| Message ID | 20201223112624.78955-4-jefflexu@linux.alibaba.com (mailing list archive) |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | Mike Snitzer |
| Headers | show |
| Series | dm: add support of iopoll | expand |
On Wed, Dec 23 2020 at 6:26am -0500, Jeffle Xu <jefflexu@linux.alibaba.com> wrote: > ->poll_fn is introduced in commit ea435e1b9392 ("block: add a poll_fn > callback to struct request_queue") for supporting non-mq queues such as > nvme multipath, but removed in commit 529262d56dbe ("block: remove > ->poll_fn"). > > To add support of IO polling for non-mq device, this method need to be > back. Since commit c62b37d96b6e ("block: move ->make_request_fn to > struct block_device_operations") has moved all callbacks into struct > block_device_operations in gendisk, we also add the new method named > ->iopoll in block_device_operations. Please update patch subject and header to: block: add iopoll method to support bio-based IO polling ->poll_fn was introduced in commit ea435e1b9392 ("block: add a poll_fn callback to struct request_queue") to support bio-based queues such as nvme multipath, but was later removed in commit 529262d56dbe ("block: remove ->poll_fn"). Given commit c62b37d96b6e ("block: move ->make_request_fn to struct block_device_operations") restore the possibility of bio-based IO polling support by adding an ->iopoll method to gendisk->fops. Elevate bulk of blk_mq_poll() implementation to blk_poll() and reduce blk_mq_poll() to blk-mq specific code that is called from blk_poll(). > Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> > --- > block/blk-core.c | 79 ++++++++++++++++++++++++++++++++++++++++++ > block/blk-mq.c | 70 +++++-------------------------------- > include/linux/blk-mq.h | 3 ++ > include/linux/blkdev.h | 1 + > 4 files changed, 92 insertions(+), 61 deletions(-) > > diff --git a/block/blk-core.c b/block/blk-core.c > index 96e5fcd7f071..2f5c51ce32e3 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -1131,6 +1131,85 @@ blk_qc_t submit_bio(struct bio *bio) > } > EXPORT_SYMBOL(submit_bio); > > +static bool blk_poll_hybrid(struct request_queue *q, blk_qc_t cookie) > +{ > + struct blk_mq_hw_ctx *hctx; > + > + /* TODO: bio-based device doesn't support hybrid poll. */ > + if (!queue_is_mq(q)) > + return false; > + > + hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; > + if (blk_mq_poll_hybrid(q, hctx, cookie)) > + return true; > + > + hctx->poll_considered++; > + return false; > +} I don't see where you ever backfill bio-based hybrid support (in the following patches in this series, so it is lingering TODO). > + > +/** > + * blk_poll - poll for IO completions > + * @q: the queue > + * @cookie: cookie passed back at IO submission time > + * @spin: whether to spin for completions > + * > + * Description: > + * Poll for completions on the passed in queue. Returns number of > + * completed entries found. If @spin is true, then blk_poll will continue > + * looping until at least one completion is found, unless the task is > + * otherwise marked running (or we need to reschedule). > + */ > +int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) > +{ > + long state; > + > + if (!blk_qc_t_valid(cookie) || > + !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) > + return 0; > + > + if (current->plug) > + blk_flush_plug_list(current->plug, false); > + > + /* > + * If we sleep, have the caller restart the poll loop to reset > + * the state. Like for the other success return cases, the > + * caller is responsible for checking if the IO completed. If > + * the IO isn't complete, we'll get called again and will go > + * straight to the busy poll loop. If specified not to spin, > + * we also should not sleep. > + */ > + if (spin && blk_poll_hybrid(q, cookie)) > + return 1; > + > + state = current->state; > + do { > + int ret; > + struct gendisk *disk = queue_to_disk(q); > + > + if (disk->fops->iopoll) > + ret = disk->fops->iopoll(q, cookie); > + else > + ret = blk_mq_poll(q, cookie); Really don't like that blk-mq is needlessly getting gendisk and checking disk->fops->iopoll. This is just to give an idea, whitespace damaged due to coding in mail client, but why not remove above blk_poll_hybrid() and do: struct blk_mq_hw_ctx *hctx = NULL; struct gendisk *disk = NULL; ... if (queue_is_mq(q)) { /* * If we sleep, have the caller restart the poll loop to reset * the state. Like for the other success return cases, the * caller is responsible for checking if the IO completed. If * the IO isn't complete, we'll get called again and will go * straight to the busy poll loop. If specified not to spin, * we also should not sleep. */ hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; if (spin && blk_mq_poll_hybrid(q, hctx, cookie)) return 1; hctx->poll_considered++; } else { disk = queue_to_disk(q); } do { int ret; if (hctx) ret = blk_mq_poll(q, hctx, cookie); else if (disk->fops->iopoll) ret = disk->fops->iopoll(q, cookie); > + if (ret > 0) { > + __set_current_state(TASK_RUNNING); > + return ret; > + } > + > + if (signal_pending_state(state, current)) > + __set_current_state(TASK_RUNNING); > + > + if (current->state == TASK_RUNNING) > + return 1; > + if (ret < 0 || !spin) > + break; > + cpu_relax(); > + } while (!need_resched()); > + > + __set_current_state(TASK_RUNNING); > + return 0; > +} > +EXPORT_SYMBOL_GPL(blk_poll); > + > /** > * blk_cloned_rq_check_limits - Helper function to check a cloned request > * for the new queue limits > diff --git a/block/blk-mq.c b/block/blk-mq.c > index