linux-kernel - [PATCH 4/6] block: set .bi_max_vecs as actual allocated vector number

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Message-Id: <20201230003255.3450874-5-ming.lei@redhat.com>
Date:   Wed, 30 Dec 2020 08:32:53 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-block@...r.kernel.org, Christoph Hellwig <hch@....de>,
        linux-kernel@...r.kernel.org, Ming Lei <ming.lei@...hat.com>
Subject: [PATCH 4/6] block: set .bi_max_vecs as actual allocated vector number

bvec_alloc() may allocate more bio vectors than requested, so set .bi_max_vecs as
actual allocated vector number, instead of the requested number. This way can help
fs build bigger bio because new bio often won't be allocated until the current one
becomes full.

Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
 block/bio.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index 3991a5aab1bc..e567feb380b6 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -502,12 +502,13 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, unsigned int nr_iovecs,
 			goto err_free;
 
 		bio->bi_flags |= idx << BVEC_POOL_OFFSET;
+		bio->bi_max_vecs = bvec_nr_vecs(idx);
 	} else if (nr_iovecs) {
 		bvl = bio->bi_inline_vecs;
+		bio->bi_max_vecs = inline_vecs;
 	}
 
 	bio->bi_pool = bs;
-	bio->bi_max_vecs = nr_iovecs;
 	bio->bi_io_vec = bvl;
 	return bio;
 
-- 
2.28.0