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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Fri, 21 Sep 2018 17:43:58 -0700
Message-ID: <CAPcyv4js9hWfXPK++a0DhDwtk1pBazMvb9H-X2OQy18uemUhGw@mail.gmail.com>
Subject: Re: [PATCH 2/3] libnvdimm: nd_region flush callback support
To:     Pankaj Gupta <pagupta@redhat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        KVM list <kvm@vger.kernel.org>,
        Qemu Developers <qemu-devel@nongnu.org>,
        linux-nvdimm <linux-nvdimm@ml01.01.org>, Jan Kara <jack@suse.cz>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Rik van Riel <riel@surriel.com>,
        Nitesh Narayan Lal <nilal@redhat.com>,
        Kevin Wolf <kwolf@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        "Zwisler, Ross" <ross.zwisler@intel.com>,
        David Hildenbrand <david@redhat.com>,
        Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
        Christoph Hellwig <hch@infradead.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        niteshnarayanlal@hotmail.com, lcapitulino@redhat.com,
        Igor Mammedov <imammedo@redhat.com>,
        Eric Blake <eblake@redhat.com>
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Sender: linux-kernel-owner@vger.kernel.org
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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
>