libfs: Support RENAME_EXCHANGE in simple_rename()

Allow atomic exchange via RENAME_EXCHANGE when using simple_rename. This affects binderfs, ramfs, hubetlbfs and bpffs. Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Daniel Borkmann <[email protected]> Acked-by: Christian Brauner <[email protected]> Cc: Al Viro <[email protected]> Cc: Miklos Szeredi <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
niw · Nov 3, 2021 · 3871cb8 · 3871cb8
1 parent 6429e46
commit 3871cb8
Showing 1 changed file with 4 additions and 1 deletion.
diff --git a/fs/libfs.c b/fs/libfs.c
@@ -479,9 +479,12 @@ int simple_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
 	struct inode *inode = d_inode(old_dentry);
 	int they_are_dirs = d_is_dir(old_dentry);
 
-	if (flags & ~RENAME_NOREPLACE)
+	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
 		return -EINVAL;
 
+	if (flags & RENAME_EXCHANGE)
+		return simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
+
 	if (!simple_empty(new_dentry))
 		return -ENOTEMPTY;