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Date:   Fri, 6 Jan 2023 13:22:42 -0800
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Subject: Re: [PATCH v2 1/1] NFSD: enhance inter-server copy cleanup
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To:     Olga Kornievskaia <aglo@umich.edu>
Cc:     "jlayton@kernel.org" <jlayton@kernel.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        Chuck Lever <chuck.lever@oracle.com>
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From:   dai.ngo@oracle.com
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On 1/6/23 12:11 PM, Olga Kornievskaia wrote:
> On Thu, Jan 5, 2023 at 4:11 PM Olga Kornievskaia <aglo@umich.edu> wrote:
>> On Thu, Jan 5, 2023 at 3:00 PM <dai.ngo@oracle.com> wrote:
>>> Hi Olga,
>>>
>>> On 1/5/23 8:10 AM, Olga Kornievskaia wrote:
>>>> On Tue, Jan 3, 2023 at 11:14 AM Chuck Lever III <chuck.lever@oracle.com> wrote:
>>>>>
>>>>>> On Dec 18, 2022, at 7:55 PM, Dai Ngo <dai.ngo@oracle.com> wrote:
>>>>>>
>>>>>> Currently nfsd4_setup_inter_ssc returns the vfsmount of the source
>>>>>> server's export when the mount completes. After the copy is done
>>>>>> nfsd4_cleanup_inter_ssc is called with the vfsmount of the source
>>>>>> server and it searches nfsd_ssc_mount_list for a matching entry
>>>>>> to do the clean up.
>>>>>>
>>>>>> The problems with this approach are (1) the need to search the
>>>>>> nfsd_ssc_mount_list and (2) the code has to handle the case where
>>>>>> the matching entry is not found which looks ugly.
>>>>>>
>>>>>> The enhancement is instead of nfsd4_setup_inter_ssc returning the
>>>>>> vfsmount, it returns the nfsd4_ssc_umount_item which has the
>>>>>> vfsmount embedded in it. When nfsd4_cleanup_inter_ssc is called
>>>>>> it's passed with the nfsd4_ssc_umount_item directly to do the
>>>>>> clean up so no searching is needed and there is no need to handle
>>>>>> the 'not found' case.
>>>>>>
>>>>>> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
>>>>>> ---
>>>>>> V2: fix compile error when CONFIG_NFSD_V4_2_INTER_SSC not defined.
>>>>>>      Reported by kernel test robot.
>>>>> Hello Dai - I've looked at this, nothing to comment on so far. I
>>>>> plan to go over it again sometime this week.
>>>>>
>>>>> I'd like to hear from others before applying it.
>>>> I have looked at it and logically it seems ok to me.
>>> Thank you for reviewing the patch.
>>>
>>>>    I have tested it
>>>> (sorta. i'm rarely able to finish). But I keep running into the other
>>>> problem (nfsd4_state_shrinker_count soft lockup that's been already
>>>> reported). I find it interesting that only my destination server hits
>>>> the problem (but not the source server). I don't believe this patch
>>>> has anything to do with this problem, but I found it interesting that
>>>> ssc testing seems to trigger it 100%.
>>> It's strange that you and Mike keep having this problem, I've been trying
>>> to reproduce the problem using Mike's procedure with no success.
>>>
>>>   From Mike's report it seems that the struct delayed_work, part of the
>>> nfsd_net, was freed when nfsd4_state_shrinker_count was called. I'm trying
>>> to see why this could happen. Currently we call unregister_shrinker from
>>> nfsd_exit_net. Perhaps there is another path that the nfsd_net can be
>>> freed?
>>>
>>> Can you share your test procedure so I can try?
>> I have nothing special. I have 3 RHEL8 VMs running upstream kernels. 2
>> servers and 1 client. I'm just running nfstest_ssc --runtest inter01.
>> Given that the trace says it's kswapd that has this trace, doesn't it
>> mean my VM is stressed for memory perhaps. So perhaps see if you can
>> reduce your VM memsize? My VM has 2G of memory.
>>
>> I have reverted a1049eb47f20 commit but that didn't help.
> Ops. I reverted the wrong commit(s). Reverted 44df6f439a17,
> 3959066b697b, and the tracepoint one for cb_recall_any. I can run
> clean thru the ssc tests with this new patch.

