| Message ID | 20191218194156.29430-1-dmitry.fomichev@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: streamline merge possibility checks | expand |
On 12/19/19 3:41 AM, Dmitry Fomichev wrote: > Checks for data direction in attempt_merge() and blk_rq_merge_ok() > are redundant and will always succeed when the both I/O request > operations are equal. Therefore, remove them. > > Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com> > --- > block/blk-merge.c | 7 +------ > 1 file changed, 1 insertion(+), 6 deletions(-) > > diff --git a/block/blk-merge.c b/block/blk-merge.c > index d783bdc4559b..796451aed7d6 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -745,8 +745,7 @@ static struct request *attempt_merge(struct request_queue *q, > if (req_op(req) != req_op(next)) > return NULL; > > - if (rq_data_dir(req) != rq_data_dir(next) > - || req->rq_disk != next->rq_disk) > + if (req->rq_disk != next->rq_disk) > return NULL; > > if (req_op(req) == REQ_OP_WRITE_SAME && > @@ -868,10 +867,6 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio) > if (req_op(rq) != bio_op(bio)) > return false; > > - /* different data direction or already started, don't merge */ > - if (bio_data_dir(bio) != rq_data_dir(rq)) > - return false; > - Reviewed-by: Bob Liu <bob.liu@oracle.com> > /* must be same device */ > if (rq->rq_disk != bio->bi_disk) > return false; >
On 2019/12/19 4:42, Dmitry Fomichev wrote: > Checks for data direction in attempt_merge() and blk_rq_merge_ok() > are redundant and will always succeed when the both I/O request > operations are equal. Therefore, remove them. > > Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com> > --- > block/blk-merge.c | 7 +------ > 1 file changed, 1 insertion(+), 6 deletions(-) > > diff --git a/block/blk-merge.c b/block/blk-merge.c > index d783bdc4559b..796451aed7d6 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -745,8 +745,7 @@ static struct request *attempt_merge(struct request_queue *q, > if (req_op(req) != req_op(next)) > return NULL; > > - if (rq_data_dir(req) != rq_data_dir(next) > - || req->rq_disk != next->rq_disk) > + if (req->rq_disk != next->rq_disk) > return NULL; > > if (req_op(req) == REQ_OP_WRITE_SAME && > @@ -868,10 +867,6 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio) > if (req_op(rq) != bio_op(bio)) > return false; > > - /* different data direction or already started, don't merge */ > - if (bio_data_dir(bio) != rq_data_dir(rq)) > - return false; > - > /* must be same device */ > if (rq->rq_disk != bio->bi_disk) > return false; > Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
On 12/19/19 3:41 AM, Dmitry Fomichev wrote: > Checks for data direction in attempt_merge() and blk_rq_merge_ok() Speak about these two functions, do you think attempt_merge() can be built on blk_rq_merge_ok()? Things like.. diff --git a/block/blk-merge.c b/block/blk-merge.c index 48e6725..2a00c4c 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -724,28 +724,7 @@ static enum elv_merge blk_try_req_merge(struct request *req, static struct request *attempt_merge(struct request_queue *q, struct request *req, struct request *next) { - if (!rq_mergeable(req) || !rq_mergeable(next)) - return NULL; - - if (req_op(req) != req_op(next)) - return NULL; - - if (rq_data_dir(req) != rq_data_dir(next) - || req->rq_disk != next->rq_disk) - return NULL; - - if (req_op(req) == REQ_OP_WRITE_SAME && - !blk_write_same_mergeable(req->bio, next->bio)) - return NULL; - - /* - * Don't allow merge of different write hints, or for a hint with - * non-hint IO. - */ - if (req->write_hint != next->write_hint) - return NULL; - - if (req->ioprio != next->ioprio) + if (!blk_rq_merge_ok(req, next->bio)) return NULL; > are redundant and will always succeed when the both I/O request > operations are equal. Therefore, remove them. > > Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com> > --- > block/blk-merge.c | 7 +------ > 1 file changed, 1 insertion(+), 6 deletions(-) > > diff --git a/block/blk-merge.c b/block/blk-merge.c > index d783bdc4559b..796451aed7d6 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -745,8 +745,7 @@ static struct request *attempt_merge(struct request_queue *q, > if (req_op(req) != req_op(next)) > return NULL; > > - if (rq_data_dir(req) != rq_data_dir(next) > - || req->rq_disk != next->rq_disk) > + if (req->rq_disk != next->rq_disk) > return NULL; > > if (req_op(req) == REQ_OP_WRITE_SAME && > @@ -868,10 +867,6 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio) > if (req_op(rq) != bio_op(bio)) > return false; > > - /* different data direction or already started, don't merge */ > - if (bio_data_dir(bio) != rq_data_dir(rq)) > - return false; > - > /* must be same device */ > if (rq->rq_disk != bio->bi_disk) > return false; >
On Wed, Dec 18, 2019 at 02:41:56PM -0500, Dmitry Fomichev wrote: > Checks for data direction in attempt_merge() and blk_rq_merge_ok() > are redundant and will always succeed when the both I/O request > operations are equal. Therefore, remove them. > > Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com> Looks good, Reviewed-by: Christoph Hellwig <hch@lst.de>
On Fri, Dec 20, 2019 at 02:50:05PM +0800, Bob Liu wrote: > On 12/19/19 3:41 AM, Dmitry Fomichev wrote: > > Checks for data direction in attempt_merge() and blk_rq_merge_ok() > > Speak about these two functions, do you think attempt_merge() can be built on blk_rq_merge_ok()? > Things like.. > diff --git a/block/blk-merge.c b/block/blk-merge.c > index 48e6725..2a00c4c 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -724,28 +724,7 @@ static enum elv_merge blk_try_req_merge(struct request *req, > static struct request *attempt_merge(struct request_queue *q, > struct request *req, struct request *next) > { > - if (!rq_mergeable(req) || !rq_mergeable(next)) > - return NULL; > - > - if (req_op(req) != req_op(next)) > - return NULL; > - > - if (rq_data_dir(req) != rq_data_dir(next) > - || req->rq_disk != next->rq_disk) > - return NULL; > - > - if (req_op(req) == REQ_OP_WRITE_SAME && > - !blk_write_same_mergeable(req->bio, next->bio)) > - return NULL; > - > - /* > - * Don't allow merge of different write hints, or for a hint with > - * non-hint IO. > - */ > - if (req->write_hint != next->write_hint) > - return NULL; > - > - if (req->ioprio != next->ioprio) > + if (!blk_rq_merge_ok(req, next->bio)) > return NULL; This looks sensible, but we might have to be a bit more careful. rq_mergeable checks for RQF_NOMERGE_FLAGS and various ops, while bio_mergeable is missing those. So I think you need to go through carefully if we need to keep any extra checks, but otherwise using blk_rq_merge_ok looks sensible.
