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    SubjectRe: [PATCH 2/3] libnvdimm: nd_region flush callback support
    On Fri, Aug 31, 2018 at 6:32 AM Pankaj Gupta <pagupta@redhat.com> wrote:
    >
    > This patch adds functionality to perform flush from guest
    > to host over VIRTIO. We are registering a callback based
    > on 'nd_region' type. virtio_pmem driver requires this special
    > flush function. For rest of the region types we are registering
    > existing flush function. Report error returned by host fsync
    > failure to userspace.
    >
    > Signed-off-by: Pankaj Gupta <pagupta@redhat.com>

    This looks ok to me, just some nits below.

    > ---
    > drivers/acpi/nfit/core.c | 7 +++++--
    > drivers/nvdimm/claim.c | 3 ++-
    > drivers/nvdimm/pmem.c | 12 ++++++++----
    > drivers/nvdimm/region_devs.c | 12 ++++++++++--
    > include/linux/libnvdimm.h | 4 +++-
    > 5 files changed, 28 insertions(+), 10 deletions(-)
    >
    > diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
    > index b072cfc..cd63b69 100644
    > --- a/drivers/acpi/nfit/core.c
    > +++ b/drivers/acpi/nfit/core.c
    > @@ -2216,6 +2216,7 @@ static void write_blk_ctl(struct nfit_blk *nfit_blk, unsigned int bw,
    > {
    > u64 cmd, offset;
    > struct nfit_blk_mmio *mmio = &nfit_blk->mmio[DCR];
    > + struct nd_region *nd_region = nfit_blk->nd_region;
    >
    > enum {
    > BCW_OFFSET_MASK = (1ULL << 48)-1,
    > @@ -2234,7 +2235,7 @@ 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);
    > + nd_region->flush(nd_region);

    I would keep the indirect function call override inside of
    nvdimm_flush. Then this hunk can go away...

    >
    > if (nfit_blk->dimm_flags & NFIT_BLK_DCR_LATCH)
    > readq(mmio->addr.base + offset);
    > @@ -2245,6 +2246,7 @@ static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
    > unsigned int lane)
    > {
    > struct nfit_blk_mmio *mmio = &nfit_blk->mmio[BDW];
    > + struct nd_region *nd_region = nfit_blk->nd_region;
    > unsigned int copied = 0;
    > u64 base_offset;
    > int rc;
    > @@ -2283,7 +2285,8 @@ static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
    > }
    >
    > if (rw)
    > - nvdimm_flush(nfit_blk->nd_region);
    > + nd_region->flush(nd_region);
    > +
    >

    ...ditto, no need to touch this code.

    > rc = read_blk_stat(nfit_blk, lane) ? -EIO : 0;
    > return rc;
    > diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c
    > index fb667bf..49dce9c 100644
    > --- a/drivers/nvdimm/claim.c
    > +++ b/drivers/nvdimm/claim.c
    > @@ -262,6 +262,7 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
    > {
    > struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
    > unsigned int sz_align = ALIGN(size + (offset & (512 - 1)), 512);
    > + struct nd_region *nd_region = to_nd_region(ndns->dev.parent);
    > sector_t sector = offset >> 9;
    > int rc = 0;
    >
    > @@ -301,7 +302,7 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
    > }
    >
    > memcpy_flushcache(nsio->addr + offset, buf, size);
    > - nvdimm_flush(to_nd_region(ndns->dev.parent));
    > + nd_region->flush(nd_region);

    For this you would need to teach nsio_rw_bytes() that the flush can fail.

    >
    > return rc;
    > }
    > diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
    > index 6071e29..ba57cfa 100644
    > --- a/drivers/nvdimm/pmem.c
    > +++ b/drivers/nvdimm/pmem.c
    > @@ -201,7 +201,8 @@ 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)
    > - nvdimm_flush(nd_region);
    > + bio->bi_status = nd_region->flush(nd_region);
    > +

    Let's have nvdimm_flush() return 0 or -EIO if it fails since thats
    what nsio_rw_bytes() expects, and you'll need to translate that to:
    BLK_STS_IOERR

    >
    > do_acct = nd_iostat_start(bio, &start);
    > bio_for_each_segment(bvec, bio, iter) {
    > @@ -216,7 +217,7 @@ 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)
    > - nvdimm_flush(nd_region);
    > + bio->bi_status = nd_region->flush(nd_region);

    Same comment.

