From: Jens Axboe <axboe@kernel.dk>
Date: Wed, 11 Aug 2021 09:20:04 -0600
Subject: [PATCH] bio: optimize initialization of a bio
Git-commit: da521626ac620d8719d674a48b8ec3620eefd42a
Patch-mainline: v5.15-rc1
References: jsc#PED-1183

The memset() used is measurably slower in targeted benchmarks, wasting
about 1% of the total runtime, or 50% of the (later) hot path cached
bio alloc. Get rid of it and fill in the bio manually.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 block/bio.c | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 1fab762e079b..6fa5c653283b 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -246,12 +246,40 @@ static void bio_free(struct bio *bio)
 void bio_init(struct bio *bio, struct bio_vec *table,
 	      unsigned short max_vecs)
 {
-	memset(bio, 0, sizeof(*bio));
+	bio->bi_next = NULL;
+	bio->bi_bdev = NULL;
+	bio->bi_opf = 0;
+	bio->bi_flags = 0;
+	bio->bi_ioprio = 0;
+	bio->bi_write_hint = 0;
+	bio->bi_status = 0;
+	bio->bi_iter.bi_sector = 0;
+	bio->bi_iter.bi_size = 0;
+	bio->bi_iter.bi_idx = 0;
+	bio->bi_iter.bi_bvec_done = 0;
+	bio->bi_end_io = NULL;
+	bio->bi_private = NULL;
+#ifdef CONFIG_BLK_CGROUP
+	bio->bi_blkg = NULL;
+	bio->bi_issue.value = 0;
+#ifdef CONFIG_BLK_CGROUP_IOCOST
+	bio->bi_iocost_cost = 0;
+#endif
+#endif
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+	bio->bi_crypt_context = NULL;
+#endif
+#ifdef CONFIG_BLK_DEV_INTEGRITY
+	bio->bi_integrity = NULL;
+#endif
+	bio->bi_vcnt = 0;
+
 	atomic_set(&bio->__bi_remaining, 1);
 	atomic_set(&bio->__bi_cnt, 1);
 
-	bio->bi_io_vec = table;
 	bio->bi_max_vecs = max_vecs;
+	bio->bi_io_vec = table;
+	bio->bi_pool = NULL;
 }
 EXPORT_SYMBOL(bio_init);
 
-- 
2.35.3