Re: [PATCH 2/3] libnvdimm: nd_region flush callback support

[Pankaj Gupta <pagupta@redhat.com>]

> > 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...

Sure. Will change.

> 
> >
> >         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.

Sure.

> 
> >         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.

Sure.

> 
> >
> >         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

o.k. Will change it as per suggestion.

> 
> >
> >         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.

Sure.

> 
> >
> >         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().

o.k

> 
> >
> >         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.

o.k

> 
> >
> >         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().

Sure.

> 
> >         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.

Will remove this.

> 
> >  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
> >
> 

Thanks,
Pankaj