| Message ID | 20210726060855.108250-2-pankaj.gupta.linux@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | virtio-pmem: Asynchronous flush | expand |
On Sun, Jul 25, 2021 at 11:09 PM Pankaj Gupta <pankaj.gupta.linux@gmail.com> wrote: > > From: Pankaj Gupta <pankaj.gupta@ionos.com> > > Implement asynchronous flush for virtio pmem using work queue > to solve the preflush ordering issue. Also, coalesce the flush > requests when a flush is already in process. > > Signed-off-by: Pankaj Gupta <pankaj.gupta@ionos.com> > --- > drivers/nvdimm/nd_virtio.c | 72 ++++++++++++++++++++++++++++-------- > drivers/nvdimm/virtio_pmem.c | 10 ++++- > drivers/nvdimm/virtio_pmem.h | 14 +++++++ > 3 files changed, 79 insertions(+), 17 deletions(-) > > diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c > index 10351d5b49fa..61b655b583be 100644 > --- a/drivers/nvdimm/nd_virtio.c > +++ b/drivers/nvdimm/nd_virtio.c > @@ -97,29 +97,69 @@ static int virtio_pmem_flush(struct nd_region *nd_region) > return err; > }; > > +static void submit_async_flush(struct work_struct *ws); > + > /* The asynchronous flush callback function */ > int async_pmem_flush(struct nd_region *nd_region, struct bio *bio) > { > - /* > - * Create child bio for asynchronous flush and chain with > - * parent bio. Otherwise directly call nd_region flush. > + /* queue asynchronous flush and coalesce the flush requests */ > + struct virtio_device *vdev = nd_region->provider_data; > + struct virtio_pmem *vpmem = vdev->priv; > + ktime_t req_start = ktime_get_boottime(); > + > + spin_lock_irq(&vpmem->lock); > + /* flush requests wait until ongoing flush completes, > + * hence coalescing all the pending requests. > */ > - if (bio && bio->bi_iter.bi_sector != -1) { > - struct bio *child = bio_alloc(GFP_ATOMIC, 0); > - > - if (!child) > - return -ENOMEM; > - bio_copy_dev(child, bio); > - child->bi_opf = REQ_PREFLUSH; > - child->bi_iter.bi_sector = -1; > - bio_chain(child, bio); > - submit_bio(child); > - return 0; > + wait_event_lock_irq(vpmem->sb_wait, > + !vpmem->flush_bio || > + ktime_before(req_start, vpmem->prev_flush_start), > + vpmem->lock); > + /* new request after previous flush is completed */ > + if (ktime_after(req_start, vpmem->prev_flush_start)) { > + WARN_ON(vpmem->flush_bio); > + vpmem->flush_bio = bio; > + bio = NULL; > + } Why the dance with ->prev_flush_start vs just calling queue_work() again. queue_work() is naturally coalescing in that if the last work request has not started execution another queue attempt will be dropped. > + spin_unlock_irq(&vpmem->lock); > + > + if (!bio) { > + INIT_WORK(&vpmem->flush_work, submit_async_flush); I expect this only needs to be initialized once at driver init time. > + queue_work(vpmem->pmem_wq, &vpmem->flush_work); > + return 1; > + } > + > + /* flush completed in other context while we waited */ > + if (bio && (bio->bi_opf & REQ_PREFLUSH)) { > + bio->bi_opf &= ~REQ_PREFLUSH; > + submit_bio(bio); > + } else if (bio && (bio->bi_opf & REQ_FUA)) { > + bio->bi_opf &= ~REQ_FUA; > + bio_endio(bio); It's not clear to me how this happens, shouldn't all flush completions be driven from the work completion? > } > - if (virtio_pmem_flush(nd_region)) > - return -EIO; > > return 0; > }; > EXPORT_SYMBOL_GPL(async_pmem_flush); > + > +static void submit_async_flush(struct work_struct *ws) > +{ > + struct virtio_pmem *vpmem = container_of(ws, struct virtio_pmem, flush_work); > + struct bio *bio = vpmem->flush_bio; > + > + vpmem->start_flush = ktime_get_boottime(); > + bio->bi_status = errno_to_blk_status(virtio_pmem_flush(vpmem->nd_region)); > + vpmem->prev_flush_start = vpmem->start_flush; > + vpmem->flush_bio = NULL; > + wake_up(&vpmem->sb_wait); > + > + /* Submit parent bio only for PREFLUSH */ > + if (bio && (bio->bi_opf & REQ_PREFLUSH)) { > + bio->bi_opf &= ~REQ_PREFLUSH; > + submit_bio(bio); > + } else if (bio && (bio->bi_opf & REQ_FUA)) { > + bio->bi_opf &= ~REQ_FUA; > + bio_endio(bio); > + } Shouldn't the wait_event_lock_irq() be here rather than in async_pmem_flush()? That will cause the workqueue to back up and flush requests to coalesce. > +} > MODULE_LICENSE("GPL"); > diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c > index 726c7354d465..56780a6140c7 100644 > --- a/drivers/nvdimm/virtio_pmem.c > +++ b/drivers/nvdimm/virtio_pmem.c > @@ -24,6 +24,7 @@ static int init_vq(struct virtio_pmem *vpmem) > return PTR_ERR(vpmem->req_vq); > > spin_lock_init(&vpmem->pmem_lock); > + spin_lock_init(&vpmem->lock); Why 2 locks?
Hi Dan, Thank you for the review. Please see my reply inline. > > Implement asynchronous flush for virtio pmem using work queue > > to solve the preflush ordering issue. Also, coalesce the flush > > requests when a flush is already in process. > > > > Signed-off-by: Pankaj Gupta <pankaj.gupta@ionos.com> > > --- > > drivers/nvdimm/nd_virtio.c | 72 ++++++++++++++++++++++++++++-------- > > drivers/nvdimm/virtio_pmem.c | 10 ++++- > > drivers/nvdimm/virtio_pmem.h | 14 +++++++ > > 3 files changed, 79 insertions(+), 17 deletions(-) > > > > diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c > > index 10351d5b49fa..61b655b583be 100644 > > --- a/drivers/nvdimm/nd_virtio.c > > +++ b/drivers/nvdimm/nd_virtio.c > > @@ -97,29 +97,69 @@ static int virtio_pmem_flush(struct nd_region *nd_region) > > return err; > > }; > > > > +static void submit_async_flush(struct work_struct *ws); > > + > > /* The asynchronous flush callback function */ > > int async_pmem_flush(struct nd_region *nd_region, struct bio *bio) > > { > > - /* > > - * Create child bio for asynchronous flush and chain with > > - * parent bio. Otherwise directly call nd_region flush. > > + /* queue asynchronous flush and coalesce the flush requests */ > > + struct virtio_device *vdev = nd_region->provider_data; > > + struct virtio_pmem *vpmem = vdev->priv; > > + ktime_t req_start = ktime_get_boottime(); > > + > > + spin_lock_irq(&vpmem->lock); > > + /* flush requests wait until ongoing flush completes, > > + * hence coalescing all the pending requests. > > */ > > - if (bio && bio->bi_iter.bi_sector != -1) { > > - struct bio *child = bio_alloc(GFP_ATOMIC, 0); > > - > > - if (!child) > > - return -ENOMEM; > > - bio_copy_dev(child, bio); > > - child->bi_opf = REQ_PREFLUSH; > > - child->bi_iter.bi_sector = -1; > > - bio_chain(child, bio); > > - submit_bio(child); > > - return 0; > > + wait_event_lock_irq(vpmem->sb_wait, > > + !vpmem->flush_bio || > > + ktime_before(req_start, vpmem->prev_flush_start), > > + vpmem->lock); > > + /* new request after previous flush is completed */ > > + if (ktime_after(req_start, vpmem->prev_flush_start)) { > > + WARN_ON(vpmem->flush_bio); > > + vpmem->flush_bio = bio; > > + bio = NULL; > > + } > > Why the dance with ->prev_flush_start vs just calling queue_work() > again. queue_work() is naturally coalescing in that if the last work > request has not started execution another queue attempt will be > dropped. How parent flush request will know when corresponding flush is completed? > > > + spin_unlock_irq(&vpmem->lock); > > + > > + if (!bio) { > > + INIT_WORK(&vpmem->flush_work, submit_async_flush); > > I expect this only needs to be initialized once at driver init time. yes, will fix this. > > > + queue_work(vpmem->pmem_wq, &vpmem->flush_work); > > + return 1; > > + } > > + > > + /* flush completed in other context while we waited */ > > + if (bio && (bio->bi_opf & REQ_PREFLUSH)) { > > + bio->bi_opf &= ~REQ_PREFLUSH; > > + submit_bio(bio); > > + } else if (bio && (bio->bi_opf & REQ_FUA)) { > > + bio->bi_opf &= ~REQ_FUA; > > + bio_endio(bio); > > It's not clear to me how this happens, shouldn't all flush completions > be driven from the work completion? Requests should progress after notified by ongoing flush completion event. > > > } > > - if (virtio_pmem_flush(nd_region)) > > - return -EIO; > > > > return 0; > > }; > > EXPORT_SYMBOL_GPL(async_pmem_flush); > > + > > +static void submit_async_flush(struct work_struct *ws) > > +{ > > + struct virtio_pmem *vpmem = container_of(ws, struct virtio_pmem, flush_work); > > + struct bio *bio = vpmem->flush_bio; > > + > > + vpmem->start_flush = ktime_get_boottime(); > > + bio->bi_status = errno_to_blk_status(virtio_pmem_flush(vpmem->nd_region)); > > + vpmem->prev_flush_start = vpmem->start_flush; > > + vpmem->flush_bio = NULL; > > + wake_up(&vpmem->sb_wait); > > + > > + /* Submit parent bio only for PREFLUSH */ > > + if (bio && (bio->bi_opf & REQ_PREFLUSH)) { > > + bio->bi_opf &= ~REQ_PREFLUSH; > > + submit_bio(bio); > > + } else if (bio && (bio->bi_opf & REQ_FUA)) { > > + bio->bi_opf &= ~REQ_FUA; > > + bio_endio(bio); > > + } > > Shouldn't the wait_event_lock_irq() be here rather than in > async_pmem_flush()? That will cause the workqueue to back up and flush > requests to coalesce. but this is coalesced flush request? > > +} > > MODULE_LICENSE("GPL"); > > diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c > > index 726c7354d465..56780a6140c7 100644 > > --- a/drivers/nvdimm/virtio_pmem.c > > +++ b/drivers/nvdimm/virtio_pmem.c > > @@ -24,6 +24,7 @@ static int init_vq(struct virtio_pmem *vpmem) > > return PTR_ERR(vpmem->req_vq); > > > > spin_lock_init(&vpmem->pmem_lock); > > + spin_lock_init(&vpmem->lock); > > Why 2 locks? One lock is for work queue and other for virtio flush completion. Thanks, Pankaj
On Wed, Aug 25, 2021 at 1:02 PM Pankaj Gupta <pankaj.gupta.linux@gmail.com> wrote: > > Hi Dan, > > Thank you for the review. Please see my reply inline. > > > > Implement asynchronous flush for virtio pmem using work queue > > > to solve the preflush ordering issue. Also, coalesce the flush > > > requests when a flush is already in process. > > > > > > Signed-off-by: Pankaj Gupta <pankaj.gupta@ionos.com> > > > --- > > > drivers/nvdimm/nd_virtio.c | 72 ++++++++++++++++++++++++++++-------- > > > drivers/nvdimm/virtio_pmem.c | 10 ++++- > > > drivers/nvdimm/virtio_pmem.h | 14 +++++++ > > > 3 files changed, 79 insertions(+), 17 deletions(-) > > > > > > diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c > > > index 10351d5b49fa..61b655b583be 100644 > > > --- a/drivers/nvdimm/nd_virtio.c > > > +++ b/drivers/nvdimm/nd_virtio.c > > > @@ -97,29 +97,69 @@ static int virtio_pmem_flush(struct nd_region *nd_region) > > > return err; > > > }; > > > > > > +static void submit_async_flush(struct work_struct *ws); > > > + > > > /* The asynchronous flush callback function */ > > > int async_pmem_flush(struct nd_region *nd_region, struct bio *bio) > > > { > > > - /* > > > - * Create child bio for asynchronous flush and chain with > > > - * parent bio. Otherwise