block: Generalized bio pool freeing

With the old code, when you allocate a bio from a bio pool you have to
implement your own destructor that knows how to find the bio pool the
bio was originally allocated from.

This adds a new field to struct bio (bi_pool) and changes
bio_alloc_bioset() to use it. This makes various bio destructors
unnecessary, so they're then deleted.

v6: Explain the temporary if statement in bio_put

Signed-off-by: Kent Overstreet <koverstreet@google.com>
CC: Jens Axboe <axboe@kernel.dk>
CC: NeilBrown <neilb@suse.de>
CC: Alasdair Kergon <agk@redhat.com>
CC: Nicholas Bellinger <nab@linux-iscsi.org>
CC: Lars Ellenberg <lars.ellenberg@linbit.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

8 files changed, 21 insertions, 103 deletions

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index f93a0320e952..f55683ad4ffa 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -162,23 +162,12 @@ static const struct block_device_operations drbd_ops = {
         .release = drbd_release,
 };
 
-static void bio_destructor_drbd(struct bio *bio)
-{
-        bio_free(bio, drbd_md_io_bio_set);
-}
-
 struct bio *bio_alloc_drbd(gfp_t gfp_mask)
 {
-        struct bio *bio;
-
         if (!drbd_md_io_bio_set)
                 return bio_alloc(gfp_mask, 1);
 
-        bio = bio_alloc_bioset(gfp_mask, 1, drbd_md_io_bio_set);
-        if (!bio)
-                return NULL;
-        bio->bi_destructor = bio_destructor_drbd;
-        return bio;
+        return bio_alloc_bioset(gfp_mask, 1, drbd_md_io_bio_set);
 }
 
 #ifdef __CHECKER__
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 664743d6a6cd..3c0acba042b6 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -798,14 +798,6 @@ static int crypt_convert(struct crypt_config *cc,
         return 0;
 }
 
-static void dm_crypt_bio_destructor(struct bio *bio)
-{
-        struct dm_crypt_io *io = bio->bi_private;
-        struct crypt_config *cc = io->cc;
-
-        bio_free(bio, cc->bs);
-}
-
 /*
  * Generate a new unfragmented bio with the given size
  * This should never violate the device limitations
@@ -974,7 +966,6 @@ static void clone_init(struct dm_crypt_io *io, struct bio *clone)
         clone->bi_end_io  = crypt_endio;
         clone->bi_bdev    = cc->dev->bdev;
         clone->bi_rw      = io->base_bio->bi_rw;
-        clone->bi_destructor = dm_crypt_bio_destructor;
 }
 
 static int kcryptd_io_read(struct dm_crypt_io *io, gfp_t gfp)
diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index ea5dd289fe2a..1c46f97d6664 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -249,16 +249,6 @@ static void vm_dp_init(struct dpages *dp, void *data)
         dp->context_ptr = data;
 }
 
-static void dm_bio_destructor(struct bio *bio)
-{
-        unsigned region;
-        struct io *io;
-
-        retrieve_io_and_region_from_bio(bio, &io, &region);
-
-        bio_free(bio, io->client->bios);
-}
-
 /*
  * Functions for getting the pages from kernel memory.
  */
@@ -317,7 +307,6 @@ static void do_region(int rw, unsigned region, struct dm_io_region *where,
                 bio->bi_sector = where->sector + (where->count - remaining);
                 bio->bi_bdev = where->bdev;
                 bio->bi_end_io = endio;
-                bio->bi_destructor = dm_bio_destructor;
                 store_io_and_region_in_bio(bio, io, region);
 
                 if (rw & REQ_DISCARD) {
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 4e09b6ff5b49..0c3d6dd51897 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -681,11 +681,6 @@ static void clone_endio(struct bio *bio, int error)
                 }
         }
 
-        /*
-         * Store md for cleanup instead of tio which is about to get freed.
-         */
-        bio->bi_private = md->bs;
-
         free_tio(md, tio);
         bio_put(bio);
         dec_pending(io, error);
@@ -1032,11 +1027,6 @@ static void __map_bio(struct dm_target *ti, struct bio *clone,
                 /* error the io and bail out, or requeue it if needed */
                 md = tio->io->md;
                 dec_pending(tio->io, r);
-                /*
-                 * Store bio_set for cleanup.
-                 */
-                clone->bi_end_io = NULL;
-                clone->bi_private = md->bs;
                 bio_put(clone);
                 free_tio(md, tio);
         } else if (r) {
@@ -1055,13 +1045,6 @@ struct clone_info {
         unsigned short idx;
 };
 
