Re: [PATCH] virtio pmem: fix async flush ordering

Pankaj Gupta
2019-11-21T06:44:43Z

>
> > Remove logic to create child bio in the async flush function which
> > causes child bio to get executed after parent bio 'pmem_make_request'
> > completes. This resulted in wrong ordering of REQ_PREFLUSH with the
> > data write request.
> >
> > Instead we are performing flush from the parent bio to maintain the
> > correct order. Also, returning from function 'pmem_make_request' if
> > REQ_PREFLUSH returns an error.
> >
> > Reported-by: Jeff Moyer <jmoyer@redhat.com>
> > Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
>
> There's a slight change in behavior for the error path in the
> virtio_pmem driver. Previously, all errors from virtio_pmem_flush were
> converted to -EIO. Now, they are reported as-is. I think this is
> actually an improvement.

yes.

>
> I'll also note that the current behavior can result in data corruption,
> so this should be tagged for stable.

Agree.

>
> The patch looks good to me.
>
> Thanks!
>
> Reviewed-by: Jeff Moyer <jmoyer@redhat.com>

Thank you!

Pankaj

>
> > ---
> > drivers/acpi/nfit/core.c | 4 ++--
> > drivers/nvdimm/claim.c | 2 +-
> > drivers/nvdimm/nd.h | 2 +-
> > drivers/nvdimm/nd_virtio.c | 29 ++---------------------------
> > drivers/nvdimm/pmem.c | 14 ++++++++++----
> > drivers/nvdimm/region_devs.c | 6 +++---
> > drivers/nvdimm/virtio_pmem.c | 2 +-
> > drivers/nvdimm/virtio_pmem.h | 2 +-
> > include/linux/libnvdimm.h | 4 ++--
> > 9 files changed, 23 insertions(+), 42 deletions(-)
> >
> > diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
> > index 14e68f202f81..afbd5e2b2ea8 100644
> > --- a/drivers/acpi/nfit/core.c
> > +++ b/drivers/acpi/nfit/core.c
> > @@ -2426,7 +2426,7 @@ static void write_blk_ctl(struct nfit_blk *nfit_blk,
> > unsigned int bw,
> > offset = to_interleave_offset(offset, mmio);
> >
> > writeq(cmd, mmio->addr.base + offset);
> > - nvdimm_flush(nfit_blk->nd_region, NULL);
> > + nvdimm_flush(nfit_blk->nd_region);
> >
> > if (nfit_blk->dimm_flags & NFIT_BLK_DCR_LATCH)
> > readq(mmio->addr.base + offset);
> > @@ -2475,7 +2475,7 @@ static int acpi_nfit_blk_single_io(struct nfit_blk
> > *nfit_blk,
> > }
> >
> > if (rw)
> > - nvdimm_flush(nfit_blk->nd_region, NULL);
> > + nvdimm_flush(nfit_blk->nd_region);
> >
> > rc = read_blk_stat(nfit_blk, lane) ? -EIO : 0;
> > return rc;
> > diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c
> > index 2985ca949912..0fedb2fbfcbe 100644
> > --- a/drivers/nvdimm/claim.c
> > +++ b/drivers/nvdimm/claim.c
> > @@ -293,7 +293,7 @@ static int nsio_rw_bytes(struct nd_namespace_common
> > *ndns,
> > }
> >
> > memcpy_flushcache(nsio->addr + offset, buf, size);
> > - ret = nvdimm_flush(to_nd_region(ndns->dev.parent), NULL);
> > + ret = nvdimm_flush(to_nd_region(ndns->dev.parent));
> > if (ret)
> > rc = ret;
> >
> > diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
> > index ee5c04070ef9..77d8b9f0c34a 100644
> > --- a/drivers/nvdimm/nd.h
> > +++ b/drivers/nvdimm/nd.h
> > @@ -155,7 +155,7 @@ struct nd_region {
> > struct badblocks bb;
> > struct nd_interleave_set *nd_set;
> > struct nd_percpu_lane __percpu *lane;
> > - int (*flush)(struct nd_region *nd_region, struct bio *bio);
> > + int (*flush)(struct nd_region *nd_region);
> > struct nd_mapping mapping[0];
> > };
> >
> > diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c
> > index 10351d5b49fa..9604ba08a68a 100644
> > --- a/drivers/nvdimm/nd_virtio.c
> > +++ b/drivers/nvdimm/nd_virtio.c
> > @@ -35,7 +35,7 @@ void virtio_pmem_host_ack(struct virtqueue *vq)
> > EXPORT_SYMBOL_GPL(virtio_pmem_host_ack);
> >
> > /* The request submission function */
> > -static int virtio_pmem_flush(struct nd_region *nd_region)
> > +int virtio_pmem_flush(struct nd_region *nd_region)
> > {
> > struct virtio_device *vdev = nd_region->provider_data;
> > struct virtio_pmem *vpmem = vdev->priv;
> > @@ -96,30 +96,5 @@ static int virtio_pmem_flush(struct nd_region
> > *nd_region)
> > kfree(req_data);
> > return err;
> > };
> > -
> > -/* 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.
> > - */
> > - 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;
> > - }
> > - if (virtio_pmem_flush(nd_region))
> > - return -EIO;
> > -
> > - return 0;
> > -};
> > -EXPORT_SYMBOL_GPL(async_pmem_flush);
> > +EXPORT_SYMBOL_GPL(virtio_pmem_flush);
> > MODULE_LICENSE("GPL");
> > diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> > index f9f76f6ba07b..b3ca641668a2 100644