directly call nd_region flush. > > > + /* queue asynchronous flush and coalesce the flush requests */ > > > + struct virtio_device *vdev = nd_region->provider_data; > > > + struct virtio_pmem *vpmem = vdev->priv; > > > + ktime_t req_start = ktime_get_boottime(); > > > + > > > + spin_lock_irq(&vpmem->lock); > > > + /* flush requests wait until ongoing flush completes, > > > + * hence coalescing all the pending requests. > > > */ > > > - if (bio && bio->bi_iter.bi_sector != -1) { > > > - struct bio *child = bio_alloc(GFP_ATOMIC, 0); > > > - > > > - if (!child) > > > - return -ENOMEM; > > > - bio_copy_dev(child, bio); > > > - child->bi_opf = REQ_PREFLUSH; > > > - child->bi_iter.bi_sector = -1; > > > - bio_chain(child, bio); > > > - submit_bio(child); > > > - return 0; > > > + wait_event_lock_irq(vpmem->sb_wait, > > > + !vpmem->flush_bio || > > > + ktime_before(req_start, vpmem->prev_flush_start), > > > + vpmem->lock); > > > + /* new request after previous flush is completed */ > > > + if (ktime_after(req_start, vpmem->prev_flush_start)) { > > > + WARN_ON(vpmem->flush_bio); > > > + vpmem->flush_bio = bio; > > > + bio = NULL; > > > + } > > > > Why the dance with ->prev_flush_start vs just calling queue_work() > > again. queue_work() is naturally coalescing in that if the last work > > request has not started execution another queue attempt will be > > dropped. > > How parent flush request will know when corresponding flush is completed? The eventual bio_endio() is what signals upper layers that the flush completed... Hold on... it's been so long that I forgot that you are copying md_flush_request() here. It would help immensely if that was mentioned in the changelog and at a minimum have a comment in the code that this was copied from md. In fact it would be extra helpful if you refactored a common helper that bio based block drivers could share for implementing flush handling, but that can come later. Let me go re-review this with respect to whether the md case is fully applicable here.
> > Hi Dan, > > > > Thank you for the review. Please see my reply inline. > > > > > > Implement asynchronous flush for virtio pmem using work queue > > > > to solve the preflush ordering issue. Also, coalesce the flush > > > > requests when a flush is already in process. > > > > > > > > Signed-off-by: Pankaj Gupta <pankaj.gupta@ionos.com> > > > > --- > > > > drivers/nvdimm/nd_virtio.c | 72 ++++++++++++++++++++++++++++-------- > > > > drivers/nvdimm/virtio_pmem.c | 10 ++++- > > > > drivers/nvdimm/virtio_pmem.h | 14 +++++++ > > > > 3 files changed, 79 insertions(+), 17 deletions(-) > > > > > > > > diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c > > > > index 10351d5b49fa..61b655b583be 100644 > > > > --- a/drivers/nvdimm/nd_virtio.c > > > > +++ b/drivers/nvdimm/nd_virtio.c > > > > @@ -97,29 +97,69 @@ static int virtio_pmem_flush(struct nd_region *nd_region) > > > > return err; > > > > }; > > > > > > > > +static void submit_async_flush(struct work_struct *ws); > > > > + > > > > /* The asynchronous flush callback function */ > > > > int async_pmem_flush(struct nd_region *nd_region, struct bio *bio) > > > > { > > > > - /* > > > > - * Create child bio for asynchronous flush and chain with > > > > - * parent bio. Otherwise directly call nd_region flush. > > > > + /* queue asynchronous flush and coalesce the flush requests */ > > > > + struct virtio_device *vdev = nd_region->provider_data; > > > > + struct virtio_pmem *vpmem = vdev->priv; > > > > + ktime_t req_start = ktime_get_boottime(); > > > > + > > > > + spin_lock_irq(&vpmem->lock); > > > > + /* flush requests wait until ongoing flush completes, > > > > + * hence coalescing all the pending requests. > > > > */ > > > > - if (bio && bio->bi_iter.bi_sector != -1) { > > > > - struct bio *child = bio_alloc(GFP_ATOMIC, 0); > > > > - > > > > - if (!child) > > > > - return -ENOMEM; > > > > - bio_copy_dev(child, bio); > > > > - child->bi_opf = REQ_PREFLUSH; > > > > - child->bi_iter.bi_sector = -1; > > > > - bio_chain(child, bio); > > > > - submit_bio(child); > > > > - return 0; > > > > + wait_event_lock_irq(vpmem->sb_wait, > > > > + !vpmem->flush_bio || > > > > + ktime_before(req_start, vpmem->prev_flush_start), > > > > + vpmem->lock); > > > > + /* new request after previous flush is completed */ > > > > + if (ktime_after(req_start, vpmem->prev_flush_start)) { > > > > + WARN_ON(vpmem->flush_bio); > > > > + vpmem->flush_bio = bio; > > > > + bio = NULL; > > > > + } > > > > > > Why the dance with ->prev_flush_start vs just calling queue_work() > > > again. queue_work() is naturally coalescing in that if the last work > > > request has not started execution another queue attempt will be > > > dropped. > > > > How parent flush request will know when corresponding flush is completed? > > The eventual bio_endio() is what signals upper layers that the flush > completed... > > > Hold on... it's been so long that I forgot that you are copying > md_flush_request() here. It would help immensely if that was mentioned > in the changelog and at a minimum have a comment in the code that this > was copied from md. In fact it would be extra helpful if you My bad. I only mentioned this in the cover letter. > refactored a common helper that bio based block drivers could share > for implementing flush handling, but that can come later. Sure. > > Let me go re-review this with respect to whether the md case is fully > applicable here. o.k. Best regards, Pankaj
On Wed, Aug 25, 2021 at 3:01 PM Pankaj Gupta <pankaj.gupta@ionos.com> wrote: > > > > Hi Dan, > > > > > > Thank you for the review. Please see my reply inline. > > > > > > > > Implement asynchronous flush for virtio pmem using work queue > > > > > to solve the preflush ordering issue. Also, coalesce the flush > > > > > requests when a flush is already in process. > > > > > > > > > > Signed-off-by: Pankaj Gupta <pankaj.gupta@ionos.com> > > > > > --- > > > > > drivers/nvdimm/nd_virtio.c | 72 ++++++++++++++++++++++++++++-------- > > > > > drivers/nvdimm/virtio_pmem.c | 10 ++++- > > > > > drivers/nvdimm/virtio_pmem.h | 14 +++++++ > > > > > 3 files changed, 79 insertions(+), 17 deletions(-) > > > > > > > > > > diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c > > > > > index 10351d5b49fa..61b655b583be 100644 > > > > > --- a/drivers/nvdimm/nd_virtio.c > > > > > +++ b/drivers/nvdimm/nd_virtio.c > > > > > @@ -97,29 +97,69 @@ static int virtio_pmem_flush(struct nd_region *nd_region) > > > > > return err; > > > > > }; > > > > > > > > > > +static void submit_async_flush(struct work_struct *ws); > > > > > + > > > > > /* The asynchronous flush callback function */ > > > > > int async_pmem_flush(struct nd_region *nd_region, struct bio *bio) > > > > > { > > > > > - /* > > > > > - * Create child bio for asynchronous flush and chain with > > > > > - * parent bio. Otherwise directly call nd_region flush. > > > > > + /* queue asynchronous flush and coalesce the flush requests */ > > > > > + struct virtio_device *vdev = nd_region->provider_data; > > > > > + struct virtio_pmem *vpmem = vdev->priv; > > > > > + ktime_t req_start = ktime_get_boottime(); > > > > > + > > > > > + spin_lock_irq(&vpmem->lock); > > > > > + /* flush requests wait until ongoing flush completes, > > > > > + * hence coalescing all the pending requests. > > > > > */ > > > > > - if (bio && bio->bi_iter.bi_sector != -1) { > > > > > - struct bio *child = bio_alloc(GFP_ATOMIC, 0); > > > > > - > > > > > - if (!child) > > > > > - return -ENOMEM; > > > > > - bio_copy_dev(child, bio); > > > > > - child->bi_opf = REQ_PREFLUSH; > > > > > - child->bi_iter.bi_sector = -1; > > > > > - bio_chain(child, bio); > > > > > - submit_bio(child); > > > > > - return 0; > > > > > + wait_event_lock_irq(vpmem->sb_wait, > > > > > + !vpmem->flush_bio || > > > > > + ktime_before(req_start, vpmem->prev_flush_start), > > > > > + vpmem->lock); > > > > > + /* new request after previous flush is completed */ > > > > > + if (ktime_after(req_start, vpmem->prev_flush_start)) { > > > > > + WARN_ON(vpmem->flush_bio); > > > > > + vpmem->flush_bio = bio; > > > > > + bio = NULL; > > > > > + } > > > > > > > > Why the dance with ->prev_flush_start vs just calling queue_work() > > > > again. queue_work() is naturally coalescing in that if the last work > > > > request has not started execution another queue attempt will be > > > > dropped. > > > > > > How parent flush request will know when corresponding flush is completed? > > > > The eventual bio_endio() is what signals upper layers that the flush > > completed... > > > > > > Hold on... it's been so long that I forgot that you are copying > > md_flush_request() here. It would help immensely if that was mentioned > > in the changelog and at a minimum have a comment in the code that this > > was copied from md. In fact it would be extra helpful if you > > My bad. I only mentioned this in the cover letter. Yeah, sorry about that. Having come back to this after so long I just decided to jump straight into the patches, but even if I had read that cover I still would have given the feedback that md_flush_request() heritage should also be noted with a comment in the code.
> > > > > > Implement asynchronous flush for virtio pmem using work queue > > > > > > to solve the preflush ordering issue. Also, coalesce the flush > > > > > > requests when a flush is already in process. > > > > > > > > > > > > Signed-off-by: Pankaj Gupta <pankaj.gupta@ionos.com> > > > > > > --- > > > > > > drivers/nvdimm/nd_virtio.c | 72 ++++++++++++++++++++++++++++-------- > > > > > > drivers/nvdimm/virtio_pmem.c | 10 ++++- > > > > > > drivers/nvdimm/virtio_pmem.h | 14 +++++++ > > > > > > 3 files changed, 79 insertions(+), 17 deletions(-) > > > > > > > > > > > > diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c > > > > > > index 10351d5b49fa..61b655b583be 100644 > > > > > > --- a/drivers/nvdimm/nd_virtio.c > > > > > > +++ b/drivers/nvdimm/nd_virtio.c > > > > > > @@ -97,29 +97,69 @@ static int virtio_pmem_flush(struct nd_region *nd_region) > > > > > > return err; > > > > > > }; > > > > > > > > > > > > +static void submit_async_flush(struct work_struct *ws); > > > > > > + > > > > > > /* The asynchronous flush callback function */ > > > > > > int async_pmem_flush(struct nd_region *nd_region, struct bio *bio) > > > > > > { > > > > > > - /* > > > > > > - * Create child bio for asynchronous flush and chain with > > > > > > - * parent bio. Otherwise directly call nd_region flush. > > > > > > + /* queue asynchronous flush and coalesce the flush requests */ > > > > > > + struct virtio_device *vdev = nd_region->provider_data; > > > > > > + struct virtio_pmem *vpmem = vdev->priv; > > > > > > + ktime_t req_start = ktime_get_boottime(); > > > > > > + > > > > > > + spin_lock_irq(&vpmem->lock); > > > > > > + /* flush requests wait until ongoing flush completes, > > > > > > + * hence coalescing all the pending requests. > > > > > > */ > > > > > > - if (bio && bio->bi_iter.bi_sector != -1) { > > > > > > - struct bio *child = bio_alloc(GFP_ATOMIC, 0); > > > > > > - > > > > > > - if (!child) > > > > > > - return -ENOMEM; > > > > > > - bio_copy_dev(child, bio); > > > > > > - child->bi_opf = REQ_PREFLUSH; > > > > > > - child->bi_iter.bi_sector = -1; > > > > > > - bio_chain(child, bio); > > > > > > - submit_bio(child); > > > > > > - return 0; > > > > > > + wait_event_lock_irq(vpmem->sb_wait, > > > > > > + !vpmem->flush_bio || > > > > > > + ktime_before(req_start, vpmem->prev_flush_start), > > > > > > + vpmem->lock); > > > > > > + /* new request after previous flush is completed */ > > > > > > + if (ktime_after(req_start, vpmem->prev_flush_start)) { > > > > > > + WARN_ON(vpmem->flush_bio); > > > > > > + vpmem->flush_bio = bio; > > > > > > + bio = NULL; > > > > > > + } > > > > > > > > > > Why the dance with ->prev_flush_start vs just calling queue_work() > > > > > again. queue_work() is naturally coalescing in that if the last work > > > > > request has not started execution another queue attempt will be > > > > > dropped. > > > > > > > > How parent flush request will know when corresponding flush is completed? > > > > > > The eventual bio_endio() is what signals upper layers that the flush > > > completed... > > > > > > > > > Hold on... it's been so long that I forgot that you are copying > > > md_flush_request() here. It would help immensely if that was mentioned > > > in the changelog and at a minimum have a comment in the code that this > > > was copied from md. In fact it would be extra helpful if you > > > > My bad. I only mentioned this in the cover letter. > > Yeah, sorry about that. Having come back to this after so long I just > decided to jump straight into the patches, but even if I had read that > cover I still would have given the feedback that md_flush_request() > heritage should also be noted with a comment in the code. Sure. Thanks, Pankaj
diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c index 10351d5b49fa..61b655b583be 100644 --- a/drivers/nvdimm/nd_virtio.c +++ b/drivers/nvdimm/nd_virtio.c @@ -97,29 +97,69 @@ static int virtio_pmem_flush(struct nd_region *nd_region) return err; }; +static void submit_async_flush(struct work_struct *ws); + /* The asynchronous flush callback function */ int async_pmem_flush(struct nd_region *nd_region, struct bio *bio) { - /* - * Create child bio for asynchronous flush and chain with - * parent bio. Otherwise directly call nd_region flush. + /* queue asynchronous flush and coalesce the flush requests */ + struct virtio_device *vdev = nd_region->provider_data; + struct virtio_pmem *vpmem = vdev->priv; + ktime_t req_start = ktime_get_boottime(); + + spin_lock_irq(&vpmem->lock); + /* flush requests wait until ongoing flush completes, + * hence coalescing all the pending requests. */ - if (bio && bio->bi_iter.bi_sector != -1) { - struct bio *child = bio_alloc(GFP_ATOMIC, 0); - - if (!child) - return -ENOMEM; - bio_copy_dev(child, bio); - child->bi_opf = REQ_PREFLUSH; - child->bi_iter.bi_sector = -1; - bio_chain(child, bio); - submit_bio(child); - return 0; + wait_event_lock_irq(vpmem->sb_wait, + !vpmem->flush_bio || + ktime_before(req_start, vpmem->prev_flush_start), + vpmem->lock); + /* new request after previous flush is completed */ + if (ktime_after(req_start, vpmem->prev_flush_start)) { + WARN_ON(vpmem->flush_bio); + vpmem->flush_bio = bio; + bio = NULL; + } + spin_unlock_irq(&vpmem->lock); + + if (!bio) { + INIT_WORK(&vpmem->flush_work, submit_async_flush); + queue_work(vpmem->pmem_wq, &vpmem->flush_work); + return 1; + } + + /* flush completed in other context while we waited */ + if (bio && (bio->bi_opf & REQ_PREFLUSH)) { + bio->bi_opf &= ~REQ_PREFLUSH; + submit_bio(bio); + } else if (bio && (bio->bi_opf & REQ_FUA)) { + bio->bi_opf &= ~REQ_FUA; + bio_endio(bio); } - if (virtio_pmem_flush(nd_region)) - return -EIO; return 0; }; EXPORT_SYMBOL_GPL(async_pmem_flush); + +static void submit_async_flush(struct work_struct *ws) +{ + struct virtio_pmem *vpmem = container_of(ws, struct virtio_pmem, flush_work); + struct bio *bio = vpmem->flush_bio; + + vpmem->start_flush = ktime_get_boottime(); + bio->bi_status = errno_to_blk_status(virtio_pmem_flush(vpmem->nd_region)); + vpmem->prev_flush_start = vpmem->start_flush; + vpmem->flush_bio = NULL; + wake_up(&vpmem->sb_wait); + + /* Submit parent bio only for PREFLUSH */ + if (bio && (bio->bi_opf & REQ_PREFLUSH)) { + bio->bi_opf &= ~REQ_PREFLUSH; + submit_bio(bio); + } else if (bio && (bio->bi_opf & REQ_FUA)) { + bio->bi_opf &= ~REQ_FUA; + bio_endio(bio); + } +} MODULE_LICENSE("GPL"); diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c index 726c7354d465..56780a6140c7 100644 --- a/drivers/nvdimm/virtio_pmem.c +++ b/drivers/nvdimm/virtio_pmem.c @@ -24,6 +24,7 @@ static int init_vq(struct virtio_pmem *vpmem) return PTR_ERR(vpmem->req_vq); spin_lock_init(&vpmem->pmem_lock); + spin_lock_init(&vpmem->lock); INIT_LIST_HEAD(&vpmem->req_list); return 0; @@ -57,7 +58,12 @@ static int virtio_pmem_probe(struct virtio_device *vdev) dev_err(&vdev->dev, "failed to initialize virtio pmem vq's\n"); goto out_err; } - + vpmem->pmem_wq = alloc_workqueue("vpmem_wq", WQ_MEM_RECLAIM, 0); + if (!vpmem->pmem_wq) { + err = -ENOMEM; + goto out_err; + } + init_waitqueue_head(&vpmem->sb_wait); virtio_cread_le(vpmem->vdev, struct virtio_pmem_config, start, &vpmem->start); virtio_cread_le(vpmem->vdev, struct virtio_pmem_config, @@ -90,10 +96,12 @@ static int virtio_pmem_probe(struct virtio_device *vdev) goto out_nd; } nd_region->provider_data = dev_to_virtio(nd_region->dev.parent->parent); + vpmem->nd_region = nd_region; return 0; out_nd: nvdimm_bus_unregister(vpmem->nvdimm_bus); out_vq: + destroy_workqueue(vpmem->pmem_wq); vdev->config->del_vqs(vdev); out_err: return err; diff --git a/drivers/nvdimm/virtio_pmem.h b/drivers/nvdimm/virtio_pmem.h index 0dddefe594c4..d9abc8d052b6 100644 --- a/drivers/nvdimm/virtio_pmem.h +++ b/drivers/nvdimm/virtio_pmem.h @@ -35,9 +35,23 @@ struct virtio_pmem { /* Virtio pmem request queue */ struct virtqueue *req_vq; + struct bio *flush_bio; + /* last_flush is when the last completed flush was started */ + ktime_t prev_flush_start, start_flush; + + /* work queue for deferred flush */ + struct work_struct flush_work; + struct workqueue_struct *pmem_wq; + + /* Synchronize flush wait queue data */ + spinlock_t lock; + /* for waiting for previous flush to complete */ + wait_queue_head_t sb_wait; + /* nvdimm bus registers virtio pmem device */ struct nvdimm_bus *nvdimm_bus; struct nvdimm_bus_descriptor nd_desc; + struct nd_region *nd_region; /* List to store deferred work if virtqueue is full */ struct list_head req_list;