On Fri, Dec 17, 2021 at 5:07 PM <trondmy@xxxxxxxxxx> wrote:
>
> From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
>
> According to RFC1813: "If count is 0, the WRITE will succeed
> and return a count of 0, barring errors due to permissions checking."
Yes, I'm surprised we're not already doing this right.
I wonder how far back this bug goes.
The svc.c code is from 8154ef2776aa "NFSD: Clean up legacy NFS WRITE
argument XDR decoders", but the behavior might predate that code. The
nfsd_vfs_write() logic, I'm not sure I understand.
We have a pynfs test for the v4 case (WRT4), but I guess we must have
nothing testing the v3 case.
--b.
>
> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> ---
> fs/nfsd/vfs.c | 3 +++
> net/sunrpc/svc.c | 2 +-
> 2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 4d57befdac6e..38fdfcbb079e 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -969,6 +969,9 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
>
> trace_nfsd_write_opened(rqstp, fhp, offset, *cnt);
>
> + if (!*cnt)
> + return nfs_ok;
> +
> if (sb->s_export_op)
> exp_op_flags = sb->s_export_op->flags;
>
> diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
> index a3bbe5ce4570..d1ccf37a4588 100644
> --- a/net/sunrpc/svc.c
> +++ b/net/sunrpc/svc.c
> @@ -1692,7 +1692,7 @@ unsigned int svc_fill_write_vector(struct svc_rqst *rqstp, struct page **pages,
> * entirely in rq_arg.pages. In this case, @first is empty.
> */
> i = 0;
> - if (first->iov_len) {
> + if (first->iov_len || !total) {
> vec[i].iov_base = first->iov_base;
> vec[i].iov_len = min_t(size_t, total, first->iov_len);
> total -= vec[i].iov_len;
> --
> 2.33.1
>
