Re: [PATCH] nfsd: map EBUSY for all operations

[Trond Myklebust <trondmy@hammerspace.com>]

On Mon, 2025-01-20 at 18:20 +0100, Amir Goldstein wrote:
> v4 client maps NFS4ERR_FILE_OPEN => EBUSY for all operations.
> 
> v4 server only maps EBUSY => NFS4ERR_FILE_OPEN for rmdir()/unlink()
> although it is also possible to get EBUSY from rename() for the same
> reason (victim is a local mount point).
> 
> Filesystems could return EBUSY for other operations, so just map it
> in server for all operations.
> 
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
> 
> Chuck,
> 
> I ran into this error with a FUSE filesystem and returns -EBUSY on
> open,
> but I noticed that vfs can also return EBUSY at least for rename().
> 
> Thanks,
> Amir.
> 
>  fs/nfsd/vfs.c | 10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 29cb7b812d713..a61f99c081894 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -100,6 +100,7 @@ nfserrno (int errno)
>  		{ nfserr_perm, -ENOKEY },
>  		{ nfserr_no_grace, -ENOGRACE},
>  		{ nfserr_io, -EBADMSG },
> +		{ nfserr_file_open, -EBUSY},
>  	};
>  	int	i;
>  
> @@ -2006,14 +2007,7 @@ nfsd_unlink(struct svc_rqst *rqstp, struct
> svc_fh *fhp, int type,
>  out_drop_write:
>  	fh_drop_write(fhp);
>  out_nfserr:
> -	if (host_err == -EBUSY) {
> -		/* name is mounted-on. There is no perfect
> -		 * error status.
> -		 */
> -		err = nfserr_file_open;
> -	} else {
> -		err = nfserrno(host_err);
> -	}
> +	err = nfserrno(host_err);
>  out:
>  	return err;
>  out_unlock:

If this is a transient error, then it would seem that NFS4ERR_DELAY
would be more appropriate. NFS4ERR_FILE_OPEN is not supposed to apply
to directories, and so clients would be very confused about how to
recover if you were to return it in this situation.

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com