On Mon, 2022-10-17 at 22:15 -0700, Dai Ngo wrote:
> The delegation shrinker is scheduled to run on every shrinker's
> 'count' callback. It scans the client list and sends the
> courtesy CB_RECALL_ANY to the clients that hold delegations.
>
> To avoid flooding the clients with CB_RECALL_ANY requests, the
> delegation shrinker is scheduled to run after a 5 seconds delay.
>
But...when the kernel needs memory, it generally needs it _now_, and 5s
is a long time. It'd be better to not delay the initial sending of
CB_RECALL_ANY callbacks this much.
Maybe the logic should be changed such that it runs no more frequently
than once every 5s, but don't delay the initial sending of
CB_RECALL_ANYs.
> Signed-off-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
> ---
> fs/nfsd/netns.h | 3 +++
> fs/nfsd/nfs4state.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
> fs/nfsd/state.h | 1 +
> 3 files changed, 73 insertions(+), 1 deletion(-)
>
> diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
> index 8c854ba3285b..394a05fb46d8 100644
> --- a/fs/nfsd/netns.h
> +++ b/fs/nfsd/netns.h
> @@ -196,6 +196,9 @@ struct nfsd_net {
> atomic_t nfsd_courtesy_clients;
> struct shrinker nfsd_client_shrinker;
> struct delayed_work nfsd_shrinker_work;
> +
> + struct shrinker nfsd_deleg_shrinker;
> + struct delayed_work nfsd_deleg_shrinker_work;
> };
>
> /* Simple check to find out if a given net was properly initialized */
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index c60c937dece6..bdaea0e6e72f 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -4392,11 +4392,32 @@ nfsd_courtesy_client_scan(struct shrinker *shrink, struct shrink_control *sc)
> return SHRINK_STOP;
> }
>
> +static unsigned long
> +nfsd_deleg_shrinker_count(struct shrinker *shrink, struct shrink_control *sc)
> +{
> + unsigned long cnt;
> + struct nfsd_net *nn = container_of(shrink,
> + struct nfsd_net, nfsd_deleg_shrinker);
> +
> + cnt = atomic_long_read(&num_delegations);
> + if (cnt)
> + mod_delayed_work(laundry_wq,
> + &nn->nfsd_deleg_shrinker_work, 5 * HZ);
> + return cnt;
> +}
> +
What's the rationale for doing all of this in the count callback? Why
not just return the value here and leave scheduling to the scan
callback?
> +static unsigned long
> +nfsd_deleg_shrinker_scan(struct shrinker *shrink, struct shrink_control *sc)
> +{
> + return SHRINK_STOP;
> +}
> +
> int
> nfsd4_init_leases_net(struct nfsd_net *nn)
> {
> struct sysinfo si;
> u64 max_clients;
> + int retval;
>
> nn->nfsd4_lease = 90; /* default lease time */
> nn->nfsd4_grace = 90;
> @@ -4417,13 +4438,23 @@ nfsd4_init_leases_net(struct nfsd_net *nn)
> nn->nfsd_client_shrinker.scan_objects = nfsd_courtesy_client_scan;
> nn->nfsd_client_shrinker.count_objects = nfsd_courtesy_client_count;
> nn->nfsd_client_shrinker.seeks = DEFAULT_SEEKS;
> - return register_shrinker(&nn->nfsd_client_shrinker, "nfsd-client");
> + retval = register_shrinker(&nn->nfsd_client_shrinker, "nfsd-client");
> + if (retval)
> + return retval;
> + nn->nfsd_deleg_shrinker.scan_objects = nfsd_deleg_shrinker_scan;
> + nn->nfsd_deleg_shrinker.count_objects = nfsd_deleg_shrinker_count;
> + nn->nfsd_deleg_shrinker.seeks = DEFAULT_SEEKS;
> + retval = register_shrinker(&nn->nfsd_deleg_shrinker, "nfsd-delegation");
> + if (retval)
> + unregister_shrinker(&nn->nfsd_client_shrinker);
> + return retval;
> }
>
> void
> nfsd4_leases_net_shutdown(struct nfsd_net *nn)
> {
> unregister_shrinker(&nn->nfsd_client_shrinker);
> + unregister_shrinker(&nn->nfsd_deleg_shrinker);
> }
>
> static void init_nfs4_replay(struct nfs4_replay *rp)
> @@ -6162,6 +6193,42 @@ courtesy_client_reaper(struct work_struct *reaper)
> nfs4_process_client_reaplist(&reaplist);
> }
>
> +static void
> +deleg_reaper(struct work_struct *deleg_work)
> +{
> + struct list_head *pos, *next;
> + struct nfs4_client *clp;
> + struct list_head cblist;
> + struct delayed_work *dwork = to_delayed_work(deleg_work);
> + struct nfsd_net *nn = container_of(dwork, struct nfsd_net,
> + nfsd_deleg_shrinker_work);
> +
> + INIT_LIST_HEAD(&cblist);
> + spin_lock(&nn->client_lock);
> + list_for_each_safe(pos, next, &nn->client_lru) {
> + clp = list_entry(pos, struct nfs4_client, cl_lru);
> + if (clp->cl_state != NFSD4_ACTIVE ||
> + list_empty(&clp->cl_delegations) ||
> + atomic_read(&clp->cl_delegs_in_recall) ||
> + clp->cl_recall_any_busy) {
> + continue;
> + }
> + clp->cl_recall_any_busy = true;
> + list_add(&clp->cl_recall_any_cblist, &cblist);
> +
> + /* release in nfsd4_cb_recall_any_release */
> + atomic_inc(&clp->cl_rpc_users);
> + }
> + spin_unlock(&nn->client_lock);
> + list_for_each_safe(pos, next, &cblist) {
> + clp = list_entry(pos, struct nfs4_client, cl_recall_any_cblist);
> + list_del_init(&clp->cl_recall_any_cblist);
> + clp->cl_recall_any_bm = BIT(RCA4_TYPE_MASK_RDATA_DLG) |
> + BIT(RCA4_TYPE_MASK_WDATA_DLG);
> + nfsd4_run_cb(&clp->cl_recall_any);
> + }
> +}
> +
> static inline __be32 nfs4_check_fh(struct svc_fh *fhp, struct nfs4_stid *stp)
> {
> if (!fh_match(&fhp->fh_handle, &stp->sc_file->fi_fhandle))
> @@ -7985,6 +8052,7 @@ static int nfs4_state_create_net(struct net *net)
>
> INIT_DELAYED_WORK(&nn->laundromat_work, laundromat_main);
> INIT_DELAYED_WORK(&nn->nfsd_shrinker_work, courtesy_client_reaper);
> + INIT_DELAYED_WORK(&nn->nfsd_deleg_shrinker_work, deleg_reaper);
> get_net(net);
>
> return 0;
> diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
> index 49ca06169642..05b572ce6605 100644
> --- a/fs/nfsd/state.h
> +++ b/fs/nfsd/state.h
> @@ -415,6 +415,7 @@ struct nfs4_client {
> bool cl_recall_any_busy;
> uint32_t cl_recall_any_bm;
> struct nfsd4_callback cl_recall_any;
> + struct list_head cl_recall_any_cblist;
> };
>
> /* struct nfs4_client_reset
--
Jeff Layton <jlayton@xxxxxxxxxx>
