Messages in this thread Patch in this message | | | From | Toshi Kani <> | Subject | [PATCH] dax: Split pmd map when fallback on COW | Date | Mon, 23 Nov 2015 13:05:20 -0700 |
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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> Cc: 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> --- fs/dax.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/dax.c b/fs/dax.c index 43671b6..3405583 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -546,8 +546,10 @@ 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_page_pmd(vma, address, pmd); return VM_FAULT_FALLBACK; + } /* If the PMD would extend outside the VMA */ if (pmd_addr < vma->vm_start) return VM_FAULT_FALLBACK;
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