[PATCH] libnvdimm/region: Update nvdimm_has_flush() to handle ND_REGION_ASYNC

[PATCH] libnvdimm/region: Update nvdimm_has_flush() to handle ND_REGION_ASYNC

[Vaibhav Jain]

In case a platform doesn't provide explicit flush-hints but provides an
explicit flush callback via ND_REGION_ASYNC region flag, then
nvdimm_has_flush() still returns '0' indicating that writes do not
require flushing. This happens on PPC64 with patch at [1] applied,
where 'deep_flush' of a region was denied even though an explicit
flush function was provided.

Fix this by adding a condition to nvdimm_has_flush() to test for the
ND_REGION_ASYNC flag on the region and see if a 'region->flush'
callback is assigned.

References:
[1] "powerpc/papr_scm: Implement support for H_SCM_FLUSH hcall"
https://lore.kernel.org/linux-nvdimm/161703936121.36.7260632399	582101498.stgit@e1fbed493c87

Reported-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>
Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
---
 drivers/nvdimm/region_devs.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index ef23119db574..e05cc9f8a9fd 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1239,6 +1239,11 @@ int nvdimm_has_flush(struct nd_region *nd_region)
 			|| !IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API))
 		return -ENXIO;
 
+	/* Test if an explicit flush function is defined */
+	if (test_bit(ND_REGION_ASYNC, &nd_region->flags) && nd_region->flush)
+		return 1;
+
+	/* Test if any flush hints for the region are available */
 	for (i = 0; i < nd_region->ndr_mappings; i++) {
 		struct nd_mapping *nd_mapping = &nd_region->mapping[i];
 		struct nvdimm *nvdimm = nd_mapping->nvdimm;
@@ -1249,8 +1254,8 @@ int nvdimm_has_flush(struct nd_region *nd_region)
 	}
 
 	/*
-	 * The platform defines dimm devices without hints, assume
-	 * platform persistence mechanism like ADR
+	 * The platform defines dimm devices without hints nor explicit flush,
+	 * assume platform persistence mechanism like ADR
 	 */
 	return 0;
 }
-- 
2.30.2
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Re: [PATCH] libnvdimm/region: Update nvdimm_has_flush() to handle ND_REGION_ASYNC

[Aneesh Kumar K.V]

Vaibhav Jain <vaibhav@linux.ibm.com> writes:

> In case a platform doesn't provide explicit flush-hints but provides an
> explicit flush callback via ND_REGION_ASYNC region flag, then
> nvdimm_has_flush() still returns '0' indicating that writes do not
> require flushing. This happens on PPC64 with patch at [1] applied,
> where 'deep_flush' of a region was denied even though an explicit
> flush function was provided.
>
> Fix this by adding a condition to nvdimm_has_flush() to test for the
> ND_REGION_ASYNC flag on the region and see if a 'region->flush'
> callback is assigned.
>

May be this should have
Fixes: c5d4355d10d4 ("libnvdimm: nd_region flush callback support")

Without this we will mark the pmem disk not having FUA support?


> References:
> [1] "powerpc/papr_scm: Implement support for H_SCM_FLUSH hcall"
> https://lore.kernel.org/linux-nvdimm/161703936121.36.7260632399	582101498.stgit@e1fbed493c87
>
> Reported-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>
> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
> ---
>  drivers/nvdimm/region_devs.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
> index ef23119db574..e05cc9f8a9fd 100644
> --- a/drivers/nvdimm/region_devs.c
> +++ b/drivers/nvdimm/region_devs.c
> @@ -1239,6 +1239,11 @@ int nvdimm_has_flush(struct nd_region *nd_region)
>  			|| !IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API))
>  		return -ENXIO;
>  
> +	/* Test if an explicit flush function is defined */
> +	if (test_bit(ND_REGION_ASYNC, &nd_region->flags) && nd_region->flush)
> +		return 1;

> +
> +	/* Test if any flush hints for the region are available */
>  	for (i = 0; i < nd_region->ndr_mappings; i++) {
>  		struct nd_mapping *nd_mapping = &nd_region->mapping[i];
>  		struct nvdimm *nvdimm = nd_mapping->nvdimm;
> @@ -1249,8 +1254,8 @@ int nvdimm_has_flush(struct nd_region *nd_region)
>  	}
>  
>  	/*
> -	 * The platform defines dimm devices without hints, assume
> -	 * platform persistence mechanism like ADR
> +	 * The platform defines dimm devices without hints nor explicit flush,
> +	 * assume platform persistence mechanism like ADR
>  	 */
>  	return 0;
>  }
> -- 
> 2.30.2
> _______________________________________________
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Re: [PATCH] libnvdimm/region: Update nvdimm_has_flush() to handle ND_REGION_ASYNC

[Dan Williams]

On Fri, Apr 2, 2021 at 2:26 AM Vaibhav Jain <vaibhav@linux.ibm.com> wrote:
>
> In case a platform doesn't provide explicit flush-hints but provides an
> explicit flush callback via ND_REGION_ASYNC region flag, then
> nvdimm_has_flush() still returns '0' indicating that writes do not
> require flushing. This happens on PPC64 with patch at [1] applied,
> where 'deep_flush' of a region was denied even though an explicit
> flush function was provided.
>
> Fix this by adding a condition to nvdimm_has_flush() to test for the
> ND_REGION_ASYNC flag on the region and see if a 'region->flush'
> callback is assigned.

