> On Dec 18, 2021, at 8:37 PM, trondmy@xxxxxxxxxx wrote:
>
> From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
>
> The fhp->fh_no_wcc flag is automatically set in nfsd_set_fh_dentry()
> when the EXPORT_OP_NOWCC flag is set. In svcxdr_encode_post_op_attr(),
> this then causes nfsd to skip returning the post-op attributes.
>
> The problem is that some of these post-op attributes are not really
> optional. In particular, we do want LOOKUP to always return post-op
> attributes for the file that is being looked up.
>
> The solution is therefore to explicitly label the attributes that we can
> safely opt out from, and only apply the 'fhp->fh_no_wcc' test in that
> case.
>
> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> Signed-off-by: Lance Shelton <lance.shelton@xxxxxxxxxxxxxxx>
> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> ---
> fs/nfsd/nfs3xdr.c | 77 +++++++++++++++++++++++++++++++----------------
> 1 file changed, 51 insertions(+), 26 deletions(-)
>
> diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
> index c3ac1b6aa3aa..6adfc40722fa 100644
> --- a/fs/nfsd/nfs3xdr.c
> +++ b/fs/nfsd/nfs3xdr.c
> @@ -415,19 +415,9 @@ svcxdr_encode_pre_op_attr(struct xdr_stream *xdr, const struct svc_fh *fhp)
> return svcxdr_encode_wcc_attr(xdr, fhp);
> }
>
> -/**
> - * svcxdr_encode_post_op_attr - Encode NFSv3 post-op attributes
> - * @rqstp: Context of a completed RPC transaction
> - * @xdr: XDR stream
> - * @fhp: File handle to encode
> - *
> - * Return values:
> - * %false: Send buffer space was exhausted
> - * %true: Success
> - */
> -bool
> -svcxdr_encode_post_op_attr(struct svc_rqst *rqstp, struct xdr_stream *xdr,
> - const struct svc_fh *fhp)
> +static bool
> +__svcxdr_encode_post_op_attr(struct svc_rqst *rqstp, struct xdr_stream *xdr,
> + const struct svc_fh *fhp, bool force)
> {
> struct dentry *dentry = fhp->fh_dentry;
> struct kstat stat;
> @@ -437,7 +427,7 @@ svcxdr_encode_post_op_attr(struct svc_rqst *rqstp, struct xdr_stream *xdr,
> * stale file handle. In this case, no attributes are
> * returned.
> */
> - if (fhp->fh_no_wcc || !dentry || !d_really_is_positive(dentry))
> + if (!force || !dentry || !d_really_is_positive(dentry))
> goto no_post_op_attrs;
> if (fh_getattr(fhp, &stat) != nfs_ok)
> goto no_post_op_attrs;
> @@ -454,6 +444,31 @@ svcxdr_encode_post_op_attr(struct svc_rqst *rqstp, struct xdr_stream *xdr,
> return xdr_stream_encode_item_absent(xdr) > 0;
> }
>
> +/**
> + * svcxdr_encode_post_op_attr - Encode NFSv3 post-op attributes
> + * @rqstp: Context of a completed RPC transaction
> + * @xdr: XDR stream
> + * @fhp: File handle to encode
> + *
> + * Return values:
> + * %false: Send buffer space was exhausted
> + * %true: Success
> + */
> +bool
> +svcxdr_encode_post_op_attr(struct svc_rqst *rqstp, struct xdr_stream *xdr,
> + const struct svc_fh *fhp)
> +{
> + return __svcxdr_encode_post_op_attr(rqstp, xdr, fhp, true);
> +}
> +
> +static bool
> +svcxdr_encode_post_op_attr_opportunistic(struct svc_rqst *rqstp,
> + struct xdr_stream *xdr,
> + const struct svc_fh *fhp)
> +{
> + return __svcxdr_encode_post_op_attr(rqstp, xdr, fhp, !fhp->fh_no_wcc);
> +}
> +
Thanks for splitting this out: the "why" is much clearer.
Wouldn't it be simpler to explicitly set fh_no_wcc to false
in each of the cases where you want to ensure the server
emits WCC? And perhaps that should be done in nfs3proc.c
instead of in nfs3xdr.c.
