[PATCH 1/2] fs: make file_dentry() a simple accessor

[Amir Goldstein <amir73il@gmail.com>]

file_dentry() is a relic from the days that overlayfs was using files with
a "fake" path, meaning, f_path on overlayfs and f_inode on underlying fs.

In those days, file_dentry() was needed to get the underlying fs dentry
that matches f_inode.

Files with "fake" path should not exist nowadays, so make file_dentry() a
simple accessor and use an assertion to make sure that file_dentry() was
not papering over filesystem bugs.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 include/linux/fs.h | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 023f37c60709..de9aa86d2624 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1078,9 +1078,20 @@ static inline struct inode *file_inode(const struct file *f)
 	return f->f_inode;
 }
 
+/*
+ * file_dentry() is a relic from the days that overlayfs was using files with a
+ * "fake" path, meaning, f_path on overlayfs and f_inode on underlying fs.
+ * In those days, file_dentry() was needed to get the underlying fs dentry that
+ * matches f_inode.
+ * Files with "fake" path should not exist nowadays, so use an assertion to make
+ * sure that file_dentry() was not papering over filesystem bugs.
+ */
 static inline struct dentry *file_dentry(const struct file *file)
 {
-	return d_real(file->f_path.dentry, file_inode(file));
+	struct dentry *dentry = file->f_path.dentry;
+
+	WARN_ON_ONCE(d_inode(dentry) != file_inode(file));
+	return dentry;
 }
 
 struct fasync_struct {
-- 
2.34.1