dax: fix __dax_pmd_fault crash
Since 4.3 introduced devm_memremap_pages() the pfns handled by DAX may
optionally have a struct page backing. When a mapped pfn reaches
vmf_insert_pfn_pmd() it fails with a crash signature like the following:
kernel BUG at mm/huge_memory.c:905!
[..]
Call Trace:
[<ffffffff812a73ba>] __dax_pmd_fault+0x2ea/0x5b0
[<ffffffffa01a4182>] xfs_filemap_pmd_fault+0x92/0x150 [xfs]
[<ffffffff811fbe02>] handle_mm_fault+0x312/0x1b50
Fix this by falling back to 4K mappings in the pfn_valid() case. Longer
term, vmf_insert_pfn_pmd() needs to grow support for architectures that
can provide a 'pmd_special' capability.
Cc: <stable@vger.kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
1 file changed