b09ce00cc6af..85258958e9f1 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -3818,8 +3818,8 @@ static bool blk_mq_poll_hybrid_sleep(struct request_queue *q, > return true; > } > > -static bool blk_mq_poll_hybrid(struct request_queue *q, > - struct blk_mq_hw_ctx *hctx, blk_qc_t cookie) > +bool blk_mq_poll_hybrid(struct request_queue *q, > + struct blk_mq_hw_ctx *hctx, blk_qc_t cookie) > { > struct request *rq; > > @@ -3843,72 +3843,20 @@ static bool blk_mq_poll_hybrid(struct request_queue *q, > return blk_mq_poll_hybrid_sleep(q, rq); > } > > -/** > - * blk_poll - poll for IO completions > - * @q: the queue > - * @cookie: cookie passed back at IO submission time > - * @spin: whether to spin for completions > - * > - * Description: > - * Poll for completions on the passed in queue. Returns number of > - * completed entries found. If @spin is true, then blk_poll will continue > - * looping until at least one completion is found, unless the task is > - * otherwise marked running (or we need to reschedule). > - */ > -int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) > +int blk_mq_poll(struct request_queue *q, blk_qc_t cookie) > { > + int ret; > struct blk_mq_hw_ctx *hctx; > - long state; > - > - if (!blk_qc_t_valid(cookie) || > - !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) > - return 0; > - > - if (current->plug) > - blk_flush_plug_list(current->plug, false); > > hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; Given my suggested code changes above, pass hctx in to blk_mq_poll() to avoid redundant code to access it in q->queue_hw_ctx[], so: int blk_mq_poll(struct request_queue *q, struct blk_mq_hw_ctx *hctx, blk_qc_t cookie) > - /* > - * If we sleep, have the caller restart the poll loop to reset > - * the state. Like for the other success return cases, the > - * caller is responsible for checking if the IO completed. If > - * the IO isn't complete, we'll get called again and will go > - * straight to the busy poll loop. If specified not to spin, > - * we also should not sleep. > - */ > - if (spin && blk_mq_poll_hybrid(q, hctx, cookie)) > - return 1; > - > - hctx->poll_considered++; > + hctx->poll_invoked++; > + ret = q->mq_ops->poll(hctx); > + if (ret > 0) > + hctx->poll_success++; > > - state = current->state; > - do { > - int ret; > - > - hctx->poll_invoked++; > - > - ret = q->mq_ops->poll(hctx); > - if (ret > 0) { > - hctx->poll_success++; > - __set_current_state(TASK_RUNNING); > - return ret; > - } > - > - if (signal_pending_state(state, current)) > - __set_current_state(TASK_RUNNING); > - > - if (current->state == TASK_RUNNING) > - return 1; > - if (ret < 0 || !spin) > - break; > - cpu_relax(); > - } while (!need_resched()); > - > - __set_current_state(TASK_RUNNING); > - return 0; > + return ret; > } > -EXPORT_SYMBOL_GPL(blk_poll); > > unsigned int blk_mq_rq_cpu(struct request *rq) > { > diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h > index 47b021952ac7..032e08ecd42e 100644 > --- a/include/linux/blk-mq.h > +++ b/include/linux/blk-mq.h > @@ -607,6 +607,9 @@ static inline void blk_rq_bio_prep(struct request *rq, struct bio *bio, > } > > blk_qc_t blk_mq_submit_bio(struct bio *bio); > +int blk_mq_poll(struct request_queue *q, blk_qc_t cookie); > +bool blk_mq_poll_hybrid(struct request_queue *q, > + struct blk_mq_hw_ctx *hctx, blk_qc_t cookie); > void blk_mq_hctx_set_fq_lock_class(struct blk_mq_hw_ctx *hctx, > struct lock_class_key *key); > > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > index 2303d06a5a82..e8965879eb90 100644 > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -1845,6 +1845,7 @@ static inline void blk_ksm_unregister(struct request_queue *q) { } > > struct block_device_operations { > blk_qc_t (*submit_bio) (struct bio *bio); > + int (*iopoll)(struct request_queue *q, blk_qc_t cookie); > int (*open) (struct block_device *, fmode_t); > void (*release) (struct gendisk *, fmode_t); > int (*rw_page)(struct block_device *, sector_t, struct page *, unsigned int); > -- > 2.27.0 > > -- > dm-devel mailing list > dm-devel@redhat.com > https://www.redhat.com/mailman/listinfo/dm-devel -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
On 1/8/21 5:47 AM, Mike Snitzer wrote: > On Wed, Dec 23 2020 at 6:26am -0500, > Jeffle Xu <jefflexu@linux.alibaba.com> wrote: > >> ->poll_fn is introduced in commit ea435e1b9392 ("block: add a poll_fn >> callback to struct request_queue") for supporting non-mq queues such as >> nvme multipath, but removed in commit 529262d56dbe ("block: remove >> ->poll_fn"). >> >> To add support of IO polling for non-mq device, this method need to be >> back. Since commit c62b37d96b6e ("block: move ->make_request_fn to >> struct block_device_operations") has moved all callbacks into struct >> block_device_operations in gendisk, we also add the new method named >> ->iopoll in block_device_operations. > > Please update patch subject and header to: > > block: add iopoll method to support bio-based IO polling > > ->poll_fn was introduced in commit ea435e1b9392 ("block: add a poll_fn > callback to struct request_queue") to support bio-based queues such as > nvme multipath, but was later removed in commit 529262d56dbe ("block: > remove ->poll_fn"). > > Given commit c62b37d96b6e ("block: move ->make_request_fn to struct > block_device_operations") restore the possibility of bio-based IO > polling support by adding an ->iopoll method to gendisk->fops. > Elevate bulk of blk_mq_poll() implementation to blk_poll() and reduce > blk_mq_poll() to blk-mq specific code that is called