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>

fs/ext4/dir.c

@@ -677,7 +677,7 @@ static int ext4_d_compare(const struct dentry *dentry, unsigned int len,
 		return memcmp(str, name->name, len);
 	}
 
-	return ext4_ci_compare(dentry->d_parent->d_inode, name, &qstr);
+	return ext4_ci_compare(dentry->d_parent->d_inode, name, &qstr, false);
 }
 
 static int ext4_d_hash(const struct dentry *dentry, struct qstr *str)

fs/ext4/ext4.h

@@ -2078,6 +2078,9 @@ struct ext4_filename {
 #ifdef CONFIG_FS_ENCRYPTION
 	struct fscrypt_str crypto_buf;
 #endif
+#ifdef CONFIG_UNICODE
+	struct fscrypt_str cf_name;
+#endif
 };
 
 #define fname_name(p) ((p)->disk_name.name)
@@ -2303,6 +2306,12 @@ extern unsigned ext4_free_clusters_after_init(struct super_block *sb,
 					      struct ext4_group_desc *gdp);
 ext4_fsblk_t ext4_inode_to_goal_block(struct inode *);
 
+#ifdef CONFIG_UNICODE
+extern void ext4_fname_setup_ci_filename(struct inode *dir,
+					 const struct qstr *iname,
+					 struct fscrypt_str *fname);
+#endif
+
 #ifdef CONFIG_FS_ENCRYPTION
 static inline void ext4_fname_from_fscrypt_name(struct ext4_filename *dst,
 						const struct fscrypt_name *src)
@@ -2329,6 +2338,10 @@ static inline int ext4_fname_setup_filename(struct inode *dir,
 		return err;
 
 	ext4_fname_from_fscrypt_name(fname, &name);
+
+#ifdef CONFIG_UNICODE
+	ext4_fname_setup_ci_filename(dir, iname, &fname->cf_name);
+#endif
 	return 0;
 }
 
@@ -2344,6 +2357,10 @@ static inline int ext4_fname_prepare_lookup(struct inode *dir,
 		return err;
 
 	ext4_fname_from_fscrypt_name(fname, &name);
+
+#ifdef CONFIG_UNICODE
+	ext4_fname_setup_ci_filename(dir, &dentry->d_name, &fname->cf_name);
+#endif
 	return 0;
 }
 
@@ -2357,6 +2374,11 @@ static inline void ext4_fname_free_filename(struct ext4_filename *fname)
 	fname->crypto_buf.name = NULL;
 	fname->usr_fname = NULL;
 	fname->disk_name.name = NULL;
+
+#ifdef CONFIG_UNICODE
+	kfree(fname->cf_name.name);
+	fname->cf_name.name = NULL;
+#endif
 }
 #else /* !CONFIG_FS_ENCRYPTION */
 static inline int ext4_fname_setup_filename(struct inode *dir,
@@ -2367,6 +2389,11 @@ static inline int ext4_fname_setup_filename(struct inode *dir,
 	fname->usr_fname = iname;
 	fname->disk_name.name = (unsigned char *) iname->name;
 	fname->disk_name.len = iname->len;
+
+#ifdef CONFIG_UNICODE
+	ext4_fname_setup_ci_filename(dir, iname, &fname->cf_name);
+#endif
+
 	return 0;
 }
 
@@ -2377,7 +2404,13 @@ static inline int ext4_fname_prepare_lookup(struct inode *dir,
 	return ext4_fname_setup_filename(dir, &dentry->d_name, 1, fname);
 }
 
-static inline void ext4_fname_free_filename(struct ext4_filename *fname) { }
+static inline void ext4_fname_free_filename(struct ext4_filename *fname)
+{
+#ifdef CONFIG_UNICODE
+	kfree(fname->cf_name.name);
+	fname->cf_name.name = NULL;
+#endif
+}
 #endif /* !CONFIG_FS_ENCRYPTION */
 
 /* dir.c */
@@ -3120,8 +3153,8 @@ extern int ext4_handle_dirty_dirent_node(handle_t *handle,
 					 struct inode *inode,
 					 struct buffer_head *bh);
 extern int ext4_ci_compare(const struct inode *parent,
-			   const struct qstr *name,
-			   const struct qstr *entry);
+			   const struct qstr *fname,
+			   const struct qstr *entry, bool quick);
 
