race in state manager leads to failed recovery

Commit Message

Olga Kornievskaia June 8, 2017, 7:47 p.m. UTC

Trond, any thoughts on this?

Another idea I had and tested to be effective was to introduce a new
state bit "NFS_STATE_RECLAIM_INPROGRESS". If it's set then the new
calls to nfs4_state_mark_reclaim_nograce() are just ignored.

  set_bit(NFS_OWNER_RECLAIM_NOGRACE, &state->owner->so_flags);
@@ -1522,6 +1524,7 @@ static int nfs4_reclaim_open_state(struct
nfs4_state_owner *sp, const struct nfs
  continue;
  atomic_inc(&state->count);
  spin_unlock(&sp->so_lock);
+ set_bit(NFS_STATE_RECLAIM_INPROGRESS, &state->flags);
  status = ops->recover_open(sp, state);
  if (status >= 0) {
  status = nfs4_reclaim_locks(state, ops);
@@ -1538,6 +1541,8 @@ static int nfs4_reclaim_open_state(struct
nfs4_state_owner *sp, const struct nfs
  }
  clear_bit(NFS_STATE_RECLAIM_NOGRACE,
  &state->flags);
+ clear_bit(NFS_STATE_RECLAIM_INPROGRESS,
+ &state->flags);
  nfs4_put_open_state(state);
  spin_lock(&sp->so_lock);
  goto restart;

