linux-kernel - [PATCH bpf-next v3 2/4] libfs: support RENAME_EXCHANGE in simple

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Date:   Thu, 28 Oct 2021 10:47:22 +0100
From:   Lorenz Bauer <lmb@...udflare.com>
To:     viro@...iv.linux.org.uk, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
Cc:     mszeredi@...hat.com, gregkh@...uxfoundation.org,
        Lorenz Bauer <lmb@...udflare.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH bpf-next v3 2/4] 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 <lmb@...udflare.com>
---
 fs/libfs.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/libfs.c b/fs/libfs.c
index 1cf144dc9ed2..ba7438ab9371 100644
--- 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;
 
-- 
2.32.0