from blk_poll(). > >> Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> >> --- >> block/blk-core.c | 79 ++++++++++++++++++++++++++++++++++++++++++ >> block/blk-mq.c | 70 +++++-------------------------------- >> include/linux/blk-mq.h | 3 ++ >> include/linux/blkdev.h | 1 + >> 4 files changed, 92 insertions(+), 61 deletions(-) >> >> diff --git a/block/blk-core.c b/block/blk-core.c >> index 96e5fcd7f071..2f5c51ce32e3 100644 >> --- a/block/blk-core.c >> +++ b/block/blk-core.c >> @@ -1131,6 +1131,85 @@ blk_qc_t submit_bio(struct bio *bio) >> } >> EXPORT_SYMBOL(submit_bio); >> >> +static bool blk_poll_hybrid(struct request_queue *q, blk_qc_t cookie) >> +{ >> + struct blk_mq_hw_ctx *hctx; >> + >> + /* TODO: bio-based device doesn't support hybrid poll. */ >> + if (!queue_is_mq(q)) >> + return false; >> + >> + hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; >> + if (blk_mq_poll_hybrid(q, hctx, cookie)) >> + return true; >> + >> + hctx->poll_considered++; >> + return false; >> +} > > I don't see where you ever backfill bio-based hybrid support (in > the following patches in this series, so it is lingering TODO). Yes the hybrid polling is not implemented and thus bypassed for bio-based device currently. > >> + >> +/** >> + * blk_poll - poll for IO completions >> + * @q: the queue >> + * @cookie: cookie passed back at IO submission time >> + * @spin: whether to spin for completions >> + * >> + * Description: >> + * Poll for completions on the passed in queue. Returns number of >> + * completed entries found. If @spin is true, then blk_poll will continue >> + * looping until at least one completion is found, unless the task is >> + * otherwise marked running (or we need to reschedule). >> + */ >> +int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) >> +{ >> + long state; >> + >> + if (!blk_qc_t_valid(cookie) || >> + !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) >> + return 0; >> + >> + if (current->plug) >> + blk_flush_plug_list(current->plug, false); >> + >> + /* >> + * If we sleep, have the caller restart the poll loop to reset >> + * the state. Like for the other success return cases, the >> + * caller is responsible for checking if the IO completed. If >> + * the IO isn't complete, we'll get called again and will go >> + * straight to the busy poll loop. If specified not to spin, >> + * we also should not sleep. >> + */ >> + if (spin && blk_poll_hybrid(q, cookie)) >> + return 1; >> + >> + state = current->state; >> + do { >> + int ret; >> + struct gendisk *disk = queue_to_disk(q); >> + >> + if (disk->fops->iopoll) >> + ret = disk->fops->iopoll(q, cookie); >> + else >> + ret = blk_mq_poll(q, cookie); The original code is indeed buggy. For bio-based device, ->iopoll() may not be implemented while QUEUE_FLAG_POLL flag is still set, in which case blk_mq_poll() will be called for this bio-based device. > > Really don't like that blk-mq is needlessly getting gendisk and checking > disk->fops->iopoll. > > This is just to give an idea, whitespace damaged due to coding in mail > client, but why not remove above blk_poll_hybrid() and do: > > struct blk_mq_hw_ctx *hctx = NULL; > struct gendisk *disk = NULL; > ... > > if (queue_is_mq(q)) { > /* > * If we sleep, have the caller restart the poll loop to reset > * the state. Like for the other success return cases, the > * caller is responsible for checking if the IO completed. If > * the IO isn't complete, we'll get called again and will go > * straight to the busy poll loop. If specified not to spin, > * we also should not sleep. > */ > hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; > if (spin && blk_mq_poll_hybrid(q, hctx, cookie)) > return 1; > hctx->poll_considered++; > } else { > disk = queue_to_disk(q); > } > > do { > int ret; > > if (hctx) > ret = blk_mq_poll(q, hctx, cookie); > else if (disk->fops->iopoll) > ret = disk->fops->iopoll(q, cookie); > Regards. >> + if (ret > 0) { >> + __set_current_state(TASK_RUNNING); >> + return ret; >> + } >> + >> + if (signal_pending_state(state, current)) >> + __set_current_state(TASK_RUNNING); >> + >> + if (current->state == TASK_RUNNING) >> + return 1; >> + if (ret < 0 || !spin) >> + break; >> + cpu_relax(); >> + } while (!need_resched()); >> + >> + __set_current_state(TASK_RUNNING); >> + return 0; >> +} >> +EXPORT_SYMBOL_GPL(blk_poll); >> + >> /** >> * blk_cloned_rq_check_limits - Helper function to check a cloned request >> * for the new queue limits >> diff --git a/block/blk-mq.c b/block/blk-mq.c >> index b09ce00cc6af..85258958e9f1 100644 >> --- a/block/blk-mq.c >> +++ b/block/blk-mq.c >> @@ -3818,8 +3818,8 @@ static bool blk_mq_poll_hybrid_sleep(struct request_queue *q, >> return true; >> } >> >> -static bool blk_mq_poll_hybrid(struct request_queue *q, >> - struct blk_mq_hw_ctx *hctx, blk_qc_t cookie) >> +bool blk_mq_poll_hybrid(struct request_queue *q, >> + struct blk_mq_hw_ctx *hctx, blk_qc_t cookie) >> { >> struct request *rq; >> >> @@ -3843,72 +3843,20 @@ static bool blk_mq_poll_hybrid(struct request_queue *q, >> return blk_mq_poll_hybrid_sleep(q, rq); >> } >> >> -/** >> - * blk_poll - poll for IO completions >> - * @q: the queue >> - * @cookie: cookie passed back at IO submission time >> - * @spin: whether to spin for completions >> - * >> - * Description: >> - * Poll for completions on the passed in queue. Returns number of >> - * completed entries found. If @spin is true, then blk_poll will continue >> - * looping until at least one completion is found, unless the task is >> - * otherwise marked running (or we need to reschedule). >> - */ >> -int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) >> +int blk_mq_poll(struct request_queue *q, blk_qc_t cookie) >> { >> + int ret; >> struct blk_mq_hw_ctx *hctx; >> - long state; >> - >> - if (!blk_qc_t_valid(cookie) || >> - !