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

Amir Goldstein
2025-01-24T10:42:56Z

On Thu, Jan 23, 2025 at 10:07 PM Chuck Lever <chuck.lever@oracle.com> wrote:
>
> On 1/23/25 3:43 PM, Jeff Layton wrote:
> > 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?
>
> Check out nfsd_unlink()'s callers to see what they pass as the type
> parameter. Unfortunately we have to compare against S_IFDIR here.
>

Not exactly. nfsd4_remove() is the only caller that needs to get
nfserr_file_open and this caller calls with type = 0, so type here
is going to be the actual type of the inode and (type == S_ISREG)
would be correct. No?

Thanks,
Amir.