Re: [PATCH v3 1/2] NFSD: delay unmount source's export after inter-server copy completed.

dai.ngo@xxxxxxxxxx · Thu, 22 Apr 2021 11:42:26 -0700

Thank you Olga for reviewing the patch and doing the performance
testing, greatly appreciated!

On 4/21/21 5:31 PM, Olga Kornievskaia wrote:
On Fri, Apr 9, 2021 at 2:07 PM Dai Ngo <dai.ngo@xxxxxxxxxx> wrote:
Currently the source's export is mounted and unmounted on every
inter-server copy operation. This patch is an enhancement to delay
the unmount of the source export for a certain period of time to
eliminate the mount and unmount overhead on subsequent copy operations.

After a copy operation completes, a delayed task is scheduled to
unmount the export after a configurable idle time. Each time the
export is being used again, its expire time is extended to allow
the export to remain mounted.

The unmount task and the mount operation of the copy request are
synced to make sure the export is not unmounted while it's being
used.
I have done performance testing of this patch on the hardware used to
test initial SSC code and there is improvement on the lower end copy
filesize (4MB-16MB) with this. Unfortunately, I can't quantify how
much difference this patch makes. Why? Because I'm getting very
different results on every set of runs (each set does 10runs to get
the mean and compute standard deviation too).  The most varied time
from run to run is commit time. However, standard deviation for both
types of runs (traditional and ssc) is (most of the time) <1% which
should still make the runs acceptable (i did re-runs for others).
Runs with filesize 128MB+ have more consistent performance but they
also don't show as much improvement with this patch. Note I didn't
concentrate on  >1G performance at all this time around.

I think user would appreciate more if copying of large files is
faster since that reduces the time the user has to wait for the
copy to complete. Copying of small files happen so quickly (<1 sec)
it's hard to see the different.


Also, what I discovered is what also makes a difference is the
following COMMIT rpc. The saving seems to come from doing an
vfs_fsync() after the copy on the server (just like what is done for
the CLONE i might note) and I'm hoping to propose a patch for it some
time in the next few days.

I think this is a good enhancement.


A few general comments on the patch:
1. Shouldn't the "nsui_refcnt" be a refcount_t structure type?

I will convert to refcount_t in the v2 patch.

2. Why is the value of 20HZ to retry was chosen?

This is when a thread doing the mount and either (1) there is another
thread doing another mount to the same source server or (2) the export
of that server is being unmounted by the delayed task. In this case
the thread has to wait for the other thread to be done with the source
server and try again.

I think we should not have the thread waits forever so I just pick
20secs which I think should be long enough for the mount/unmount to
complete in normal condition. I'm open to suggestion on how to handle
this case.

3. "work" gets allocated but instead of checking the allocation
failure and dealing with it then, the code has "if (work)" sections.
seems like extra indentation and the need to think why "work" can be
null be removed?

There is nothing that we need to do if the allocation of work fails.
We still have to continue to do the mount and just skip the work of
setting it up for the delayed unmount.


Here are some numbers. Comparing pure 5.12-rc6 code with 5.12-rc6 code
with Dai's delay umount code and for kicks the last set of numbers is
+delay umount +vfs_fsync() on the server. In general over 128MB
provides 50% improvement over traditional copy in all cases. With
delayed umount, we see better numbers (~30% improvement) with copies
4MB-128MB but still some dips and for copies over 128MB over 50%
improvement.

I think the improvement from the delayed mount and commit optimization
is significant.

