From dac56212e8127dbc0bff7be35c508bc280213309 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 17 Apr 2015 16:23:59 -0600 Subject: bio: skip atomic inc/dec of ->bi_cnt for most use cases Struct bio has a reference count that controls when it can be freed. Most uses cases is allocating the bio, which then returns with a single reference to it, doing IO, and then dropping that single reference. We can remove this atomic_dec_and_test() in the completion path, if nobody else is holding a reference to the bio. If someone does call bio_get() on the bio, then we flag the bio as now having valid count and that we must properly honor the reference count when it's being put. Tested-by: Robert Elliott Signed-off-by: Jens Axboe --- include/linux/blk_types.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include/linux/blk_types.h') diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index 8b07e06..93d2e71 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -92,7 +92,7 @@ struct bio { unsigned short bi_max_vecs; /* max bvl_vecs we can hold */ - atomic_t bi_cnt; /* pin count */ + atomic_t __bi_cnt; /* pin count */ struct bio_vec *bi_io_vec; /* the actual vec list */ @@ -123,6 +123,7 @@ struct bio { #define BIO_QUIET 9 /* Make BIO Quiet */ #define BIO_SNAP_STABLE 10 /* bio data must be snapshotted during write */ #define BIO_CHAIN 11 /* chained bio, ->bi_remaining in effect */ +#define BIO_REFFED 12 /* bio has elevated ->bi_cnt */ /* * Flags starting here get preserved by bio_reset() - this includes -- cgit v1.1