[PATCH Version 3 0/1] NFSv4.1: Fix an NFSv4.1 state renewal regression

[PATCH Version 3 0/1] NFSv4.1: Fix an NFSv4.1 state renewal regression

[andros]

From: Andy Adamson <andros@netapp.com>

Version 3 responds to a review request by Trond:

The problem here isn't that we're failing to send a SEQUENCE in a
situation where we're not required to do so by the spec. The problem
is that we're failing to rearm renewd when we skip that SEQUENCE call.

Instead of removing them, could you rather please modify the above
lines to return an error, and then have nfs4_renew_state() respond by
calling nfs4_schedule_state_renewal(), instead of just skipping it as
we do today. In fact, AFAICS we want to do the same when the renew
call fails due to ENOMEM (but not when it returns EIO, since that
signals that the nfs_client is in the process of shutting down).

Andy Adamson (1):
  NFSv4.1: Fix an NFSv4.1 state renewal      regression

 fs/nfs/nfs4proc.c   |  2 +-
 fs/nfs/nfs4renewd.c | 14 ++++++++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)

-- 
1.8.3.1

[PATCH Version 3 1/1] NFSv4.1: Fix an NFSv4.1 state renewal regression

[andros]

From: Andy Adamson <andros@netapp.com>

Commit 2f60ea6b8ced ("NFSv4: The NFSv4.0 client must send RENEW calls if it holds a delegation") set the NFS4_RENEW_TIMEOUT flag in nfs4_renew_state, and does
not put an nfs41_proc_async_sequence call, the NFSv4.1 lease renewal heartbeat
call, on the wire to renew the NFSv4.1 state if the flag was not set.

The NFS4_RENEW_TIMEOUT flag is set when "now" is after the last renewal
(cl_last_renewal) plus the lease time divided by 3. This is arbitrary and
sometimes does the following:

In normal operation, the only way a future state renewal call is put on the
wire is via a call to nfs4_schedule_state_renewal, which schedules a
nfs4_renew_state workqueue task. nfs4_renew_state determines if the
NFS4_RENEW_TIMEOUT should be set, and the calls nfs41_proc_async_sequence,
which only gets sent if the NFS4_RENEW_TIMEOUT flag is set.
Then the nfs41_proc_async_sequence rpc_release function schedules
another state remewal via nfs4_schedule_state_renewal.

Without this change we can get into a state where an application stops
accessing the NFSv4.1 share, state renewal calls stop due to the
NFS4_RENEW_TIMEOUT flag _not_ being set. The only way to recover
from this situation is with a clientid re-establishment, once the application
resumes and the server has timed out the lease and so returns
NFS4ERR_BAD_SESSION on the subsequent SEQUENCE operation.

An example application:
open, lock, write a file.

sleep for 6 * lease (could be less)

ulock, close.

In the above example with NFSv4.1 delegations enabled, without this change,
there are no OP_SEQUENCE state renewal calls during the sleep, and the
clientid is recovered due to lease expiration on the close.

This issue does not occur with NFSv4.1 delegations disabled, nor with
NFSv4.0, with or without delegations enabled.

Signed-off-by: Andy Adamson <andros@netapp.com>
---
 fs/nfs/nfs4proc.c   |  2 +-
 fs/nfs/nfs4renewd.c | 14 ++++++++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 288be08..ed25f38 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -7349,7 +7349,7 @@ static int nfs41_proc_async_sequence(struct nfs_client *clp, struct rpc_cred *cr
 	int ret = 0;
 
 	if ((renew_flags & NFS4_RENEW_TIMEOUT) == 0)
-		return 0;
+		return -EAGAIN;
 	task = _nfs41_proc_sequence(clp, cred, false);
 	if (IS_ERR(task))
 		ret = PTR_ERR(task);
diff --git a/fs/nfs/nfs4renewd.c b/fs/nfs/nfs4renewd.c
index 1720d32..b00e1e2 100644
--- a/fs/nfs/nfs4renewd.c
+++ b/fs/nfs/nfs4renewd.c
@@ -88,16 +88,26 @@ nfs4_renew_state(struct work_struct *work)
 			}
 			nfs_expire_all_delegations(clp);
 		} else {
+			int ret;
+
 			/* Queue an asynchronous RENEW. */
-			ops->sched_state_renewal(clp, cred, renew_flags);
+			ret = ops->sched_state_renewal(clp, cred, renew_flags);
 			put_rpccred(cred);
-			goto out_exp;
+			switch (ret) {
+			case 0:
+			default:
+				goto out_exp;
+			case -EAGAIN:
+			case -ENOMEM:
+				goto out_sched;
+			}
 		}
 	} else {
 		dprintk("%s: failed to call renewd. Reason: lease not expired \n",
 				__func__);
 		spin_unlock(&clp->cl_lock);
 	}
+out_sched:
 	nfs4_schedule_state_renewal(clp);
 out_exp:
 	nfs_expire_unreferenced_delegations(clp);
-- 
1.8.3.1

Re: [PATCH Version 3 1/1] NFSv4.1: Fix an NFSv4.1 state renewal regression

[Trond Myklebust]