-Dai


pure 5.12-rc6
     INFO: 14:11:16.819155 - Server-side COPY: 0.472602200508 seconds
(mean), standard deviation: 0.504127857283
     INFO: 14:11:16.819252 - Traditional COPY: 0.247301483154 seconds
(mean), standard deviation: 0.0325181306537
     FAIL: SSC should outperform traditional copy, performance
degradation for a 4MB file: 91%

     INFO: 14:12:54.584129 - Server-side COPY: 0.401613616943 seconds
(mean), standard deviation: 0.100666012531
     INFO: 14:12:54.584223 - Traditional COPY: 0.376980066299 seconds
(mean), standard deviation: 0.0149147531532
     FAIL: SSC should outperform traditional copy, performance
degradation for a 8MB file: 6%

     INFO: 14:14:37.430685 - Server-side COPY: 0.727260971069 seconds
(mean), standard deviation: 0.24591675709
     INFO: 14:14:37.430787 - Traditional COPY: 0.858516097069 seconds
(mean), standard deviation: 0.203399239696
     PASS: SSC should outperform traditional copy, performance
improvement for a 16MB file: 18%

     INFO: 14:16:25.318145 - Server-side COPY: 1.08072230816 seconds
(mean), standard deviation: 0.168767973425
     INFO: 14:16:25.318245 - Traditional COPY: 1.21966302395 seconds
(mean), standard deviation: 0.0862109147556
     PASS: SSC should outperform traditional copy, performance
improvement for a 32MB file: 12%

     INFO: 14:18:20.913090 - Server-side COPY: 1.47459042072 seconds
(mean), standard deviation: 0.118534392658
     INFO: 14:18:20.913186 - Traditional COPY: 1.74257912636 seconds
(mean), standard deviation: 0.041726092735
     PASS: SSC should outperform traditional copy, performance
improvement for a 64MB file: 18%

     INFO: 14:20:40.794478 - Server-side COPY: 2.27927930355 seconds
(mean), standard deviation: 0.0502558652592
     INFO: 14:20:40.794579 - Traditional COPY: 3.3685300827 seconds
(mean), standard deviation: 0.0232078152411
     PASS: SSC should outperform traditional copy, performance
improvement for a 128MB file: 47%

     INFO: 14:23:54.480951 - Server-side COPY: 4.36852009296 seconds
(mean), standard deviation: 0.0421940712129
     INFO: 14:23:54.481059 - Traditional COPY: 6.58469381332 seconds
(mean), standard deviation: 0.0534006595486
     PASS: SSC should outperform traditional copy, performance
improvement for a 256MB file: 50%

     INFO: 14:28:57.776217 - Server-side COPY: 8.61689963341 seconds
(mean), standard deviation: 0.110919967983
     INFO: 14:28:57.776361 - Traditional COPY: 13.0591681957 seconds
(mean), standard deviation: 0.0766741218971
     PASS: SSC should outperform traditional copy, performance
improvement for a 512MB file: 51%

     INFO: 14:36:45.693363 - Server-side COPY: 15.330485177 seconds
(mean), standard deviation: 1.08275054089
     INFO: 14:36:45.693547 - Traditional COPY: 22.6392157316 seconds
(mean), standard deviation: 0.62612602097
     PASS: SSC should outperform traditional copy, performance
improvement for a 1GB file: 47%

     (another run for 1g to get a better deviation)
     INFO: 15:33:08.457225 - Server-side COPY: 14.7443211555 seconds
(mean), standard deviation: 0.19152031268
     INFO: 15:33:08.457401 - Traditional COPY: 23.3897125483 seconds
(mean), standard deviation: 0.634745610516
     PASS: SSC should outperform traditional copy, performance
improvement for a 1GB file: 58%

This run is with delayed umount:
     INFO: 16:57:09.750669 - Server-side COPY: 0.264265751839 seconds
(mean), standard deviation: 0.114140867309
     INFO: 16:57:09.750767 - Traditional COPY: 0.277241683006 seconds
(mean), standard deviation: 0.0429385806753
     PASS: SSC should outperform traditional copy, performance
improvement for a 4MB file: 4%

     INFO: 16:58:48.514208 - Server-side COPY: 0.301608347893 seconds
(mean), standard deviation: 0.027625417442
     INFO: 16:58:48.514305 - Traditional COPY: 0.376611542702 seconds
(mean), standard deviation: 0.0256646541006
     PASS: SSC should outperform traditional copy, performance
improvement for a 8MB file: 24%

