Merge tag 'vfs-6.11.casefold' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull vfs casefolding updates from Christian Brauner:
 "This contains some work to simplify the handling of casefolded names:

   - Simplify the handling of casefolded names in f2fs and ext4 by
     keeping the names as a qstr to avoiding unnecessary conversions

   - Introduce a new generic_ci_match() libfs case-insensitive lookup
     helper and use it in both f2fs and ext4 allowing to remove the
     filesystem specific implementations

   - Remove a bunch of ifdefs by making the unicode build checks part of
     the code flow"

* tag 'vfs-6.11.casefold' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  f2fs: Move CONFIG_UNICODE defguards into the code flow
  ext4: Move CONFIG_UNICODE defguards into the code flow
  f2fs: Reuse generic_ci_match for ci comparisons
  ext4: Reuse generic_ci_match for ci comparisons
  libfs: Introduce case-insensitive string comparison helper
  f2fs: Simplify the handling of cached casefolded names
  ext4: Simplify the handling of cached casefolded names

fs/ext4/crypto.c

@@ -31,11 +31,10 @@ int ext4_fname_setup_filename(struct inode *dir, const struct qstr *iname,
 
 	ext4_fname_from_fscrypt_name(fname, &name);
 
-#if IS_ENABLED(CONFIG_UNICODE)
 	err = ext4_fname_setup_ci_filename(dir, iname, fname);
 	if (err)
 		ext4_fname_free_filename(fname);
-#endif
+
 	return err;
 }
 
@@ -51,11 +50,9 @@ int ext4_fname_prepare_lookup(struct inode *dir, struct dentry *dentry,
 
 	ext4_fname_from_fscrypt_name(fname, &name);
 
-#if IS_ENABLED(CONFIG_UNICODE)
 	err = ext4_fname_setup_ci_filename(dir, &dentry->d_name, fname);
 	if (err)
 		ext4_fname_free_filename(fname);
-#endif
 	return err;
 }
 
@@ -70,10 +67,7 @@ void ext4_fname_free_filename(struct ext4_filename *fname)
 	fname->usr_fname = NULL;
 	fname->disk_name.name = NULL;
 
-#if IS_ENABLED(CONFIG_UNICODE)
-	kfree(fname->cf_name.name);
-	fname->cf_name.name = NULL;
-#endif
+	ext4_fname_free_ci_filename(fname);
 }
 
 static bool uuid_is_zero(__u8 u[16])

fs/ext4/ext4.h

@@ -2511,7 +2511,7 @@ struct ext4_filename {
 	struct fscrypt_str crypto_buf;
 #endif
 #if IS_ENABLED(CONFIG_UNICODE)
-	struct fscrypt_str cf_name;
+	struct qstr cf_name;
 #endif
 };
 
@@ -2745,8 +2745,25 @@ ext4_fsblk_t ext4_inode_to_goal_block(struct inode *);
 
 #if IS_ENABLED(CONFIG_UNICODE)
 extern int ext4_fname_setup_ci_filename(struct inode *dir,
-					 const struct qstr *iname,
-					 struct ext4_filename *fname);
+					const struct qstr *iname,
+					struct ext4_filename *fname);
+
+static inline void ext4_fname_free_ci_filename(struct ext4_filename *fname)
+{
+	kfree(fname->cf_name.name);
+	fname->cf_name.name = NULL;
+}
+#else
+static inline int ext4_fname_setup_ci_filename(struct inode *dir,
+					       const struct qstr *iname,
+					       struct ext4_filename *fname)
+{
+	return 0;
+}
+
+static inline void ext4_fname_free_ci_filename(struct ext4_filename *fname)
+{
+}
 #endif
 
 /* ext4 encryption related stuff goes here crypto.c */
@@ -2769,16 +2786,11 @@ 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;
 
