * Copy all pages from bio to iov_iter.
1100  * Returns 0 on success, or error on failure.
1101  */
1102 static int bio_copy_to_iter(struct bio *bio, struct iov_iter iter)
1103 {
1104     int i;
1105     struct bio_vec *bvec;
1106 
1107     bio_for_each_segment_all(bvec, bio, i) {
1108         ssize_t ret;
1109 
1110         ret = copy_page_to_iter(bvec->bv_page,
1111                     bvec->bv_offset,
1112                     bvec->bv_len,
1113                     &iter);
1114 
1115         if (!iov_iter_count(&iter))
1116             break;
1117 
1118         if (ret < bvec->bv_len)
1119             return -EFAULT;
1120     }
1121 
1122     return 0;
1123 }
1124 
1125 void bio_free_pages(struct bio *bio)
1126 {
1127     struct bio_vec *bvec;
1128     int i;
1129 
1130     bio_for_each_segment_all(bvec, bio, i)
1131         __free_page(bvec->bv_page);
1132 }
1133 EXPORT_SYMBOL(bio_free_pages);
1134 
1135 /**
1136  *  bio_uncopy_user -   finish previously mapped bio
1137  *  @bio: bio being terminated
1138  *
1139  *  Free pages allocated from bio_copy_user_iov() and write back data
1140  *  to user space in case of a read.
1141  */
1142 int bio_uncopy_user(struct bio *bio)
1143 {
1144     struct bio_map_data *bmd = bio->bi_private;
1145     int ret = 0;
1146 
1147     if (!bio_flagged(bio, BIO_NULL_MAPPED)) {
1148         /*
1149          * if we're in a workqueue, the request is orphaned, so
1150          * don't copy into a random user address space, just free
1151          * and return -EINTR so user space doesn't expect any data.
1152          */
1153         if (!current->mm)
1154             ret = -EINTR;
1155         else if (bio_data_dir(bio) == READ)
1156             ret = bio_copy_to_iter(bio, bmd->iter);
1157         if (bmd->is_our_pages)
1158             bio_free_pages(bio);
1159     }
1160     kfree(bmd);
1161     bio_put(bio);
1162     return ret;
1163 }
1164 
1165 /**
1166  *  bio_copy_user_iov   -   copy user data to bio
1167  *  @q:     destination block queue
1168  *  @map_data:  pointer to the rq_map_data holding pages (if necessary)
1169  *  @iter:      iovec iterator
1170  *  @gfp_mask:  memory allocation flags
1171  *
1172  *  Prepares and returns a bio for indirect user io, bouncing data
1173  *  to/from kernel pages as necessary. Must be paired with
1174  *  call bio_uncopy_user() on io completion.
1175  */
1176 struct bio *bio_copy_user_iov(struct request_queue *q,
1177                   struct rq_map_data *map_data,
1178                   const struct iov_iter *iter,
1179                   gfp_t gfp_mask)
1180 {
1181     struct bio_map_data *bmd;
1182     struct page *page;
1183     struct bio *bio;
1184     int i, ret;
1185     int nr_pages = 0;
1186     unsigned int len = iter->count;
1187     unsigned int offset = map_data ? offset_in_page(map_data->offset) : 0;
1188 
1189     for (i = 0; i < iter->nr_segs; i++) {
1190         unsigned long uaddr;
1191         unsigned long end;
1192         unsigned long start;
1193 
1194         uaddr = (unsigned long) iter->iov[i].iov_base;
1195         end = (uaddr + iter->iov[i].iov_len + PAGE_SIZE - 1)
1196             >> PAGE_SHIFT;
1197         start = uaddr >> PAGE_SHIFT;
1198 
1199         /*
1200          * Overflow, abort
1201          */
1202         if (end < start)
1203             return ERR_PTR(-EINVAL);
1204 
1205         nr_pages += end - start;
1206     }
1207 
1208     if (offset)
1209         nr_pages++;
1210 
1211     bmd = bio_alloc_map_data(iter->nr_segs, gfp_mask);
1212     if (!bmd)
1213         return ERR_PTR(-ENOMEM);
1214 
1215     /*
1216      * We need to do a deep copy of the iov_iter including the iovecs.
1217      * The caller provided iov might point to an on-stack or otherwise
1218      * shortlived one.
