From: Lorenz Bauer <lmb@cloudflare.com>
Date: Thu, 28 Oct 2021 10:47:21 +0100
Subject: libfs: Move shmem_exchange to simple_rename_exchange
Patch-mainline: v5.16-rc1
Git-commit: 6429e46304ac7820eebbea2bf5d73b90c18e0e06
References: jsc#PED-1377

Move shmem_exchange and make it available to other callers.

Suggested-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/bpf/20211028094724.59043-2-lmb@cloudflare.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 fs/libfs.c         |   24 ++++++++++++++++++++++++
 include/linux/fs.h |    2 ++
 mm/shmem.c         |   24 +-----------------------
 3 files changed, 27 insertions(+), 23 deletions(-)

--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -448,6 +448,30 @@ int simple_rmdir(struct inode *dir, stru
 }
 EXPORT_SYMBOL(simple_rmdir);
 
+int simple_rename_exchange(struct inode *old_dir, struct dentry *old_dentry,
+			   struct inode *new_dir, struct dentry *new_dentry)
+{
+	bool old_is_dir = d_is_dir(old_dentry);
+	bool new_is_dir = d_is_dir(new_dentry);
+
+	if (old_dir != new_dir && old_is_dir != new_is_dir) {
+		if (old_is_dir) {
+			drop_nlink(old_dir);
+			inc_nlink(new_dir);
+		} else {
+			drop_nlink(new_dir);
+			inc_nlink(old_dir);
+		}
+	}
+	old_dir->i_ctime = old_dir->i_mtime =
+	new_dir->i_ctime = new_dir->i_mtime =
+	d_inode(old_dentry)->i_ctime =
+	d_inode(new_dentry)->i_ctime = current_time(old_dir);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(simple_rename_exchange);
+
 int simple_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
 		  struct dentry *old_dentry, struct inode *new_dir,
 		  struct dentry *new_dentry, unsigned int flags)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3455,6 +3455,8 @@ extern int simple_open(struct inode *ino
 extern int simple_link(struct dentry *, struct inode *, struct dentry *);
 extern int simple_unlink(struct inode *, struct dentry *);
 extern int simple_rmdir(struct inode *, struct dentry *);
+extern int simple_rename_exchange(struct inode *old_dir, struct dentry *old_dentry,
+				  struct inode *new_dir, struct dentry *new_dentry);
 extern int simple_rename(struct user_namespace *, struct inode *,
 			 struct dentry *, struct inode *, struct dentry *,
 			 unsigned int);
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2960,28 +2960,6 @@ static int shmem_rmdir(struct inode *dir
 	return shmem_unlink(dir, dentry);
 }
 
-static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
-{
-	bool old_is_dir = d_is_dir(old_dentry);
-	bool new_is_dir = d_is_dir(new_dentry);
-
-	if (old_dir != new_dir && old_is_dir != new_is_dir) {
-		if (old_is_dir) {
-			drop_nlink(old_dir);
-			inc_nlink(new_dir);
-		} else {
-			drop_nlink(new_dir);
-			inc_nlink(old_dir);
-		}
-	}
-	old_dir->i_ctime = old_dir->i_mtime =
-	new_dir->i_ctime = new_dir->i_mtime =
-	d_inode(old_dentry)->i_ctime =
-	d_inode(new_dentry)->i_ctime = current_time(old_dir);
-
-	return 0;
-}
-
 static int shmem_whiteout(struct user_namespace *mnt_userns,
 			  struct inode *old_dir, struct dentry *old_dentry)
 {
@@ -3027,7 +3005,7 @@ static int shmem_rename2(struct user_nam
 		return -EINVAL;
 
 	if (flags & RENAME_EXCHANGE)
-		return shmem_exchange(old_dir, old_dentry, new_dir, new_dentry);
+		return simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
 
 	if (!simple_empty(new_dentry))
 		return -ENOTEMPTY;