-#if IS_ENABLED(CONFIG_UNICODE)
-	err = ext4_fname_setup_ci_filename(dir, iname, fname);
-#endif
-
-	return err;
+	return ext4_fname_setup_ci_filename(dir, iname, fname);
 }
 
 static inline int ext4_fname_prepare_lookup(struct inode *dir,
@@ -2790,10 +2802,7 @@ static inline int ext4_fname_prepare_lookup(struct inode *dir,
 
 static inline void ext4_fname_free_filename(struct ext4_filename *fname)
 {
-#if IS_ENABLED(CONFIG_UNICODE)
-	kfree(fname->cf_name.name);
-	fname->cf_name.name = NULL;
-#endif
+	ext4_fname_free_ci_filename(fname);
 }
 
 static inline int ext4_ioctl_get_encryption_pwsalt(struct file *filp,

fs/ext4/namei.c

@@ -1390,62 +1390,11 @@ static void dx_insert_block(struct dx_frame *frame, u32 hash, ext4_lblk_t block)
 }
 
 #if IS_ENABLED(CONFIG_UNICODE)
-/*
- * Test whether a case-insensitive directory entry matches the filename
- * 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.
- */
-static int ext4_ci_compare(const struct inode *parent, const struct qstr *name,
-			   u8 *de_name, size_t de_name_len, bool quick)
-{
-	const struct super_block *sb = parent->i_sb;
-	const struct unicode_map *um = sb->s_encoding;
-	struct fscrypt_str decrypted_name = FSTR_INIT(NULL, de_name_len);
-	struct qstr entry = QSTR_INIT(de_name, de_name_len);
-	int ret;
-
-	if (IS_ENCRYPTED(parent)) {
-		const struct fscrypt_str encrypted_name =
-				FSTR_INIT(de_name, de_name_len);
-
-		decrypted_name.name = kmalloc(de_name_len, GFP_KERNEL);
-		if (!decrypted_name.name)
-			return -ENOMEM;
-		ret = fscrypt_fname_disk_to_usr(parent, 0, 0, &encrypted_name,
-						&decrypted_name);
-		if (ret < 0)
-			goto out;
-		entry.name = decrypted_name.name;
-		entry.len = decrypted_name.len;
-	}
-
-	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.
-		 */
-		if (sb_has_strict_encoding(sb))
-			ret = -EINVAL;
-		else if (name->len != entry.len)
-			ret = 1;
-		else
-			ret = !!memcmp(name->name, entry.name, entry.len);
-	}
-out:
-	kfree(decrypted_name.name);
-	return ret;
-}
-
 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 qstr *cf_name = &name->cf_name;
+	unsigned char *buf;
 	struct dx_hash_info *hinfo = &name->hinfo;
 	int len;
 
@@ -1455,18 +1404,18 @@ int ext4_fname_setup_ci_filename(struct inode *dir, const struct qstr *iname,
 		return 0;
 	}
 
-	cf_name->name = kmalloc(EXT4_NAME_LEN, GFP_NOFS);
-	if (!cf_name->name)
+	buf = kmalloc(EXT4_NAME_LEN, GFP_NOFS);
+	if (!buf)
 		return -ENOMEM;
 
-	len = utf8_casefold(dir->i_sb->s_encoding,
-			    iname, cf_name->name,
-			    EXT4_NAME_LEN);
+	len = utf8_casefold(dir->i_sb->s_encoding, iname, buf, EXT4_NAME_LEN);
 	if (len <= 0) {
-		kfree(cf_name->name);
-		cf_name->name = NULL;
+		kfree(buf);
+		buf = NULL;
 	}
+	cf_name->name = buf;
 	cf_name->len = (unsigned) len;
+
 	if (!IS_ENCRYPTED(dir))
 		return 0;
 