     INFO: 17:00:32.726180 - Server-side COPY: 0.804727435112 seconds
(mean), standard deviation: 0.282478573802
     INFO: 17:00:32.726284 - Traditional COPY: 0.750376915932 seconds
(mean), standard deviation: 0.188426980103
     FAIL: SSC should outperform traditional copy, performance
degradation for a 16MB file: 7%

another run for 16MB for better deviation
     INFO: 17:26:05.710048 - Server-side COPY: 0.561978292465 seconds
(mean), standard deviation: 0.176039123641
     INFO: 17:26:05.710155 - Traditional COPY: 0.761225438118 seconds
(mean), standard deviation: 0.229373528254
     PASS: SSC should outperform traditional copy, performance
improvement for a 16MB file: 35%

     INFO: 17:02:21.387772 - Server-side COPY: 0.895572972298 seconds
(mean), standard deviation: 0.18919321178
     INFO: 17:02:21.387866 - Traditional COPY: 1.28307352066 seconds
(mean), standard deviation: 0.0755687243879
     PASS: SSC should outperform traditional copy, performance
improvement for a 32MB file: 43%

     INFO: 17:04:18.530852 - Server-side COPY: 1.44412658215 seconds
(mean), standard deviation: 0.0680101210746
     INFO: 17:04:18.530946 - Traditional COPY: 1.7353479147 seconds
(mean), standard deviation: 0.0147682451688
     PASS: SSC should outperform traditional copy, performance
improvement for a 64MB file: 20%

     INFO: 17:06:40.127898 - Server-side COPY: 2.18924453259 seconds
(mean), standard deviation: 0.0339712202148
     INFO: 17:06:40.127995 - Traditional COPY: 3.39783103466 seconds
(mean), standard deviation: 0.0439455560873
     PASS: SSC should outperform traditional copy, performance
improvement for a 128MB file: 55%

     INFO: 17:09:56.186889 - Server-side COPY: 4.2961766243 seconds
(mean), standard deviation: 0.0486465355758
     INFO: 17:09:56.186988 - Traditional COPY: 6.56641271114 seconds
(mean), standard deviation: 0.0259688949944
     PASS: SSC should outperform traditional copy, performance
improvement for a 256MB file: 52%

     INFO: 17:15:02.522089 - Server-side COPY: 8.4736330986 seconds
(mean), standard deviation: 0.0896888780618
     INFO: 17:15:02.522242 - Traditional COPY: 13.074249053 seconds
(mean), standard deviation: 0.0805015369838
     PASS: SSC should outperform traditional copy, performance
improvement for a 512MB file: 54%

     INFO: 17:22:59.745446 - Server-side COPY: 15.9621772766 seconds
(mean), standard deviation: 2.70296237945
     INFO: 17:22:59.745625 - Traditional COPY: 22.5955899239 seconds
(mean), standard deviation: 0.682459618149
     PASS: SSC should outperform traditional copy, performance
improvement for a 1GB file: 41%

another run for 1GB to get a better deviation:
     INFO: 17:35:02.846602 - Server-side COPY: 14.6351578712 seconds
(mean), standard deviation: 0.19192309658
     INFO: 17:35:02.846781 - Traditional COPY: 22.8912801266 seconds
(mean), standard deviation: 0.682718216033
     PASS: SSC should outperform traditional copy, performance
improvement for a 1GB file: 56%

And this run is for yet unpublished patch of delayed umount +
vfs_fsync after the copy
     INFO: 18:28:34.764202 - Server-side COPY: 0.209130239487 seconds
(mean), standard deviation: 0.0366357417649
     INFO: 18:28:34.764297 - Traditional COPY: 0.275605249405 seconds
(mean), standard deviation: 0.030773788804
     PASS: SSC should outperform traditional copy, performance
improvement for a 4MB file: 31%

     INFO: 18:30:12.278362 - Server-side COPY: 0.263212919235 seconds
(mean), standard deviation: 0.017764772065
     INFO: 18:30:12.278459 - Traditional COPY: 0.373342609406 seconds
(mean), standard deviation: 0.0235488678036
     PASS: SSC should outperform traditional copy, performance
improvement for a 8MB file: 41%

