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, 13 insertions, 18 deletions

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)) {