-static void dm_bio_destructor(struct bio *bio)
-{
-        struct bio_set *bs = bio->bi_private;
-
-        bio_free(bio, bs);
-}
-
 /*
  * Creates a little bio that just does part of a bvec.
  */
@@ -1073,7 +1056,6 @@ static struct bio *split_bvec(struct bio *bio, sector_t sector,
         struct bio_vec *bv = bio->bi_io_vec + idx;
 
         clone = bio_alloc_bioset(GFP_NOIO, 1, bs);
-        clone->bi_destructor = dm_bio_destructor;
         *clone->bi_io_vec = *bv;
 
         clone->bi_sector = sector;
@@ -1105,7 +1087,6 @@ static struct bio *clone_bio(struct bio *bio, sector_t sector,
 
         clone = bio_alloc_bioset(GFP_NOIO, bio->bi_max_vecs, bs);
         __bio_clone(clone, bio);
-        clone->bi_destructor = dm_bio_destructor;
         clone->bi_sector = sector;
         clone->bi_idx = idx;
         clone->bi_vcnt = idx + bv_count;
@@ -1150,7 +1131,6 @@ static void __issue_target_request(struct clone_info *ci, struct dm_target *ti,
          */
         clone = bio_alloc_bioset(GFP_NOIO, ci->bio->bi_max_vecs, ci->md->bs);
         __bio_clone(clone, ci->bio);
-        clone->bi_destructor = dm_bio_destructor;
         if (len) {
                 clone->bi_sector = ci->sector;
                 clone->bi_size = to_bytes(len);
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 3f6203a4c7ea..b8eebe357b2b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -155,32 +155,17 @@ static int start_readonly;
  * like bio_clone, but with a local bio set
  */
 
-static void mddev_bio_destructor(struct bio *bio)
-{
-        struct mddev *mddev, **mddevp;
-
-        mddevp = (void*)bio;
-        mddev = mddevp[-1];
-
-        bio_free(bio, mddev->bio_set);
-}
-
 struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs,
                             struct mddev *mddev)
 {
         struct bio *b;
-        struct mddev **mddevp;
 
         if (!mddev || !mddev->bio_set)
                 return bio_alloc(gfp_mask, nr_iovecs);
 
-        b = bio_alloc_bioset(gfp_mask, nr_iovecs,
-                             mddev->bio_set);
+        b = bio_alloc_bioset(gfp_mask, nr_iovecs, mddev->bio_set);
         if (!b)
                 return NULL;
-        mddevp = (void*)b;
-        mddevp[-1] = mddev;
-        b->bi_destructor = mddev_bio_destructor;
         return b;
 }
 EXPORT_SYMBOL_GPL(bio_alloc_mddev);
@@ -189,18 +174,14 @@ struct bio *bio_clone_mddev(struct bio *bio, gfp_t gfp_mask,
                             struct mddev *mddev)
 {
         struct bio *b;
-        struct mddev **mddevp;
 
         if (!mddev || !mddev->bio_set)
                 return bio_clone(bio, gfp_mask);
 
-        b = bio_alloc_bioset(gfp_mask, bio->bi_max_vecs,
-                             mddev->bio_set);
+        b = bio_alloc_bioset(gfp_mask, bio->bi_max_vecs, mddev->bio_set);
         if (!b)
                 return NULL;
-        mddevp = (void*)b;
-        mddevp[-1] = mddev;
-        b->bi_destructor = mddev_bio_destructor;
+
         __bio_clone(b, bio);
         if (bio_integrity(bio)) {
                 int ret;
@@ -5006,8 +4987,7 @@ int md_run(struct mddev *mddev)
         }
 
         if (mddev->bio_set == NULL)
-                mddev->bio_set = bioset_create(BIO_POOL_SIZE,
-                                               sizeof(struct mddev *));
+                mddev->bio_set = bioset_create(BIO_POOL_SIZE, 0);
 
         spin_lock(&pers_lock);
         pers = find_pers(mddev->level, mddev->clevel);
diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
index 76db75e836ed..e58cd7d2fce4 100644
--- a/drivers/target/target_core_iblock.c
+++ b/drivers/target/target_core_iblock.c
@@ -543,14 +543,6 @@ static void iblock_complete_cmd(struct se_cmd *cmd)
         kfree(ibr);
 }
 