Can you elaborate on the nfsd4_state_shrinker_count soft lockup
encountered when running the ssc tests with the above commits?
I'd like to make sure these are the same problems that Mike
reported.

Thanks,
-Dai
  

>
>>
>>> Thanks,
>>> -Dai
>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>>> fs/nfsd/nfs4proc.c      | 94 +++++++++++++++++++------------------------------
>>>>>> fs/nfsd/xdr4.h          |  2 +-
>>>>>> include/linux/nfs_ssc.h |  2 +-
>>>>>> 3 files changed, 38 insertions(+), 60 deletions(-)
>>>>>>
>>>>>> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
>>>>>> index b79ee65ae016..6515b00520bc 100644
>>>>>> --- a/fs/nfsd/nfs4proc.c
>>>>>> +++ b/fs/nfsd/nfs4proc.c
>>>>>> @@ -1295,15 +1295,15 @@ extern void nfs_sb_deactive(struct super_block *sb);
>>>>>>    * setup a work entry in the ssc delayed unmount list.
>>>>>>    */
>>>>>> static __be32 nfsd4_ssc_setup_dul(struct nfsd_net *nn, char *ipaddr,
>>>>>> -             struct nfsd4_ssc_umount_item **retwork, struct vfsmount **ss_mnt)
>>>>>> +             struct nfsd4_ssc_umount_item **nsui)
>>>>>> {
>>>>>>         struct nfsd4_ssc_umount_item *ni = NULL;
>>>>>>         struct nfsd4_ssc_umount_item *work = NULL;
>>>>>>         struct nfsd4_ssc_umount_item *tmp;
>>>>>>         DEFINE_WAIT(wait);
>>>>>> +     __be32 status = 0;
>>>>>>
>>>>>> -     *ss_mnt = NULL;
>>>>>> -     *retwork = NULL;
>>>>>> +     *nsui = NULL;
>>>>>>         work = kzalloc(sizeof(*work), GFP_KERNEL);
>>>>>> try_again:
>>>>>>         spin_lock(&nn->nfsd_ssc_lock);
>>>>>> @@ -1326,12 +1326,12 @@ static __be32 nfsd4_ssc_setup_dul(struct nfsd_net *nn, char *ipaddr,
>>>>>>                         finish_wait(&nn->nfsd_ssc_waitq, &wait);
>>>>>>                         goto try_again;
>>>>>>                 }
>>>>>> -             *ss_mnt = ni->nsui_vfsmount;
>>>>>> +             *nsui = ni;
>>>>>>                 refcount_inc(&ni->nsui_refcnt);
>>>>>>                 spin_unlock(&nn->nfsd_ssc_lock);
>>>>>>                 kfree(work);
>>>>>>
>>>>>> -             /* return vfsmount in ss_mnt */
>>>>>> +             /* return vfsmount in (*nsui)->nsui_vfsmount */
>>>>>>                 return 0;
>>>>>>         }
>>>>>>         if (work) {
>>>>>> @@ -1339,10 +1339,11 @@ static __be32 nfsd4_ssc_setup_dul(struct nfsd_net *nn, char *ipaddr,
>>>>>>                 refcount_set(&work->nsui_refcnt, 2);
>>>>>>                 work->nsui_busy = true;
>>>>>>                 list_add_tail(&work->nsui_list, &nn->nfsd_ssc_mount_list);
>>>>>> -             *retwork = work;
>>>>>> -     }
>>>>>> +             *nsui = work;
>>>>>> +     } else
>>>>>> +             status = nfserr_resource;
>>>>>>         spin_unlock(&nn->nfsd_ssc_lock);
>>>>>> -     return 0;
>>>>>> +     return status;
>>>>>> }
>>>>>>
>>>>>> static void nfsd4_ssc_update_dul_work(struct nfsd_net *nn,
>>>>>> @@ -1371,7 +1372,7 @@ static void nfsd4_ssc_cancel_dul_work(struct nfsd_net *nn,
>>>>>>    */
>>>>>> static __be32
>>>>>> nfsd4_interssc_connect(struct nl4_server *nss, struct svc_rqst *rqstp,
>>>>>> -                    struct vfsmount **mount)
>>>>>> +                     struct nfsd4_ssc_umount_item **nsui)