1219      */
1220     bmd->is_our_pages = map_data ? 0 : 1;
1221     memcpy(bmd->iov, iter->iov, sizeof(struct iovec) * iter->nr_segs);
1222     iov_iter_init(&bmd->iter, iter->type, bmd->iov,
1223             iter->nr_segs, iter->count);
1224 
1225     ret = -ENOMEM;
1226     bio = bio_kmalloc(gfp_mask, nr_pages);
1227     if (!bio)
1228         goto out_bmd;
1229 
1230     if (iter->type & WRITE)
1231         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
1232 
1233     ret = 0;
1234 
1235     if (map_data) {
1236         nr_pages = 1 << map_data->page_order;
1237         i = map_data->offset / PAGE_SIZE;
1238     }
1239     while (len) {
1240         unsigned int bytes = PAGE_SIZE;
1241 
1242         bytes -= offset;
1243 
1244         if (bytes > len)
1245             bytes = len;
1246 
1247         if (map_data) {
1248             if (i == map_data->nr_entries * nr_pages) {
1249                 ret = -ENOMEM;
1250                 break;
1251             }
1252 
1253             page = map_data->pages[i / nr_pages];
1254             page += (i % nr_pages);
1255 
1256             i++;
1257         } else {
1258             page = alloc_page(q->bounce_gfp | gfp_mask);
1259             if (!page) {
1260                 ret = -ENOMEM;
1261                 break;
1262             }
1263         }
1264 
1265         if (bio_add_pc_page(q, bio, page, bytes, offset) < bytes)
1266             break;
1267 
1268         len -= bytes;
1269         offset = 0;
1270     }
1271 
1272     if (ret)
1273         goto cleanup;
1274 
1275     /*
1276      * success
1277      */
1278     if (((iter->type & WRITE) && (!map_data || !map_data->null_mapped)) ||
1279         (map_data && map_data->from_user)) {
1280         ret = bio_copy_from_iter(bio, *iter);
1281         if (ret)
1282             goto cleanup;
1283     }
1284 
1285     bio->bi_private = bmd;
1286     return bio;
1287 cleanup:
1288     if (!map_data)
1289         bio_free_pages(bio);
1290     bio_put(bio);
1291 out_bmd:
1292     kfree(bmd);
1293     return ERR_PTR(ret);
1294 }
1295 
1296 /**
1297  *  bio_map_user_iov - map user iovec into bio
1298  *  @q:     the struct request_queue for the bio
1299  *  @iter:      iovec iterator
1300  *  @gfp_mask:  memory allocation flags
1301  *
1302  *  Map the user space address into a bio suitable for io to a block
1303  *  device. Returns an error pointer in case of error.
1304  */
1305 struct bio *bio_map_user_iov(struct request_queue *q,
1306                  const struct iov_iter *iter,
1307                  gfp_t gfp_mask)
1308 {
1309     int j;
1310     int nr_pages = 0;
1311     struct page **pages;
1312     struct bio *bio;
1313     int cur_page = 0;
1314     int ret, offset;
1315     struct iov_iter i;
1316     struct iovec iov;
1317 
1318     iov_for_each(iov, i, *iter) {
1319         unsigned long uaddr = (unsigned long) iov.iov_base;
1320         unsigned long len = iov.iov_len;
1321         unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1322         unsigned long start = uaddr >> PAGE_SHIFT;
1323 
1324         /*
1325          * Overflow, abort
1326          */
1327         if (end < start)
1328             return ERR_PTR(-EINVAL);
1329 
1330         nr_pages += end - start;
1331         /*
1332          * buffer must be aligned to at least logical block size for now
1333          */
1334         if (uaddr & queue_dma_alignment(q))
1335             return ERR_PTR(-EINVAL);
1336     }
1337 
1338     if (!nr_pages)
1339         return ERR_PTR(-EINVAL);
1340 
1341     bio = bio_kmalloc(gfp_mask, nr_pages);
1342     if (!bio)
1343         return ERR_PTR(-ENOMEM);
1344 
1345     ret = -ENOMEM;
1346     pages = kcalloc(nr_pages, sizeof(struct page *), gfp_mask);
1347     if (!pages)
1348         goto out;
1349 
1350     iov_for_each(iov, i, *iter) {
1351         unsigned long uaddr = (unsigned long) iov.iov_base;
1352         unsigned long len = iov.iov_len;
1353         unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1354         unsigned long start = uaddr >> PAGE_SHIFT;
1355         const int local_nr_pages = end - start;
1356         const int page_limit = cur_page + local_nr_pages;
1357 
1358         ret = get_user_pages_fast(uaddr, local_nr_pages,
1359                 (iter->type & WRITE) != WRITE,
1360                 &pages[cur_page]);
1361         if (ret < local_nr_pages) {
1362             ret = -EFAULT;
1363             goto out_unmap;
1364         }
1365 
1366         offset = offset_in_page(uaddr);
1367         for (j = cur_page; j < page_limit; j++) {
1368             unsigned int bytes = PAGE_SIZE - offset;
1369 
1370             if (len <= 0)
1371                 break;
1372             
1373             if (bytes > len)
1374                 bytes = len;
1375 
1376             /*
1377              * sorry...
