[PATCH v2 3/3] block: bio: introduce BIO_ALLOCED flag and check it in bio_free

[Johannes Thumshirn <jthumshirn@suse.de>]

When we're submitting a bio from stack and this ends up being split, we
call bio_put(). bio_put() will eventually call bio_free() if the reference
count drops to 0. But freeing the bio is wrong, as it was never allocated
out of the bio's mempool.

Flag each normally allocated bio as 'BIO_ALLOCATED' and skip freeing if the
flag isn't set.

Fixes: 189ce2b9dcc3 ("block: fast-path for small and simple direct I/O requests")
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
---
 block/bio.c               | 4 ++++
 include/linux/blk_types.h | 1 +
 2 files changed, 5 insertions(+)

diff --git a/block/bio.c b/block/bio.c
index 87a515e93bee..ba6949f111b7 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -255,6 +255,9 @@ static void bio_free(struct bio *bio)
 
 	bio_uninit(bio);
 
+	if (!bio_flagged(bio, BIO_ALLOCED))
+		return;
+
 	if (bs) {
 		bvec_free(&bs->bvec_pool, bio->bi_io_vec, BVEC_POOL_IDX(bio));
 
@@ -523,6 +526,7 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, unsigned int nr_iovecs,
 		bvl = bio->bi_inline_vecs;
 	}
 
+	bio_set_flag(bio, BIO_ALLOCED);
 	bio->bi_pool = bs;
 	bio->bi_max_vecs = nr_iovecs;
 	bio->bi_io_vec = bvl;
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 1d28992a20f0..19d7402a9af3 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -229,6 +229,7 @@ enum {
 				 * of this bio. */
 	BIO_QUEUE_ENTERED,	/* can use blk_queue_enter_live() */
 	BIO_TRACKED,		/* set if bio goes through the rq_qos path */
+	BIO_ALLOCED,		/* bio allocated by bio_alloc_bioset */
 	BIO_FLAG_LAST
 };
 
-- 
2.16.4