>>>>>> {
>>>>>>         struct file_system_type *type;
>>>>>>         struct vfsmount *ss_mnt;
>>>>>> @@ -1382,7 +1383,6 @@ nfsd4_interssc_connect(struct nl4_server *nss, struct svc_rqst *rqstp,
>>>>>>         char *ipaddr, *dev_name, *raw_data;
>>>>>>         int len, raw_len;
>>>>>>         __be32 status = nfserr_inval;
>>>>>> -     struct nfsd4_ssc_umount_item *work = NULL;
>>>>>>         struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
>>>>>>
>>>>>>         naddr = &nss->u.nl4_addr;
>>>>>> @@ -1390,6 +1390,7 @@ nfsd4_interssc_connect(struct nl4_server *nss, struct svc_rqst *rqstp,
>>>>>>                                          naddr->addr_len,
>>>>>>                                          (struct sockaddr *)&tmp_addr,
>>>>>>                                          sizeof(tmp_addr));
>>>>>> +     *nsui = NULL;
>>>>>>         if (tmp_addrlen == 0)
>>>>>>                 goto out_err;
>>>>>>
>>>>>> @@ -1432,10 +1433,10 @@ nfsd4_interssc_connect(struct nl4_server *nss, struct svc_rqst *rqstp,
>>>>>>                 goto out_free_rawdata;
>>>>>>         snprintf(dev_name, len + 5, "%s%s%s:/", startsep, ipaddr, endsep);
>>>>>>
>>>>>> -     status = nfsd4_ssc_setup_dul(nn, ipaddr, &work, &ss_mnt);
>>>>>> +     status = nfsd4_ssc_setup_dul(nn, ipaddr, nsui);
>>>>>>         if (status)
>>>>>>                 goto out_free_devname;
>>>>>> -     if (ss_mnt)
>>>>>> +     if ((*nsui)->nsui_vfsmount)
>>>>>>                 goto out_done;
>>>>>>
>>>>>>         /* Use an 'internal' mount: SB_KERNMOUNT -> MNT_INTERNAL */
>>>>>> @@ -1443,15 +1444,12 @@ nfsd4_interssc_connect(struct nl4_server *nss, struct svc_rqst *rqstp,
>>>>>>         module_put(type->owner);
>>>>>>         if (IS_ERR(ss_mnt)) {
>>>>>>                 status = nfserr_nodev;
>>>>>> -             if (work)
>>>>>> -                     nfsd4_ssc_cancel_dul_work(nn, work);
>>>>>> +             nfsd4_ssc_cancel_dul_work(nn, *nsui);
>>>>>>                 goto out_free_devname;
>>>>>>         }
>>>>>> -     if (work)
>>>>>> -             nfsd4_ssc_update_dul_work(nn, work, ss_mnt);
>>>>>> +     nfsd4_ssc_update_dul_work(nn, *nsui, ss_mnt);
>>>>>> out_done:
>>>>>>         status = 0;
>>>>>> -     *mount = ss_mnt;
>>>>>>
>>>>>> out_free_devname:
>>>>>>         kfree(dev_name);
>>>>>> @@ -1474,8 +1472,7 @@ nfsd4_interssc_connect(struct nl4_server *nss, struct svc_rqst *rqstp,
>>>>>>    */
>>>>>> static __be32
>>>>>> nfsd4_setup_inter_ssc(struct svc_rqst *rqstp,
>>>>>> -                   struct nfsd4_compound_state *cstate,
>>>>>> -                   struct nfsd4_copy *copy, struct vfsmount **mount)
>>>>>> +             struct nfsd4_compound_state *cstate, struct nfsd4_copy *copy)
>>>>>> {
>>>>>>         struct svc_fh *s_fh = NULL;
>>>>>>         stateid_t *s_stid = &copy->cp_src_stateid;
>>>>>> @@ -1488,7 +1485,8 @@ nfsd4_setup_inter_ssc(struct svc_rqst *rqstp,
>>>>>>         if (status)
>>>>>>                 goto out;
>>>>>>
>>>>>> -     status = nfsd4_interssc_connect(copy->cp_src, rqstp, mount);
>>>>>> +     status = nfsd4_interssc_connect(copy->cp_src, rqstp,
>>>>>> +                             &copy->ss_nsui);