1378              */
1379             if (bio_add_pc_page(q, bio, pages[j], bytes, offset) <
1380                         bytes)
1381                 break;
1382 
1383             len -= bytes;
1384             offset = 0;
1385         }
1386 
1387         cur_page = j;
1388         /*
1389          * release the pages we didn't map into the bio, if any
1390          */
1391         while (j < page_limit)
1392             put_page(pages[j++]);
1393     }
1394 
1395     kfree(pages);
1396 
1397     /*
1398      * set data direction, and check if mapped pages need bouncing
1399      */
1400     if (iter->type & WRITE)
1401         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
1402 
1403     bio_set_flag(bio, BIO_USER_MAPPED);
1404 
1405     /*
1406      * subtle -- if __bio_map_user() ended up bouncing a bio,
1407      * it would normally disappear when its bi_end_io is run.
1408      * however, we need it for the unmap, so grab an extra
1409      * reference to it
1410      */
1411     bio_get(bio);
1412     return bio;
1413 
1414  out_unmap:
1415     for (j = 0; j < nr_pages; j++) {
1416         if (!pages[j])
1417             break;
1418         put_page(pages[j]);
1419     }
1420  out:
1421     kfree(pages);
1422     bio_put(bio);
1423     return ERR_PTR(ret);
1424 }
1425 
1426 static void __bio_unmap_user(struct bio *bio)
1427 {
1428     struct bio_vec *bvec;
1429     int i;
1430 
1431     /*
1432      * make sure we dirty pages we wrote to
1433      */
1434     bio_for_each_segment_all(bvec, bio, i) {
1435         if (bio_data_dir(bio) == READ)
1436             set_page_dirty_lock(bvec->bv_page);
1437 
1438         put_page(bvec->bv_page);
1439     }
1440 
1441     bio_put(bio);
1442 }
1443 
1444 /**
1445  *  bio_unmap_user  -   unmap a bio
1446  *  @bio:       the bio being unmapped
1447  *
1448  *  Unmap a bio previously mapped by bio_map_user(). Must be called with
1449  *  a process context.
1450  *
1451  *  bio_unmap_user() may sleep.
1452  */
1453 void bio_unmap_user(struct bio *bio)
1454 {
1455     __bio_unmap_user(bio);
1456     bio_put(bio);
1457 }
1458 
1459 static void bio_map_kern_endio(struct bio *bio)
1460 {
1461     bio_put(bio);
1462 }
1463 
1464 /**
1465  *  bio_map_kern    -   map kernel address into bio
1466  *  @q: the struct request_queue for the bio
1467  *  @data: pointer to buffer to map
1468  *  @len: length in bytes
1469  *  @gfp_mask: allocation flags for bio allocation
1470  *
1471  *  Map the kernel address into a bio suitable for io to a block
1472  *  device. Returns an error pointer in case of error.