     INFO: 18:31:56.740901 - Server-side COPY: 0.653366684914 seconds
(mean), standard deviation: 0.201038063193
     INFO: 18:31:56.741007 - Traditional COPY: 0.719534230232 seconds
(mean), standard deviation: 0.144084877516
     PASS: SSC should outperform traditional copy, performance
improvement for a 16MB file: 10%

another run for 16Mb
     INFO: 20:18:09.533128 - Server-side COPY: 0.508768010139 seconds
(mean), standard deviation: 0.172117325138
     INFO: 20:18:09.533224 - Traditional COPY: 0.712138915062 seconds
(mean), standard deviation: 0.162059202594
     PASS: SSC should outperform traditional copy, performance
improvement for a 16MB file: 39%

     INFO: 18:33:44.203037 - Server-side COPY: 0.774861812592 seconds
(mean), standard deviation: 0.141729231937
     INFO: 18:33:44.203140 - Traditional COPY: 1.24551167488 seconds
(mean), standard deviation: 0.0520878630978
     PASS: SSC should outperform traditional copy, performance
improvement for a 32MB file: 60%

     INFO: 18:35:44.104048 - Server-side COPY: 1.50374240875 seconds
(mean), standard deviation: 0.132060247445
     INFO: 18:35:44.104168 - Traditional COPY: 1.76330254078 seconds
(mean), standard deviation: 0.0339954657686
     PASS: SSC should outperform traditional copy, performance
improvement for a 64MB file: 17%

another run for 64MB
     INFO: 20:22:39.668006 - Server-side COPY: 1.32221701145 seconds
(mean), standard deviation: 0.0595545335408
     INFO: 20:22:39.668108 - Traditional COPY: 1.73985309601 seconds
(mean), standard deviation: 0.0301114835769
     PASS: SSC should outperform traditional copy, performance
improvement for a 64MB file: 31%

     INFO: 18:38:06.184631 - Server-side COPY: 2.11796813011 seconds
(mean), standard deviation: 0.0407036659715
     INFO: 18:38:06.184726 - Traditional COPY: 3.36791093349 seconds
(mean), standard deviation: 0.029777196608
     PASS: SSC should outperform traditional copy, performance
improvement for a 128MB file: 59%

     INFO: 18:41:20.944541 - Server-side COPY: 4.19641048908 seconds
(mean), standard deviation: 0.041610728753
     INFO: 18:41:20.944641 - Traditional COPY: 6.569201684 seconds
(mean), standard deviation: 0.0398935239857
     PASS: SSC should outperform traditional copy, performance
improvement for a 256MB file: 56%

     INFO: 18:46:23.973364 - Server-side COPY: 8.34293022156 seconds
(mean), standard deviation: 0.108239167667
     INFO: 18:46:23.973562 - Traditional COPY: 13.0458415985 seconds
(mean), standard deviation: 0.0399096580857
     PASS: SSC should outperform traditional copy, performance
improvement for a 512MB file: 56%

     INFO: 18:54:05.741343 - Server-side COPY: 14.4749611855 seconds
(mean), standard deviation: 0.122991853502
     INFO: 18:54:05.741549 - Traditional COPY: 22.6955966711 seconds
(mean), standard deviation: 0.461425661742
     PASS: SSC should outperform traditional copy, performance
improvement for a 1GB file: 56%



Signed-off-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
---
  fs/nfsd/nfs4proc.c      | 171 ++++++++++++++++++++++++++++++++++++++++++++++--
  fs/nfsd/nfsd.h          |   4 ++
  fs/nfsd/nfssvc.c        |   3 +
  include/linux/nfs_ssc.h |  20 ++++++
  4 files changed, 194 insertions(+), 4 deletions(-)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index dd9f38d..66dea2f 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -55,6 +55,81 @@
  MODULE_PARM_DESC(inter_copy_offload_enable,
                  "Enable inter server to server copy offload. Default: false");