> -----Original Message----- > From: Christoph Hellwig <hch@infradead.org> > Sent: Wednesday, January 8, 2020 8:45 AM > To: Bob Liu <bob.liu@oracle.com> > Cc: Dmitry Fomichev <Dmitry.Fomichev@wdc.com>; linux- > block@vger.kernel.org; Jens Axboe <axboe@kernel.dk>; Damien Le Moal > <Damien.LeMoal@wdc.com> > Subject: Re: [PATCH] block: streamline merge possibility checks > > On Fri, Dec 20, 2019 at 02:50:05PM +0800, Bob Liu wrote: > > On 12/19/19 3:41 AM, Dmitry Fomichev wrote: > > > Checks for data direction in attempt_merge() and blk_rq_merge_ok() > > > > Speak about these two functions, do you think attempt_merge() can be > built on blk_rq_merge_ok()? > > Things like.. > > diff --git a/block/blk-merge.c b/block/blk-merge.c > > index 48e6725..2a00c4c 100644 > > --- a/block/blk-merge.c > > +++ b/block/blk-merge.c > > @@ -724,28 +724,7 @@ static enum elv_merge blk_try_req_merge(struct > request *req, > > static struct request *attempt_merge(struct request_queue *q, > > struct request *req, struct request *next) > > { > > - if (!rq_mergeable(req) || !rq_mergeable(next)) > > - return NULL; > > - > > - if (req_op(req) != req_op(next)) > > - return NULL; > > - > > - if (rq_data_dir(req) != rq_data_dir(next) > > - || req->rq_disk != next->rq_disk) > > - return NULL; > > - > > - if (req_op(req) == REQ_OP_WRITE_SAME && > > - !blk_write_same_mergeable(req->bio, next->bio)) > > - return NULL; > > - > > - /* > > - * Don't allow merge of different write hints, or for a hint with > > - * non-hint IO. > > - */ > > - if (req->write_hint != next->write_hint) > > - return NULL; > > - > > - if (req->ioprio != next->ioprio) > > + if (!blk_rq_merge_ok(req, next->bio)) > > return NULL; > > This looks sensible, but we might have to be a bit more careful. > rq_mergeable checks for RQF_NOMERGE_FLAGS and various ops, while > bio_mergeable is missing those. So I think you need to go through > carefully if we need to keep any extra checks, but otherwise using > blk_rq_merge_ok looks sensible. I tried this patch as is and, indeed, it leads to blktests failures and filesystem errors, apparently because of the RQF_NOMERGE_FLAGS difference. However, the patch below seems to work - I've been running my host system with it for a couple of days with no issues. This one is added on top of "block: streamline merge possibility checks" patch. From: Dmitry Fomichev <dmitry.fomichev@wdc.com> Date: Wed, 8 Jan 2020 14:24:06 -0500 Subject: [PATCH] block: simplify merge checks The code parts to decide on merge possibility in attempt_merge() and blk_rq_merge_ok() look very similar. It is possible to move these checks to a common inline helper function. Suggested-by: Bob Liu <bob.liu@oracle.com> Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com> --- block/blk-merge.c | 56 +++++++++++++++++++++++++++-------------------- 1 file changed, 32 insertions(+), 24 deletions(-) diff --git a/block/blk-merge.c b/block/blk-merge.c index f68d67b367d6..49052a53051f 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -732,6 +732,36 @@ static enum elv_merge blk_try_req_merge(struct request *req, return ELEVATOR_NO_MERGE; } +static inline bool blk_rq_mergeable(struct request *rq, struct bio *bio) +{ + if (!rq_mergeable(rq)) + return false; + + if (req_op(rq) != bio_op(bio)) + return false; + + /* must be same device */ + if (rq->rq_disk != bio->bi_disk) + return false; + + /* must be using the same buffer */ + if (req_op(rq) == REQ_OP_WRITE_SAME && + !blk_write_same_mergeable(rq->bio, bio)) + return false; + + /* + * Don't allow merge of different write hints, or for a hint with + * non-hint IO. + */ + if (rq->write_hint != bio->bi_write_hint) + return false; + + if (rq->ioprio != bio_prio(bio)) + return false; + + return true; +} + /* * For non-mq, this has to be called with the request spinlock acquired. * For mq with scheduling, the appropriate queue wide lock should be