1473  */
1474 struct bio *bio_map_kern(struct request_queue *q, void *data, unsigned int len,
1475              gfp_t gfp_mask)
1476 {
1477     unsigned long kaddr = (unsigned long)data;
1478     unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1479     unsigned long start = kaddr >> PAGE_SHIFT;
1480     const int nr_pages = end - start;
1481     int offset, i;
1482     struct bio *bio;
1483 
1484     bio = bio_kmalloc(gfp_mask, nr_pages);
1485     if (!bio)
1486         return ERR_PTR(-ENOMEM);
1487 
1488     offset = offset_in_page(kaddr);
1489     for (i = 0; i < nr_pages; i++) {
1490         unsigned int bytes = PAGE_SIZE - offset;
1491 
1492         if (len <= 0)
1493             break;
1494 
1495         if (bytes > len)
1496             bytes = len;
1497 
1498         if (bio_add_pc_page(q, bio, virt_to_page(data), bytes,
1499                     offset) < bytes) {
1500             /* we don't support partial mappings */
1501             bio_put(bio);
1502             return ERR_PTR(-EINVAL);
1503         }
1504 
1505         data += bytes;
1506         len -= bytes;
1507         offset = 0;
1508     }
1509 
1510     bio->bi_end_io = bio_map_kern_endio;
1511     return bio;
1512 }
1513 EXPORT_SYMBOL(bio_map_kern);
1514 
1515 static void bio_copy_kern_endio(struct bio *bio)
1516 {
1517     bio_free_pages(bio);
1518     bio_put(bio);
1519 }
1520 
1521 static void bio_copy_kern_endio_read(struct bio *bio)
1522 {
1523     char *p = bio->bi_private;
1524     struct bio_vec *bvec;
1525     int i;
1526 
1527     bio_for_each_segment_all(bvec, bio, i) {
1528         memcpy(p, page_address(bvec->bv_page), bvec->bv_len);
1529         p += bvec->bv_len;
1530     }
1531 
1532     bio_copy_kern_endio(bio);
1533 }
1534 
1535 /**
1536  *  bio_copy_kern   -   copy kernel address into bio
1537  *  @q: the struct request_queue for the bio
1538  *  @data: pointer to buffer to copy
1539  *  @len: length in bytes
1540  *  @gfp_mask: allocation flags for bio and page allocation
1541  *  @reading: data direction is READ
1542  *
1543  *  copy the kernel address into a bio suitable for io to a block
1544  *  device. Returns an error pointer in case of error.
1545  */
1546 struct bio *bio_copy_kern(struct request_queue *q, void *data, unsigned int len,
1547               gfp_t gfp_mask, int reading)
1548 {
1549     unsigned long kaddr = (unsigned long)data;
1550     unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1551     unsigned long start = kaddr >> PAGE_SHIFT;
1552     struct bio *bio;
1553     void *p = data;
1554     int nr_pages = 0;
1555 
1556     /*
1557      * Overflow, abort
1558      */
1559     if (end < start)
1560         return ERR_PTR(-EINVAL);
1561 
1562     nr_pages = end - start;
1563     bio = bio_kmalloc(gfp_mask, nr_pages);
1564     if (!bio)
1565         return ERR_PTR(-ENOMEM);
1566 
1567     while (len) {
1568         struct page *page;
1569         unsigned int bytes = PAGE_SIZE;
1570 
1571         if (bytes > len)
1572             bytes = len;
1573 
1574         page = alloc_page(q->bounce_gfp | gfp_mask);
1575         if (!page)
1576             goto cleanup;
1577 
1578         if (!reading)
1579             memcpy(page_address(page), p, bytes);
1580 
1581         if (bio_add_pc_page(q, bio, page, bytes, 0) < bytes)
1582             break;
1583 
1584         len -= bytes;
1585         p += bytes;
1586     }
1587 
1588     if (reading) {
1589         bio->bi_end_io = bio_copy_kern_endio_read;
1590         bio->bi_private = data;
1591     } else {
1592         bio->bi_end_io = bio_copy_kern_endio;
1593         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
1594     }
1595 
1596     return bio;
1597 
1598 cleanup:
1599     bio_free_pages(bio);
1600     bio_put(bio);
1601     return ERR_PTR(-ENOMEM);
1602 }
1603 
1604 /*
1605  * bio_set_pages_dirty() and bio_check_pages_dirty() are support functions
1606  * for performing direct-IO in BIOs.
1607  *
1608  * The problem is that we cannot run set_page_dirty() from interrupt context
1609  * because the required locks are not interrupt-safe.  So what we can do is to
1610  * mark the pages dirty _before_ performing IO.  And in interrupt context,
1611  * check that the pages are still dirty.   If so, fine.  If not, redirty them
1612  * in process context.
1613  *
1614  * We special-case compound pages here: normally this means reads into hugetlb
1615  * pages.  The logic in here doesn't really work right for compound pages
1616  * because the VM does not uniformly chase down the head page in all cases.
1617  * But dirtiness of compound pages is pretty meaningless anyway: the VM doesn't
1618  * handle them at all.  So we skip compound pages here at an early stage.
