Re: [PATCH v2] nfsd: recall deleg if a requested dir attr change can't be encoded

["Chuck Lever" <cel@kernel.org>]

On Fri, Jun 19, 2026, at 5:32 PM, Jeff Layton wrote:
> When the client requested NOTIFY4_CHANGE_DIR_ATTRS,
> nfsd4_cb_notify_prepare() tried to append the dir attribute change to
> the CB_NOTIFY, but silently dropped it if the attrmask space
> reservation failed or nfsd4_encode_dir_attr_change() failed to marshal
> the change into the buffer. It then returned true and transmitted a
> CB_NOTIFY lacking the requested notification, leaving the client's
> cached directory attributes stale with no indication.
>
> RFC 8881 s10.9.4 requires the server to recall the delegation when the
> directory changes in a way that is not covered by the notification.
> Treat a failure to encode the dir attribute change like the per-event
> encode failures already handled in the loop above: set error and fall
> through to out_recall.
>
> The granted notification mask and the requested dir attribute mask come
> from independent fields of the GET_DIR_DELEGATION request, so a client
> can be granted NOTIFY4_CHANGE_DIR_ATTRS while requesting no specific dir
> attributes. nfsd4_encode_dir_attr_change() now distinguishes a genuine
> encode failure (which forces the recall) from that benign case (which
> simply omits the event).
>
> While we're in there, also remove an unneeded check for
> NOTIFY4_CHANGE_DIR_ATTRS from nfsd4_encode_dir_attr_change().
>
> Fixes: 757a16cd93d5 ("nfsd: add support to CB_NOTIFY for dir attribute 
> changes")
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
> This version should address Chuck's comments about the NULL pointer
> handling.
> ---
> Changes in v2:
> - Allow nfsd4_encode_dir_attr_change() to return ERR_PTR when there are 
> errors
> - Drop unneeded NOTIFY4_CHANGE_DIR_ATTRS check
> - Link to v1: 
> https://lore.kernel.org/r/20260617-dir-deleg-fixes-v1-0-32b85b366c29@kernel.org
> ---
>  fs/nfsd/nfs4state.c | 43 ++++++++++++++++++++++++++++---------------
>  fs/nfsd/nfs4xdr.c   | 30 +++++++++++++++++-------------
>  2 files changed, 45 insertions(+), 28 deletions(-)

Sashiko reports (and gpt-5.5 agrees):

Pre-existing issues:
- [High] Genuine encode failures and `vfs_getattr` failures are silently masked as 0-length attributes, causing the directory attribute change event to be erroneously omitted instead of triggering a delegation recall.

But this isn’t really a pre-existing issue. It pre-exists this fix, yes,
but it was introduced by “nfsd: add support to CB_NOTIFY for dir
attribute changes”. What that means is this patch is not yet a complete
fix.


-- 
Chuck Lever