ext4: optimize case-insensitive lookups

Temporarily cache a casefolded version of the file name under lookup in
ext4_filename, to avoid repeatedly casefolding it.  I got up to 30%
speedup on lookups of large directories (>100k entries), depending on
the length of the string under lookup.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/unicode.h b/include/linux/unicode.h
index aec2c6d800aa..990aa97d8049 100644
--- a/include/linux/unicode.h
+++ b/include/linux/unicode.h
@@ -17,6 +17,9 @@ int utf8_strncmp(const struct unicode_map *um,
 
 int utf8_strncasecmp(const struct unicode_map *um,
 		 const struct qstr *s1, const struct qstr *s2);
+int utf8_strncasecmp_folded(const struct unicode_map *um,
+			    const struct qstr *cf,
+			    const struct qstr *s1);
 
 int utf8_normalize(const struct unicode_map *um, const struct qstr *str,
 		   unsigned char *dest, size_t dlen);