1619  *
1620  * Note that this code is very hard to test under normal circumstances because
1621  * direct-io pins the pages with get_user_pages().  This makes
1622  * is_page_cache_freeable return false, and the VM will not clean the pages.
1623  * But other code (eg, flusher threads) could clean the pages if they are mapped
1624  * pagecache.
1625  *
1626  * Simply disabling the call to bio_set_pages_dirty() is a good way to test the
1627  * deferred bio dirtying paths.
1628  */
1629 
1630 /*
1631  * bio_set_pages_dirty() will mark all the bio's pages as dirty.
1632  */
1633 void bio_set_pages_dirty(struct bio *bio)
1634 {
1635     struct bio_vec *bvec;
1636     int i;
1637 
1638     bio_for_each_segment_all(bvec, bio, i) {
1639         struct page *page = bvec->bv_page;
1640 
1641         if (page && !PageCompound(page))
1642             set_page_dirty_lock(page);
1643     }
1644 }
1645 
1646 static void bio_release_pages(struct bio *bio)
1647 {
1648     struct bio_vec *bvec;
1649     int i;
1650 
1651     bio_for_each_segment_all(bvec, bio, i) {
1652         struct page *page = bvec->bv_page;
1653 
1654         if (page)
1655             put_page(page);
1656     }
1657 }
1658 
1659 /*
1660  * bio_check_pages_dirty() will check that all the BIO's pages are still dirty.
1661  * If they are, then fine.  If, however, some pages are clean then they must
1662  * have been written out during the direct-IO read.  So we take another ref on
1663  * the BIO and the offending pages and re-dirty the pages in process context.
1664  *
1665  * It is expected that bio_check_pages_dirty() will wholly own the BIO from
1666  * here on.  It will run one put_page() against each page and will run one
1667  * bio_put() against the BIO.
1668  */
1669 
1670 static void bio_dirty_fn(struct work_struct *work);
1671 
1672 static DECLARE_WORK(bio_dirty_work, bio_dirty_fn);
1673 static DEFINE_SPINLOCK(bio_dirty_lock);
1674 static struct bio *bio_dirty_list;
1675 
1676 /*
1677  * This runs in process context
1678  */
1679 static void bio_dirty_fn(struct work_struct *work)
1680 {
1681     unsigned long flags;
1682     struct bio *bio;
1683 
1684     spin_lock_irqsave(&bio_dirty_lock, flags);
1685     bio = bio_dirty_list;
1686     bio_dirty_list = NULL;
1687     spin_unlock_irqrestore(&bio_dirty_lock, flags);
1688 
1689     while (bio) {
1690         struct bio *next = bio->bi_private;
1691 
1692         bio_set_pages_dirty(bio);
1693         bio_release_pages(bio);
1694         bio_put(bio);
1695         bio = next;
1696     }
1697 }
1698 
1699 void bio_check_pages_dirty(struct bio *bio)
1700 {
1701     struct bio_vec *bvec;
1702     int nr_clean_pages = 0;
1703     int i;
1704 
1705     bio_for_each_segment_all(bvec, bio, i) {
1706         struct page *page = bvec->bv_page;
1707 
1708         if (PageDirty(page) || PageCompound(page)) {
1709             put_page(page);
1710             bvec->bv_page = NULL;
1711         } else {
1712             nr_clean_pages++;
1713         }
1714     }
1715 
1716     if (nr_clean_pages) {
1717         unsigned long flags;
1718 
1719         spin_lock_irqsave(&bio_dirty_lock, flags);
1720         bio->bi_private = bio_dirty_list;
1721         bio_dirty_list = bio;
1722         spin_unlock_irqrestore(&bio_dirty_lock, flags);
1723         schedule_work(&bio_dirty_work);
1724     } else {
1725         bio_put(bio);
1726     }
1727 }
1728 
1729 void generic_start_io_acct(int rw, unsigned long sectors,
1730                struct hd_struct *part)
1731 {
1732     int cpu = part_stat_lock();
1733 
1734     part_round_stats(cpu, part);
1735     part_stat_inc(cpu, part, ios[rw]);
1736     part_stat_add(cpu, part, sectors[rw], sectors);
1737     part_inc_in_flight(part, rw);
1738 
1739     part_stat_unlock();
1740 }
1741 EXPORT_SYMBOL(generic_start_io_acct);
1742 
1743 void generic_end_io_acct(int rw, struct hd_struct *part,
1744              unsigned long start_time)
1745 {
1746     unsigned long duration = jiffies - start_time;
1747     int cpu = part_stat_lock();
1748 
1749     part_stat_add(cpu, part, ticks[rw], duration);
1750     part_round_stats(cpu, part);
1751     part_dec_in_flight(part, rw);
1752 
1753     part_stat_unlock();
1754 }
1755 EXPORT_SYMBOL(generic_end_io_acct);
1756 
1757 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
1758 void bio_flush_dcache_pages(struct bio *bi)
1759 {
1760     struct bio_vec bvec;
1761     struct bvec_iter iter;
1762 
1763     bio_for_each_segment(bvec, bi, iter)
1764         flush_dcache_page(bvec.bv_page);
1765 }
1766 EXPORT_SYMBOL(bio_flush_dcache_pages);
1767 #endif
1768 
1769 static inline bool bio_remaining_done(struct bio *bio)
1770 {
1771     /*
1772      * If we're not chaining, then ->__bi_remaining is always 1 and
1773      * we always end io on the first invocation.
