vfs: export check_sticky()

It's already duplicated in btrfs and about to be used in overlayfs too.

Move the sticky bit check to an inline helper and call the out-of-line
helper only in the unlikly case of the sticky bit being set.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 5419df70a835..55cc0a319baa 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2259,6 +2259,7 @@ extern int notify_change(struct dentry *, struct iattr *, struct inode **);
 extern int inode_permission(struct inode *, int);
 extern int __inode_permission(struct inode *, int);
 extern int generic_permission(struct inode *, int);
+extern int __check_sticky(struct inode *dir, struct inode *inode);
 
 static inline bool execute_ok(struct inode *inode)
 {
@@ -2745,6 +2746,14 @@ static inline int is_sxid(umode_t mode)
         return (mode & S_ISUID) || ((mode & S_ISGID) && (mode & S_IXGRP));
 }
 
+static inline int check_sticky(struct inode *dir, struct inode *inode)
+{
+        if (!(dir->i_mode & S_ISVTX))
+                return 0;
+
+        return __check_sticky(dir, inode);
+}
+
 static inline void inode_has_no_xattr(struct inode *inode)
 {
         if (!is_sxid(inode->i_mode) && (inode->i_sb->s_flags & MS_NOSEC))