held. @@ -739,7 +769,7 @@ static enum elv_merge blk_try_req_merge(struct request *req, static struct request *attempt_merge(struct request_queue *q, struct request *req, struct request *next) { - if (!blk_rq_merge_ok(req, next->bio)) + if (!rq_mergeable(next) || !blk_rq_mergeable(req, next->bio)) return NULL; /* @@ -841,35 +871,13 @@ int blk_attempt_req_merge(struct request_queue *q, struct request *rq, bool blk_rq_merge_ok(struct request *rq, struct bio *bio) { - if (!rq_mergeable(rq) || !bio_mergeable(bio)) - return false; - - if (req_op(rq) != bio_op(bio)) - return false; - - /* must be same device */ - if (rq->rq_disk != bio->bi_disk) + if (!bio_mergeable(bio) || !blk_rq_mergeable(rq, bio)) return false; /* only merge integrity protected bio into ditto rq */ if (blk_integrity_merge_bio(rq->q, rq, bio) == false) return false; - /* must be using the same buffer */ - if (req_op(rq) == REQ_OP_WRITE_SAME && - !blk_write_same_mergeable(rq->bio, bio)) - return false; - - /* - * Don't allow merge of different write hints, or for a hint with - * non-hint IO. - */ - if (rq->write_hint != bio->bi_write_hint) - return false; - - if (rq->ioprio != bio_prio(bio)) - return false; - return true; }
On 1/9/20 6:02 AM, Dmitry Fomichev wrote: >> -----Original Message----- >> From: Christoph Hellwig <hch@infradead.org> >> Sent: Wednesday, January 8, 2020 8:45 AM >> To: Bob Liu <bob.liu@oracle.com> >> Cc: Dmitry Fomichev <Dmitry.Fomichev@wdc.com>; linux- >> block@vger.kernel.org; Jens Axboe <axboe@kernel.dk>; Damien Le Moal >> <Damien.LeMoal@wdc.com> >> Subject: Re: [PATCH] block: streamline merge possibility checks >> >> On Fri, Dec 20, 2019 at 02:50:05PM +0800, Bob Liu wrote: >>> On 12/19/19 3:41 AM, Dmitry Fomichev wrote: >>>> Checks for data direction in attempt_merge() and blk_rq_merge_ok() >>> >>> Speak about these two functions, do you think attempt_merge() can be >> built on blk_rq_merge_ok()? >>> Things like.. >>> diff --git a/block/blk-merge.c b/block/blk-merge.c >>> index 48e6725..2a00c4c 100644 >>> --- a/block/blk-merge.c >>> +++ b/block/blk-merge.c >>> @@ -724,28 +724,7 @@ static enum elv_merge blk_try_req_merge(struct >> request *req, >>> static struct request *attempt_merge(struct request_queue *q, >>> struct request *req, struct request *next) >>> { >>> - if (!rq_mergeable(req) || !rq_mergeable(next)) >>> - return NULL; >>> - >>> - if (req_op(req) != req_op(next)) >>> - return NULL; >>> - >>> - if (rq_data_dir(req) != rq_data_dir(next) >>> - || req->rq_disk != next->rq_disk) >>> - return NULL; >>> - >>> - if (req_op(req) == REQ_OP_WRITE_SAME && >>> - !blk_write_same_mergeable(req->bio, next->bio)) >>> - return NULL; >>> - >>> - /* >>> - * Don't allow merge of different write hints, or for a hint with >>> - * non-hint IO. >>> - */ >>> - if (req->write_hint != next->write_hint) >>> - return NULL; >>> - >>> - if (req->ioprio != next->ioprio) >>> + if (!blk_rq_merge_ok(req, next->bio)) >>> return NULL; >> >> This looks sensible, but we might have to be a bit more careful. >> rq_mergeable checks for RQF_NOMERGE_FLAGS and various ops, while >> bio_mergeable is missing those. So I think you need to go through >> carefully if we need to keep any extra checks, but otherwise using >> blk_rq_merge_ok looks sensible. > > I tried this patch as is and, indeed, it leads to blktests failures and filesystem > errors, apparently because of the RQF_NOMERGE_FLAGS difference. > However, the patch below seems to work - I've been running my host system > with it for a couple of days with no issues. This one is added on top of > "block: streamline merge possibility checks" patch. > > From: Dmitry Fomichev <dmitry.fomichev@wdc.com> > Date: Wed, 8 Jan 2020 14:24:06 -0500 > Subject: [PATCH] block: simplify merge checks > > The code parts to decide on merge possibility in attempt_merge() and > blk_rq_merge_ok() look very similar. It is possible to