From: Jan Kara <jack@suse.cz>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: linux-mm@kvack.org, dan.j.williams@intel.com,
linuxppc-dev@lists.ozlabs.org, linux-nvdimm@lists.01.org
Subject: Re: [PATCH v3 3/6] mm/nvdimm: Add page size and struct page size to pfn superblock
Date: Tue, 11 Jun 2019 12:37:29 +0200 [thread overview]
Message-ID: <20190611103729.GA27635@quack2.suse.cz> (raw)
In-Reply-To: <20190604091357.32213-3-aneesh.kumar@linux.ibm.com>
On Tue 04-06-19 14:43:54, Aneesh Kumar K.V wrote:
> This is needed so that we don't wrongly initialize a namespace
> which doesn't have enough space reserved for holding struct pages
> with the current kernel.
>
> We also increment PFN_MIN_VERSION to make sure that older kernel
> won't initialize namespace created with newer kernel.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
...
> diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
> index 00c57805cad3..e01eee9efafe 100644
> --- a/drivers/nvdimm/pfn_devs.c
> +++ b/drivers/nvdimm/pfn_devs.c
> @@ -467,6 +467,15 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
> if (__le16_to_cpu(pfn_sb->version_minor) < 2)
> pfn_sb->align = 0;
>
> + if (__le16_to_cpu(pfn_sb->version_minor) < 3) {
> + /*
> + * For a large part we use PAGE_SIZE. But we
> + * do have some accounting code using SZ_4K.
> + */
> + pfn_sb->page_struct_size = cpu_to_le16(64);
> + pfn_sb->page_size = cpu_to_le32(SZ_4K);
> + }
> +
> switch (le32_to_cpu(pfn_sb->mode)) {
> case PFN_MODE_RAM:
> case PFN_MODE_PMEM:
As we discussed with Aneesh privately, this actually means that existing
NVDIMM namespaces on PPC64 will stop working due to these defaults for old
superblocks. I don't think that's a good thing as upgrading kernels is
going to be nightmare due to this on PPC64. So I believe we should make
defaults for old superblocks such that working setups keep working without
sysadmin having to touch anything.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2019-06-11 10:39 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-04 9:13 [PATCH v3 1/6] nvdimm: Consider probe return -EOPNOTSUPP as success Aneesh Kumar K.V
2019-06-04 9:13 ` [PATCH v3 2/6] mm/nvdimm: Add PFN_MIN_VERSION support Aneesh Kumar K.V
2019-06-04 9:13 ` [PATCH v3 3/6] mm/nvdimm: Add page size and struct page size to pfn superblock Aneesh Kumar K.V
2019-06-11 10:37 ` Jan Kara [this message]
2019-06-04 9:13 ` [PATCH v3 4/6] mm/nvdimm: Use correct #defines instead of opencoding Aneesh Kumar K.V
2019-06-04 9:13 ` [PATCH v3 5/6] mm/nvdimm: Pick the right alignment default when creating dax devices Aneesh Kumar K.V
2019-06-04 9:13 ` [PATCH v3 6/6] mm/nvdimm: Use correct alignment when looking at first pfn from a region Aneesh Kumar K.V
2019-06-11 9:29 ` [PATCH v3 1/6] nvdimm: Consider probe return -EOPNOTSUPP as success Aneesh Kumar K.V
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