[PATCH v4 04/10] ext4: Implement ci comparison using unicode_name

[Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>]

By using a new type here, we can hide most of the caching casefold logic
from ext4.  The condition in ext4_match is now quite redundant, but this
is addressed in the next patch.

This doesn't use ext4_filename to keep it generic, since the function
will be moved to libfs to be shared with f2fs.

Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>

--
Changes since v1:
  - Instead of (ab)using fscrypt_name, create a new type (ebiggers).
---
 fs/ext4/namei.c    | 32 +++++++++++++++-----------------
 include/linux/fs.h |  5 +++++
 2 files changed, 20 insertions(+), 17 deletions(-)

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 84fdb23f09b8..5296ced2e43e 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1321,20 +1321,19 @@ static void dx_insert_block(struct dx_frame *frame, u32 hash, ext4_lblk_t block)
 /**
  * ext4_match_ci() - Match (case-insensitive) a name with a dirent.
  * @parent: Inode of the parent of the dentry.
- * @name: name under lookup.
+ * @uname: name under lookup.
  * @de_name: Dirent name.
  * @de_name_len: dirent name length.
- * @quick: whether @name is already casefolded.
  *
  * Test whether a case-insensitive directory entry matches the filename
- * being searched.  If quick is set, the @name being looked up is
- * already in the casefolded form.
+ * being searched.
  *
  * Return: > 0 if the directory entry matches, 0 if it doesn't match, or
  * < 0 on error.
  */
-static int ext4_match_ci(const struct inode *parent, const struct qstr *name,
-			 u8 *de_name, size_t de_name_len, bool quick)
+static int ext4_match_ci(const struct inode *parent,
+			 const struct unicode_name *uname,
+			 u8 *de_name, size_t de_name_len)
 {
 	const struct super_block *sb = parent->i_sb;
 	const struct unicode_map *um = sb->s_encoding;
@@ -1357,10 +1356,10 @@ static int ext4_match_ci(const struct inode *parent, const struct qstr *name,
 		entry.len = decrypted_name.len;
 	}
 
-	if (quick)
-		ret = utf8_strncasecmp_folded(um, name, &entry);
+	if (uname->folded_name->name)
+		ret = utf8_strncasecmp_folded(um, uname->folded_name, &entry);
 	else
-		ret = utf8_strncasecmp(um, name, &entry);
+		ret = utf8_strncasecmp(um, uname->usr_name, &entry);
 
 	if (!ret)
 		match = true;
@@ -1370,8 +1369,8 @@ static int ext4_match_ci(const struct inode *parent, const struct qstr *name,
 		 * the names have invalid characters.
 		 */
 		ret = 0;
-		match = ((name->len == entry.len) &&
-			 !memcmp(name->name, entry.name, entry.len));
+		match = ((uname->usr_name->len == entry.len) &&
+			 !memcmp(uname->usr_name->name, entry.name, entry.len));
 	}
 
 out:
@@ -1441,6 +1440,10 @@ static bool ext4_match(struct inode *parent,
 #if IS_ENABLED(CONFIG_UNICODE)
 	if (parent->i_sb->s_encoding && IS_CASEFOLDED(parent) &&
 	    (!IS_ENCRYPTED(parent) || fscrypt_has_encryption_key(parent))) {
+		struct unicode_name u = {
+			.folded_name = &fname->cf_name,
+			.usr_name = fname->usr_fname
+		};
 		int ret;
 
 		if (fname->cf_name.name) {
@@ -1452,14 +1455,9 @@ static bool ext4_match(struct inode *parent,
 					return false;
 				}
 			}
-
-			ret = ext4_match_ci(parent, &fname->cf_name, de->name,
-					    de->name_len, true);
-		} else {
-			ret = ext4_match_ci(parent, fname->usr_fname,
-					    de->name, de->name_len, false);
 		}
 
+		ret = ext4_match_ci(parent, &u, de->name, de->name_len);
 		if (ret < 0) {
 			/*
 			 * Treat comparison errors as not a match.  The
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e2d892b201b0..3f76a18a5f40 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3358,6 +3358,11 @@ extern int generic_file_fsync(struct file *, loff_t, loff_t, int);
 
 extern int generic_check_addressable(unsigned, u64);
 
+struct unicode_name {
+	const struct qstr *folded_name;
+	const struct qstr *usr_name;
+};
+
 extern void generic_set_encrypted_ci_d_ops(struct dentry *dentry);
 
 #ifdef CONFIG_MIGRATION
-- 
2.36.1