On 2017/7/1 上午4:42, bcache@xxxxxxxxxxxxxxxxxx wrote: > From: Eric Wheeler <git@xxxxxxxxxxxxxxxxxx> > > Bypass if: bio->bi_opf & (REQ_RAHEAD|REQ_BACKGROUND) > > Writeback if: op_is_sync(bio->bi_opf) || bio->bi_opf & (REQ_META|REQ_PRIO) > Hi Eric, Could you please explain a bit how the above policy is designed ? I'd like to understand it more. Thanks. Coly > Signed-off-by: Eric Wheeler <bcache@xxxxxxxxxxxxxxxxxx> > --- > drivers/md/bcache/request.c | 3 +++ > drivers/md/bcache/writeback.h | 3 ++- > 2 files changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c > index a95609f..4629b0c 100644 > --- a/drivers/md/bcache/request.c > +++ b/drivers/md/bcache/request.c > @@ -386,6 +386,9 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio) > op_is_write(bio_op(bio)))) > goto skip; > > + if (bio->bi_opf & (REQ_RAHEAD|REQ_BACKGROUND)) > + goto skip; > + > /* If the ioprio already exists on the bio, use that. We assume that > * the upper layer properly assigned the calling process's ioprio to > * the bio being passed to bcache. Otherwise, use current's ioc. */ > diff --git a/drivers/md/bcache/writeback.h b/drivers/md/bcache/writeback.h > index cd82fe8..ea2f92e 100644 > --- a/drivers/md/bcache/writeback.h > +++ b/drivers/md/bcache/writeback.h > @@ -81,7 +81,8 @@ static inline bool should_writeback(struct cached_dev *dc, struct bio *bio, > return true; > } > > - return op_is_sync(bio->bi_opf) || in_use <= CUTOFF_WRITEBACK; > + return op_is_sync(bio->bi_opf) || bio->bi_opf & (REQ_META|REQ_PRIO) > + || in_use <= CUTOFF_WRITEBACK; > } > > static inline void bch_writeback_queue(struct cached_dev *dc) >
