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Subject[PATCH 4.9 39/78] block: bvec_nr_vecs() returns value for wrong slab
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Greg Edwards <gedwards@ddn.com>

[ Upstream commit d6c02a9beb67f13d5f14f23e72fa9981e8b84477 ]

In commit ed996a52c868 ("block: simplify and cleanup bvec pool
handling"), the value of the slab index is incremented by one in
bvec_alloc() after the allocation is done to indicate an index value of
0 does not need to be later freed.

bvec_nr_vecs() was not updated accordingly, and thus returns the wrong
value. Decrement idx before performing the lookup.

Fixes: ed996a52c868 ("block: simplify and cleanup bvec pool handling")
Signed-off-by: Greg Edwards <gedwards@ddn.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
block/bio.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/block/bio.c
+++ b/block/bio.c
@@ -155,7 +155,7 @@ out:

unsigned int bvec_nr_vecs(unsigned short idx)
{
- return bvec_slabs[idx].nr_vecs;
+ return bvec_slabs[--idx].nr_vecs;
}

void bvec_free(mempool_t *pool, struct bio_vec *bv, unsigned int idx)

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