1774      */
1775     if (!bio_flagged(bio, BIO_CHAIN))
1776         return true;
1777 
1778     BUG_ON(atomic_read(&bio->__bi_remaining) <= 0);
1779 
1780     if (atomic_dec_and_test(&bio->__bi_remaining)) {
1781         bio_clear_flag(bio, BIO_CHAIN);
1782         return true;
1783     }
1784 
1785     return false;
1786 }
1787 
1788 /**
1789  * bio_endio - end I/O on a bio
1790  * @bio:    bio
1791  *
1792  * Description:
1793  *   bio_endio() will end I/O on the whole bio. bio_endio() is the preferred
1794  *   way to end I/O on a bio. No one should call bi_end_io() directly on a
1795  *   bio unless they own it and thus know that it has an end_io function.
1796  **/
1797 void bio_endio(struct bio *bio)
1798 {
1799 again:
1800     if (!bio_remaining_done(bio))
1801         return;
1802 
1803     /*
1804      * Need to have a real endio function for chained bios, otherwise
1805      * various corner cases will break (like stacking block devices that
1806      * save/restore bi_end_io) - however, we want to avoid unbounded
1807      * recursion and blowing the stack. Tail call optimization would
1808      * handle this, but compiling with frame pointers also disables
1809      * gcc's sibling call optimization.
1810      */
1811     if (bio->bi_end_io == bio_chain_endio) {
1812         bio = __bio_chain_endio(bio);
1813         goto again;
1814     }
1815 
1816     if (bio->bi_end_io)
1817         bio->bi_end_io(bio);
1818 }
1819 EXPORT_SYMBOL(bio_endio);
1820 
1821 /**
1822  * bio_split - split a bio
1823  * @bio:    bio to split
1824  * @sectors:    number of sectors to split from the front of @bio
1825  * @gfp:    gfp mask
1826  * @bs:     bio set to allocate from
1827  *
1828  * Allocates and returns a new bio which represents @sectors from the start of
1829  * @bio, and updates @bio to represent the remaining sectors.
1830  *
1831  * Unless this is a discard request the newly allocated bio will point
1832  * to @bio's bi_io_vec; it is the caller's responsibility to ensure that
1833  * @bio is not freed before the split.
1834  */
1835 struct bio *bio_split(struct bio *bio, int sectors,
1836               gfp_t gfp, struct bio_set *bs)
1837 {
1838     struct bio *split = NULL;
1839 
1840     BUG_ON(sectors <= 0);
1841     BUG_ON(sectors >= bio_sectors(bio));
1842 
1843     split = bio_clone_fast(bio, gfp, bs);
1844     if (!split)
1845         return NULL;
1846 
1847     split->bi_iter.bi_size = sectors << 9;
1848 
1849     if (bio_integrity(split))
1850         bio_integrity_trim(split, 0, sectors);
1851 
1852     bio_advance(bio, split->bi_iter.bi_size);
1853 
1854     return split;
1855 }
1856 EXPORT_SYMBOL(bio_split);
1857 
1858 /**
1859  * bio_trim - trim a bio
1860  * @bio:    bio to trim
1861  * @offset: number of sectors to trim from the front of @bio
1862  * @size:   size we want to trim @bio to, in sectors
1863  */
1864 void bio_trim(struct bio *bio, int offset, int size)
1865 {
1866     /* 'bio' is a cloned bio which we need to trim to match
1867      * the given offset and size.
