[PATCH v7 8/8] ext4: Optimize match for casefolded encrypted dirs

[Daniel Rosenberg <drosen@google.com>]

Matching names with casefolded encrypting directories requires
decrypting entries to confirm case since we are case preserving. We can
avoid needing to decrypt if our hash values don't match.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
---
 fs/ext4/ext4.h  | 17 ++++++++-------
 fs/ext4/namei.c | 55 ++++++++++++++++++++++++++-----------------------
 2 files changed, 38 insertions(+), 34 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 9ee9cdd686ce0..40cf3171ef005 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2447,9 +2447,9 @@ extern unsigned ext4_free_clusters_after_init(struct super_block *sb,
 ext4_fsblk_t ext4_inode_to_goal_block(struct inode *);
 
 #ifdef CONFIG_UNICODE
-extern void ext4_fname_setup_ci_filename(struct inode *dir,
+extern int ext4_fname_setup_ci_filename(struct inode *dir,
 					 const struct qstr *iname,
-					 struct fscrypt_str *fname);
+					 struct ext4_filename *fname);
 #endif
 
 #ifdef CONFIG_FS_ENCRYPTION
@@ -2480,9 +2480,9 @@ static inline int ext4_fname_setup_filename(struct inode *dir,
 	ext4_fname_from_fscrypt_name(fname, &name);
 
 #ifdef CONFIG_UNICODE
-	ext4_fname_setup_ci_filename(dir, iname, &fname->cf_name);
+	err = ext4_fname_setup_ci_filename(dir, iname, fname);
 #endif
-	return 0;
+	return err;
 }
 
 static inline int ext4_fname_prepare_lookup(struct inode *dir,
@@ -2499,9 +2499,9 @@ static inline int ext4_fname_prepare_lookup(struct inode *dir,
 	ext4_fname_from_fscrypt_name(fname, &name);
 
 #ifdef CONFIG_UNICODE
-	ext4_fname_setup_ci_filename(dir, &dentry->d_name, &fname->cf_name);
+	err = ext4_fname_setup_ci_filename(dir, &dentry->d_name, fname);
 #endif
-	return 0;
+	return err;
 }
 
 static inline void ext4_fname_free_filename(struct ext4_filename *fname)
@@ -2526,15 +2526,16 @@ static inline int ext4_fname_setup_filename(struct inode *dir,
 					    int lookup,
 					    struct ext4_filename *fname)
 {
+	int err = 0;
 	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);
+	err = ext4_fname_setup_ci_filename(dir, iname, fname);
 #endif
 
-	return 0;
+	return err;
 }
 
 static inline int ext4_fname_prepare_lookup(struct inode *dir,
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index ae53c6f759740..ac848b22f0ad3 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -791,7 +791,9 @@ dx_probe(struct ext4_filename *fname, struct inode *dir,
 	if (hinfo->hash_version <= DX_HASH_TEA)
 		hinfo->hash_version += EXT4_SB(dir->i_sb)->s_hash_unsigned;
 	hinfo->seed = EXT4_SB(dir->i_sb)->s_hash_seed;
-	if (fname && fname_name(fname))
+	/* hash is already computed for encrypted casefolded directory */
+	if (fname && fname_name(fname) &&
+				!(IS_ENCRYPTED(dir) && IS_CASEFOLDED(dir)))
 		ext4fs_dirhash(dir, fname_name(fname), fname_len(fname), hinfo);
 	hash = hinfo->hash;
 
