block: fix bio-cache for passthru IO

commit <8af870aa> ("block: enable bio caching use for passthru IO")
introduced bio-cache for passthru IO. In case when nr_vecs are greater
than BIO_INLINE_VECS, bio and bvecs are allocated from mempool (instead
of percpu cache) and REQ_ALLOC_CACHE is cleared. This causes the side
effect of not freeing bio/bvecs into mempool on completion.

This patch lets the passthru IO fallback to allocation using bio_kmalloc
when nr_vecs are greater than BIO_INLINE_VECS. The corresponding bio
is freed during call to blk_mq_map_bio_put during completion.

Cc: stable@vger.kernel.org # 6.1
fixes <8af870aa> ("block: enable bio caching use for passthru IO")
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Link: https://lore.kernel.org/r/20230523111709.145676-1-anuj20.g@samsung.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-map.c

@@ -248,7 +248,7 @@ static struct bio *blk_rq_map_bio_alloc(struct request *rq,
 {
 	struct bio *bio;
 
-	if (rq->cmd_flags & REQ_ALLOC_CACHE) {
+	if (rq->cmd_flags & REQ_ALLOC_CACHE && (nr_vecs <= BIO_INLINE_VECS)) {
 		bio = bio_alloc_bioset(NULL, nr_vecs, rq->cmd_flags, gfp_mask,
 					&fs_bio_set);
 		if (!bio)