Re: [PATCH v2 001/118] NFSD: Fix returned READDIR offset cookie

[Bruce Fields <bfields@fieldses.org>]

On Sat, Nov 21, 2020 at 11:15:54AM -0500, Chuck Lever wrote:
> 
> 
> > 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 ?

Sure, seems fine, and if it confused you then it'd probably confuse
someone else.

--b.