+#ifdef CONFIG_NFSD_V4_2_INTER_SSC
+static int nfsd4_ssc_umount_timeout = 900000;          /* default to 15 mins */
+module_param(nfsd4_ssc_umount_timeout, int, 0644);
+MODULE_PARM_DESC(nfsd4_ssc_umount_timeout,
+               "idle msecs before unmount export from source server");
+
+static void nfsd4_ssc_expire_umount(struct work_struct *work);
+static struct nfsd4_ssc_umount nfsd4_ssc_umount;
+
+/* nfsd4_ssc_umount.nsu_lock must be held */
+static void nfsd4_scc_update_umnt_timo(void)
+{
+       struct nfsd4_ssc_umount_item *ni = 0;
+
+       cancel_delayed_work(&nfsd4_ssc_umount.nsu_umount_work);
+       if (!list_empty(&nfsd4_ssc_umount.nsu_list)) {
+               ni = list_first_entry(&nfsd4_ssc_umount.nsu_list,
+                       struct nfsd4_ssc_umount_item, nsui_list);
+               nfsd4_ssc_umount.nsu_expire = ni->nsui_expire;
+               schedule_delayed_work(&nfsd4_ssc_umount.nsu_umount_work,
+                       ni->nsui_expire - jiffies);
+       } else
+               nfsd4_ssc_umount.nsu_expire = 0;
+}
+
+static void nfsd4_ssc_expire_umount(struct work_struct *work)
+{
+       bool do_wakeup = false;
+       struct nfsd4_ssc_umount_item *ni = 0;
+       struct nfsd4_ssc_umount_item *tmp;
+
+       spin_lock(&nfsd4_ssc_umount.nsu_lock);
+       list_for_each_entry_safe(ni, tmp, &nfsd4_ssc_umount.nsu_list, nsui_list) {
+               if (time_after(jiffies, ni->nsui_expire)) {
+                       if (ni->nsui_refcnt > 0)
+                               continue;
+
+                       /* mark being unmount */
+                       ni->nsui_busy = true;
+                       spin_unlock(&nfsd4_ssc_umount.nsu_lock);
+                       mntput(ni->nsui_vfsmount);
+                       spin_lock(&nfsd4_ssc_umount.nsu_lock);
+
+                       /* waiters need to start from begin of list */
+                       list_del(&ni->nsui_list);
+                       kfree(ni);
+
+                       /* wakeup ssc_connect waiters */
+                       do_wakeup = true;
+                       continue;
+               }
+               break;
+       }
+       nfsd4_scc_update_umnt_timo();
+       if (do_wakeup)
+               wake_up_all(&nfsd4_ssc_umount.nsu_waitq);
+       spin_unlock(&nfsd4_ssc_umount.nsu_lock);
+}
+
+static DECLARE_DELAYED_WORK(nfsd4, nfsd4_ssc_expire_umount);
+
+void nfsd4_ssc_init_umount_work(void)
+{
+       if (nfsd4_ssc_umount.nsu_inited)
+               return;
+       INIT_DELAYED_WORK(&nfsd4_ssc_umount.nsu_umount_work,
+               nfsd4_ssc_expire_umount);
+       INIT_LIST_HEAD(&nfsd4_ssc_umount.nsu_list);
+       spin_lock_init(&nfsd4_ssc_umount.nsu_lock);
+       init_waitqueue_head(&nfsd4_ssc_umount.nsu_waitq);
+       nfsd4_ssc_umount.nsu_inited = true;
+}
+EXPORT_SYMBOL_GPL(nfsd4_ssc_init_umount_work);
+#endif
+
  #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
  #include <linux/security.h>

