diff options
authorDan Williams <dan.j.williams@intel.com>2015-11-12 18:33:54 -0800
committerDan Williams <dan.j.williams@intel.com>2015-11-12 18:33:54 -0800
commit152d7bd80dca5ce77ec2d7313149a2ab990e808e (patch)
parent8de5dff8bae634497f4413bc3067389f2ed267da (diff)
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 files changed, 7 insertions, 0 deletions
diff --git a/fs/dax.c b/fs/dax.c
index 131fd35ae39d..bff20cc56130 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -627,6 +627,13 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR))
goto fallback;
+ /*
+ * TODO: teach vmf_insert_pfn_pmd() to support
+ * 'pte_special' for pmds
+ */
+ if (pfn_valid(pfn))
+ goto fallback;
if (buffer_unwritten(&bh) || buffer_new(&bh)) {
int i;
for (i = 0; i < PTRS_PER_PMD; i++)