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) >> - return 0; >> - >> - if (current->plug) >> - blk_flush_plug_list(current->plug, false); >> >> hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; > > > Given my suggested code changes above, pass hctx in to blk_mq_poll() to > avoid redundant code to access it in q->queue_hw_ctx[], so: > > int blk_mq_poll(struct request_queue *q, > struct blk_mq_hw_ctx *hctx, blk_qc_t cookie) > Regards. >> - /* >> - * If we sleep, have the caller restart the poll loop to reset >> - * the state. Like for the other success return cases, the >> - * caller is responsible for checking if the IO completed. If >> - * the IO isn't complete, we'll get called again and will go >> - * straight to the busy poll loop. If specified not to spin, >> - * we also should not sleep. >> - */ >> - if (spin && blk_mq_poll_hybrid(q, hctx, cookie)) >> - return 1; >> - >> - hctx->poll_considered++; >> + hctx->poll_invoked++; >> + ret = q->mq_ops->poll(hctx); >> + if (ret > 0) >> + hctx->poll_success++; >> >> - state = current->state; >> - do { >> - int ret; >> - >> - hctx->poll_invoked++; >> - >> - ret = q->mq_ops->poll(hctx); >> - if (ret > 0) { >> - hctx->poll_success++; >> - __set_current_state(TASK_RUNNING); >> - return ret; >> - } >> - >> - if (signal_pending_state(state, current)) >> - __set_current_state(TASK_RUNNING); >> - >> - if (current->state == TASK_RUNNING) >> - return 1; >> - if (ret < 0 || !spin) >> - break; >> - cpu_relax(); >> - } while (!need_resched()); >> - >> - __set_current_state(TASK_RUNNING); >> - return 0; >> + return ret; >> } >> -EXPORT_SYMBOL_GPL(blk_poll); >> >> unsigned int blk_mq_rq_cpu(struct request *rq) >> { >> diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h >> index 47b021952ac7..032e08ecd42e 100644 >> --- a/include/linux/blk-mq.h >> +++ b/include/linux/blk-mq.h >> @@ -607,6 +607,9 @@ static inline void blk_rq_bio_prep(struct request *rq, struct bio *bio, >> } >> >> blk_qc_t blk_mq_submit_bio(struct bio *bio); >> +int blk_mq_poll(struct request_queue *q, blk_qc_t cookie); >> +bool blk_mq_poll_hybrid(struct request_queue *q, >> + struct blk_mq_hw_ctx *hctx, blk_qc_t cookie); >> void blk_mq_hctx_set_fq_lock_class(struct blk_mq_hw_ctx *hctx, >> struct lock_class_key *key); >> >> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h >> index 2303d06a5a82..e8965879eb90 100644 >> --- a/include/linux/blkdev.h >> +++ b/include/linux/blkdev.h >> @@ -1845,6 +1845,7 @@ static inline void blk_ksm_unregister(struct request_queue *q) { } >> >> struct block_device_operations { >> blk_qc_t (*submit_bio) (struct bio *bio); >> + int (*iopoll)(struct request_queue *q, blk_qc_t cookie); >> int (*open) (struct block_device *, fmode_t); >> void (*release) (struct gendisk *, fmode_t); >> int (*rw_page)(struct block_device *, sector_t, struct page *, unsigned int); >> -- >> 2.27.0 >> >> -- >> dm-devel mailing list >> dm-devel@redhat.com >> https://www.redhat.com/mailman/listinfo/dm-devel > > -- > dm-devel mailing list > dm-devel@redhat.com > https://www.redhat.com/mailman/listinfo/dm-devel >
On Thu, Jan 07 2021 at 10:24pm -0500, JeffleXu <jefflexu@linux.alibaba.com> wrote: > > > On 1/8/21 5:47 AM, Mike Snitzer wrote: > > On Wed, Dec 23 2020 at 6:26am -0500, > > Jeffle Xu <jefflexu@linux.alibaba.com> wrote: > > > >> ->poll_fn is introduced in commit ea435e1b9392 ("block: add a poll_fn > >> callback to struct request_queue") for supporting non-mq queues such as > >> nvme multipath, but removed in commit 529262d56dbe ("block: remove > >> ->poll_fn"). > >> > >> To add support of IO polling for non-mq device, this method need to be > >> back. Since commit c62b37d96b6e ("block: move ->make_request_fn to > >> struct block_device_operations") has moved all callbacks into struct > >> block_device_operations in gendisk, we also add the new method named > >> ->iopoll in block_device_operations. > > > > Please update patch subject and header to: > > > > block: add iopoll method to support bio-based IO polling > > > > ->poll_fn was introduced in commit ea435e1b9392 ("block: add a poll_fn > > callback to struct request_queue") to support bio-based queues such as > > nvme multipath, but was later removed in commit 529262d56dbe ("block: > > remove ->poll_fn"). > > > > Given commit c62b37d96b6e ("block: move ->make_request_fn to struct > > block_device_operations") restore the possibility of bio-based IO > > polling support by adding an ->iopoll method to gendisk->fops. > > Elevate bulk of blk_mq_poll() implementation to blk_poll() and reduce > > blk_mq_poll() to blk-mq specific code that is called from blk_poll(). > > > >> Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> > >> --- > >> block/blk-core.c | 79 ++++++++++++++++++++++++++++++++++++++++++ > >> block/blk-mq.c | 70 +++++-------------------------------- > >> include/linux/blk-mq.h | 3 ++ > >> include/linux/blkdev.h | 1 + > >> 4 files changed, 92 insertions(+), 61 deletions(-) > >> > >> diff --git a/block/blk-core.c b/block/blk-core.c > >> index 96e5fcd7f071..2f5c51ce32e3 100644 > >> --- a/block/blk-core.c > >> +++ b/block/blk-core.c > >> @@ -1131,6 +1131,85 @@ blk_qc_t submit_bio(struct bio *bio) > >> } > >> EXPORT_SYMBOL(submit_bio); > >> > >> +static bool blk_poll_hybrid(struct