On Tue, Jun 6, 2017 at 12:39 PM, Olga Kornievskaia <[e-mail]> wrote:
> An application can fail with EIO when the server reboots and the
> client while doing the recovery is getting into the following
> situation where it incorrectly chooses "nograce" recovery instead of
> "reboot" recovery. The necessary trigger is a pnfs mount and 2 DS
> reads on the same file fail with BAD_STATEID each read uses its own
> lock stateid (and MDS server reboots losing state). Since  server
> rebooted it will fail recovery ops with BAD_SESSION and then also
> STALE_ID triggering session and clientid recovery.
>
> 1. Thread1 gets BAD_STATEID initiates stateid recovery calls
> nfs4_state_mark_reclaim_no_grace() which sets the cl_state->flags and
> state->flags respective _NOGRACE flags.
>
> 2. State manager gets to run and it clears the _NOGRACE from the
> cl_state. Calls nfs4_do_reclaim() which sends TEST_STATEID which gets
> a BAD_SESSION.
>
> 3. Thread2 now gets control and it also processing its BAD_STATEID and
> calls nfs4_state_mark_reclaim_no_grace() and it again sets the
> state/cl_state->flags to have _NOGRACE.
>
> 4. State manager runs and continues with state recovery by sending
> DESTROY_SESSION, and then CREATE_SESSION which fails with
> STALE_CLIENTID. Now we are recovering the lease.
>
> 5. State manager in nfs4_recovery_handle_error for STALE_CLIENTID,
> calls nfs4_state_start_reclaim_reboot() calls
> nfs4_state_mark_reclaim_reboot() which has a check
>
> /* Don't recover state that expired before the reboot */
> if (test_bit(NFS_STATE_RECLAIM_NOGRACE, &state->flags)) {
>   clear_bit(NFS_STATE_RECLAIM_REBOOT, &state->flags);
>   return 0;
> }
>
> Because the _NOGRACE was set again in Step3, we end up clearing
> _RECLAIM_REBOOT and not setting _RECLAIM_REBOOT in the cl_state->flags
> and choose to do "nograce" operation instead of recovery.
>
> Removing this check removes the problem.
>
> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
> index 06274e3..2c668a0 100644
> --- a/fs/nfs/nfs4state.c
> +++ b/fs/nfs/nfs4state.c
> @@ -1321,11 +1321,6 @@ static int
> nfs4_state_mark_reclaim_reboot(struct nfs_client *clp, struct nfs4_st
>   if (!nfs4_valid_open_stateid(state))
>   return 0;
>   set_bit(NFS_STATE_RECLAIM_REBOOT, &state->flags);
> - /* Don't recover state that expired before the reboot */
> - if (test_bit(NFS_STATE_RECLAIM_NOGRACE, &state->flags)) {
> - clear_bit(NFS_STATE_RECLAIM_REBOOT, &state->flags);
> - return 0;
> - }
>   set_bit(NFS_OWNER_RECLAIM_REBOOT, &state->owner->so_flags);
>   set_bit(NFS4CLNT_RECLAIM_REBOOT, &clp->cl_state);
>   return 1;
>
> I'm confused by the comment why would we not what to recover state?
>
> When both threads execute before the state manager starts this problem
> doesn't exist.
>
> If helpful here are two annotated (**) snippet from var log message
> from the non-working and then one without the check:
>
> Jun  6 12:06:42 ipa18 kernel: nfs4_state_mark_reclaim_nograce ffff880072f50c00
>    ** first thread sets the nograce recovery
> Jun  6 12:06:42 ipa18 kernel: AGLO: nfs4_state_manager reclaim_nograce
> cleared NOGRACE from client state ffff88006fc23d28
>   ** this is from the state manager’s loop from after
> test_and_clear(NFS4CLNT_RECLAIM_NO_GRACE, cl_state)
> Jun  6 12:06:42 ipa18 kernel: AGLO: nfs4_do_reclaim start
> Jun  6 12:06:42 ipa18 kernel: NFS call  test_stateid ffff880077ac0af0
> Jun  6 12:06:42 ipa18 kernel: nfs4_state_mark_reclaim_nograce ffff880072f50c00
>    ** 2nd thread sets the nograce recovery
> Jun  6 12:06:42 ipa18 kernel: AGLO: nfs4_do_reclaim status end=-11
