xfs: create a predicate to determine if two xfs_names are the same

Create a simple predicate to determine if two xfs_names are the same
objects or have the exact same name.  The comparison is always case
sensitive.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_dir2.h

@@ -24,6 +24,18 @@ struct xfs_dir3_icleaf_hdr;
 extern const struct xfs_name	xfs_name_dotdot;
 extern const struct xfs_name	xfs_name_dot;
 
+static inline bool
+xfs_dir2_samename(
+	const struct xfs_name	*n1,
+	const struct xfs_name	*n2)
+{
+	if (n1 == n2)
+		return true;
+	if (n1->len != n2->len)
+		return false;
+	return !memcmp(n1->name, n2->name, n1->len);
+}
+
 /*
  * Convert inode mode to directory entry filetype
  */

fs/xfs/scrub/dir.c

@@ -93,11 +93,11 @@ xchk_dir_actor(
 		return -ECANCELED;
 	}
 
-	if (!strncmp(".", name->name, name->len)) {
+	if (xfs_dir2_samename(name, &xfs_name_dot)) {
 		/* If this is "." then check that the inum matches the dir. */
 		if (ino != dp->i_ino)
 			xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, offset);
-	} else if (!strncmp("..", name->name, name->len)) {
+	} else if (xfs_dir2_samename(name, &xfs_name_dotdot)) {
 		/*
 		 * If this is ".." in the root inode, check that the inum
 		 * matches this dir.