On Mon, Sep 29, 2014 at 12:31 PM,  <andros@netapp.com> wrote:
> From: Andy Adamson <andros@netapp.com>
>
> Commit 2f60ea6b8ced ("NFSv4: The NFSv4.0 client must send RENEW calls if it holds a delegation") set the NFS4_RENEW_TIMEOUT flag in nfs4_renew_state, and does
> not put an nfs41_proc_async_sequence call, the NFSv4.1 lease renewal heartbeat
> call, on the wire to renew the NFSv4.1 state if the flag was not set.
>
> The NFS4_RENEW_TIMEOUT flag is set when "now" is after the last renewal
> (cl_last_renewal) plus the lease time divided by 3. This is arbitrary and
> sometimes does the following:
>
> In normal operation, the only way a future state renewal call is put on the
> wire is via a call to nfs4_schedule_state_renewal, which schedules a
> nfs4_renew_state workqueue task. nfs4_renew_state determines if the
> NFS4_RENEW_TIMEOUT should be set, and the calls nfs41_proc_async_sequence,
> which only gets sent if the NFS4_RENEW_TIMEOUT flag is set.
> Then the nfs41_proc_async_sequence rpc_release function schedules
> another state remewal via nfs4_schedule_state_renewal.
>
> Without this change we can get into a state where an application stops
> accessing the NFSv4.1 share, state renewal calls stop due to the
> NFS4_RENEW_TIMEOUT flag _not_ being set. The only way to recover
> from this situation is with a clientid re-establishment, once the application
> resumes and the server has timed out the lease and so returns
> NFS4ERR_BAD_SESSION on the subsequent SEQUENCE operation.
>
> An example application:
> open, lock, write a file.
>
> sleep for 6 * lease (could be less)
>
> ulock, close.
>
> In the above example with NFSv4.1 delegations enabled, without this change,
> there are no OP_SEQUENCE state renewal calls during the sleep, and the
> clientid is recovered due to lease expiration on the close.
>
> This issue does not occur with NFSv4.1 delegations disabled, nor with
> NFSv4.0, with or without delegations enabled.
>
> Signed-off-by: Andy Adamson <andros@netapp.com>
> ---
>  fs/nfs/nfs4proc.c   |  2 +-
>  fs/nfs/nfs4renewd.c | 14 ++++++++++++--
>  2 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index 288be08..ed25f38 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -7349,7 +7349,7 @@ static int nfs41_proc_async_sequence(struct nfs_client *clp, struct rpc_cred *cr
>         int ret = 0;
>
>         if ((renew_flags & NFS4_RENEW_TIMEOUT) == 0)
> -               return 0;
> +               return -EAGAIN;
>         task = _nfs41_proc_sequence(clp, cred, false);
>         if (IS_ERR(task))
>                 ret = PTR_ERR(task);
> diff --git a/fs/nfs/nfs4renewd.c b/fs/nfs/nfs4renewd.c
> index 1720d32..b00e1e2 100644
> --- a/fs/nfs/nfs4renewd.c
> +++ b/fs/nfs/nfs4renewd.c
> @@ -88,16 +88,26 @@ nfs4_renew_state(struct work_struct *work)
>                         }
>                         nfs_expire_all_delegations(clp);
>                 } else {
> +                       int ret;
> +
>                         /* Queue an asynchronous RENEW. */
> -                       ops->sched_state_renewal(clp, cred, renew_flags);
> +                       ret = ops->sched_state_renewal(clp, cred, renew_flags);
>                         put_rpccred(cred);
> -                       goto out_exp;
> +                       switch (ret) {
> +                       case 0:
> +                       default:
> +                               goto out_exp;

Nit: the 0 and default cases do not need to be explicit since the
default behaviour will be to fall through anyway.

> +                       case -EAGAIN:
> +                       case -ENOMEM:
> +                               goto out_sched;
> +                       }
>                 }
>         } else {
>                 dprintk("%s: failed to call renewd. Reason: lease not expired \n",
>                                 __func__);
>                 spin_unlock(&clp->cl_lock);
>         }
> +out_sched:
>         nfs4_schedule_state_renewal(clp);
>  out_exp:
>         nfs_expire_unreferenced_delegations(clp);
> --
> 1.8.3.1
>

Thanks Andy.

-- 
Trond Myklebust

Linux NFS client maintainer, PrimaryData

trond.myklebust@primarydata.com

[PATCH Version 3 0/1] NFSv4.1: Fix an NFSv4.1 state renewal regression

[andros]

From: Andy Adamson <andros@netapp.com>

Version 3 responds to a review request by Trond:

The problem here isn't that we're failing to send a SEQUENCE in a
situation where we're not required to do so by the spec. The problem
is that we're failing to rearm renewd when we skip that SEQUENCE call.

Instead of removing them, could you rather please modify the above
lines to return an error, and then have nfs4_renew_state() respond by
calling nfs4_schedule_state_renewal(), instead of just skipping it as
we do today. In fact, AFAICS we want to do the same when the renew
call fails due to ENOMEM (but not when it returns EIO, since that
signals that the nfs_client is in the process of shutting down).

Andy Adamson (1):
  NFSv4.1: Fix an NFSv4.1 state renewal      regression

 fs/nfs/nfs4proc.c   |  2 +-
 fs/nfs/nfs4renewd.c | 14 ++++++++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)

-- 
1.8.3.1