@@ -1502,22 +1451,29 @@ static bool ext4_match(struct inode *parent,
 #if IS_ENABLED(CONFIG_UNICODE)
 	if (IS_CASEFOLDED(parent) &&
 	    (!IS_ENCRYPTED(parent) || fscrypt_has_encryption_key(parent))) {
-		if (fname->cf_name.name) {
-			struct qstr cf = {.name = fname->cf_name.name,
-					  .len = fname->cf_name.len};
-			if (IS_ENCRYPTED(parent)) {
-				if (fname->hinfo.hash != EXT4_DIRENT_HASH(de) ||
-					fname->hinfo.minor_hash !=
-						EXT4_DIRENT_MINOR_HASH(de)) {
-
-					return false;
-				}
-			}
-			return !ext4_ci_compare(parent, &cf, de->name,
-							de->name_len, true);
-		}
-		return !ext4_ci_compare(parent, fname->usr_fname, de->name,
-						de->name_len, false);
+		/*
+		 * Just checking IS_ENCRYPTED(parent) below is not
+		 * sufficient to decide whether one can use the hash for
+		 * skipping the string comparison, because the key might
+		 * have been added right after
+		 * ext4_fname_setup_ci_filename().  In this case, a hash
+		 * mismatch will be a false negative.  Therefore, make
+		 * sure cf_name was properly initialized before
+		 * considering the calculated hash.
+		 */
+		if (IS_ENCRYPTED(parent) && fname->cf_name.name &&
+		    (fname->hinfo.hash != EXT4_DIRENT_HASH(de) ||
+		     fname->hinfo.minor_hash != EXT4_DIRENT_MINOR_HASH(de)))
+			return false;
+		/*
+		 * Treat comparison errors as not a match.  The
+		 * only case where it happens is on a disk
+		 * corruption or ENOMEM.
+		 */
+
+		return generic_ci_match(parent, fname->usr_fname,
+					&fname->cf_name, de->name,
+					de->name_len) > 0;
 	}
 #endif
 
@@ -1869,8 +1825,7 @@ static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, unsi
 		}
 	}
 
-#if IS_ENABLED(CONFIG_UNICODE)
-	if (!inode && IS_CASEFOLDED(dir)) {
+	if (IS_ENABLED(CONFIG_UNICODE) && !inode && IS_CASEFOLDED(dir)) {
 		/* Eventually we want to call d_add_ci(dentry, NULL)
 		 * for negative dentries in the encoding case as
 		 * well.  For now, prevent the negative dentry
@@ -1878,7 +1833,7 @@ static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, unsi
 		 */
 		return NULL;
 	}
-#endif
+
 	return d_splice_alias(inode, dentry);
 }
 
@@ -3208,16 +3163,14 @@ static int ext4_rmdir(struct inode *dir, struct dentry *dentry)
 	ext4_fc_track_unlink(handle, dentry);
 	retval = ext4_mark_inode_dirty(handle, dir);
 
-#if IS_ENABLED(CONFIG_UNICODE)
 	/* VFS negative dentries are incompatible with Encoding and
 	 * Case-insensitiveness. Eventually we'll want avoid
 	 * invalidating the dentries here, alongside with returning the
 	 * negative dentries at ext4_lookup(), when it is better
 	 * supported by the VFS for the CI case.
 	 */
-	if (IS_CASEFOLDED(dir))
+	if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir))
 		d_invalidate(dentry);
-#endif
 
 end_rmdir:
 	brelse(bh);
@@ -3319,16 +3272,15 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry)
 		goto out_trace;
 
 	retval = __ext4_unlink(dir, &dentry->d_name, d_inode(dentry), dentry);
-#if IS_ENABLED(CONFIG_UNICODE)
+
 	/* VFS negative dentries are incompatible with Encoding and
 	 * Case-insensitiveness. Eventually we'll want avoid
 	 * invalidating the dentries here, alongside with returning the
 	 * negative dentries at ext4_lookup(), when it is  better
 	 * supported by the VFS for the CI case.
 	 */
-	if (IS_CASEFOLDED(dir))
+	if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir))
 		d_invalidate(dentry);
-#endif
 
 out_trace:
 	trace_ext4_unlink_exit(dentry, retval);

fs/ext4/super.c

@@ -3586,14 +3586,12 @@ int ext4_feature_set_ok(struct super_block *sb, int readonly)
 		return 0;
 	}
 