@@ -1181,6 +1256,9 @@ extern struct file *nfs42_ssc_open(struct vfsmount *ss_mnt,
         char *ipaddr, *dev_name, *raw_data;
         int len, raw_len;
         __be32 status = nfserr_inval;
+       struct nfsd4_ssc_umount_item *ni = 0;
+       struct nfsd4_ssc_umount_item *work, *tmp;
+       DEFINE_WAIT(wait);

         naddr = &nss->u.nl4_addr;
         tmp_addrlen = rpc_uaddr2sockaddr(SVC_NET(rqstp), naddr->addr,
@@ -1229,12 +1307,63 @@ extern struct file *nfs42_ssc_open(struct vfsmount *ss_mnt,
                 goto out_free_rawdata;
         snprintf(dev_name, len + 5, "%s%s%s:/", startsep, ipaddr, endsep);

+       work = kzalloc(sizeof(*work), GFP_KERNEL);
+try_again:
+       spin_lock(&nfsd4_ssc_umount.nsu_lock);
+       list_for_each_entry_safe(ni, tmp, &nfsd4_ssc_umount.nsu_list, nsui_list) {
+               if (strncmp(ni->nsui_ipaddr, ipaddr, sizeof(ni->nsui_ipaddr)))
+                       continue;
+               /* found a match */
+               if (ni->nsui_busy) {
+                       /*  wait - and try again */
+                       prepare_to_wait(&nfsd4_ssc_umount.nsu_waitq, &wait,
+                               TASK_INTERRUPTIBLE);
+                       spin_unlock(&nfsd4_ssc_umount.nsu_lock);
+                       if (signal_pending(current) ||
+                                       (schedule_timeout(20*HZ) == 0)) {
+                               status = nfserr_eagain;
+                               kfree(work);
+                               goto out_free_devname;
+                       }
+                       finish_wait(&nfsd4_ssc_umount.nsu_waitq, &wait);
+                       goto try_again;
+               }
+               ss_mnt = ni->nsui_vfsmount;
+               ni->nsui_refcnt++;
+               spin_unlock(&nfsd4_ssc_umount.nsu_lock);
+               kfree(work);
+               goto out_done;
+       }
+       /* create new entry, set busy, insert list, clear busy after mount */
+       if (work) {
+               strncpy(work->nsui_ipaddr, ipaddr, sizeof(work->nsui_ipaddr));
+               work->nsui_refcnt++;
+               work->nsui_busy = true;
+               list_add_tail(&work->nsui_list, &nfsd4_ssc_umount.nsu_list);
+       }
+       spin_unlock(&nfsd4_ssc_umount.nsu_lock);
+
         /* Use an 'internal' mount: SB_KERNMOUNT -> MNT_INTERNAL */
         ss_mnt = vfs_kern_mount(type, SB_KERNMOUNT, dev_name, raw_data);
         module_put(type->owner);
-       if (IS_ERR(ss_mnt))
+       if (IS_ERR(ss_mnt)) {
+               if (work) {
+                       spin_lock(&nfsd4_ssc_umount.nsu_lock);
+                       list_del(&work->nsui_list);
+                       wake_up_all(&nfsd4_ssc_umount.nsu_waitq);
+                       spin_unlock(&nfsd4_ssc_umount.nsu_lock);
+                       kfree(work);
+               }
                 goto out_free_devname;
-
+       }
+       if (work) {
+               spin_lock(&nfsd4_ssc_umount.nsu_lock);
+               work->nsui_vfsmount = ss_mnt;
+               work->nsui_busy = false;
+               wake_up_all(&nfsd4_ssc_umount.nsu_waitq);
+               spin_unlock(&nfsd4_ssc_umount.nsu_lock);
+       }
+out_done:
         status = 0;
         *mount = ss_mnt;

