Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Content-Type: text/plain;
        charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.4\))
Subject: Re: [PATCH v2 001/118] NFSD: Fix returned READDIR offset cookie
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <20201121005932.GD7705@fieldses.org>
Date:   Sat, 21 Nov 2020 11:15:54 -0500
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Content-Transfer-Encoding: 7bit
Message-Id: <771378A0-2051-4F9A-846E-91B132D698F2@oracle.com>
References: <160590425404.1340.8850646771948736468.stgit@klimt.1015granger.net>
 <160590443133.1340.6772360578279663543.stgit@klimt.1015granger.net>
 <20201121005932.GD7705@fieldses.org>
To:     Bruce Fields <bfields@fieldses.org>
Precedence: bulk


> On Nov 20, 2020, at 7:59 PM, bfields@fieldses.org wrote:
> 
> On Fri, Nov 20, 2020 at 03:33:51PM -0500, Chuck Lever wrote:
>> Code inspection shows that the server's NFSv3 READDIR implementation
>> returns the same offset cookie as the client sent, instead of the
>> last cookie it returns in the reply's dirlist. This is unlike the
>> NFSv2 READDIR, NFSv3 READDIRPLUS, and NFSv4 READDIR implementations,
>> and it's been like this since the beginning of kernel git history.
> 
> Surely this should have caused actual failures in practice.
> 
>> I copied the logic from nfsd3_proc_readdirplus().
>> 
>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
>> ---
>> fs/nfsd/nfs3proc.c |    7 ++++---
>> 1 file changed, 4 insertions(+), 3 deletions(-)
>> 
>> diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
>> index d9be589fed15..e0ad18d6b5a8 100644
>> --- a/fs/nfsd/nfs3proc.c
>> +++ b/fs/nfsd/nfs3proc.c
>> @@ -430,6 +430,7 @@ nfsd3_proc_readdir(struct svc_rqst *rqstp)
>> 	struct nfsd3_readdirargs *argp = rqstp->rq_argp;
>> 	struct nfsd3_readdirres  *resp = rqstp->rq_resp;
>> 	int		count = 0;
>> +	loff_t		offset;
>> 	struct page	**p;
>> 	caddr_t		page_addr = NULL;
>> 
>> @@ -448,7 +449,9 @@ nfsd3_proc_readdir(struct svc_rqst *rqstp)
>> 	resp->common.err = nfs_ok;
>> 	resp->buffer = argp->buffer;
>> 	resp->rqstp = rqstp;
>> -	resp->status = nfsd_readdir(rqstp, &resp->fh, (loff_t *)&argp->cookie,
> 
> Doesn't nfsd_readdir() update argp->cookie to point to the last offset?
> 
>> +	offset = argp->cookie;
>> +
>> +	resp->status = nfsd_readdir(rqstp, &resp->fh, &offset,
>> 				    &resp->common, nfs3svc_encode_entry);
>> 	memcpy(resp->verf, argp->verf, 8);
>> 	count = 0;
>> @@ -464,8 +467,6 @@ nfsd3_proc_readdir(struct svc_rqst *rqstp)
>> 	}
>> 	resp->count = count >> 2;
>> 	if (resp->offset) {
>> -		loff_t offset = argp->cookie;
> 
> So, this shouldn't be equal to the initial cookie any more.
> 
> Am I missing something?

No, my mistake. This works as we expect. Thanks for the review!

However, I find it confusing that nfsd3_proc_readdir() is structured
differently than the other three readdir proc methods, and for no
documented reason.

Would you still be willing to consider this patch relabeled as a clean-up ?


> --b.
> 
>> -
>> 		if (unlikely(resp->offset1)) {
>> 			/* we ended up with offset on a page boundary */
>> 			*resp->offset = htonl(offset >> 32);
>> 

--
Chuck Lever