> Jun  6 12:06:42 ipa18 kernel: AGLO: nfs4_begin_drain_session
> Jun  6 12:06:42 ipa18 kernel: AGLO: nfs4_state_mark_reclaim_reboot
> clears RECLAIM_REBOOT from state=ffff880072f50c00
>    ** this is from nfs4_state_mark_reclaim_reboot() and ends up not
> setting the _RECLAIM_REBOOT flag in cl_state and clears it from the
> state->flags
> Jun  6 12:06:42 ipa18 kernel: AGLO: nfs4_begin_drain_session
> Jun  6 12:06:43 ipa18 kernel: AGLO: nfs4_begin_drain_session
> Jun  6 12:06:43 ipa18 kernel: AGLO: nfs4_reclaim_lease client
> state=ffff88006fc23d28 flag has NOGRACE
> Jun  6 12:06:43 ipa18 kernel: AGLO: nfs4_state_manager reclaim_nograce
> cleared NOGRACE from client state ffff88006fc23d28
>    ** this is in the state manager loop after the "reclaim_nograce" is
> chosen and clearing the _NOGRACE flag
> Jun  6 12:06:43 ipa18 kernel: AGLO: nfs4_do_reclaim start
> Jun  6 12:06:43 ipa18 kernel: NFS call  test_stateid ffff880077ac0af0
> Jun  6 12:06:43 ipa18 kernel: NFS call  test_stateid ffff880077ac02f0
> Jun  6 12:06:43 ipa18 kernel: NFS call  test_stateid ffff880072f50c68
> Jun  6 12:06:43 ipa18 kernel: NFS: nfs4_reclaim_open_state: Lock reclaim failed!
> Jun  6 12:06:43 ipa18 kernel: NFS: nfs4_reclaim_open_state: Lock reclaim failed!
> Jun  6 12:06:43 ipa18 kernel: AGLO: nfs4_reclaim_open_state clearing
> NOGRACE from state=ffff880072f50c00
> Jun  6 12:06:43 ipa18 kernel: AGLO: nfs4_do_reclaim end=0
> Jun  6 12:06:43 ipa18 kernel: AGLO: nfs4_end_drain_session
>
> This is a snippet from when we ignore that _NOGRACE is set and proceed
> to set the _RECLAIM_REBOOT
> Jun  6 12:21:58 ipa18 kernel: nfs4_state_mark_reclaim_nograce ffff88007363bbc0
> Jun  6 12:21:58 ipa18 kernel: AGLO: nfs4_state_manager reclaim_nograce
> cleared NOGRACE from client state ffff88002febe528
> Jun  6 12:21:58 ipa18 kernel: AGLO: nfs4_do_reclaim start
> Jun  6 12:21:58 ipa18 kernel: NFS call  test_stateid ffff880077ac4cf0
> Jun  6 12:21:58 ipa18 kernel: nfs4_state_mark_reclaim_nograce ffff88007363bbc0
> Jun  6 12:21:58 ipa18 kernel: AGLO: nfs4_do_reclaim status end=-11
> Jun  6 12:21:58 ipa18 kernel: AGLO: nfs4_begin_drain_session
> Jun  6 12:21:58 ipa18 kernel: AGLO: nfs4_state_mark_reclaim_reboot NOT
> clearing _RECLAIM_REBOOT from state=ffff88007363bbc0
>     *** Removing the check and instead proceeding to set the
> _RECLAIM_REBOOT in the cl_state->flags so that
> Jun  6 12:21:58 ipa18 kernel: AGLO: nfs4_begin_drain_session
> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_begin_drain_session
> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_reclaim_lease client
> state=ffff88002febe528 flag has NOGRACE
> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_state_manager reclaim reboot
> op cl_state=ffff88002febe528
>    *** Unlike the previous case the state manager now goes into the
> reclaim reboot state.
> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_do_reclaim start
> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_reclaim_open_state clearing
> NOGRACE from state=ffff88007363bbc0
> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_do_reclaim end=0
> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_state_manager reclaim_nograce
> cleared NOGRACE from client state ffff88002febe528
> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_do_reclaim start
> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_do_reclaim end=0
> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_end_drain_session
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Comments