request_queue *q, blk_qc_t cookie) > >> +{ > >> + struct blk_mq_hw_ctx *hctx; > >> + > >> + /* TODO: bio-based device doesn't support hybrid poll. */ > >> + if (!queue_is_mq(q)) > >> + return false; > >> + > >> + hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; > >> + if (blk_mq_poll_hybrid(q, hctx, cookie)) > >> + return true; > >> + > >> + hctx->poll_considered++; > >> + return false; > >> +} > > > > I don't see where you ever backfill bio-based hybrid support (in > > the following patches in this series, so it is lingering TODO). > > Yes the hybrid polling is not implemented and thus bypassed for > bio-based device currently. > > > > >> + > >> +/** > >> + * blk_poll - poll for IO completions > >> + * @q: the queue > >> + * @cookie: cookie passed back at IO submission time > >> + * @spin: whether to spin for completions > >> + * > >> + * Description: > >> + * Poll for completions on the passed in queue. Returns number of > >> + * completed entries found. If @spin is true, then blk_poll will continue > >> + * looping until at least one completion is found, unless the task is > >> + * otherwise marked running (or we need to reschedule). > >> + */ > >> +int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) > >> +{ > >> + long state; > >> + > >> + if (!blk_qc_t_valid(cookie) || > >> + !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) > >> + return 0; > >> + > >> + if (current->plug) > >> + blk_flush_plug_list(current->plug, false); > >> + > >> + /* > >> + * If we sleep, have the caller restart the poll loop to reset > >> + * the state. Like for the other success return cases, the > >> + * caller is responsible for checking if the IO completed. If > >> + * the IO isn't complete, we'll get called again and will go > >> + * straight to the busy poll loop. If specified not to spin, > >> + * we also should not sleep. > >> + */ > >> + if (spin && blk_poll_hybrid(q, cookie)) > >> + return 1; > >> + > >> + state = current->state; > >> + do { > >> + int ret; > >> + struct gendisk *disk = queue_to_disk(q); > >> + > >> + if (disk->fops->iopoll) > >> + ret = disk->fops->iopoll(q, cookie); > >> + else > >> + ret = blk_mq_poll(q, cookie); > > The original code is indeed buggy. For bio-based device, ->iopoll() may > not be implemented while QUEUE_FLAG_POLL flag is still set, in which > case blk_mq_poll() will be called for this bio-based device. Yes, here is the patch I created to capture my suggestions. Provided it looks good to you, please fold it into patch 3 when you rebase for posting a v2 of your patchset: From: Mike Snitzer <snitzer@redhat.com> Date: Thu, 7 Jan 2021 20:45:17 -0500 Subject: [PATCH] fixup patch 3 --- block/blk-core.c | 51 +++++++++++++++++++++----------------------------- block/blk-mq.c | 6 ++---- include/linux/blk-mq.h | 3 ++- 3 files changed, 25 insertions(+), 35 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index e6671f6ce1a4..44f62dc0fa9f 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1212,22 +1212,6 @@ int blk_bio_poll(struct request_queue *q, blk_qc_t cookie) } EXPORT_SYMBOL(blk_bio_poll); -static bool blk_poll_hybrid(struct request_queue *q, blk_qc_t cookie) -{ - struct blk_mq_hw_ctx *hctx; - - /* TODO: bio-based device doesn't support hybrid poll. */ - if (!queue_is_mq(q)) - return false; - - hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; - if (blk_mq_poll_hybrid(q, hctx, cookie)) - return true; - - hctx->poll_considered++; - return false; -} - /** * blk_poll - poll for IO completions * @q: the queue @@ -1243,6 +1227,8 @@ static bool blk_poll_hybrid(struct request_queue *q, blk_qc_t cookie) int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) { long state; + struct blk_mq_hw_ctx *hctx = NULL; + struct gendisk *disk = NULL; if (!blk_qc_t_valid(cookie) || !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) @@ -1251,26 +1237,31 @@ int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) if (current->plug) blk_flush_plug_list(current->plug, false); - /* - * If we sleep, have the caller restart the poll loop to reset - * the state. Like for the other success return cases, the - * caller is responsible for checking if the IO completed. If - * the IO isn't complete, we'll get called again and will go - * straight to the busy poll loop. If specified not to spin, - * we also should not sleep. - */ - if (spin && blk_poll_hybrid(q, cookie)) - return 1; + if (queue_is_mq(q)) { + /* + * If we sleep, have the caller restart the poll loop to reset + * the state. Like for the other success return cases, the + * caller is responsible for checking if the IO completed. If + * the IO isn't complete, we'll get called again and will go + * straight to the busy poll loop. If specified not to spin, + * we also should not sleep. + */ + hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; + if (spin && blk_mq_poll_hybrid(q, hctx, cookie)) + return 1; + hctx->poll_considered++; + } else + disk = queue_to_disk(q); state = current->state; do { int ret; - struct gendisk *disk = queue_to_disk(q); - if (disk->fops->iopoll) + if (hctx) + ret = blk_mq_poll(q, hctx, cookie); + else if (disk->fops->iopoll) ret = disk->fops->iopoll(q, cookie); - else - ret = blk_mq_poll(q, cookie); + if (ret > 0) { __set_current_state(TASK_RUNNING); return ret; diff --git a/block/blk-mq.c b/block/blk-mq.c index fcb44604f806..90d8dead1da5 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -3826,12 +3826,10 @@ bool blk_mq_poll_hybrid(struct request_queue *q, return blk_mq_poll_hybrid_sleep(q, rq); } -int blk_mq_poll(struct