@@ -1356,19 +1358,21 @@ 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)
+int ext4_fname_setup_ci_filename(struct inode *dir, const struct qstr *iname,
+				  struct ext4_filename *name)
 {
+	struct fscrypt_str *cf_name = &name->cf_name;
+	struct dx_hash_info *hinfo = &name->hinfo;
 	int len;
 
 	if (!needs_casefold(dir)) {
 		cf_name->name = NULL;
-		return;
+		return 0;
 	}
 
 	cf_name->name = kmalloc(EXT4_NAME_LEN, GFP_NOFS);
 	if (!cf_name->name)
-		return;
+		return -ENOMEM;
 
 	len = utf8_casefold(dir->i_sb->s_encoding,
 			    iname, cf_name->name,
@@ -1376,10 +1380,18 @@ void ext4_fname_setup_ci_filename(struct inode *dir, const struct qstr *iname,
 	if (len <= 0) {
 		kfree(cf_name->name);
 		cf_name->name = NULL;
-		return;
 	}
 	cf_name->len = (unsigned) len;
+	if (!IS_ENCRYPTED(dir))
+		return 0;
 
+	hinfo->hash_version = DX_HASH_SIPHASH;
+	hinfo->seed = NULL;
+	if (cf_name->name)
+		ext4fs_dirhash(dir, cf_name->name, cf_name->len, hinfo);
+	else
+		ext4fs_dirhash(dir, iname->name, iname->len, hinfo);
+	return 0;
 }
 #endif
 
@@ -1409,16 +1421,12 @@ static bool ext4_match(struct inode *parent,
 			struct qstr cf = {.name = fname->cf_name.name,
 					  .len = fname->cf_name.len};
 			if (IS_ENCRYPTED(parent)) {
-				struct dx_hash_info hinfo;
-
-				hinfo.hash_version = DX_HASH_SIPHASH;
-				hinfo.seed = NULL;
-				ext4fs_dirhash(parent, fname->cf_name.name,
-						fname_len(fname), &hinfo);
-				if (hinfo.hash != EXT4_DIRENT_HASH(de) ||
-						hinfo.minor_hash !=
-						    EXT4_DIRENT_MINOR_HASH(de))
+				if (fname->hinfo.hash != EXT4_DIRENT_HASH(de) ||
+					fname->hinfo.minor_hash !=
+						EXT4_DIRENT_MINOR_HASH(de)) {
+
 					return 0;
+				}
 			}
 			return !ext4_ci_compare(parent, &cf, de->name,
 							de->name_len, true);
@@ -2043,15 +2051,11 @@ void ext4_insert_dentry(struct inode *dir,
 	de->name_len = fname_len(fname);
 	memcpy(de->name, fname_name(fname), fname_len(fname));
 	if (ext4_hash_in_dirent(dir)) {
-		struct dx_hash_info hinfo;
+		struct dx_hash_info *hinfo = &fname->hinfo;
 
-		hinfo.hash_version = DX_HASH_SIPHASH;
-		hinfo.seed = NULL;
-		ext4fs_dirhash(dir, fname_usr_name(fname),
-				fname_len(fname), &hinfo);
-		EXT4_EXTENDED_DIRENT(de)->hash = cpu_to_le32(hinfo.hash);
+		EXT4_EXTENDED_DIRENT(de)->hash = cpu_to_le32(hinfo->hash);
 		EXT4_EXTENDED_DIRENT(de)->minor_hash =
-				cpu_to_le32(hinfo.minor_hash);
+						cpu_to_le32(hinfo->minor_hash);
 	}
 }
 
@@ -2202,10 +2206,9 @@ static int make_indexed_dir(handle_t *handle, struct ext4_filename *fname,
 	if (fname->hinfo.hash_version <= DX_HASH_TEA)
 		fname->hinfo.hash_version += EXT4_SB(dir->i_sb)->s_hash_unsigned;
 	fname->hinfo.seed = EXT4_SB(dir->i_sb)->s_hash_seed;
-	if (ext4_hash_in_dirent(dir))
-		ext4fs_dirhash(dir, fname_usr_name(fname),
-				fname_len(fname), &fname->hinfo);
-	else
+
+	/* casefolded encrypted hashes are computed on fname setup */
+	if (!ext4_hash_in_dirent(dir))
 		ext4fs_dirhash(dir, fname_name(fname),
 				fname_len(fname), &fname->hinfo);
 
-- 
2.25.0.341.g760bfbb309-goog