On Tue, 2020-12-01 at 14:35 -0500, J. Bruce Fields wrote:
> On Mon, Nov 30, 2020 at 11:14:27PM -0500, trondmy@xxxxxxxxxx wrote:
> > From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> >
> > For the case of NFSv4, specify to the client that the the pre/post-
> > op
> > attributes were not recorded atomically with the main operation.
> >
> > Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> > ---
> > fs/nfs/export.c | 3 ++-
> > fs/nfsd/nfsfh.c | 4 ++++
> > fs/nfsd/nfsfh.h | 5 +++++
> > fs/nfsd/xdr4.h | 2 +-
> > include/linux/exportfs.h | 3 +++
> > 5 files changed, 15 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/nfs/export.c b/fs/nfs/export.c
> > index 48b879cfe6e3..7412bb164fa7 100644
> > --- a/fs/nfs/export.c
> > +++ b/fs/nfs/export.c
> > @@ -172,5 +172,6 @@ const struct export_operations nfs_export_ops =
> > {
> > .fh_to_dentry = nfs_fh_to_dentry,
> > .get_parent = nfs_get_parent,
> > .flags = EXPORT_OP_NOWCC|EXPORT_OP_NOSUBTREECHK|
> > - EXPORT_OP_CLOSE_BEFORE_UNLINK|EXPORT_OP_REMOTE_FS,
> > + EXPORT_OP_CLOSE_BEFORE_UNLINK|EXPORT_OP_REMOTE_FS|
> > + EXPORT_OP_NOATOMIC_ATTR,
>
> So I still don't understand why we need a new flag for this.
>
> Before you said it was because a filesystem might want to turn off
> the
> v4 atomic flag but still return v3 post-wcc attributes.
>
> But it seems that a) we have no example of a filesystem that wants to
> do
> that, b) it would violate the protocol anyway.
>
> Is that right?
>
> If so, then let's just stick to one flag for both.
The "atomic" flag in NFSv4 is very specifically tied to a single
attribute (the change attribute) and how it is collected in a very
limited set of operations. The truth is that we probably _can_
eventually set it when re-exporting NFSv4 as NFSv4, assuming that the
server actually supplies us with an atomic update.
The same is not true of WCC. We might be able to supply knfsd with
atomic updates for some operations, but certainly not for something
like READ or WRITE.
So I do think this needs to be separate flags. It is definitely
describing completely different functionality.
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@xxxxxxxxxxxxxxx