> > --- a/drivers/nvdimm/pmem.c
> > +++ b/drivers/nvdimm/pmem.c
> > @@ -194,7 +194,13 @@ static blk_qc_t pmem_make_request(struct request_queue
> > *q, struct bio *bio)
> > struct nd_region *nd_region = to_region(pmem);
> >
> > if (bio->bi_opf & REQ_PREFLUSH)
> > - ret = nvdimm_flush(nd_region, bio);
> > + ret = nvdimm_flush(nd_region);
> > +
> > + if (ret) {
> > + bio->bi_status = errno_to_blk_status(ret);
> > + bio_endio(bio);
> > + return BLK_QC_T_NONE;
> > + }
> >
> > do_acct = nd_iostat_start(bio, &start);
> > bio_for_each_segment(bvec, bio, iter) {
> > @@ -209,7 +215,7 @@ static blk_qc_t pmem_make_request(struct request_queue
> > *q, struct bio *bio)
> > nd_iostat_end(bio, start);
> >
> > if (bio->bi_opf & REQ_FUA)
> > - ret = nvdimm_flush(nd_region, bio);
> > + ret = nvdimm_flush(nd_region);
> >
> > if (ret)
> > bio->bi_status = errno_to_blk_status(ret);
> > @@ -549,14 +555,14 @@ static int nd_pmem_remove(struct device *dev)
> > sysfs_put(pmem->bb_state);
> > pmem->bb_state = NULL;
> > }
> > - nvdimm_flush(to_nd_region(dev->parent), NULL);
> > + nvdimm_flush(to_nd_region(dev->parent));
> >
> > return 0;
> > }
> >
> > static void nd_pmem_shutdown(struct device *dev)
> > {
> > - nvdimm_flush(to_nd_region(dev->parent), NULL);
> > + nvdimm_flush(to_nd_region(dev->parent));
> > }
> >
> > static void nd_pmem_notify(struct device *dev, enum nvdimm_event event)
> > diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
> > index ef423ba1a711..cfd96a0d52f2 100644
> > --- a/drivers/nvdimm/region_devs.c
> > +++ b/drivers/nvdimm/region_devs.c
> > @@ -287,7 +287,7 @@ static ssize_t deep_flush_store(struct device *dev,
> > struct device_attribute *att
> > return rc;
> > if (!flush)
> > return -EINVAL;
> > - rc = nvdimm_flush(nd_region, NULL);
> > + rc = nvdimm_flush(nd_region);
> > if (rc)
> > return rc;
> >
> > @@ -1079,14 +1079,14 @@ struct nd_region
> > *nvdimm_volatile_region_create(struct nvdimm_bus *nvdimm_bus,
> > }
> > EXPORT_SYMBOL_GPL(nvdimm_volatile_region_create);
> >
> > -int nvdimm_flush(struct nd_region *nd_region, struct bio *bio)
> > +int nvdimm_flush(struct nd_region *nd_region)
> > {
> > int rc = 0;
> >
> > if (!nd_region->flush)
> > rc = generic_nvdimm_flush(nd_region);
> > else {
> > - if (nd_region->flush(nd_region, bio))
> > + if (nd_region->flush(nd_region))
> > rc = -EIO;
> > }
> >
> > diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
> > index 5e3d07b47e0c..a6234466674d 100644
> > --- a/drivers/nvdimm/virtio_pmem.c
> > +++ b/drivers/nvdimm/virtio_pmem.c
> > @@ -80,7 +80,7 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
> >
> > ndr_desc.res = &res;
> > ndr_desc.numa_node = nid;
> > - ndr_desc.flush = async_pmem_flush;
> > + ndr_desc.flush = virtio_pmem_flush;
> > set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
> > set_bit(ND_REGION_ASYNC, &ndr_desc.flags);
> > nd_region = nvdimm_pmem_region_create(vpmem->nvdimm_bus, &ndr_desc);
> > diff --git a/drivers/nvdimm/virtio_pmem.h b/drivers/nvdimm/virtio_pmem.h
> > index 0dddefe594c4..4f9ee19aad90 100644
> > --- a/drivers/nvdimm/virtio_pmem.h
> > +++ b/drivers/nvdimm/virtio_pmem.h
> > @@ -51,5 +51,5 @@ struct virtio_pmem {
> > };
> >
> > void virtio_pmem_host_ack(struct virtqueue *vq);
> > -int async_pmem_flush(struct nd_region *nd_region, struct bio *bio);
> > +int virtio_pmem_flush(struct nd_region *nd_region);
> > #endif
> > diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
> > index b6eddf912568..211c87edb4eb 100644
> > --- a/include/linux/libnvdimm.h
> > +++ b/include/linux/libnvdimm.h
> > @@ -130,7 +130,7 @@ struct nd_region_desc {
> > int target_node;
> > unsigned long flags;
> > struct device_node *of_node;
> > - int (*flush)(struct nd_region *nd_region, struct bio *bio);
> > + int (*flush)(struct nd_region *nd_region);
> > };
> >
> > struct device;
> > @@ -261,7 +261,7 @@ unsigned long nd_blk_memremap_flags(struct
> > nd_blk_region *ndbr);
> > unsigned int nd_region_acquire_lane(struct nd_region *nd_region);
> > void nd_region_release_lane(struct nd_region *nd_region, unsigned int
> > lane);
> > u64 nd_fletcher64(void *addr, size_t len, bool le);
> > -int nvdimm_flush(struct nd_region *nd_region, struct bio *bio);
> > +int nvdimm_flush(struct nd_region *nd_region);
> > int generic_nvdimm_flush(struct nd_region *nd_region);
> > int nvdimm_has_flush(struct nd_region *nd_region);
> > int nvdimm_has_cache(struct nd_region *nd_region);
>