Date:   Wed, 15 May 2019 14:07:23 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Pankaj Gupta <pagupta@...hat.com>
Cc:     linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
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        Ross Zwisler <zwisler@...nel.org>,
        Vishal L Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
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        yuval shaia <yuval.shaia@...cle.com>, jstaron@...gle.com
Subject: Re: [PATCH v9 1/7] libnvdimm: nd_region flush callback support

On Tue, May 14, 2019 at 7:55 AM Pankaj Gupta <pagupta@...hat.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@...hat.com>
> ---
>  drivers/acpi/nfit/core.c     |  4 ++--
>  drivers/nvdimm/claim.c       |  6 ++++--
>  drivers/nvdimm/nd.h          |  1 +
>  drivers/nvdimm/pmem.c        | 13 ++++++++-----
>  drivers/nvdimm/region_devs.c | 26 ++++++++++++++++++++++++--
>  include/linux/libnvdimm.h    |  8 +++++++-
>  6 files changed, 46 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
> index 5a389a4f4f65..08dde76cf459 100644
> --- a/drivers/acpi/nfit/core.c
> +++ b/drivers/acpi/nfit/core.c
> @@ -2434,7 +2434,7 @@ 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);
> +       nvdimm_flush(nfit_blk->nd_region, NULL);
>
>         if (nfit_blk->dimm_flags & NFIT_BLK_DCR_LATCH)
>                 readq(mmio->addr.base + offset);
> @@ -2483,7 +2483,7 @@ static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
>         }
>
>         if (rw)
> -               nvdimm_flush(nfit_blk->nd_region);
> +               nvdimm_flush(nfit_blk->nd_region, NULL);
>
>         rc = read_blk_stat(nfit_blk, lane) ? -EIO : 0;
>         return rc;
> diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c
> index fb667bf469c7..13510bae1e6f 100644
> --- a/drivers/nvdimm/claim.c
> +++ b/drivers/nvdimm/claim.c
> @@ -263,7 +263,7 @@ 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);
>         sector_t sector = offset >> 9;
> -       int rc = 0;
> +       int rc = 0, ret = 0;
>
>         if (unlikely(!size))
>                 return 0;
> @@ -301,7 +301,9 @@ 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));
> +       ret = nvdimm_flush(to_nd_region(ndns->dev.parent), NULL);
> +       if (ret)
> +               rc = ret;
>
>         return rc;
>  }
> diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
> index a5ac3b240293..0c74d2428bd7 100644
> --- a/drivers/nvdimm/nd.h
> +++ b/drivers/nvdimm/nd.h
> @@ -159,6 +159,7 @@ 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);

So this triggers:

In file included from drivers/nvdimm/e820.c:7:
./include/linux/libnvdimm.h:140:51: warning: ‘struct bio’ declared
inside parameter list will not be visible outside of this definition
or declaration
  int (*flush)(struct nd_region *nd_region, struct bio *bio);
                                                   ^~~
I was already feeling uneasy about trying to squeeze this into v5.2,
but this warning and the continued drip of comments leads me to
conclude that this driver would do well to wait one more development
cycle. Lets close out the final fixups and let this driver soak in
-next. Then for the v5.3 cycle I'll redouble my efforts towards the
goal of closing patch acceptance at the -rc6 / -rc7 development
milestone.

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