bio: only mempool back the largest bio_vec slab cache

We only very rarely need the mempool backing, so it makes sense to
get rid of all but one of the mempool in a bio_set. So keep the
largest bio_vec count mempool so we can always honor the largest
allocation, and "upgrade" callers that fail.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 3ed714eb54d9..d76e4bf22f29 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -397,13 +397,14 @@ static inline void bio_set_completion_cpu(struct bio *bio, unsigned int cpu)
  */
 #define BIO_POOL_SIZE 2
 #define BIOVEC_NR_POOLS 6
+#define BIOVEC_MAX_IDX  (BIOVEC_NR_POOLS - 1)
 
 struct bio_set {
         mempool_t *bio_pool;
 #if defined(CONFIG_BLK_DEV_INTEGRITY)
         mempool_t *bio_integrity_pool;
 #endif
-        mempool_t *bvec_pools[BIOVEC_NR_POOLS];
+        mempool_t *bvec_pool;
 };
 
 struct biovec_slab {