Olga Kornievskaia June 14, 2017, 3:48 p.m. UTC | #1

Hi Trond,

Can you comment on what your thoughts on this one? There is great
interest in trying to get this fixed so that it could be included in
various distros.

Thanks.

On Thu, Jun 8, 2017 at 3:47 PM, Olga Kornievskaia <[e-mail]> wrote:
> Trond, any thoughts on this?
>
> Another idea I had and tested to be effective was to introduce a new
> state bit "NFS_STATE_RECLAIM_INPROGRESS". If it's set then the new
> calls to nfs4_state_mark_reclaim_nograce() are just ignored.
>
> diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
> index af285cc..0f20f12 100644
> --- a/fs/nfs/nfs4_fs.h
> +++ b/fs/nfs/nfs4_fs.h
> @@ -158,6 +158,7 @@ enum {
>   NFS_O_RDWR_STATE, /* OPEN stateid has read/write state */
>   NFS_STATE_RECLAIM_REBOOT, /* OPEN stateid server rebooted */
>   NFS_STATE_RECLAIM_NOGRACE, /* OPEN stateid needs to recover state */
> + NFS_STATE_RECLAIM_INPROGRESS, /* OPEN stateid recovery is in progress */
>   NFS_STATE_POSIX_LOCKS, /* Posix locks are supported */
>   NFS_STATE_RECOVERY_FAILED, /* OPEN stateid state recovery failed */
>   NFS_STATE_MAY_NOTIFY_LOCK, /* server may CB_NOTIFY_LOCK */
> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
> index b34de03..4eef2eb 100644
> --- a/fs/nfs/nfs4state.c
> +++ b/fs/nfs/nfs4state.c
> @@ -1335,6 +1335,8 @@ int nfs4_state_mark_reclaim_nograce(struct
> nfs_client *clp, struct nfs4_state *s
>  {
>   if (!nfs4_valid_open_stateid(state))
>   return 0;
> + if (test_bit(NFS_STATE_RECLAIM_INPROGRESS, &state->flags))
> + return 1;
>   set_bit(NFS_STATE_RECLAIM_NOGRACE, &state->flags);
>   clear_bit(NFS_STATE_RECLAIM_REBOOT, &state->flags);
>   set_bit(NFS_OWNER_RECLAIM_NOGRACE, &state->owner->so_flags);
> @@ -1522,6 +1524,7 @@ static int nfs4_reclaim_open_state(struct
> nfs4_state_owner *sp, const struct nfs
>   continue;
>   atomic_inc(&state->count);
>   spin_unlock(&sp->so_lock);
> + set_bit(NFS_STATE_RECLAIM_INPROGRESS, &state->flags);
>   status = ops->recover_open(sp, state);
>   if (status >= 0) {
>   status = nfs4_reclaim_locks(state, ops);
> @@ -1538,6 +1541,8 @@ static int nfs4_reclaim_open_state(struct
> nfs4_state_owner *sp, const struct nfs
>   }
>   clear_bit(NFS_STATE_RECLAIM_NOGRACE,
>   &state->flags);
> + clear_bit(NFS_STATE_RECLAIM_INPROGRESS,
> + &state->flags);
>   nfs4_put_open_state(state);
>   spin_lock(&sp->so_lock);
>   goto restart;
>
> On Tue, Jun 6, 2017 at 12:39 PM, Olga Kornievskaia <[e-mail]> wrote:
>> An application can fail with EIO when the server reboots and the
>> client while doing the recovery is getting into the following
>> situation where it incorrectly chooses "nograce" recovery instead of
>> "reboot" recovery. The necessary trigger is a pnfs mount and 2 DS
>> reads on the same file fail with BAD_STATEID each read uses its own
>> lock stateid (and MDS server reboots losing state). Since  server
>> rebooted it will fail recovery ops with BAD_SESSION and then also
>> STALE_ID triggering session and clientid recovery.
>>
>> 1. Thread1 gets BAD_STATEID initiates stateid recovery calls
>> nfs4_state_mark_reclaim_no_grace() which sets the cl_state->flags and
>> state->flags respective _NOGRACE flags.
>>
>> 2. State manager gets to run and it clears the _NOGRACE from the
>> cl_state. Calls nfs4_do_reclaim() which sends TEST_STATEID which gets
>> a BAD_SESSION.
>>
>> 3. Thread2 now gets control and it also processing its BAD_STATEID and
>> calls nfs4_state_mark_reclaim_no_grace() and it again sets the
>> state/cl_state->flags to have _NOGRACE.
>>
>> 4. State manager runs and continues with state recovery by sending
>> DESTROY_SESSION, and then CREATE_SESSION which fails with
>> STALE_CLIENTID. Now we are recovering the lease.
>>
>> 5. State manager in nfs4_recovery_handle_error for STALE_CLIENTID,
>> calls nfs4_state_start_reclaim_reboot() calls
>> nfs4_state_mark_reclaim_reboot() which has a check
>>
>> /* Don't recover state that expired before the reboot */
>> if (test_bit(NFS_STATE_RECLAIM_NOGRACE, &state->flags)) {
>>   clear_bit(NFS_STATE_RECLAIM_REBOOT, &state->flags);
>>   return 0;
>> }
>>
>> Because the _NOGRACE was set again in Step3, we end up clearing
>> _RECLAIM_REBOOT and not setting _RECLAIM_REBOOT in the cl_state->flags
>> and choose to do "nograce" operation instead of recovery.
>>
>> Removing this check removes the problem.
>>
>> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
>> index 06274e3..2c668a0 100644
>> --- a/fs/nfs/nfs4state.c
>> +++ b/fs/nfs/nfs4state.c
>> @@ -1321,11 +1321,6 @@ static int
>> nfs4_state_mark_reclaim_reboot(struct nfs_client *clp, struct nfs4_st
>>   if (!nfs4_valid_open_stateid(state))
>>   return 0;
>>   set_bit(NFS_STATE_RECLAIM_REBOOT, &state->flags);
>> - /* Don't recover state that expired before the reboot */