@@ -1301,10 +1430,44 @@ extern struct file *nfs42_ssc_open(struct vfsmount *ss_mnt,
  nfsd4_cleanup_inter_ssc(struct vfsmount *ss_mnt, struct nfsd_file *src,
                         struct nfsd_file *dst)
  {
+       bool found = false;
+       long timeout;
+       struct nfsd4_ssc_umount_item *tmp;
+       struct nfsd4_ssc_umount_item *ni = 0;
+
         nfs42_ssc_close(src->nf_file);
-       fput(src->nf_file);
         nfsd_file_put(dst);
-       mntput(ss_mnt);
+       fput(src->nf_file);
+
+       timeout = msecs_to_jiffies(nfsd4_ssc_umount_timeout);
+       spin_lock(&nfsd4_ssc_umount.nsu_lock);
+       list_for_each_entry_safe(ni, tmp, &nfsd4_ssc_umount.nsu_list,
+               nsui_list) {
+               if (ni->nsui_vfsmount->mnt_sb == ss_mnt->mnt_sb) {
+                       list_del(&ni->nsui_list);
+                       /*
+                        * vfsmount can be shared by multiple exports,
+                        * decrement refcnt and schedule delayed task
+                        * if it drops to 0.
+                        */
+                       ni->nsui_refcnt--;
+                       ni->nsui_expire = jiffies + timeout;
+                       list_add_tail(&ni->nsui_list, &nfsd4_ssc_umount.nsu_list);
+                       found = true;
+                       break;
+               }
+       }
+       if (!found) {
+               spin_unlock(&nfsd4_ssc_umount.nsu_lock);
+               mntput(ss_mnt);
+               return;
+       }
+       if (ni->nsui_refcnt == 0 && !nfsd4_ssc_umount.nsu_expire) {
+               nfsd4_ssc_umount.nsu_expire = ni->nsui_expire;
+               schedule_delayed_work(&nfsd4_ssc_umount.nsu_umount_work,
+                               timeout);
+       }
+       spin_unlock(&nfsd4_ssc_umount.nsu_lock);
  }

  #else /* CONFIG_NFSD_V4_2_INTER_SSC */
diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
index 8bdc37a..b3bf8a5 100644
--- a/fs/nfsd/nfsd.h
+++ b/fs/nfsd/nfsd.h
@@ -483,6 +483,10 @@ static inline bool nfsd_attrs_supported(u32 minorversion, const u32 *bmval)
  extern int nfsd4_is_junction(struct dentry *dentry);
  extern int register_cld_notifier(void);
  extern void unregister_cld_notifier(void);
+#ifdef CONFIG_NFSD_V4_2_INTER_SSC
+extern void nfsd4_ssc_init_umount_work(void);
+#endif
+
  #else /* CONFIG_NFSD_V4 */
  static inline int nfsd4_is_junction(struct dentry *dentry)
  {
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 6de4063..2558db5 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -322,6 +322,9 @@ static int nfsd_startup_generic(int nrservs)
         ret = nfs4_state_start();
         if (ret)
                 goto out_file_cache;
+#ifdef CONFIG_NFSD_V4_2_INTER_SSC
+       nfsd4_ssc_init_umount_work();
+#endif
         return 0;

  out_file_cache:
diff --git a/include/linux/nfs_ssc.h b/include/linux/nfs_ssc.h
index f5ba0fb..bb9ed6f 100644
--- a/include/linux/nfs_ssc.h
+++ b/include/linux/nfs_ssc.h
@@ -8,6 +8,7 @@
   */

  #include <linux/nfs_fs.h>
+#include <linux/sunrpc/svc.h>

  extern struct nfs_ssc_client_ops_tbl nfs_ssc_client_tbl;

@@ -52,6 +53,25 @@ static inline void nfs42_ssc_close(struct file *filep)
         if (nfs_ssc_client_tbl.ssc_nfs4_ops)
                 (*nfs_ssc_client_tbl.ssc_nfs4_ops->sco_close)(filep);
  }
+
+struct nfsd4_ssc_umount_item {
+       struct list_head nsui_list;
+       bool nsui_busy;
+       int nsui_refcnt;
+       unsigned long nsui_expire;
+       struct vfsmount *nsui_vfsmount;
+       char nsui_ipaddr[RPC_MAX_ADDRBUFLEN];
+};
+
+struct nfsd4_ssc_umount {
+       struct list_head nsu_list;
+       struct delayed_work nsu_umount_work;
+       spinlock_t nsu_lock;
+       unsigned long nsu_expire;
+       wait_queue_head_t nsu_waitq;
+       bool nsu_inited;
+};
+
  #endif

  /*
--
1.8.3.1







