From: Lorenz Bauer <lmb@cloudflare.com>
Date: Thu, 28 Oct 2021 10:47:22 +0100
Subject: libfs: Support RENAME_EXCHANGE in simple_rename()
Patch-mainline: v5.16-rc1
Git-commit: 3871cb8cf741dcd8ebaec4f960be9479da2f176b
References: jsc#PED-1377
Allow atomic exchange via RENAME_EXCHANGE when using simple_rename.
This affects binderfs, ramfs, hubetlbfs and bpffs.
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/bpf/20211028094724.59043-3-lmb@cloudflare.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
fs/libfs.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -479,9 +479,12 @@ int simple_rename(struct user_namespace
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;