ext4: fix dcache lookup of !casefolded directories

Found by visual inspection, this wasn't caught by my xfstest, since it's
effect is ignoring positive dentries in the cache the fallback just goes
to the disk.  it was introduced in the last iteration of the
case-insensitive patch.

d_compare should return 0 when the entries match, so make sure we are
correctly comparing the entire string if the encoding feature is set and
we are on a case-INsensitive directory.

Fixes: b886ee3e778e ("ext4: Support case-insensitive file name lookups")
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index 884a6e7..c7843b1 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -671,7 +671,7 @@
 	if (!IS_CASEFOLDED(dentry->d_parent->d_inode)) {
 		if (len != name->len)
 			return -1;
-		return !memcmp(str, name, len);
+		return memcmp(str, name->name, len);
 	}
 
 	return ext4_ci_compare(dentry->d_parent->d_inode, name, &qstr);