mm: use new helper functions around the i_mmap_mutex

Convert all open coded mutex_lock/unlock calls to the
i_mmap_[lock/unlock]_write() helpers.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: "Kirill A. Shutemov" <kirill@shutemov.name>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/fork.c b/kernel/fork.c
index 9ca8418..4dc2dda 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -433,7 +433,7 @@
 			get_file(file);
 			if (tmp->vm_flags & VM_DENYWRITE)
 				atomic_dec(&inode->i_writecount);
-			mutex_lock(&mapping->i_mmap_mutex);
+			i_mmap_lock_write(mapping);
 			if (tmp->vm_flags & VM_SHARED)
 				atomic_inc(&mapping->i_mmap_writable);
 			flush_dcache_mmap_lock(mapping);
@@ -445,7 +445,7 @@
 				vma_interval_tree_insert_after(tmp, mpnt,
 							&mapping->i_mmap);
 			flush_dcache_mmap_unlock(mapping);
-			mutex_unlock(&mapping->i_mmap_mutex);
+			i_mmap_unlock_write(mapping);
 		}
 
 		/*