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| author | Jens Axboe <axboe@fb.com> | 2015-04-18 01:23:59 +0300 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2015-05-05 22:32:49 +0300 |
| commit | dac56212e8127dbc0bff7be35c508bc280213309 (patch) | |
| tree | a1a066d7f6deb7d66403137b8edafb394ce0ca6a /include | |
| parent | c4cf5261f8bffd9de132b50660a69148e7575bd6 (diff) | |
| download | linux-dac56212e8127dbc0bff7be35c508bc280213309.tar.xz | |
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 <elliott@hp.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/bio.h | 16 | ||||
| -rw-r--r-- | include/linux/blk_types.h | 3 |
2 files changed, 17 insertions, 2 deletions
diff --git a/include/linux/bio.h b/include/linux/bio.h index 8bfe9eee6d1a..7486ea103f6e 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -290,7 +290,21 @@ static inline unsigned bio_segments(struct bio *bio) * returns. and then bio would be freed memory when if (bio->bi_flags ...) * runs */ -#define bio_get(bio) atomic_inc(&(bio)->bi_cnt) +static inline void bio_get(struct bio *bio) +{ + bio->bi_flags |= (1 << BIO_REFFED); + smp_mb__before_atomic(); + atomic_inc(&bio->__bi_cnt); +} + +static inline void bio_cnt_set(struct bio *bio, unsigned int count) +{ + if (count != 1) { + bio->bi_flags |= (1 << BIO_REFFED); + smp_mb__before_atomic(); + } + atomic_set(&bio->__bi_cnt, count); +} enum bip_flags { BIP_BLOCK_INTEGRITY = 1 << 0, /* block layer owns integrity data */ diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index 8b07e0603887..93d2e7153816 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 |