>>>>>>         if (status)
>>>>>>                 goto out;
>>>>>>
>>>>>> @@ -1506,61 +1504,42 @@ nfsd4_setup_inter_ssc(struct svc_rqst *rqstp,
>>>>>> }
>>>>>>
>>>>>> static void
>>>>>> -nfsd4_cleanup_inter_ssc(struct vfsmount *ss_mnt, struct file *filp,
>>>>>> +nfsd4_cleanup_inter_ssc(struct nfsd4_ssc_umount_item *ni, struct file *filp,
>>>>>>                         struct nfsd_file *dst)
>>>>>> {
>>>>>> -     bool found = false;
>>>>>>         long timeout;
>>>>>> -     struct nfsd4_ssc_umount_item *tmp;
>>>>>> -     struct nfsd4_ssc_umount_item *ni = NULL;
>>>>>>         struct nfsd_net *nn = net_generic(dst->nf_net, nfsd_net_id);
>>>>>>
>>>>>>         nfs42_ssc_close(filp);
>>>>>>         nfsd_file_put(dst);
>>>>>>         fput(filp);
>>>>>>
>>>>>> -     if (!nn) {
>>>>>> -             mntput(ss_mnt);
>>>>>> -             return;
>>>>>> -     }
>>>>>>         spin_lock(&nn->nfsd_ssc_lock);
>>>>>>         timeout = msecs_to_jiffies(nfsd4_ssc_umount_timeout);
>>>>>> -     list_for_each_entry_safe(ni, tmp, &nn->nfsd_ssc_mount_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. If the count drops to 1 it
>>>>>> -                      * will be unmounted when nsui_expire expires.
>>>>>> -                      */
>>>>>> -                     refcount_dec(&ni->nsui_refcnt);
>>>>>> -                     ni->nsui_expire = jiffies + timeout;
>>>>>> -                     list_add_tail(&ni->nsui_list, &nn->nfsd_ssc_mount_list);
>>>>>> -                     found = true;
>>>>>> -                     break;
>>>>>> -             }
>>>>>> -     }
>>>>>> +     list_del(&ni->nsui_list);
>>>>>> +     /*
>>>>>> +      * vfsmount can be shared by multiple exports,
>>>>>> +      * decrement refcnt. If the count drops to 1 it
>>>>>> +      * will be unmounted when nsui_expire expires.
>>>>>> +      */
>>>>>> +     refcount_dec(&ni->nsui_refcnt);
>>>>>> +     ni->nsui_expire = jiffies + timeout;
>>>>>> +     list_add_tail(&ni->nsui_list, &nn->nfsd_ssc_mount_list);
>>>>>>         spin_unlock(&nn->nfsd_ssc_lock);
>>>>>> -     if (!found) {
>>>>>> -             mntput(ss_mnt);
>>>>>> -             return;
>>>>>> -     }
>>>>>> }
>>>>>>
>>>>>> #else /* CONFIG_NFSD_V4_2_INTER_SSC */
>>>>>>
>>>>>> static __be32
>>>>>> nfsd4_setup_inter_ssc(struct svc_rqst *rqstp,
>>>>>> -                   struct nfsd4_compound_state *cstate,
>>>>>> -                   struct nfsd4_copy *copy,
>>>>>> -                   struct vfsmount **mount)
>>>>>> +                     struct nfsd4_compound_state *cstate,
>>>>>> +                     struct nfsd4_copy *copy)
>>>>>> {
>>>>>> -     *mount = NULL;
>>>>>>         return nfserr_inval;
>>>>>> }
>>>>>>
>>>>>> static void
>>>>>> -nfsd4_cleanup_inter_ssc(struct vfsmount *ss_mnt, struct file *filp,
>>>>>> +nfsd4_cleanup_inter_ssc(struct nfsd4_ssc_umount_item *ni, struct file *filp,
>>>>>>                         struct nfsd_file *dst)
>>>>>> {
>>>>>> }
>>>>>> @@ -1700,7 +1679,7 @@ static void dup_copy_fields(struct nfsd4_copy *src, struct nfsd4_copy *dst)
>>>>>>         memcpy(dst->cp_src, src->cp_src, sizeof(struct nl4_server));
>>>>>>         memcpy(&dst->stateid, &src->stateid, sizeof(src->stateid));
