Re: [PATCH v2 0/3] fs/nfsd: accept a backdated timestamp from a delegation holder

[Chuck Lever]

On Wed, Sep 2, 2026, at 2:54 PM, Jeff Layton wrote:
> The main problem is that an attribute delegation has strict rules about
> updates can be done, and that prevents applications that backdate
> timestamps on files after writing them, (e.g. tar -x, cp -p, etc.) from
> setting them properly.
>
> We could fix this on the client by making it always issue an RPC for the
> SETATTR, but that would harm performance in these common use-cases.
> This set allows the server to accept some of these backdated mtime
> updates, by changing how the ctime is handled.
>
> It'd be nice to see this in v7.4.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> Changes in v2:
> - Split the change into three patches
> - Stamp now in inode_set_ctime_deleg() for a stale update, so nfsd need
>   not compare
> - Drop a SETATTR report that matches the inode, so an untouched file
>   keeps its change attribute
> - Set dl_setattr only on the branch that carries a c/mtime update
> - Compare against the inode, not the grant-time snapshots (Chuck)
> - Set the ctime whenever a CB_GETATTR moves the mtime
> - Take i_rwsem before the CB_GETATTR comparison
> - Drop the unused dl_atime, dl_mtime and dl_ctime, and make
>   nfsd4_vet_deleg_time() static
> - Link to v1: 
> https://lore.kernel.org/r/20260901-delegts-v1-1-9937f7ee4370@xxxxxxxxxx
>
> ---
> Jeff Layton (3):
>       fs: stamp the current time for a stale delegated ctime update
>       nfsd: accept a backdated timestamp from a delegation holder
>       nfsd: compare CB_GETATTR times against the inode
>
>  fs/inode.c          | 17 +++++++++++----
>  fs/nfsd/nfs4proc.c  | 63 +++++++++++++++++++++++++++++++++++++++++++----------
>  fs/nfsd/nfs4state.c | 49 ++++++++++++++++++++++++++---------------
>  fs/nfsd/state.h     |  8 -------
>  4 files changed, 95 insertions(+), 42 deletions(-)
> ---
> base-commit: ac579868af0c900d8fd9c8cfe9e10db46ccc5a75
> change-id: 20260901-delegts-e91a648f1427
>
> Best regards,
> -- 
> Jeff Layton <jlayton@xxxxxxxxxx>

Since the series modifies fs/inode.c, Christian will want to take it
through the VFS tree.

Acked-by: Chuck Lever <cel@xxxxxxxxxx>


-- 
Chuck Lever (Come to NFS bake-a-thon! https://nfsv4bat.org)