-static void iblock_bio_destructor(struct bio *bio)
-{
-        struct se_cmd *cmd = bio->bi_private;
-        struct iblock_dev *ib_dev = cmd->se_dev->dev_ptr;
-
-        bio_free(bio, ib_dev->ibd_bio_set);
-}
-
 static struct bio *
 iblock_get_bio(struct se_cmd *cmd, sector_t lba, u32 sg_num)
 {
@@ -572,7 +564,6 @@ iblock_get_bio(struct se_cmd *cmd, sector_t lba, u32 sg_num)
 
         bio->bi_bdev = ib_dev->ibd_bd;
         bio->bi_private = cmd;
-        bio->bi_destructor = iblock_bio_destructor;
         bio->bi_end_io = &iblock_bio_done;
         bio->bi_sector = lba;
         return bio;
diff --git a/fs/bio.c b/fs/bio.c
index 71072ab99128..e017f7a5cdc6 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -272,10 +272,6 @@ EXPORT_SYMBOL(bio_init);
  *   bio_alloc_bioset will try its own mempool to satisfy the allocation.
  *   If %__GFP_WAIT is set then we will block on the internal pool waiting
  *   for a &struct bio to become free.
- *
- *   Note that the caller must set ->bi_destructor on successful return
- *   of a bio, to do the appropriate freeing of the bio once the reference
- *   count drops to zero.
  **/
 struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
 {
@@ -290,6 +286,7 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
         bio = p + bs->front_pad;
 
         bio_init(bio);
+        bio->bi_pool = bs;
 
         if (unlikely(!nr_iovecs))
                 goto out_set;
@@ -316,11 +313,6 @@ err_free:
 }
 EXPORT_SYMBOL(bio_alloc_bioset);
 
-static void bio_fs_destructor(struct bio *bio)
-{
-        bio_free(bio, fs_bio_set);
-}
-
 /**
  *      bio_alloc - allocate a new bio, memory pool backed
  *      @gfp_mask: allocation mask to use
@@ -342,12 +334,7 @@ static void bio_fs_destructor(struct bio *bio)
  */
 struct bio *bio_alloc(gfp_t gfp_mask, unsigned int nr_iovecs)
 {
-        struct bio *bio = bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);
-
-        if (bio)
-                bio->bi_destructor = bio_fs_destructor;
-
-        return bio;
+        return bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);
 }
 EXPORT_SYMBOL(bio_alloc);
 
@@ -423,7 +410,16 @@ void bio_put(struct bio *bio)
         if (atomic_dec_and_test(&bio->bi_cnt)) {
                 bio_disassociate_task(bio);
                 bio->bi_next = NULL;
-                bio->bi_destructor(bio);
+
+                /*
+                 * This if statement is temporary - bi_pool is replacing
+                 * bi_destructor, but bi_destructor will be taken out in another
+                 * patch.
+                 */
+                if (bio->bi_pool)
+                        bio_free(bio, bio->bi_pool);
+                else
+                        bio->bi_destructor(bio);
         }
 }
 EXPORT_SYMBOL(bio_put);
@@ -474,12 +470,11 @@ EXPORT_SYMBOL(__bio_clone);
  */
 struct bio *bio_clone(struct bio *bio, gfp_t gfp_mask)
 {
-        struct bio *b = bio_alloc_bioset(gfp_mask, bio->bi_max_vecs, fs_bio_set);
+        struct bio *b = bio_alloc(gfp_mask, bio->bi_max_vecs);
 
         if (!b)
                 return NULL;
 
-        b->bi_destructor = bio_fs_destructor;
         __bio_clone(b, bio);
 
         if (bio_integrity(bio)) {
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 7b7ac9ccec7a..af9dd9d2efc4 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -80,6 +80,9 @@ struct bio {
         struct bio_integrity_payload *bi_integrity;  /* data integrity */
 #endif
 
+        /* If bi_pool is non NULL, bi_destructor is not called */
+        struct bio_set          *bi_pool;
+
         bio_destructor_t        *bi_destructor; /* destructor */
 
         /*