Re: [PATCH v5 01/10] nfsd: fix handling of delegated change attr in CB_GETATTR

Chuck Lever
2025-01-19T15:19:32Z

On 12/9/24 4:13 PM, Jeff Layton wrote:
> RFC8881, section 10.4.3 has some specific guidance as to how the
> delegated change attribute should be handled. We currently don't follow
> that guidance properly.
>
> In particular, when the file is modified, the server always reports the
> initial change attribute + 1. Section 10.4.3 however indicates that it
> should be incremented on every GETATTR request from other clients.
>
> Only request the change attribute until the file has been modified. If
> there is an outstanding delegation, then increment the cached change
> attribute on every GETATTR.
>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>

After review of LTS backport instructions in the candidate patches for
v6.14, this commit stuck out. Should it have a Fixes: or Cc: stable ?

How about

Fixes: 6487a13b5c6b ("NFSD: add support for CB_GETATTR callback") ??

> ---
> fs/nfsd/nfs4callback.c | 8 +++++---
> fs/nfsd/nfs4xdr.c | 15 +++++++++------
> 2 files changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
> index 3877b53e429fd89899d7dc35086bee8bda6eed07..25acb8624b854f5d0d184efec660e1f72cad8885 100644
> --- a/fs/nfsd/nfs4callback.c
> +++ b/fs/nfsd/nfs4callback.c
> @@ -361,12 +361,14 @@ static void
> encode_cb_getattr4args(struct xdr_stream *xdr, struct nfs4_cb_compound_hdr *hdr,
> struct nfs4_cb_fattr *fattr)
> {
> - struct nfs4_delegation *dp =
> - container_of(fattr, struct nfs4_delegation, dl_cb_fattr);
> + struct nfs4_delegation *dp = container_of(fattr, struct nfs4_delegation, dl_cb_fattr);
> struct knfsd_fh *fh = &dp->dl_stid.sc_file->fi_fhandle;
> + struct nfs4_cb_fattr *ncf = &dp->dl_cb_fattr;
> u32 bmap[1];
>
> - bmap[0] = FATTR4_WORD0_CHANGE | FATTR4_WORD0_SIZE;
> + bmap[0] = FATTR4_WORD0_SIZE;
> + if (!ncf->ncf_file_modified)
> + bmap[0] |= FATTR4_WORD0_CHANGE;
>
> encode_nfs_cb_opnum4(xdr, OP_CB_GETATTR);
> encode_nfs_fh4(xdr, fh);
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 53fac037611c05ff8ba2618f9e324a9cb54c3890..c8e8d3f0dff4bb5288186369aad821906e684db7 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2919,6 +2919,7 @@ struct nfsd4_fattr_args {
> struct kstat stat;
> struct kstatfs statfs;
> struct nfs4_acl *acl;
> + u64 change_attr;
> #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
> void *context;
> int contextlen;
> @@ -3018,7 +3019,6 @@ static __be32 nfsd4_encode_fattr4_change(struct xdr_stream *xdr,
> const struct nfsd4_fattr_args *args)
> {
> const struct svc_export *exp = args->exp;
> - u64 c;
>
> if (unlikely(exp->ex_flags & NFSEXP_V4ROOT)) {
> u32 flush_time = convert_to_wallclock(exp->cd->flush_time);
> @@ -3029,9 +3029,7 @@ static __be32 nfsd4_encode_fattr4_change(struct xdr_stream *xdr,
> return nfserr_resource;
> return nfs_ok;
> }
> -
> - c = nfsd4_change_attribute(&args->stat);
> - return nfsd4_encode_changeid4(xdr, c);
> + return nfsd4_encode_changeid4(xdr, args->change_attr);
> }
>
> static __be32 nfsd4_encode_fattr4_size(struct xdr_stream *xdr,
> @@ -3556,11 +3554,16 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr,
> if (dp) {
> struct nfs4_cb_fattr *ncf = &dp->dl_cb_fattr;
>
> - if (ncf->ncf_file_modified)
> + if (ncf->ncf_file_modified) {
> + ++ncf->ncf_initial_cinfo;
> args.stat.size = ncf->ncf_cur_fsize;
> -
> + }
> + args.change_attr = ncf->ncf_initial_cinfo;
> nfs4_put_stid(&dp->dl_stid);
> + } else {
> + args.change_attr = nfsd4_change_attribute(&args.stat);
> }
> +
> if (err)
> goto out_nfserr;
>
>

--
Chuck Lever