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

[Chuck Lever <chuck.lever@oracle.com>]

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.


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


-- 
Chuck Lever