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authorToshi Kani <toshi.kani@hpe.com>2016-01-16 03:56:05 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-01-16 04:56:32 +0300
commit59bf4fb9d386601cbaa70a9b00159abb846dedaa (patch)
tree0735bb6400f6ed0a3c3be69e1e10018a17fe6a63
parent01871e59af5cc1cbf290ad6b4b95cd2f0cec9e8c (diff)
downloadlinux-59bf4fb9d386601cbaa70a9b00159abb846dedaa.tar.xz
dax: Split pmd map when fallback on COW
An infinite loop of PMD faults was observed when attempted to mlock() a private read-only PMD mmap'd range of a DAX file. __dax_pmd_fault() simply returns with VM_FAULT_FALLBACK when falling back to PTE on COW. However, __handle_mm_fault() returns without falling back to handle_pte_fault() because a PMD map is present in this case. Change __dax_pmd_fault() to split the PMD map, if present, before returning with VM_FAULT_FALLBACK. Signed-off-by: Toshi Kani <toshi.kani@hpe.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Matthew Wilcox <willy@linux.intel.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/dax.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/fs/dax.c b/fs/dax.c
index 5c548d821a2a..3220da70ee20 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -578,8 +578,10 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
return VM_FAULT_FALLBACK;
/* Fall back to PTEs if we're going to COW */
- if (write && !(vma->vm_flags & VM_SHARED))
+ if (write && !(vma->vm_flags & VM_SHARED)) {
+ split_huge_pmd(vma, pmd, address);
return VM_FAULT_FALLBACK;
+ }
/* If the PMD would extend outside the VMA */
if (pmd_addr < vma->vm_start)
return VM_FAULT_FALLBACK;