| Message ID | 1444077174-22016-4-git-send-email-ross.zwisler@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
diff --git a/fs/dax.c b/fs/dax.c index f364c90..d42217d 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -534,6 +534,13 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, unsigned long pfn; int result = 0; + /* + * There is currently a deadlock in the DAX PMD fault path. Disable + * this path and fall back to the normal dax_fault() path for now + * while we rework locking. + */ + return VM_FAULT_FALLBACK; + /* Fall back to PTEs if we're going to COW */ if (write && !(vma->vm_flags & VM_SHARED)) return VM_FAULT_FALLBACK;
There is currently a deadlock in the DAX PMD fault path because it ends up taking the same mapping->i_mmap_rwsem twice. The first take is a i_mmap_lock_read() near the beginning of __dax_pmd_fault(), and the second is __dax_pmd_fault() -> unmap_mapping_range() -> i_mmap_lock_write(). We are re-working the way that DAX does its locking for v4.4, so for now just disable DAX PMD faults and fall back to PAGE_SIZE faults to make sure we don't hit this deadlock. Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> --- fs/dax.c | 7 +++++++ 1 file changed, 7 insertions(+)