1868      */
1869 
1870     size <<= 9;
1871     if (offset == 0 && size == bio->bi_iter.bi_size)
1872         return;
1873 
1874     bio_clear_flag(bio, BIO_SEG_VALID);
1875 
1876     bio_advance(bio, offset << 9);
1877 
1878     bio->bi_iter.bi_size = size;
1879 }
1880 EXPORT_SYMBOL_GPL(bio_trim);
1881 
1882 /*
1883  * create memory pools for biovec's in a bio_set.
1884  * use the global biovec slabs created for general use.
1885  */
1886 mempool_t *biovec_create_pool(int pool_entries)
1887 {
1888     struct biovec_slab *bp = bvec_slabs + BVEC_POOL_MAX;
1889 
1890     return mempool_create_slab_pool(pool_entries, bp->slab);
1891 }
1892 
1893 void bioset_free(struct bio_set *bs)
1894 {
1895     if (bs->rescue_workqueue)
1896         destroy_workqueue(bs->rescue_workqueue);
1897 
1898     if (bs->bio_pool)
1899         mempool_destroy(bs->bio_pool);
1900 
1901     if (bs->bvec_pool)
1902         mempool_destroy(bs->bvec_pool);
1903 
1904     bioset_integrity_free(bs);
1905     bio_put_slab(bs);
1906 
1907     kfree(bs);
1908 }
1909 EXPORT_SYMBOL(bioset_free);
1910 
1911 static struct bio_set *__bioset_create(unsigned int pool_size,
1912                        unsigned int front_pad,
1913                        bool create_bvec_pool)
1914 {
1915     unsigned int back_pad = BIO_INLINE_VECS * sizeof(struct bio_vec);
1916     struct bio_set *bs;
1917 
1918     bs = kzalloc(sizeof(*bs), GFP_KERNEL);
1919     if (!bs)
1920         return NULL;
1921 
1922     bs->front_pad = front_pad;
1923 
1924     spin_lock_init(&bs->rescue_lock);
1925     bio_list_init(&bs->rescue_list);
1926     INIT_WORK(&bs->rescue_work, bio_alloc_rescue);
1927 
1928     bs->bio_slab = bio_find_or_create_slab(front_pad + back_pad);
1929     if (!bs->bio_slab) {
1930         kfree(bs);
1931         return NULL;
1932     }
1933 
1934     bs->bio_pool = mempool_create_slab_pool(pool_size, bs->bio_slab);
1935     if (!bs->bio_pool)
1936         goto bad;
1937 
1938     if (create_bvec_pool) {
1939         bs->bvec_pool = biovec_create_pool(pool_size);
1940         if (!bs->bvec_pool)
1941             goto bad;
1942     }
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 
1954 /**
1955  * bioset_create  - Create a bio_set
1956  * @pool_size:  Number of bio and bio_vecs to cache in the mempool
1957  * @front_pad:  Number of bytes to allocate in front of the returned bio
1958  *
1959  * Description:
1960  *    Set up a bio_set to be used with @bio_alloc_bioset. Allows the caller
1961  *    to ask for a number of bytes to be allocated in front of the bio.
1962  *    Front pad allocation is useful for embedding the bio inside
1963  *    another structure, to avoid allocating extra data to go with the bio.
1964  *    Note that the bio must be embedded at the END of that structure always,
1965  *    or things will break badly.
1966  */
1967 struct bio_set *bioset_create(unsigned int pool_size, unsigned int front_pad)
1968 {
1969     return __bioset_create(pool_size, front_pad, true);
1970 }
1971 EXPORT_SYMBOL(bioset_create);
1972 
1973 /**
1974  * bioset_create_nobvec  - Create a bio_set without bio_vec mempool
1975  * @pool_size:  Number of bio to cache in the mempool
1976  * @front_pad:  Number of bytes to allocate in front of the returned bio
1977  *
1978  * Description:
1979  *    Same functionality as bioset_create() except that mempool is not
1980  *    created for bio_vecs. Saving some memory for bio_clone_fast() users.
1981  */
1982 struct bio_set *bioset_create_nobvec(unsigned int pool_size, unsigned int front_pad)
1983 {
1984     return __bioset_create(pool_size, front_pad, false);
1985 }
1986 EXPORT_SYMBOL(bioset_create_nobvec);
1987 
1988 #ifdef CONFIG_BLK_CGROUP
1989 
1990 /**
1991  * bio_associate_blkcg - associate a bio with the specified blkcg
1992  * @bio: target bio
1993  * @blkcg_css: css of the blkcg to associate
1994  *
1995  * Associate @bio with the blkcg specified by @blkcg_css.  Block layer will
1996  * treat @bio as if it were issued by a task which belongs to the blkcg.
