[PATCH v5 01/10] fs: Expose helper to check if a directory needs casefolding

[Gabriel Krisman Bertazi <krisman@xxxxxxx>]

In preparation to use it in ecryptfs, move needs_casefolding into a
public header and give it a namespaced name.

Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxx>
---
 fs/libfs.c         | 14 ++------------
 include/linux/fs.h | 21 +++++++++++++++++++++
 2 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/fs/libfs.c b/fs/libfs.c
index 5b851315eeed..8d0b64cfd5da 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -1381,16 +1381,6 @@ bool is_empty_dir_inode(struct inode *inode)
 }
 
 #if IS_ENABLED(CONFIG_UNICODE)
-/*
- * Determine if the name of a dentry should be casefolded.
- *
- * Return: if names will need casefolding
- */
-static bool needs_casefold(const struct inode *dir)
-{
-	return IS_CASEFOLDED(dir) && dir->i_sb->s_encoding;
-}
-
 /**
  * generic_ci_d_compare - generic d_compare implementation for casefolding filesystems
  * @dentry:	dentry whose name we are checking against
@@ -1411,7 +1401,7 @@ static int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
 	char strbuf[DNAME_INLINE_LEN];
 	int ret;
 
-	if (!dir || !needs_casefold(dir))
+	if (!dir || !dir_is_casefolded(dir))
 		goto fallback;
 	/*
 	 * If the dentry name is stored in-line, then it may be concurrently
@@ -1453,7 +1443,7 @@ static int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
 	const struct unicode_map *um = sb->s_encoding;
 	int ret = 0;
 
-	if (!dir || !needs_casefold(dir))
+	if (!dir || !dir_is_casefolded(dir))
 		return 0;
 
 	ret = utf8_casefold_hash(um, dentry, str);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6867512907d6..e3b631c6d24a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3213,6 +3213,27 @@ static inline bool dir_relax_shared(struct inode *inode)
 	return !IS_DEADDIR(inode);
 }
 
+/**
+ * dir_is_casefolded - Safely determine if filenames inside of a
+ * directory should be casefolded.
+ * @dir: The directory inode to be checked
+ *
+ * Filesystems should usually rely on this instead of checking the
+ * S_CASEFOLD flag directly when handling inodes, to avoid surprises
+ * with corrupted volumes.  Checking i_sb->s_encoding ensures the
+ * filesystem knows how to deal with case-insensitiveness.
+ *
+ * Return: if names will need casefolding
+ */
+static inline bool dir_is_casefolded(const struct inode *dir)
+{
+#if IS_ENABLED(CONFIG_UNICODE)
+	return IS_CASEFOLDED(dir) && dir->i_sb->s_encoding;
+#else
+	return false;
+#endif
+}
+
 extern bool path_noexec(const struct path *path);
 extern void inode_nohighmem(struct inode *inode);
 
-- 
2.41.0