 #define S_SHIFT 12
 static const unsigned char ext4_type_by_mode[(S_IFMT >> S_SHIFT) + 1] = {

fs/ext4/namei.c

@@ -1259,19 +1259,24 @@ static void dx_insert_block(struct dx_frame *frame, u32 hash, ext4_lblk_t block)
 #ifdef CONFIG_UNICODE
 /*
  * Test whether a case-insensitive directory entry matches the filename
- * being searched for.
+ * being searched for.  If quick is set, assume the name being looked up
+ * is already in the casefolded form.
  *
  * Returns: 0 if the directory entry matches, more than 0 if it
  * doesn't match or less than zero on error.
  */
 int ext4_ci_compare(const struct inode *parent, const struct qstr *name,
-		    const struct qstr *entry)
+		    const struct qstr *entry, bool quick)
 {
 	const struct ext4_sb_info *sbi = EXT4_SB(parent->i_sb);
 	const struct unicode_map *um = sbi->s_encoding;
 	int ret;
 
-	ret = utf8_strncasecmp(um, name, entry);
+	if (quick)
+		ret = utf8_strncasecmp_folded(um, name, entry);
+	else
+		ret = utf8_strncasecmp(um, name, entry);
+
 	if (ret < 0) {
 		/* Handle invalid character sequence as either an error
 		 * or as an opaque byte sequence.
@@ -1287,6 +1292,27 @@ int ext4_ci_compare(const struct inode *parent, const struct qstr *name,
 
 	return ret;
 }
+
+void ext4_fname_setup_ci_filename(struct inode *dir, const struct qstr *iname,
+				  struct fscrypt_str *cf_name)
+{
+	if (!IS_CASEFOLDED(dir)) {
+		cf_name->name = NULL;
+		return;
+	}
+
+	cf_name->name = kmalloc(EXT4_NAME_LEN, GFP_NOFS);
+	if (!cf_name->name)
+		return;
+
+	cf_name->len = utf8_casefold(EXT4_SB(dir->i_sb)->s_encoding,
+				     iname, cf_name->name,
+				     EXT4_NAME_LEN);
+	if (cf_name->len <= 0) {
+		kfree(cf_name->name);
+		cf_name->name = NULL;
+	}
+}
 #endif
 
 /*
@@ -1313,8 +1339,15 @@ static inline bool ext4_match(const struct inode *parent,
 #endif
 
 #ifdef CONFIG_UNICODE
-	if (EXT4_SB(parent->i_sb)->s_encoding && IS_CASEFOLDED(parent))
-		return (ext4_ci_compare(parent, fname->usr_fname, &entry) == 0);
+	if (EXT4_SB(parent->i_sb)->s_encoding && IS_CASEFOLDED(parent)) {
+		if (fname->cf_name.name) {
+			struct qstr cf = {.name = fname->cf_name.name,
+					  .len = fname->cf_name.len};
+			return !ext4_ci_compare(parent, &cf, &entry, true);
+		}
+		return !ext4_ci_compare(parent, fname->usr_fname, &entry,
+					false);
+	}
 #endif
 
 	return fscrypt_match_name(&f, de->name, de->name_len);

fs/unicode/utf8-core.c

@@ -73,6 +73,34 @@ int utf8_strncasecmp(const struct unicode_map *um,
 }
 EXPORT_SYMBOL(utf8_strncasecmp);
 
+/* String cf is expected to be a valid UTF-8 casefolded
+ * string.
+ */
+int utf8_strncasecmp_folded(const struct unicode_map *um,
+			    const struct qstr *cf,
+			    const struct qstr *s1)
+{
+	const struct utf8data *data = utf8nfdicf(um->version);
+	struct utf8cursor cur1;
+	int c1, c2;
+	int i = 0;
+
+	if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
+		return -EINVAL;
+
+	do {
+		c1 = utf8byte(&cur1);
+		c2 = cf->name[i++];
+		if (c1 < 0)
+			return -EINVAL;
+		if (c1 != c2)
+			return 1;
+	} while (c1);
+
+	return 0;
+}
+EXPORT_SYMBOL(utf8_strncasecmp_folded);
+
 int utf8_casefold(const struct unicode_map *um, const struct qstr *str,
 		  unsigned char *dest, size_t dlen)
 {

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);