1997  *
1998  * This function takes an extra reference of @blkcg_css which will be put
1999  * when @bio is released.  The caller must own @bio and is responsible for
2000  * synchronizing calls to this function.
2001  */
2002 int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css)
2003 {
2004     if (unlikely(bio->bi_css))
2005         return -EBUSY;
2006     css_get(blkcg_css);
2007     bio->bi_css = blkcg_css;
2008     return 0;
2009 }
2010 EXPORT_SYMBOL_GPL(bio_associate_blkcg);
2011 
2012 /**
2013  * bio_associate_current - associate a bio with %current
2014  * @bio: target bio
2015  *
2016  * Associate @bio with %current if it hasn't been associated yet.  Block
2017  * layer will treat @bio as if it were issued by %current no matter which
2018  * task actually issues it.
2019  *
2020  * This function takes an extra reference of @task's io_context and blkcg
2021  * which will be put when @bio is released.  The caller must own @bio,
2022  * ensure %current->io_context exists, and is responsible for synchronizing
2023  * calls to this function.
2024  */
2025 int bio_associate_current(struct bio *bio)
2026 {
2027     struct io_context *ioc;
2028 
2029     if (bio->bi_css)
2030         return -EBUSY;
2031 
2032     ioc = current->io_context;
2033     if (!ioc)
2034         return -ENOENT;
2035 
2036     get_io_context_active(ioc);
2037     bio->bi_ioc = ioc;
2038     bio->bi_css = task_get_css(current, io_cgrp_id);
2039     return 0;
2040 }
2041 EXPORT_SYMBOL_GPL(bio_associate_current);
2042 
2043 /**
2044  * bio_disassociate_task - undo bio_associate_current()
2045  * @bio: target bio
2046  */
2047 void bio_disassociate_task(struct bio *bio)
2048 {
2049     if (bio->bi_ioc) {
2050         put_io_context(bio->bi_ioc);
2051         bio->bi_ioc = NULL;
2052     }
2053     if (bio->bi_css) {
2054         css_put(bio->bi_css);
2055         bio->bi_css = NULL;
2056     }
2057 }
2058 
2059 /**
2060  * bio_clone_blkcg_association - clone blkcg association from src to dst bio
2061  * @dst: destination bio
2062  * @src: source bio
2063  */
2064 void bio_clone_blkcg_association(struct bio *dst, struct bio *src)
2065 {
2066     if (src->bi_css)
2067         WARN_ON(bio_associate_blkcg(dst, src->bi_css));
2068 }
2069 
2070 #endif /* CONFIG_BLK_CGROUP */
2071 
2072 static void __init biovec_init_slabs(void)
2073 {
2074     int i;
2075 
2076     for (i = 0; i < BVEC_POOL_NR; i++) {
2077         int size;
2078         struct biovec_slab *bvs = bvec_slabs + i;
2079 
2080         if (bvs->nr_vecs <= BIO_INLINE_VECS) {
2081             bvs->slab = NULL;
2082             continue;
2083         }
2084 
2085         size = bvs->nr_vecs * sizeof(struct bio_vec);
2086         bvs->slab = kmem_cache_create(bvs->name, size, 0,
2087                                 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
2088     }
2089 }
2090 
2091 static int __init init_bio(void)
2092 {
2093     bio_slab_max = 2;
2094     bio_slab_nr = 0;
2095     bio_slabs = kzalloc(bio_slab_max * sizeof(struct bio_slab), GFP_KERNEL);
2096     if (!bio_slabs)
2097         panic("bio: can't allocate bios\n");
2098 
2099     bio_integrity_init();
2100     biovec_init_slabs();
2101 
2102     fs_bio_set = bioset_create(BIO_POOL_SIZE, 0);
2103     if (!fs_bio_set)
2104         panic("bio: can't allocate bios\n");
2105 
2106     if (bioset_integrity_create(fs_bio_set, BIO_POOL_SIZE))
2107         panic("bio: can't create integrity pool\n");
2108 
2109     return 0;
2110 }
2111 subsys_initcall(init_bio);