Re: [PATCH v2] powerpc/nvdimm: Update vmemmap_populated to check sub-section range

[Michael Ellerman <patch-notifications@ellerman.id.au>]

On Tue, 2019-09-17 at 12:38:51 UTC, "Aneesh Kumar K.V" wrote:
> With commit: 7cc7867fb061 ("mm/devm_memremap_pages: enable sub-section remap")
> pmem namespaces are remapped in 2M chunks. On architectures like ppc64 we
> can map the memmap area using 16MB hugepage size and that can cover
> a memory range of 16G.
> 
> While enabling new pmem namespaces, since memory is added in sub-section chunks,
> before creating a new memmap mapping, kernel should check whether there is an
> existing memmap mapping covering the new pmem namespace. Currently, this is
> validated by checking whether the section covering the range is already
> initialized or not. Considering there can be multiple namespaces in the same
> section this can result in wrong validation. Update this to check for
> sub-sections in the range. This is done by checking for all pfns in the range we
> are mapping.
> 
> We could optimize this by checking only just one pfn in each sub-section. But
> since this is not fast-path we keep this simple.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/5f5d6e40a01e70b731df843d8b5a61b4b28b19d9

cheers