-#if !IS_ENABLED(CONFIG_UNICODE)
-	if (ext4_has_feature_casefold(sb)) {
+	if (!IS_ENABLED(CONFIG_UNICODE) && ext4_has_feature_casefold(sb)) {
 		ext4_msg(sb, KERN_ERR,
 			 "Filesystem with casefold feature cannot be "
 			 "mounted without CONFIG_UNICODE");
 		return 0;
 	}
-#endif
 
 	if (readonly)
 		return 1;

fs/f2fs/dir.c

@@ -42,35 +42,49 @@ static unsigned int bucket_blocks(unsigned int level)
 		return 4;
 }
 
+#if IS_ENABLED(CONFIG_UNICODE)
 /* If @dir is casefolded, initialize @fname->cf_name from @fname->usr_fname. */
 int f2fs_init_casefolded_name(const struct inode *dir,
 			      struct f2fs_filename *fname)
 {
-#if IS_ENABLED(CONFIG_UNICODE)
 	struct super_block *sb = dir->i_sb;
+	unsigned char *buf;
+	int len;
 
 	if (IS_CASEFOLDED(dir) &&
 	    !is_dot_dotdot(fname->usr_fname->name, fname->usr_fname->len)) {
-		fname->cf_name.name = f2fs_kmem_cache_alloc(f2fs_cf_name_slab,
-					GFP_NOFS, false, F2FS_SB(sb));
-		if (!fname->cf_name.name)
+		buf = f2fs_kmem_cache_alloc(f2fs_cf_name_slab,
+					    GFP_NOFS, false, F2FS_SB(sb));
+		if (!buf)
 			return -ENOMEM;
-		fname->cf_name.len = utf8_casefold(sb->s_encoding,
-						   fname->usr_fname,
-						   fname->cf_name.name,
-						   F2FS_NAME_LEN);
-		if ((int)fname->cf_name.len <= 0) {
-			kmem_cache_free(f2fs_cf_name_slab, fname->cf_name.name);
-			fname->cf_name.name = NULL;
+
+		len = utf8_casefold(sb->s_encoding, fname->usr_fname,
+				    buf, F2FS_NAME_LEN);
+		if (len <= 0) {
+			kmem_cache_free(f2fs_cf_name_slab, buf);
 			if (sb_has_strict_encoding(sb))
 				return -EINVAL;
 			/* fall back to treating name as opaque byte sequence */
+			return 0;
 		}
+		fname->cf_name.name = buf;
+		fname->cf_name.len = len;
 	}
-#endif
+
 	return 0;
 }
 
+void f2fs_free_casefolded_name(struct f2fs_filename *fname)
+{
+	unsigned char *buf = (unsigned char *)fname->cf_name.name;
+
+	if (buf) {
+		kmem_cache_free(f2fs_cf_name_slab, buf);
+		fname->cf_name.name = NULL;
+	}
+}
+#endif /* CONFIG_UNICODE */
+
 static int __f2fs_setup_filename(const struct inode *dir,
 				 const struct fscrypt_name *crypt_name,
 				 struct f2fs_filename *fname)
@@ -142,12 +156,7 @@ void f2fs_free_filename(struct f2fs_filename *fname)
 	kfree(fname->crypto_buf.name);
 	fname->crypto_buf.name = NULL;
 #endif
-#if IS_ENABLED(CONFIG_UNICODE)
-	if (fname->cf_name.name) {
-		kmem_cache_free(f2fs_cf_name_slab, fname->cf_name.name);
-		fname->cf_name.name = NULL;
-	}
-#endif
+	f2fs_free_casefolded_name(fname);
 }
 
 static unsigned long dir_block_index(unsigned int level,
@@ -176,58 +185,6 @@ static struct f2fs_dir_entry *find_in_block(struct inode *dir,
 	return f2fs_find_target_dentry(&d, fname, max_slots);
 }
 
