[PATCH v2 2/8] unicode: Create utf8_check_strict_name

["André Almeida" <andrealmeid@igalia.com>]

Create a helper function for filesystems do the checks required for
casefold directories and strict enconding.

Suggested-by: Gabriel Krisman Bertazi <gabriel@krisman.be>
Signed-off-by: André Almeida <andrealmeid@igalia.com>
---
 fs/unicode/utf8-core.c  | 26 ++++++++++++++++++++++++++
 include/linux/unicode.h |  2 ++
 2 files changed, 28 insertions(+)

diff --git a/fs/unicode/utf8-core.c b/fs/unicode/utf8-core.c
index 0400824ef493..4966e175ed71 100644
--- a/fs/unicode/utf8-core.c
+++ b/fs/unicode/utf8-core.c
@@ -214,3 +214,29 @@ void utf8_unload(struct unicode_map *um)
 }
 EXPORT_SYMBOL(utf8_unload);
 
+/**
+ * utf8_check_strict_name - Check if a given name is suitable for a directory
+ *
+ * This functions checks if the proposed filename is suitable for the parent
+ * directory. That means that only valid UTF-8 filenames will be accepted for
+ * casefold directories from filesystems created with the strict enconding flags.
+ * That also means that any name will be accepted for directories that doesn't
+ * have casefold enabled, or aren't being strict with the enconding.
+ *
+ * @inode: inode of the directory where the new file will be created
+ * @d_name: name of the new file
+ *
+ * Returns:
+ *  * True if the filename is suitable for this directory. It can be true if a
+ *  given name is not suitable for a strict enconding directory, but the
+ *  directory being used isn't strict
+ *  * False if the filename isn't suitable for this directory. This only happens
+ *  when a directory is casefolded and is strict about its encoding.
+ */
+bool utf8_check_strict_name(struct inode *dir, struct qstr *d_name)
+{
+	return !(IS_CASEFOLDED(dir) && dir->i_sb->s_encoding &&
+	       sb_has_strict_encoding(dir->i_sb) &&
+	       utf8_validate(dir->i_sb->s_encoding, d_name));
+}
+EXPORT_SYMBOL(utf8_check_strict_name);
diff --git a/include/linux/unicode.h b/include/linux/unicode.h
index 4d39e6e11a95..fb56fb5e686c 100644
--- a/include/linux/unicode.h
+++ b/include/linux/unicode.h
@@ -76,4 +76,6 @@ int utf8_casefold_hash(const struct unicode_map *um, const void *salt,
 struct unicode_map *utf8_load(unsigned int version);
 void utf8_unload(struct unicode_map *um);
 
+bool utf8_check_strict_name(struct inode *dir, struct qstr *d_name);
+
 #endif /* _LINUX_UNICODE_H */
-- 
2.46.0