request_queue *q, blk_qc_t cookie) +int blk_mq_poll(struct request_queue *q, + struct blk_mq_hw_ctx *hctx, blk_qc_t cookie) { int ret; - struct blk_mq_hw_ctx *hctx; - - hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; hctx->poll_invoked++; ret = q->mq_ops->poll(hctx); diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 2f3742207df5..b95f2ffa866f 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -607,7 +607,8 @@ static inline void blk_rq_bio_prep(struct request *rq, struct bio *bio, } blk_qc_t blk_mq_submit_bio(struct bio *bio); -int blk_mq_poll(struct request_queue *q, blk_qc_t cookie); +int blk_mq_poll(struct request_queue *q, + struct blk_mq_hw_ctx *hctx, blk_qc_t cookie); bool blk_mq_poll_hybrid(struct request_queue *q, struct blk_mq_hw_ctx *hctx, blk_qc_t cookie); void blk_mq_hctx_set_fq_lock_class(struct blk_mq_hw_ctx *hctx,
On 1/9/21 1:33 AM, Mike Snitzer wrote: > On Thu, Jan 07 2021 at 10:24pm -0500, > JeffleXu <jefflexu@linux.alibaba.com> wrote: > >> >> >> On 1/8/21 5:47 AM, Mike Snitzer wrote: >>> On Wed, Dec 23 2020 at 6:26am -0500, >>> Jeffle Xu <jefflexu@linux.alibaba.com> wrote: >>> >>>> ->poll_fn is introduced in commit ea435e1b9392 ("block: add a poll_fn >>>> callback to struct request_queue") for supporting non-mq queues such as >>>> nvme multipath, but removed in commit 529262d56dbe ("block: remove >>>> ->poll_fn"). >>>> >>>> To add support of IO polling for non-mq device, this method need to be >>>> back. Since commit c62b37d96b6e ("block: move ->make_request_fn to >>>> struct block_device_operations") has moved all callbacks into struct >>>> block_device_operations in gendisk, we also add the new method named >>>> ->iopoll in block_device_operations. >>> >>> Please update patch subject and header to: >>> >>> block: add iopoll method to support bio-based IO polling >>> >>> ->poll_fn was introduced in commit ea435e1b9392 ("block: add a poll_fn >>> callback to struct request_queue") to support bio-based queues such as >>> nvme multipath, but was later removed in commit 529262d56dbe ("block: >>> remove ->poll_fn"). >>> >>> Given commit c62b37d96b6e ("block: move ->make_request_fn to struct >>> block_device_operations") restore the possibility of bio-based IO >>> polling support by adding an ->iopoll method to gendisk->fops. >>> Elevate bulk of blk_mq_poll() implementation to blk_poll() and reduce >>> blk_mq_poll() to blk-mq specific code that is called from blk_poll(). >>> >>>> Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> >>>> --- >>>> block/blk-core.c | 79 ++++++++++++++++++++++++++++++++++++++++++ >>>> block/blk-mq.c | 70 +++++-------------------------------- >>>> include/linux/blk-mq.h | 3 ++ >>>> include/linux/blkdev.h | 1 + >>>> 4 files changed, 92 insertions(+), 61 deletions(-) >>>> >>>> diff --git a/block/blk-core.c b/block/blk-core.c >>>> index 96e5fcd7f071..2f5c51ce32e3 100644 >>>> --- a/block/blk-core.c >>>> +++ b/block/blk-core.c >>>> @@ -1131,6 +1131,85 @@ blk_qc_t submit_bio(struct bio *bio) >>>> } >>>> EXPORT_SYMBOL(submit_bio); >>>> >>>> +static bool blk_poll_hybrid(struct request_queue *q, blk_qc_t cookie) >>>> +{ >>>> + struct blk_mq_hw_ctx *hctx; >>>> + >>>> + /* TODO: bio-based device doesn't support hybrid poll. */ >>>> + if (!queue_is_mq(q)) >>>> + return false; >>>> + >>>> + hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; >>>> + if (blk_mq_poll_hybrid(q, hctx, cookie)) >>>> + return true; >>>> + >>>> + hctx->poll_considered++; >>>> + return false; >>>> +} >>> >>> I don't see where you ever backfill bio-based hybrid support (in >>> the following patches in this series, so it is lingering TODO). >> >> Yes the hybrid polling is not implemented and thus bypassed for >> bio-based device currently. >> >>> >>>> + >>>> +/** >>>> + * blk_poll - poll for IO completions >>>> + * @q: the queue >>>> + * @cookie: cookie passed back at IO submission time >>>> + * @spin: whether to spin for completions >>>> + * >>>> + * Description: >>>> + * Poll for completions on the passed in queue. Returns number of >>>> + * completed entries found. If @spin is true, then blk_poll will continue >>>> + * looping until at least one completion is found, unless the task is >>>> + * otherwise marked running (or we need to reschedule). >>>> + */ >>>> +int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) >>>> +{ >>>> + long state; >>>> + >>>> + if (!blk_qc_t_valid(cookie) || >>>> + !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) >>>> + return 0; >>>> + >>>> + if (current->plug) >>>> + blk_flush_plug_list(current->plug, false); >>>> + >>>> + /* >>>> + * If we sleep, have the caller restart the poll loop to reset >>>> + * the state. Like for the other success return cases, the >>>> + * caller is responsible for checking if the IO completed. If >>>> + * the IO isn't complete, we'll get called again and will go >>>> + * straight to the busy poll loop. If specified not to spin, >>>> + * we also should not sleep. >>>> + */ >>>> + if (spin && blk_poll_hybrid(q, cookie)) >>>> + return 1; >>>> + >>>> + state = current->state; >>>> + do { >>>> + int ret; >>>> + struct gendisk *disk = queue_to_disk(q); >>>> + >>>> + if (disk->fops->iopoll) >>>> + ret = disk->fops->iopoll(q, cookie); >>>> + else >>>> + ret = blk_mq_poll(q, cookie); >> >> The original code is indeed buggy. For bio-based device, ->iopoll() may >> not be implemented while QUEUE_FLAG_POLL flag is still set, in which >> case blk_mq_poll() will be called for this bio-based device. > > Yes, here is the patch I created to capture my