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/mm/mremap.c b/mm/mremap.c
index b147f66..426b448 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -119,7 +119,7 @@
 	if (need_rmap_locks) {
 		if (vma->vm_file) {
 			mapping = vma->vm_file->f_mapping;
-			mutex_lock(&mapping->i_mmap_mutex);
+			i_mmap_lock_write(mapping);
 		}
 		if (vma->anon_vma) {
 			anon_vma = vma->anon_vma;
@@ -156,7 +156,7 @@
 	if (anon_vma)
 		anon_vma_unlock_write(anon_vma);
 	if (mapping)
-		mutex_unlock(&mapping->i_mmap_mutex);
+		i_mmap_unlock_write(mapping);
 }
 
 #define LATENCY_LIMIT	(64 * PAGE_SIZE)