>> - if (test_bit(NFS_STATE_RECLAIM_NOGRACE, &state->flags)) {
>> - clear_bit(NFS_STATE_RECLAIM_REBOOT, &state->flags);
>> - return 0;
>> - }
>>   set_bit(NFS_OWNER_RECLAIM_REBOOT, &state->owner->so_flags);
>>   set_bit(NFS4CLNT_RECLAIM_REBOOT, &clp->cl_state);
>>   return 1;
>>
>> I'm confused by the comment why would we not what to recover state?
>>
>> When both threads execute before the state manager starts this problem
>> doesn't exist.
>>
>> If helpful here are two annotated (**) snippet from var log message
>> from the non-working and then one without the check:
>>
>> Jun  6 12:06:42 ipa18 kernel: nfs4_state_mark_reclaim_nograce ffff880072f50c00
>>    ** first thread sets the nograce recovery
>> Jun  6 12:06:42 ipa18 kernel: AGLO: nfs4_state_manager reclaim_nograce
>> cleared NOGRACE from client state ffff88006fc23d28
>>   ** this is from the state manager’s loop from after
>> test_and_clear(NFS4CLNT_RECLAIM_NO_GRACE, cl_state)
>> Jun  6 12:06:42 ipa18 kernel: AGLO: nfs4_do_reclaim start
>> Jun  6 12:06:42 ipa18 kernel: NFS call  test_stateid ffff880077ac0af0
>> Jun  6 12:06:42 ipa18 kernel: nfs4_state_mark_reclaim_nograce ffff880072f50c00
>>    ** 2nd thread sets the nograce recovery
>> Jun  6 12:06:42 ipa18 kernel: AGLO: nfs4_do_reclaim status end=-11
>> Jun  6 12:06:42 ipa18 kernel: AGLO: nfs4_begin_drain_session
>> Jun  6 12:06:42 ipa18 kernel: AGLO: nfs4_state_mark_reclaim_reboot
>> clears RECLAIM_REBOOT from state=ffff880072f50c00
>>    ** this is from nfs4_state_mark_reclaim_reboot() and ends up not
>> setting the _RECLAIM_REBOOT flag in cl_state and clears it from the
>> state->flags
>> Jun  6 12:06:42 ipa18 kernel: AGLO: nfs4_begin_drain_session
>> Jun  6 12:06:43 ipa18 kernel: AGLO: nfs4_begin_drain_session
>> Jun  6 12:06:43 ipa18 kernel: AGLO: nfs4_reclaim_lease client
>> state=ffff88006fc23d28 flag has NOGRACE
>> Jun  6 12:06:43 ipa18 kernel: AGLO: nfs4_state_manager reclaim_nograce
>> cleared NOGRACE from client state ffff88006fc23d28
>>    ** this is in the state manager loop after the "reclaim_nograce" is
>> chosen and clearing the _NOGRACE flag
>> Jun  6 12:06:43 ipa18 kernel: AGLO: nfs4_do_reclaim start
>> Jun  6 12:06:43 ipa18 kernel: NFS call  test_stateid ffff880077ac0af0
>> Jun  6 12:06:43 ipa18 kernel: NFS call  test_stateid ffff880077ac02f0
>> Jun  6 12:06:43 ipa18 kernel: NFS call  test_stateid ffff880072f50c68
>> Jun  6 12:06:43 ipa18 kernel: NFS: nfs4_reclaim_open_state: Lock reclaim failed!
>> Jun  6 12:06:43 ipa18 kernel: NFS: nfs4_reclaim_open_state: Lock reclaim failed!
>> Jun  6 12:06:43 ipa18 kernel: AGLO: nfs4_reclaim_open_state clearing
>> NOGRACE from state=ffff880072f50c00
>> Jun  6 12:06:43 ipa18 kernel: AGLO: nfs4_do_reclaim end=0
>> Jun  6 12:06:43 ipa18 kernel: AGLO: nfs4_end_drain_session
>>
>> This is a snippet from when we ignore that _NOGRACE is set and proceed
>> to set the _RECLAIM_REBOOT
>> Jun  6 12:21:58 ipa18 kernel: nfs4_state_mark_reclaim_nograce ffff88007363bbc0
>> Jun  6 12:21:58 ipa18 kernel: AGLO: nfs4_state_manager reclaim_nograce
>> cleared NOGRACE from client state ffff88002febe528
>> Jun  6 12:21:58 ipa18 kernel: AGLO: nfs4_do_reclaim start
>> Jun  6 12:21:58 ipa18 kernel: NFS call  test_stateid ffff880077ac4cf0
>> Jun  6 12:21:58 ipa18 kernel: nfs4_state_mark_reclaim_nograce ffff88007363bbc0
>> Jun  6 12:21:58 ipa18 kernel: AGLO: nfs4_do_reclaim status end=-11
>> Jun  6 12:21:58 ipa18 kernel: AGLO: nfs4_begin_drain_session
>> Jun  6 12:21:58 ipa18 kernel: AGLO: nfs4_state_mark_reclaim_reboot NOT
>> clearing _RECLAIM_REBOOT from state=ffff88007363bbc0
>>     *** Removing the check and instead proceeding to set the
>> _RECLAIM_REBOOT in the cl_state->flags so that
>> Jun  6 12:21:58 ipa18 kernel: AGLO: nfs4_begin_drain_session
>> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_begin_drain_session
>> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_reclaim_lease client
>> state=ffff88002febe528 flag has NOGRACE
>> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_state_manager reclaim reboot
>> op cl_state=ffff88002febe528
>>    *** Unlike the previous case the state manager now goes into the
>> reclaim reboot state.
>> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_do_reclaim start
>> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_reclaim_open_state clearing
>> NOGRACE from state=ffff88007363bbc0
>> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_do_reclaim end=0
>> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_state_manager reclaim_nograce
>> cleared NOGRACE from client state ffff88002febe528
>> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_do_reclaim start
>> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_do_reclaim end=0
>> Jun  6 12:21:59 ipa18 kernel: AGLO: nfs4_end_drain_session
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Patch

