linux-ext4 - [PATCH 3/5] ext4: Implement ci comparison using fscrypt

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Date:   Mon, 21 Mar 2022 23:00:02 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     tytso@....edu
Cc:     ebiggers@...nel.org, jaegeuk@...nel.org,
        linux-ext4@...r.kernel.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel@...labora.com
Subject: [PATCH 3/5] ext4: Implement ci comparison using fscrypt_name

By using fscrypt_name 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.

Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
---
 fs/ext4/namei.c         | 26 ++++++++++++--------------
 include/linux/fscrypt.h |  4 ++++
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 8976e5a28c73..71b4b05fae89 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1321,10 +1321,9 @@ static void dx_insert_block(struct dx_frame *frame, u32 hash, ext4_lblk_t block)
 /**
  * ext4_ci_compare() - Match (case-insensitive) a name with a dirent.
  * @parent: Inode of the parent of the dentry.
- * @name: name under lookup.
+ * @fname: 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
@@ -1333,8 +1332,9 @@ static void dx_insert_block(struct dx_frame *frame, u32 hash, ext4_lblk_t block)
  * Return: > 0 if the directory entry matches, 0 if it doesn't match, or
  * < 0 on error.
  */
-static int ext4_ci_compare(const struct inode *parent, const struct qstr *name,
-			   u8 *de_name, size_t de_name_len, bool quick)
+static int ext4_ci_compare(const struct inode *parent,
+			   const struct fscrypt_name *fname,
+			   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 +1357,10 @@ static int ext4_ci_compare(const struct inode *parent, const struct qstr *name,
 		entry.len = decrypted_name.len;
 	}
 
-	if (quick)
-		ret = utf8_strncasecmp_folded(um, name, &entry);
+	if (fname->cf_name.name)
+		ret = utf8_strncasecmp_folded(um, &fname->cf_name, &entry);
 	else
-		ret = utf8_strncasecmp(um, name, &entry);
+		ret = utf8_strncasecmp(um, fname->usr_fname, &entry);
 
 	if (!ret)
 		match = true;
@@ -1370,8 +1370,8 @@ static int ext4_ci_compare(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 = ((fname->usr_fname->len == entry.len) &&
+			 !memcmp(fname->usr_fname->name, entry.name, entry.len));
 	}
 
 out:
@@ -1440,6 +1440,8 @@ static bool ext4_match(struct inode *parent,
 #endif
 
 #if IS_ENABLED(CONFIG_UNICODE)
+	f.cf_name = fname->cf_name;
+
 	if (parent->i_sb->s_encoding && IS_CASEFOLDED(parent) &&
 	    (!IS_ENCRYPTED(parent) || fscrypt_has_encryption_key(parent))) {
 		if (fname->cf_name.name) {
@@ -1451,13 +1453,9 @@ static bool ext4_match(struct inode *parent,
 					return false;
 				}
 			}
-			ret = ext4_ci_compare(parent, &fname->cf_name, de->name,
-					      de->name_len, true);
-		} else {
-			ret = ext4_ci_compare(parent, fname->usr_fname,
-					      de->name, de->name_len, false);
 		}
 
+		ret = ext4_ci_compare(parent, &f, de->name, de->name_len);
 		if (ret < 0) {
 			/*
 			 * Treat comparison errors as not a match.  The
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index 91ea9477e9bd..5dc4b3c805e4 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -36,6 +36,10 @@ struct fscrypt_name {
 	u32 minor_hash;
 	struct fscrypt_str crypto_buf;
 	bool is_nokey_name;
+
+#ifdef CONFIG_UNICODE
+	struct qstr cf_name;
+#endif
 };
 
 #define FSTR_INIT(n, l)		{ .name = n, .len = l }
-- 
2.35.1