Re: [PATCH] nfs: Subsequent READDIR calls should carry non-zero cookieverifier

[Trond Myklebust <trondmy@hammerspace.com>]

On Tue, 2021-03-16 at 10:25 +0000, Nagendra Tomar wrote:
> From: Nagendra S Tomar <natomar@microsoft.com>
> 
> If the loop in nfs_readdir_xdr_to_array() runs more than once,
> subsequent
> READDIR RPCs may wrongly carry a zero cookie verifier and non-zero
> cookie.
> Make sure subsequent calls to READDIR carry the cookie verifier
> returned
> by the first call.
> 
> Signed-off-by: Nagendra S Tomar <natomar@microsoft.com>
> ---
> diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
> index fc4f490f2d78..08a1e2e31d0b 100644
> --- a/fs/nfs/dir.c
> +++ b/fs/nfs/dir.c
> @@ -866,6 +866,8 @@ static int nfs_readdir_xdr_to_array(struct
> nfs_readdir_descriptor *desc,
>                         break;
>                 }
>  
> +               verf_arg = verf_res;
> +
>                 status = nfs_readdir_page_filler(desc, entry, pages,
> pglen,
>                                                  arrays, narrays);
>         } while (!status && nfs_readdir_page_needs_filling(page));

That looks good to me. However when looking over that code, I think I
spotted a similar issue when we're doing uncached readdir in order to
try to recover a missing cookie. I therefore Cced you on the posting
for that patch.

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