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index af285cc..0f20f12 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -158,6 +158,7 @@  enum {
  NFS_O_RDWR_STATE, /* OPEN stateid has read/write state */
  NFS_STATE_RECLAIM_REBOOT, /* OPEN stateid server rebooted */
  NFS_STATE_RECLAIM_NOGRACE, /* OPEN stateid needs to recover state */
+ NFS_STATE_RECLAIM_INPROGRESS, /* OPEN stateid recovery is in progress */
  NFS_STATE_POSIX_LOCKS, /* Posix locks are supported */
  NFS_STATE_RECOVERY_FAILED, /* OPEN stateid state recovery failed */
  NFS_STATE_MAY_NOTIFY_LOCK, /* server may CB_NOTIFY_LOCK */
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index b34de03..4eef2eb 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -1335,6 +1335,8 @@  int nfs4_state_mark_reclaim_nograce(struct
nfs_client *clp, struct nfs4_state *s
 {
  if (!nfs4_valid_open_stateid(state))
  return 0;
+ if (test_bit(NFS_STATE_RECLAIM_INPROGRESS, &state->flags))
+ return 1;
  set_bit(NFS_STATE_RECLAIM_NOGRACE, &state->flags);
  clear_bit(NFS_STATE_RECLAIM_REBOOT, &state->flags);