-#if IS_ENABLED(CONFIG_UNICODE)
-/*
- * Test whether a case-insensitive directory entry matches the filename
- * being searched for.
- *
- * Returns 1 for a match, 0 for no match, and -errno on an error.
- */
-static int f2fs_match_ci_name(const struct inode *dir, const struct qstr *name,
-			       const u8 *de_name, u32 de_name_len)
-{
-	const struct super_block *sb = dir->i_sb;
-	const struct unicode_map *um = sb->s_encoding;
-	struct fscrypt_str decrypted_name = FSTR_INIT(NULL, de_name_len);
-	struct qstr entry = QSTR_INIT(de_name, de_name_len);
-	int res;
-
-	if (IS_ENCRYPTED(dir)) {
-		const struct fscrypt_str encrypted_name =
-			FSTR_INIT((u8 *)de_name, de_name_len);
-
-		if (WARN_ON_ONCE(!fscrypt_has_encryption_key(dir)))
-			return -EINVAL;
-
-		decrypted_name.name = kmalloc(de_name_len, GFP_KERNEL);
-		if (!decrypted_name.name)
-			return -ENOMEM;
-		res = fscrypt_fname_disk_to_usr(dir, 0, 0, &encrypted_name,
-						&decrypted_name);
-		if (res < 0)
-			goto out;
-		entry.name = decrypted_name.name;
-		entry.len = decrypted_name.len;
-	}
-
-	res = utf8_strncasecmp_folded(um, name, &entry);
-	/*
-	 * In strict mode, ignore invalid names.  In non-strict mode,
-	 * fall back to treating them as opaque byte sequences.
-	 */
-	if (res < 0 && !sb_has_strict_encoding(sb)) {
-		res = name->len == entry.len &&
-				memcmp(name->name, entry.name, name->len) == 0;
-	} else {
-		/* utf8_strncasecmp_folded returns 0 on match */
-		res = (res == 0);
-	}
-out:
-	kfree(decrypted_name.name);
-	return res;
-}
-#endif /* CONFIG_UNICODE */
-
 static inline int f2fs_match_name(const struct inode *dir,
 				   const struct f2fs_filename *fname,
 				   const u8 *de_name, u32 de_name_len)
@@ -235,11 +192,11 @@ static inline int f2fs_match_name(const struct inode *dir,
 	struct fscrypt_name f;
 
 #if IS_ENABLED(CONFIG_UNICODE)
-	if (fname->cf_name.name) {
-		struct qstr cf = FSTR_TO_QSTR(&fname->cf_name);
+	if (fname->cf_name.name)
+		return generic_ci_match(dir, fname->usr_fname,
+					&fname->cf_name,
+					de_name, de_name_len);
 
-		return f2fs_match_ci_name(dir, &cf, de_name, de_name_len);
-	}
 #endif
 	f.usr_fname = fname->usr_fname;
 	f.disk_name = fname->disk_name;

fs/f2fs/f2fs.h

@@ -531,7 +531,7 @@ struct f2fs_filename {
 	 * internal operation where usr_fname is also NULL.  In all these cases
 	 * we fall back to treating the name as an opaque byte sequence.
 	 */
-	struct fscrypt_str cf_name;
+	struct qstr cf_name;
 #endif
 };
 
@@ -3533,8 +3533,22 @@ int f2fs_get_tmpfile(struct mnt_idmap *idmap, struct inode *dir,
 /*
  * dir.c
  */
+#if IS_ENABLED(CONFIG_UNICODE)
 int f2fs_init_casefolded_name(const struct inode *dir,
 			      struct f2fs_filename *fname);
+void f2fs_free_casefolded_name(struct f2fs_filename *fname);
+#else
+static inline int f2fs_init_casefolded_name(const struct inode *dir,
+					    struct f2fs_filename *fname)
+{
+	return 0;
+}
+
+static inline void f2fs_free_casefolded_name(struct f2fs_filename *fname)
+{
+}
+#endif /* CONFIG_UNICODE */
+
 int f2fs_setup_filename(struct inode *dir, const struct qstr *iname,
 			int lookup, struct f2fs_filename *fname);
 int f2fs_prepare_lookup(struct inode *dir, struct dentry *dentry,