> /*
> * Encode weak cache consistency data
> */
> @@ -481,7 +496,7 @@ svcxdr_encode_wcc_data(struct svc_rqst *rqstp, struct xdr_stream *xdr,
> neither:
> if (xdr_stream_encode_item_absent(xdr) < 0)
> return false;
> - if (!svcxdr_encode_post_op_attr(rqstp, xdr, fhp))
> + if (!svcxdr_encode_post_op_attr_opportunistic(rqstp, xdr, fhp))
> return false;
>
> return true;
> @@ -854,11 +869,13 @@ nfs3svc_encode_lookupres(struct svc_rqst *rqstp, struct xdr_stream *xdr)
> return false;
> if (!svcxdr_encode_post_op_attr(rqstp, xdr, &resp->fh))
> return false;
> - if (!svcxdr_encode_post_op_attr(rqstp, xdr, &resp->dirfh))
> + if (!svcxdr_encode_post_op_attr_opportunistic(rqstp, xdr,
> + &resp->dirfh))
> return false;
> break;
> default:
> - if (!svcxdr_encode_post_op_attr(rqstp, xdr, &resp->dirfh))
> + if (!svcxdr_encode_post_op_attr_opportunistic(rqstp, xdr,
> + &resp->dirfh))
> return false;
> }
>
> @@ -875,13 +892,15 @@ nfs3svc_encode_accessres(struct svc_rqst *rqstp, struct xdr_stream *xdr)
> return false;
> switch (resp->status) {
> case nfs_ok:
> - if (!svcxdr_encode_post_op_attr(rqstp, xdr, &resp->fh))
> + if (!svcxdr_encode_post_op_attr_opportunistic(rqstp, xdr,
> + &resp->fh))
> return false;
> if (xdr_stream_encode_u32(xdr, resp->access) < 0)
> return false;
> break;
> default:
> - if (!svcxdr_encode_post_op_attr(rqstp, xdr, &resp->fh))
> + if (!svcxdr_encode_post_op_attr_opportunistic(rqstp, xdr,
> + &resp->fh))
> return false;
> }
>
> @@ -899,7 +918,8 @@ nfs3svc_encode_readlinkres(struct svc_rqst *rqstp, struct xdr_stream *xdr)
> return false;
> switch (resp->status) {
> case nfs_ok:
> - if (!svcxdr_encode_post_op_attr(rqstp, xdr, &resp->fh))
> + if (!svcxdr_encode_post_op_attr_opportunistic(rqstp, xdr,
> + &resp->fh))
> return false;
> if (xdr_stream_encode_u32(xdr, resp->len) < 0)
> return false;
> @@ -908,7 +928,8 @@ nfs3svc_encode_readlinkres(struct svc_rqst *rqstp, struct xdr_stream *xdr)
> return false;
> break;
> default:
> - if (!svcxdr_encode_post_op_attr(rqstp, xdr, &resp->fh))
> + if (!svcxdr_encode_post_op_attr_opportunistic(rqstp, xdr,
> + &resp->fh))
> return false;
> }
>
> @@ -926,7 +947,8 @@ nfs3svc_encode_readres(struct svc_rqst *rqstp, struct xdr_stream *xdr)
> return false;
> switch (resp->status) {
> case nfs_ok:
> - if (!svcxdr_encode_post_op_attr(rqstp, xdr, &resp->fh))
> + if (!svcxdr_encode_post_op_attr_opportunistic(rqstp, xdr,
> + &resp->fh))
> return false;
> if (xdr_stream_encode_u32(xdr, resp->count) < 0)
> return false;
> @@ -940,7 +962,8 @@ nfs3svc_encode_readres(struct svc_rqst *rqstp, struct xdr_stream *xdr)
> return false;
> break;
> default:
> - if (!svcxdr_encode_post_op_attr(rqstp, xdr, &resp->fh))
> + if (!svcxdr_encode_post_op_attr_opportunistic(rqstp, xdr,
> + &resp->fh))
> return false;
> }
>
> @@ -1032,7 +1055,8 @@ nfs3svc_encode_readdirres(struct svc_rqst *rqstp, struct xdr_stream *xdr)
> return false;
> switch (resp->status) {
> case nfs_ok:
> - if (!svcxdr_encode_post_op_attr(rqstp, xdr, &resp->fh))
> + if (!svcxdr_encode_post_op_attr_opportunistic(rqstp, xdr,
> + &resp->fh))
> return false;
> if (!svcxdr_encode_cookieverf3(xdr, resp->verf))
> return false;
> @@ -1044,7 +1068,8 @@ nfs3svc_encode_readdirres(struct svc_rqst *rqstp, struct xdr_stream *xdr)
> return false;
> break;
> default:
> - if (!svcxdr_encode_post_op_attr(rqstp, xdr, &resp->fh))
> + if (!svcxdr_encode_post_op_attr_opportunistic(rqstp, xdr,
> + &resp->fh))
> return false;
> }
>
> @@ -1188,7 +1213,7 @@ svcxdr_encode_entry3_plus(struct nfsd3_readdirres *resp, const char *name,
> if (compose_entry_fh(resp, fhp, name, namlen, ino) != nfs_ok)
> goto out_noattrs;
>
> - if (!svcxdr_encode_post_op_attr(resp->rqstp, xdr, fhp))
> + if (!svcxdr_encode_post_op_attr_opportunistic(resp->rqstp, xdr, fhp))
> goto out;
> if (!svcxdr_encode_post_op_fh3(xdr, fhp))
> goto out;
> --
> 2.33.1
>
--
Chuck Lever
