On Fri, 2020-08-28 at 15:58 -0400, Chuck Lever wrote:
> If a write delegation isn't available, the Linux NFS client uses
> a zero-stateid when performing a SETATTR.
>
> If that client happens to hold a read delegation, the server will
> recall it immediately, resulting in a short delay while the
> CB_RECALL operation is done. Optimize out this delay by having the
> client return any delegation it may hold on a file before issuing a
> SETATTR(zero-stateid) on that file.
>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> fs/nfs/nfs4proc.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index dbd01548335b..53a56250cf4b 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -3314,6 +3314,7 @@ static int _nfs4_do_setattr(struct inode
> *inode,
> goto zero_stateid;
> } else {
> zero_stateid:
> + nfs4_inode_return_delegation(inode);
> nfs4_stateid_copy(&arg->stateid, &zero_stateid);
> }
> if (delegation_cred)
>
This should not be needed for NFSv4.1 or greater. Only NFSv4.0 is
incapable of identifying the caller and recognising that it is the
holder of the delegation.
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@xxxxxxxxxxxxxxx