move these > checks to a common inline helper function. > > Suggested-by: Bob Liu <bob.liu@oracle.com> > Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com> > --- > block/blk-merge.c | 56 +++++++++++++++++++++++++++-------------------- > 1 file changed, 32 insertions(+), 24 deletions(-) > > diff --git a/block/blk-merge.c b/block/blk-merge.c > index f68d67b367d6..49052a53051f 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -732,6 +732,36 @@ static enum elv_merge blk_try_req_merge(struct request *req, > return ELEVATOR_NO_MERGE; > } > > +static inline bool blk_rq_mergeable(struct request *rq, struct bio *bio) > +{ > + if (!rq_mergeable(rq)) > + return false; > + > + if (req_op(rq) != bio_op(bio)) > + return false; > + > + /* must be same device */ > + if (rq->rq_disk != bio->bi_disk) > + return false; > + > + /* must be using the same buffer */ > + if (req_op(rq) == REQ_OP_WRITE_SAME && > + !blk_write_same_mergeable(rq->bio, bio)) > + return false; > + > + /* > + * Don't allow merge of different write hints, or for a hint with > + * non-hint IO. > + */ > + if (rq->write_hint != bio->bi_write_hint) > + return false; > + > + if (rq->ioprio != bio_prio(bio)) > + return false; > + > + return true; > +} > + > /* > * For non-mq, this has to be called with the request spinlock acquired. > * For mq with scheduling, the appropriate queue wide lock should be held. > @@ -739,7 +769,7 @@ static enum elv_merge blk_try_req_merge(struct request *req, > static struct request *attempt_merge(struct request_queue *q, > struct request *req, struct request *next) > { > - if (!blk_rq_merge_ok(req, next->bio)) > + if (!rq_mergeable(next) || !blk_rq_mergeable(req, next->bio)) > return NULL; > > /* > @@ -841,35 +871,13 @@ int blk_attempt_req_merge(struct request_queue *q, struct request *rq, > > bool blk_rq_merge_ok(struct request *rq, struct bio *bio) > { > - if (!rq_mergeable(rq) || !bio_mergeable(bio)) > - return false; > - > - if (req_op(rq) != bio_op(bio)) > - return false; > - > - /* must be same device */ > - if (rq->rq_disk != bio->bi_disk) > + if (!bio_mergeable(bio) || !blk_rq_mergeable(rq, bio)) > return false; > Nitpick, I think bio_mergeable(bio) can also put inside blk_rq_mergeable(). Anyway, looks fine to me, thanks! Reviewed-by: Bob Liu <bob.liu@oracle.com> > /* only merge integrity protected bio into ditto rq */ > if (blk_integrity_merge_bio(rq->q, rq, bio) == false) > return false; > > - /* must be using the same buffer */ > - if (req_op(rq) == REQ_OP_WRITE_SAME && > - !blk_write_same_mergeable(rq->bio, bio)) > - return false; > - > - /* > - * Don't allow merge of different write hints, or for a hint with > - * non-hint IO. > - */ > - if (rq->write_hint != bio->bi_write_hint) > - return false; > - > - if (rq->ioprio != bio_prio(bio)) > - return false; > - > return true; > } > >
diff --git a/block/blk-merge.c b/block/blk-merge.c index d783bdc4559b..796451aed7d6 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -745,8 +745,7 @@ static struct request *attempt_merge(struct request_queue *q, if (req_op(req) != req_op(next)) return NULL; - if (rq_data_dir(req) != rq_data_dir(next) - || req->rq_disk != next->rq_disk) + if (req->rq_disk != next->rq_disk) return NULL; if (req_op(req) == REQ_OP_WRITE_SAME && @@ -868,10 +867,6 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio) if (req_op(rq) != bio_op(bio)) return false; - /* different data direction or already started, don't merge */ - if (bio_data_dir(bio) != rq_data_dir(rq)) - return false; - /* must be same device */ if (rq->rq_disk != bio->bi_disk) return false;
Checks for data direction in attempt_merge() and blk_rq_merge_ok() are redundant and will always succeed when the both I/O request operations are equal. Therefore, remove them. Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com> --- block/blk-merge.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-)