fs/f2fs/namei.c

@@ -576,8 +576,7 @@ static struct dentry *f2fs_lookup(struct inode *dir, struct dentry *dentry,
 		goto out_iput;
 	}
 out_splice:
-#if IS_ENABLED(CONFIG_UNICODE)
-	if (!inode && IS_CASEFOLDED(dir)) {
+	if (IS_ENABLED(CONFIG_UNICODE) && !inode && IS_CASEFOLDED(dir)) {
 		/* Eventually we want to call d_add_ci(dentry, NULL)
 		 * for negative dentries in the encoding case as
 		 * well.  For now, prevent the negative dentry
@@ -586,7 +585,7 @@ static struct dentry *f2fs_lookup(struct inode *dir, struct dentry *dentry,
 		trace_f2fs_lookup_end(dir, dentry, ino, err);
 		return NULL;
 	}
-#endif
+
 	new = d_splice_alias(inode, dentry);
 	trace_f2fs_lookup_end(dir, !IS_ERR_OR_NULL(new) ? new : dentry,
 				ino, IS_ERR(new) ? PTR_ERR(new) : err);
@@ -639,16 +638,15 @@ static int f2fs_unlink(struct inode *dir, struct dentry *dentry)
 	f2fs_delete_entry(de, page, dir, inode);
 	f2fs_unlock_op(sbi);
 
-#if IS_ENABLED(CONFIG_UNICODE)
 	/* VFS negative dentries are incompatible with Encoding and
 	 * Case-insensitiveness. Eventually we'll want avoid
 	 * invalidating the dentries here, alongside with returning the
 	 * negative dentries at f2fs_lookup(), when it is better
 	 * supported by the VFS for the CI case.
 	 */
-	if (IS_CASEFOLDED(dir))
+	if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir))
 		d_invalidate(dentry);
-#endif
+
 	if (IS_DIRSYNC(dir))
 		f2fs_sync_fs(sbi->sb, 1);
 fail:

fs/f2fs/recovery.c

@@ -46,10 +46,6 @@
 
 static struct kmem_cache *fsync_entry_slab;
 
-#if IS_ENABLED(CONFIG_UNICODE)
-extern struct kmem_cache *f2fs_cf_name_slab;
-#endif
-
 bool f2fs_space_for_roll_forward(struct f2fs_sb_info *sbi)
 {
 	s64 nalloc = percpu_counter_sum_positive(&sbi->alloc_valid_block_count);
@@ -153,11 +149,8 @@ static int init_recovered_filename(const struct inode *dir,
 		if (err)
 			return err;
 		f2fs_hash_filename(dir, fname);
-#if IS_ENABLED(CONFIG_UNICODE)
 		/* Case-sensitive match is fine for recovery */
-		kmem_cache_free(f2fs_cf_name_slab, fname->cf_name.name);
-		fname->cf_name.name = NULL;
-#endif
+		f2fs_free_casefolded_name(fname);
 	} else {
 		f2fs_hash_filename(dir, fname);
 	}

fs/f2fs/super.c

@@ -321,7 +321,7 @@ struct kmem_cache *f2fs_cf_name_slab;
 static int __init f2fs_create_casefold_cache(void)
 {
 	f2fs_cf_name_slab = f2fs_kmem_cache_create("f2fs_casefolded_name",
-							F2FS_NAME_LEN);
+						   F2FS_NAME_LEN);
 	return f2fs_cf_name_slab ? 0 : -ENOMEM;
 }
 