suggestions. Provided it > looks good to you, please fold it into patch 3 when you rebase for > posting a v2 of your patchset: Thanks, I will merge it into the next version. Thanks, Jeffle > > From: Mike Snitzer <snitzer@redhat.com> > Date: Thu, 7 Jan 2021 20:45:17 -0500 > Subject: [PATCH] fixup patch 3 > > --- > block/blk-core.c | 51 +++++++++++++++++++++----------------------------- > block/blk-mq.c | 6 ++---- > include/linux/blk-mq.h | 3 ++- > 3 files changed, 25 insertions(+), 35 deletions(-) > > diff --git a/block/blk-core.c b/block/blk-core.c > index e6671f6ce1a4..44f62dc0fa9f 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -1212,22 +1212,6 @@ int blk_bio_poll(struct request_queue *q, blk_qc_t cookie) > } > EXPORT_SYMBOL(blk_bio_poll); > > -static bool blk_poll_hybrid(struct request_queue *q, blk_qc_t cookie) > -{ > - struct blk_mq_hw_ctx *hctx; > - > - /* TODO: bio-based device doesn't support hybrid poll. */ > - if (!queue_is_mq(q)) > - return false; > - > - hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; > - if (blk_mq_poll_hybrid(q, hctx, cookie)) > - return true; > - > - hctx->poll_considered++; > - return false; > -} > - > /** > * blk_poll - poll for IO completions > * @q: the queue > @@ -1243,6 +1227,8 @@ static bool blk_poll_hybrid(struct request_queue *q, blk_qc_t cookie) > int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) > { > long state; > + struct blk_mq_hw_ctx *hctx = NULL; > + struct gendisk *disk = NULL; > > if (!blk_qc_t_valid(cookie) || > !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) > @@ -1251,26 +1237,31 @@ int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) > if (current->plug) > blk_flush_plug_list(current->plug, false); > > - /* > - * If we sleep, have the caller restart the poll loop to reset > - * the state. Like for the other success return cases, the > - * caller is responsible for checking if the IO completed. If > - * the IO isn't complete, we'll get called again and will go > - * straight to the busy poll loop. If specified not to spin, > - * we also should not sleep. > - */ > - if (spin && blk_poll_hybrid(q, cookie)) > - return 1; > + if (queue_is_mq(q)) { > + /* > + * If we sleep, have the caller restart the poll loop to reset > + * the state. Like for the other success return cases, the > + * caller is responsible for checking if the IO completed. If > + * the IO isn't complete, we'll get called again and will go > + * straight to the busy poll loop. If specified not to spin, > + * we also should not sleep. > + */ > + hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; > + if (spin && blk_mq_poll_hybrid(q, hctx, cookie)) > + return 1; > + hctx->poll_considered++; > + } else > + disk = queue_to_disk(q); > > state = current->state; > do { > int ret; > - struct gendisk *disk = queue_to_disk(q); > > - if (disk->fops->iopoll) > + if (hctx) > + ret = blk_mq_poll(q, hctx, cookie); > + else if (disk->fops->iopoll) > ret = disk->fops->iopoll(q, cookie); > - else > - ret = blk_mq_poll(q, cookie); > + > if (ret > 0) { > __set_current_state(TASK_RUNNING); > return ret; > diff --git a/block/blk-mq.c b/block/blk-mq.c > index fcb44604f806..90d8dead1da5 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -3826,12 +3826,10 @@ bool blk_mq_poll_hybrid(struct request_queue *q, > return blk_mq_poll_hybrid_sleep(q, rq); > } > > -int blk_mq_poll(struct request_queue *q, blk_qc_t cookie) > +int blk_mq_poll(struct request_queue *q, > + struct blk_mq_hw_ctx *hctx, blk_qc_t cookie) > { > int ret; > - struct blk_mq_hw_ctx *hctx; > - > - hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; > > hctx->poll_invoked++; > ret = q->mq_ops->poll(hctx); > diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h > index 2f3742207df5..b95f2ffa866f 100644 > --- a/include/linux/blk-mq.h > +++ b/include/linux/blk-mq.h > @@ -607,7 +607,8 @@ static inline void blk_rq_bio_prep(struct request *rq, struct bio *bio, > } > > blk_qc_t blk_mq_submit_bio(struct bio *bio); > -int blk_mq_poll(struct request_queue *q, blk_qc_t cookie); > +int blk_mq_poll(struct request_queue *q, > + struct blk_mq_hw_ctx *hctx, blk_qc_t cookie); > bool blk_mq_poll_hybrid(struct request_queue *q, > struct blk_mq_hw_ctx *hctx, blk_qc_t cookie); > void blk_mq_hctx_set_fq_lock_class(struct blk_mq_hw_ctx *hctx, >
diff --git a/block/blk-core.c b/block/blk-core.c index 96e5fcd7f071..2f5c51ce32e3 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1131,6 +1131,85 @@ blk_qc_t submit_bio(struct bio *bio) } EXPORT_SYMBOL(submit_bio); +static bool blk_poll_hybrid(struct request_queue *q, blk_qc_t cookie) +{ + struct blk_mq_hw_ctx *hctx; + + /* TODO: bio-based device doesn't support hybrid poll. */ + if (!queue_is_mq(q)) + return false; + + hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; + if (blk_mq_poll_hybrid(q, hctx, cookie)) + return true; + + hctx->poll_considered++; + return false; +} + +/** + * blk_poll - poll for IO completions + * @q: the queue + * @cookie: cookie passed back at IO submission time + * @spin: whether to spin for completions + * + * Description: + * Poll for completions on the passed in queue. Returns number of + * completed entries found. If @spin is true, then blk_poll will continue + * looping until at least one completion is found, unless the task is + * otherwise marked running (or we need to reschedule). + */ +int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) +{ + long state; + + if (!blk_qc_t_valid(cookie) || + !