>>>>>>         memcpy(&dst->c_fh, &src->c_fh, sizeof(src->c_fh));
>>>>>> -     dst->ss_mnt = src->ss_mnt;
>>>>>> +     dst->ss_nsui = src->ss_nsui;
>>>>>> }
>>>>>>
>>>>>> static void cleanup_async_copy(struct nfsd4_copy *copy)
>>>>>> @@ -1749,8 +1728,8 @@ static int nfsd4_do_async_copy(void *data)
>>>>>>         if (nfsd4_ssc_is_inter(copy)) {
>>>>>>                 struct file *filp;
>>>>>>
>>>>>> -             filp = nfs42_ssc_open(copy->ss_mnt, &copy->c_fh,
>>>>>> -                                   &copy->stateid);
>>>>>> +             filp = nfs42_ssc_open(copy->ss_nsui->nsui_vfsmount,
>>>>>> +                             &copy->c_fh, &copy->stateid);
>>>>>>                 if (IS_ERR(filp)) {
>>>>>>                         switch (PTR_ERR(filp)) {
>>>>>>                         case -EBADF:
>>>>>> @@ -1764,7 +1743,7 @@ static int nfsd4_do_async_copy(void *data)
>>>>>>                 }
>>>>>>                 nfserr = nfsd4_do_copy(copy, filp, copy->nf_dst->nf_file,
>>>>>>                                        false);
>>>>>> -             nfsd4_cleanup_inter_ssc(copy->ss_mnt, filp, copy->nf_dst);
>>>>>> +             nfsd4_cleanup_inter_ssc(copy->ss_nsui, filp, copy->nf_dst);
>>>>>>         } else {
>>>>>>                 nfserr = nfsd4_do_copy(copy, copy->nf_src->nf_file,
>>>>>>                                        copy->nf_dst->nf_file, false);
>>>>>> @@ -1790,8 +1769,7 @@ nfsd4_copy(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>>>>>>                         status = nfserr_notsupp;
>>>>>>                         goto out;
>>>>>>                 }
>>>>>> -             status = nfsd4_setup_inter_ssc(rqstp, cstate, copy,
>>>>>> -                             &copy->ss_mnt);
>>>>>> +             status = nfsd4_setup_inter_ssc(rqstp, cstate, copy);
>>>>>>                 if (status)
>>>>>>                         return nfserr_offload_denied;
>>>>>>         } else {
>>>>>> diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
>>>>>> index 0eb00105d845..36c3340c1d54 100644
>>>>>> --- a/fs/nfsd/xdr4.h
>>>>>> +++ b/fs/nfsd/xdr4.h
>>>>>> @@ -571,7 +571,7 @@ struct nfsd4_copy {
>>>>>>         struct task_struct      *copy_task;
>>>>>>         refcount_t              refcount;
>>>>>>
>>>>>> -     struct vfsmount         *ss_mnt;
>>>>>> +     struct nfsd4_ssc_umount_item *ss_nsui;
>>>>>>         struct nfs_fh           c_fh;
>>>>>>         nfs4_stateid            stateid;
>>>>>> };
>>>>>> diff --git a/include/linux/nfs_ssc.h b/include/linux/nfs_ssc.h
>>>>>> index 75843c00f326..22265b1ff080 100644
>>>>>> --- a/include/linux/nfs_ssc.h
>>>>>> +++ b/include/linux/nfs_ssc.h
>>>>>> @@ -53,6 +53,7 @@ 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);
>>>>>> }
>>>>>> +#endif
>>>>>>
>>>>>> struct nfsd4_ssc_umount_item {
>>>>>>         struct list_head nsui_list;
>>>>>> @@ -66,7 +67,6 @@ struct nfsd4_ssc_umount_item {
>>>>>>         struct vfsmount *nsui_vfsmount;
>>>>>>         char nsui_ipaddr[RPC_MAX_ADDRBUFLEN + 1];
>>>>>> };
>>>>>> -#endif
>>>>>>
>>>>>> /*
>>>>>>    * NFS_FS
>>>>>> --
>>>>>> 2.9.5
>>>>>>
>>>>> --
>>>>> Chuck Lever
>>>>>
>>>>>
>>>>>