@@ -1326,13 +1326,13 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
 		return -EINVAL;
 	}
 #endif
-#if !IS_ENABLED(CONFIG_UNICODE)
-	if (f2fs_sb_has_casefold(sbi)) {
+
+	if (!IS_ENABLED(CONFIG_UNICODE) && f2fs_sb_has_casefold(sbi)) {
 		f2fs_err(sbi,
 			"Filesystem with casefold feature cannot be mounted without CONFIG_UNICODE");
 		return -EINVAL;
 	}
-#endif
+
 	/*
 	 * The BLKZONED feature indicates that the drive was formatted with
 	 * zone alignment optimization. This is optional for host-aware

fs/libfs.c

@@ -1854,6 +1854,80 @@ static const struct dentry_operations generic_ci_dentry_ops = {
 	.d_revalidate = fscrypt_d_revalidate,
 #endif
 };
+
+/**
+ * generic_ci_match() - Match a name (case-insensitively) with a dirent.
+ * This is a filesystem helper for comparison with directory entries.
+ * generic_ci_d_compare should be used in VFS' ->d_compare instead.
+ *
+ * @parent: Inode of the parent of the dirent under comparison
+ * @name: name under lookup.
+ * @folded_name: Optional pre-folded name under lookup
+ * @de_name: Dirent name.
+ * @de_name_len: dirent name length.
+ *
+ * Test whether a case-insensitive directory entry matches the filename
+ * being searched.  If @folded_name is provided, it is used instead of
+ * recalculating the casefold of @name.
+ *
+ * Return: > 0 if the directory entry matches, 0 if it doesn't match, or
+ * < 0 on error.
+ */
+int generic_ci_match(const struct inode *parent,
+		     const struct qstr *name,
+		     const struct qstr *folded_name,
+		     const u8 *de_name, u32 de_name_len)
+{
+	const struct super_block *sb = parent->i_sb;
+	const struct unicode_map *um = sb->s_encoding;
+	struct fscrypt_str decrypted_name = FSTR_INIT(NULL, de_name_len);
+	struct qstr dirent = QSTR_INIT(de_name, de_name_len);
+	int res = 0;
+
+	if (IS_ENCRYPTED(parent)) {
+		const struct fscrypt_str encrypted_name =
+			FSTR_INIT((u8 *) de_name, de_name_len);
+
+		if (WARN_ON_ONCE(!fscrypt_has_encryption_key(parent)))
+			return -EINVAL;
+
+		decrypted_name.name = kmalloc(de_name_len, GFP_KERNEL);
+		if (!decrypted_name.name)
+			return -ENOMEM;
+		res = fscrypt_fname_disk_to_usr(parent, 0, 0, &encrypted_name,
+						&decrypted_name);
+		if (res < 0) {
+			kfree(decrypted_name.name);
+			return res;
+		}
+		dirent.name = decrypted_name.name;
+		dirent.len = decrypted_name.len;
+	}
+
+	/*
+	 * Attempt a case-sensitive match first. It is cheaper and
+	 * should cover most lookups, including all the sane
+	 * applications that expect a case-sensitive filesystem.
+	 */
+
+	if (dirent.len == name->len &&
+	    !memcmp(name->name, dirent.name, dirent.len))
+		goto out;
+
+	if (folded_name->name)
+		res = utf8_strncasecmp_folded(um, folded_name, &dirent);
+	else
+		res = utf8_strncasecmp(um, name, &dirent);
+
+out:
+	kfree(decrypted_name.name);
+	if (res < 0 && sb_has_strict_encoding(sb)) {
+		pr_err_ratelimited("Directory contains filename that is invalid UTF-8");
+		return 0;
+	}
+	return !res;
+}
+EXPORT_SYMBOL(generic_ci_match);
 #endif
 
 #ifdef CONFIG_FS_ENCRYPTION

include/linux/fs.h

@@ -3369,6 +3369,10 @@ extern int generic_file_fsync(struct file *, loff_t, loff_t, int);
 extern int generic_check_addressable(unsigned, u64);
 
 extern void generic_set_sb_d_ops(struct super_block *sb);
+extern int generic_ci_match(const struct inode *parent,
+			    const struct qstr *name,
+			    const struct qstr *folded_name,
+			    const u8 *de_name, u32 de_name_len);
 
 static inline bool sb_has_encoding(const struct super_block *sb)
 {