    >
    > bio_endio(bio);
    > return BLK_QC_T_NONE;
    > @@ -517,6 +518,7 @@ static int nd_pmem_probe(struct device *dev)
    > static int nd_pmem_remove(struct device *dev)
    > {
    > struct pmem_device *pmem = dev_get_drvdata(dev);
    > + struct nd_region *nd_region = to_region(pmem);
    >
    > if (is_nd_btt(dev))
    > nvdimm_namespace_detach_btt(to_nd_btt(dev));
    > @@ -528,14 +530,16 @@ static int nd_pmem_remove(struct device *dev)
    > sysfs_put(pmem->bb_state);
    > pmem->bb_state = NULL;
    > }
    > - nvdimm_flush(to_nd_region(dev->parent));
    > + nd_region->flush(nd_region);

    Not needed if the indirect function call moves inside nvdimm_flush().

    >
    > return 0;
    > }
    >
    > static void nd_pmem_shutdown(struct device *dev)
    > {
    > - nvdimm_flush(to_nd_region(dev->parent));
    > + struct nd_region *nd_region = to_nd_region(dev->parent);
    > +
    > + nd_region->flush(nd_region);
    > }
    >
    > 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 fa37afc..a170a6b 100644
    > --- a/drivers/nvdimm/region_devs.c
    > +++ b/drivers/nvdimm/region_devs.c
    > @@ -290,7 +290,7 @@ static ssize_t deep_flush_store(struct device *dev, struct device_attribute *att
    > return rc;
    > if (!flush)
    > return -EINVAL;
    > - nvdimm_flush(nd_region);
    > + nd_region->flush(nd_region);

    Let's pass the error code through if the flush fails.

    >
    > return len;
    > }
    > @@ -1065,6 +1065,11 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
    > dev->of_node = ndr_desc->of_node;
    > nd_region->ndr_size = resource_size(ndr_desc->res);
    > nd_region->ndr_start = ndr_desc->res->start;
    > + if (ndr_desc->flush)
    > + nd_region->flush = ndr_desc->flush;
    > + else
    > + nd_region->flush = nvdimm_flush;
    > +

    We'll need to rename the existing nvdimm_flush() to generic_nvdimm_flush().

    > nd_device_register(dev);
    >
    > return nd_region;
    > @@ -1109,7 +1114,7 @@ EXPORT_SYMBOL_GPL(nvdimm_volatile_region_create);
    > * nvdimm_flush - flush any posted write queues between the cpu and pmem media
    > * @nd_region: blk or interleaved pmem region
    > */
    > -void nvdimm_flush(struct nd_region *nd_region)
    > +int nvdimm_flush(struct nd_region *nd_region)
    > {
    > struct nd_region_data *ndrd = dev_get_drvdata(&nd_region->dev);
    > int i, idx;
    > @@ -1133,7 +1138,10 @@ void nvdimm_flush(struct nd_region *nd_region)
    > if (ndrd_get_flush_wpq(ndrd, i, 0))
    > writeq(1, ndrd_get_flush_wpq(ndrd, i, idx));
    > wmb();
    > +
    > + return 0;
    > }
    > +

    Needless newline.

    > EXPORT_SYMBOL_GPL(nvdimm_flush);
    >
    > /**
    > diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
    > index 097072c..3af7177 100644
    > --- a/include/linux/libnvdimm.h
    > +++ b/include/linux/libnvdimm.h
    > @@ -115,6 +115,7 @@ struct nd_mapping_desc {
    > int position;
    > };
    >
    > +struct nd_region;
    > struct nd_region_desc {
    > struct resource *res;
    > struct nd_mapping_desc *mapping;
    > @@ -126,6 +127,7 @@ struct nd_region_desc {
    > int numa_node;
    > unsigned long flags;
    > struct device_node *of_node;
    > + int (*flush)(struct nd_region *nd_region);
    > };
    >
    > struct device;
    > @@ -201,7 +203,7 @@ 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);
    > -void nvdimm_flush(struct nd_region *nd_region);
    > +int 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);
    >
    > --
    > 2.9.3
    >

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