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Subject[PATCH 3.16 068/305] bcache: fix wrong cache_misses statistics
3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "tang.junhui" <tang.junhui@zte.com.cn>

commit c157313791a999646901b3e3c6888514ebc36d62 upstream.

Currently, Cache missed IOs are identified by s->cache_miss, but actually,
there are many situations that missed IOs are not assigned a value for
s->cache_miss in cached_dev_cache_miss(), for example, a bypassed IO
(s->iop.bypass = 1), or the cache_bio allocate failed. In these situations,
it will go to out_put or out_submit, and s->cache_miss is null, which leads
bch_mark_cache_accounting() to treat this IO as a hit IO.

[ML: applied by 3-way merge]

Signed-off-by: tang.junhui <tang.junhui@zte.com.cn>
Reviewed-by: Michael Lyle <mlyle@lyle.org>
Reviewed-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/md/bcache/request.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -462,6 +462,7 @@ struct search {
unsigned recoverable:1;
unsigned write:1;
unsigned read_dirty_data:1;
+ unsigned cache_missed:1;

unsigned long start_time;

@@ -651,6 +652,7 @@ static inline struct search *search_allo

s->orig_bio = bio;
s->cache_miss = NULL;
+ s->cache_missed = 0;
s->d = d;
s->recoverable = 1;
s->write = (bio->bi_rw & REQ_WRITE) != 0;
@@ -774,7 +776,7 @@ static void cached_dev_read_done_bh(stru
struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);

bch_mark_cache_accounting(s->iop.c, s->d,
- !s->cache_miss, s->iop.bypass);
+ !s->cache_missed, s->iop.bypass);
trace_bcache_read(s->orig_bio, !s->cache_miss, s->iop.bypass);

if (s->iop.error)
@@ -793,6 +795,8 @@ static int cached_dev_cache_miss(struct
struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
struct bio *miss, *cache_bio;

+ s->cache_missed = 1;
+
if (s->cache_miss || s->iop.bypass) {
miss = bio_next_split(bio, sectors, GFP_NOIO, s->d->bio_split);
ret = miss == bio ? MAP_DONE : MAP_CONTINUE;
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