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>

1 files changed, 4 insertions, 24 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 3f6203a4c7e..b8eebe357b2 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);