mm: take i_mmap_lock in unmap_mapping_range() for DAX

DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap.

__dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from
all mappings.  We need to drop i_mmap_lock there to avoid lock deadlock.

Re-aquiring the lock should be fine since we check i_size after the
point.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 9 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 320c42e95e69..ce8e983f3c4d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2426,17 +2426,10 @@ void unmap_mapping_range(struct address_space *mapping,
         if (details.last_index < details.first_index)
                 details.last_index = ULONG_MAX;
 
-
-        /*
-         * DAX already holds i_mmap_lock to serialise file truncate vs
-         * page fault and page fault vs page fault.
-         */
-        if (!IS_DAX(mapping->host))
-                i_mmap_lock_write(mapping);
+        i_mmap_lock_write(mapping);
         if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))
                 unmap_mapping_range_tree(&mapping->i_mmap, &details);
-        if (!IS_DAX(mapping->host))
-                i_mmap_unlock_write(mapping);
+        i_mmap_unlock_write(mapping);
 }
 EXPORT_SYMBOL(unmap_mapping_range);