[RFC PATCH V2 1/3] mm/nvdimm: Add PFN_MIN_VERSION support

[Aneesh Kumar K.V]

Hi Dan,

Are you ok with this patch series? If yes I can send a non-RFC version for
this series. Since we are now marking all previously created pfn_sb on
ppc64 as not supported, (pfn_sb->page_size = SZ_4K) I would like to get
this merged early.

-aneesh

"Aneesh Kumar K.V" <aneesh.kumar at linux.ibm.com> writes:

> This allows us to make changes in a backward incompatible way. I have
> kept the PFN_MIN_VERSION in this patch '0' because we are not introducing
> any incompatible changes in this patch. We also may want to backport this
> to older kernels.
>
> The error looks like
>
>   dax0.1: init failed, superblock min version 1, kernel support version 0
>
> and the namespace is marked disabled
>
> $ndctl list -Ni
> [
>   {
>     "dev":"namespace0.0",
>     "mode":"fsdax",
>     "map":"mem",
>     "size":10737418240,
>     "uuid":"9605de6d-cefa-4a87-99cd-dec28b02cffe",
>     "state":"disabled"
>   }
> ]
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
> ---
>  drivers/nvdimm/pfn.h      |  9 ++++++++-
>  drivers/nvdimm/pfn_devs.c |  8 ++++++++
>  drivers/nvdimm/pmem.c     | 26 ++++++++++++++++++++++----
>  3 files changed, 38 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/nvdimm/pfn.h b/drivers/nvdimm/pfn.h
> index dde9853453d3..5fd29242745a 100644
> --- a/drivers/nvdimm/pfn.h
> +++ b/drivers/nvdimm/pfn.h
> @@ -20,6 +20,12 @@
>  #define PFN_SIG_LEN 16
>  #define PFN_SIG "NVDIMM_PFN_INFO\0"
>  #define DAX_SIG "NVDIMM_DAX_INFO\0"
> +/*
> + * increment this when we are making changes such that older
> + * kernel should fail to initialize that namespace.
> + */
> +
> +#define PFN_MIN_VERSION 0
>  
>  struct nd_pfn_sb {
>  	u8 signature[PFN_SIG_LEN];
> @@ -36,7 +42,8 @@ struct nd_pfn_sb {
>  	__le32 end_trunc;
>  	/* minor-version-2 record the base alignment of the mapping */
>  	__le32 align;
> -	u8 padding[4000];
> +	__le16 min_version;
> +	u8 padding[3998];
>  	__le64 checksum;
>  };
>  
> diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
> index 01f40672507f..a2268cf262f5 100644
> --- a/drivers/nvdimm/pfn_devs.c
> +++ b/drivers/nvdimm/pfn_devs.c
> @@ -439,6 +439,13 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
>  	if (nvdimm_read_bytes(ndns, SZ_4K, pfn_sb, sizeof(*pfn_sb), 0))
>  		return -ENXIO;
>  
> +	if (le16_to_cpu(pfn_sb->min_version) > PFN_MIN_VERSION) {
> +		dev_err(&nd_pfn->dev,
> +			"init failed, superblock min version %ld kernel support version %ld\n",
> +			le16_to_cpu(pfn_sb->min_version), PFN_MIN_VERSION);
> +		return -EOPNOTSUPP;
> +	}
> +
>  	if (memcmp(pfn_sb->signature, sig, PFN_SIG_LEN) != 0)
>  		return -ENODEV;
>  
> @@ -769,6 +776,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
>  	memcpy(pfn_sb->parent_uuid, nd_dev_to_uuid(&ndns->dev), 16);
>  	pfn_sb->version_major = cpu_to_le16(1);
>  	pfn_sb->version_minor = cpu_to_le16(2);
> +	pfn_sb->min_version = cpu_to_le16(PFN_MIN_VERSION);
>  	pfn_sb->start_pad = cpu_to_le32(start_pad);
>  	pfn_sb->end_trunc = cpu_to_le32(end_trunc);
>  	pfn_sb->align = cpu_to_le32(nd_pfn->align);
> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index 845c5b430cdd..406427c064d9 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -490,6 +490,7 @@ static int pmem_attach_disk(struct device *dev,
>  
>  static int nd_pmem_probe(struct device *dev)
>  {
> +	int ret;
>  	struct nd_namespace_common *ndns;
>  
>  	ndns = nvdimm_namespace_common_probe(dev);
> @@ -505,12 +506,29 @@ static int nd_pmem_probe(struct device *dev)
>  	if (is_nd_pfn(dev))
>  		return pmem_attach_disk(dev, ndns);
>  
> -	/* if we find a valid info-block we'll come back as that personality */
> -	if (nd_btt_probe(dev, ndns) == 0 || nd_pfn_probe(dev, ndns) == 0
> -			|| nd_dax_probe(dev, ndns) == 0)
> +	ret = nd_btt_probe(dev, ndns);
> +	if (ret == 0)
>  		return -ENXIO;
> +	else if (ret == -EOPNOTSUPP)
> +		return ret;
>  
> -	/* ...otherwise we're just a raw pmem device */
> +	ret = nd_pfn_probe(dev, ndns);
> +	if (ret == 0)
> +		return -ENXIO;
> +	else if (ret == -EOPNOTSUPP)
> +		return ret;
> +
> +	ret = nd_dax_probe(dev, ndns);
> +	if (ret == 0)
> +		return -ENXIO;
> +	else if (ret == -EOPNOTSUPP)
> +		return ret;
> +	/*
> +	 * We have two failure conditions here, there is no
> +	 * info reserver block or we found a valid info reserve block
> +	 * but failed to initialize the pfn superblock.
> +	 * Don't create a raw pmem disk for the second case.
> +	 */
>  	return pmem_attach_disk(dev, ndns);
>  }
>  
> -- 
> 2.21.0