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) + return 0; + + if (current->plug) + blk_flush_plug_list(current->plug, false); + + /* + * If we sleep, have the caller restart the poll loop to reset + * the state. Like for the other success return cases, the + * caller is responsible for checking if the IO completed. If + * the IO isn't complete, we'll get called again and will go + * straight to the busy poll loop. If specified not to spin, + * we also should not sleep. + */ + if (spin && blk_poll_hybrid(q, cookie)) + return 1; + + state = current->state; + do { + int ret; + struct gendisk *disk = queue_to_disk(q); + + if (disk->fops->iopoll) + ret = disk->fops->iopoll(q, cookie); + else + ret = blk_mq_poll(q, cookie); + if (ret > 0) { + __set_current_state(TASK_RUNNING); + return ret; + } + + if (signal_pending_state(state, current)) + __set_current_state(TASK_RUNNING); + + if (current->state == TASK_RUNNING) + return 1; + if (ret < 0 || !spin) + break; + cpu_relax(); + } while (!need_resched()); + + __set_current_state(TASK_RUNNING); + return 0; +} +EXPORT_SYMBOL_GPL(blk_poll); + /** * blk_cloned_rq_check_limits - Helper function to check a cloned request * for the new queue limits diff --git a/block/blk-mq.c b/block/blk-mq.c index b09ce00cc6af..85258958e9f1 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -3818,8 +3818,8 @@ static bool blk_mq_poll_hybrid_sleep(struct request_queue *q, return true; } -static bool blk_mq_poll_hybrid(struct request_queue *q, - struct blk_mq_hw_ctx *hctx, blk_qc_t cookie) +bool blk_mq_poll_hybrid(struct request_queue *q, + struct blk_mq_hw_ctx *hctx, blk_qc_t cookie) { struct request *rq; @@ -3843,72 +3843,20 @@ static bool blk_mq_poll_hybrid(struct request_queue *q, return blk_mq_poll_hybrid_sleep(q, rq); } -/** - * blk_poll - poll for IO completions - * @q: the queue - * @cookie: cookie passed back at IO submission time - * @spin: whether to spin for completions - * - * Description: - * Poll for completions on the passed in queue. Returns number of - * completed entries found. If @spin is true, then blk_poll will continue - * looping until at least one completion is found, unless the task is - * otherwise marked running (or we need to reschedule). - */ -int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) +int blk_mq_poll(struct request_queue *q, blk_qc_t cookie) { + int ret; struct blk_mq_hw_ctx *hctx; - long state; - - if (!blk_qc_t_valid(cookie) || - !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) - return 0; - - if (current->plug) - blk_flush_plug_list(current->plug, false); hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; - /* - * If we sleep, have the caller restart the poll loop to reset - * the state. Like for the other success return cases, the - * caller is responsible for checking if the IO completed. If - * the IO isn't complete, we'll get called again and will go - * straight to the busy poll loop. If specified not to spin, - * we also should not sleep. - */ - if (spin && blk_mq_poll_hybrid(q, hctx, cookie)) - return 1; - - hctx->poll_considered++; + hctx->poll_invoked++; + ret = q->mq_ops->poll(hctx); + if (ret > 0) + hctx->poll_success++; - state = current->state; - do { - int ret; - - hctx->poll_invoked++; - - ret = q->mq_ops->poll(hctx); - if (ret > 0) { - hctx->poll_success++; - __set_current_state(TASK_RUNNING); - return ret; - } - - if (signal_pending_state(state, current)) - __set_current_state(TASK_RUNNING); - - if (current->state == TASK_RUNNING) - return 1; - if (ret < 0 || !spin) - break; - cpu_relax(); - } while (!need_resched()); - - __set_current_state(TASK_RUNNING); - return 0; + return ret; } -EXPORT_SYMBOL_GPL(blk_poll); unsigned int blk_mq_rq_cpu(struct request *rq) { diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 47b021952ac7..032e08ecd42e 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -607,6 +607,9 @@ static inline void blk_rq_bio_prep(struct request *rq, struct bio *bio, } blk_qc_t blk_mq_submit_bio(struct bio *bio); +int blk_mq_poll(struct request_queue *q, blk_qc_t cookie); +bool blk_mq_poll_hybrid(struct request_queue *q, + struct blk_mq_hw_ctx *hctx, blk_qc_t cookie); void blk_mq_hctx_set_fq_lock_class(struct blk_mq_hw_ctx *hctx, struct lock_class_key *key); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 2303d06a5a82..e8965879eb90 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1845,6 +1845,7 @@ static inline void blk_ksm_unregister(struct request_queue *q) { } struct block_device_operations { blk_qc_t (*submit_bio) (struct bio *bio); + int (*iopoll)(struct request_queue *q, blk_qc_t cookie); int (*open) (struct block_device *, fmode_t); void (*release) (struct gendisk *, fmode_t); int (*rw_page)(struct block_device *, sector_t, struct page *, unsigned int);
->poll_fn is introduced in commit ea435e1b9392 ("block: add a poll_fn callback to struct request_queue") for supporting non-mq queues such as nvme multipath, but removed in commit 529262d56dbe ("block: remove ->poll_fn"). To add support of IO polling for non-mq device, this method need to be back. Since commit c62b37d96b6e ("block: move ->make_request_fn to struct block_device_operations") has moved all callbacks into struct block_device_operations in gendisk, we also add the new method named ->iopoll in block_device_operations. Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> --- block/blk-core.c | 79 ++++++++++++++++++++++++++++++++++++++++++ block/blk-mq.c | 70 +++++-------------------------------- include/linux/blk-mq.h | 3 ++ include/linux/blkdev.h | 1 + 4 files changed, 92 insertions(+), 61 deletions(-)