Looks good.

>
> References:
> [1] "powerpc/papr_scm: Implement support for H_SCM_FLUSH hcall"
> https://lore.kernel.org/linux-nvdimm/161703936121.36.7260632399 582101498.stgit@e1fbed493c87

Looks like a typo happened in that link, I can fix that up. I'll also
change this to the canonical "Link:" tag for references.

>
> Reported-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>
> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
> ---
>  drivers/nvdimm/region_devs.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
> index ef23119db574..e05cc9f8a9fd 100644
> --- a/drivers/nvdimm/region_devs.c
> +++ b/drivers/nvdimm/region_devs.c
> @@ -1239,6 +1239,11 @@ int nvdimm_has_flush(struct nd_region *nd_region)
>                         || !IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API))
>                 return -ENXIO;
>
> +       /* Test if an explicit flush function is defined */
> +       if (test_bit(ND_REGION_ASYNC, &nd_region->flags) && nd_region->flush)
> +               return 1;
> +
> +       /* Test if any flush hints for the region are available */
>         for (i = 0; i < nd_region->ndr_mappings; i++) {
>                 struct nd_mapping *nd_mapping = &nd_region->mapping[i];
>                 struct nvdimm *nvdimm = nd_mapping->nvdimm;
> @@ -1249,8 +1254,8 @@ int nvdimm_has_flush(struct nd_region *nd_region)
>         }
>
>         /*
> -        * The platform defines dimm devices without hints, assume
> -        * platform persistence mechanism like ADR
> +        * The platform defines dimm devices without hints nor explicit flush,
> +        * assume platform persistence mechanism like ADR
>          */
>         return 0;
>  }
> --
> 2.30.2
>
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Re: [PATCH] libnvdimm/region: Update nvdimm_has_flush() to handle ND_REGION_ASYNC

[Dan Williams]

On Mon, Apr 5, 2021 at 4:31 AM Aneesh Kumar K.V
<aneesh.kumar@linux.ibm.com> wrote:
>
> Vaibhav Jain <vaibhav@linux.ibm.com> writes:
>
> > In case a platform doesn't provide explicit flush-hints but provides an
> > explicit flush callback via ND_REGION_ASYNC region flag, then
> > nvdimm_has_flush() still returns '0' indicating that writes do not
> > require flushing. This happens on PPC64 with patch at [1] applied,
> > where 'deep_flush' of a region was denied even though an explicit
> > flush function was provided.
> >
> > Fix this by adding a condition to nvdimm_has_flush() to test for the
> > ND_REGION_ASYNC flag on the region and see if a 'region->flush'
> > callback is assigned.
> >
>
> May be this should have
> Fixes: c5d4355d10d4 ("libnvdimm: nd_region flush callback support")

Yes, thanks for that.

>
> Without this we will mark the pmem disk not having FUA support?

Yes.

>
>
> > References:
> > [1] "powerpc/papr_scm: Implement support for H_SCM_FLUSH hcall"
> > https://lore.kernel.org/linux-nvdimm/161703936121.36.7260632399       582101498.stgit@e1fbed493c87
> >
> > Reported-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>
> > Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
> > ---
> >  drivers/nvdimm/region_devs.c | 9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
> > index ef23119db574..e05cc9f8a9fd 100644
> > --- a/drivers/nvdimm/region_devs.c
> > +++ b/drivers/nvdimm/region_devs.c
> > @@ -1239,6 +1239,11 @@ int nvdimm_has_flush(struct nd_region *nd_region)
> >                       || !IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API))
> >               return -ENXIO;
> >
> > +     /* Test if an explicit flush function is defined */
> > +     if (test_bit(ND_REGION_ASYNC, &nd_region->flags) && nd_region->flush)
> > +             return 1;
>
> > +
> > +     /* Test if any flush hints for the region are available */
> >       for (i = 0; i < nd_region->ndr_mappings; i++) {
> >               struct nd_mapping *nd_mapping = &nd_region->mapping[i];
> >               struct nvdimm *nvdimm = nd_mapping->nvdimm;
> > @@ -1249,8 +1254,8 @@ int nvdimm_has_flush(struct nd_region *nd_region)
> >       }
> >
> >       /*
> > -      * The platform defines dimm devices without hints, assume
> > -      * platform persistence mechanism like ADR
> > +      * The platform defines dimm devices without hints nor explicit flush,
> > +      * assume platform persistence mechanism like ADR
> >        */
> >       return 0;
> >  }
> > --
> > 2.30.2
> > _______________________________________________
> > Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org
> > To unsubscribe send an email to linux-nvdimm-leave@lists.01.org
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