tmpfs: enable NOSEC optimization

Let tmpfs into the NOSEC optimization (avoiding file_remove_suid()
overhead on most common writes): set MS_NOSEC on its superblocks.

Signed-off-by: Hugh Dickins <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Cong Wang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/shmem.c

@@ -2373,6 +2373,7 @@ int shmem_fill_super(struct super_block *sb, void *data, int silent)
 		}
 	}
 	sb->s_export_op = &shmem_export_ops;
+	sb->s_flags |= MS_NOSEC;
 #else
 	sb->s_flags |= MS_NOUSER;
 #endif