Re: [RFC PATCH 2/4] NFSD: Never return NFS4ERR_FILE_OPEN when removing a directory

Jeff Layton
2025-01-23T20:43:41Z

On Thu, 2025-01-23 at 14:52 -0500, cel@kernel.org wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
>
> RFC 8881 Section 18.25.4 paragraph 5 tells us that the server
> should return NFS4ERR_FILE_OPEN only if the target object is an
> opened file. This suggests that returning this status when removing
> a directory will confuse NFS clients.
>
> This is a version-specific issue; nfsd_proc_remove/rmdir() and
> nfsd3_proc_remove/rmdir() already return nfserr_access as
> appropriate.
>
> Unfortunately there is no quick way for nfsd4_remove() to determine
> whether the target object is a file or not, so the check is done in
> to nfsd_unlink() for now.
>
> Reported-by: Trond Myklebust <trondmy@hammerspace.com>
> Fixes: 466e16f0920f ("nfsd: check for EBUSY from vfs_rmdir/vfs_unink.")
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
> fs/nfsd/vfs.c | 24 ++++++++++++++++++------
> 1 file changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 2d8e27c225f9..3ead7fb3bf04 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -1931,9 +1931,17 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
> return err;
> }
>
> -/*
> - * Unlink a file or directory
> - * N.B. After this call fhp needs an fh_put
> +/**
> + * nfsd_unlink - remove a directory entry
> + * @rqstp: RPC transaction context
> + * @fhp: the file handle of the parent directory to be modified
> + * @type: enforced file type of the object to be removed
> + * @fname: the name of directory entry to be removed
> + * @flen: length of @fname in octets
> + *
> + * After this call fhp needs an fh_put.
> + *
> + * Returns a generic NFS status code in network byte-order.
> */
> __be32
> nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
> @@ -2007,10 +2015,14 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
> fh_drop_write(fhp);
> out_nfserr:
> if (host_err == -EBUSY) {
> - /* name is mounted-on. There is no perfect
> - * error status.
> + /*
> + * See RFC 8881 Section 18.25.4 para 4: NFSv4 REMOVE
> + * distinguishes between reg file and dir.
> */
> - err = nfserr_file_open;
> + if (type != S_IFDIR)

Should that be "if (type == S_ISREG)" instead? What if the inode is a
named pipe or device file? I'm not sure you can ever get EBUSY with
those, but in case you can, what's the right error in those cases?

> + err = nfserr_file_open;
> + else
> + err = nfserr_acces;
> }
> out:
> return err != nfs_ok ? err : nfserrno(host_err);

--
Jeff Layton <jlayton@kernel.org>