[3.8.y.z extended stable] Patch "NFSv4 wait on recovery for async session errors" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    NFSv4 wait on recovery for async session errors

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.15.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 17d94dc78297c6e961550c132095fe524b615afd Mon Sep 17 00:00:00 2001
From: Andy Adamson <andros at netapp.com>
Date: Tue, 10 Dec 2013 09:35:10 -0500
Subject: NFSv4 wait on recovery for async session errors

commit 4a82fd7c4e78a1b7a224f9ae8bb7e1fd95f670e0 upstream.

When the state manager is processing the NFS4CLNT_DELEGRETURN flag, session
draining is off, but DELEGRETURN can still get a session error.
The async handler calls nfs4_schedule_session_recovery returns -EAGAIN, and
the DELEGRETURN done then restarts the RPC task in the prepare state.
With the state manager still processing the NFS4CLNT_DELEGRETURN flag with
session draining off, these DELEGRETURNs will cycle with errors filling up the
session slots.

This prevents OPEN reclaims (from nfs_delegation_claim_opens) required by the
NFS4CLNT_DELEGRETURN state manager processing from completing, hanging the
state manager in the __rpc_wait_for_completion_task in nfs4_run_open_task
as seen in this kernel thread dump:

kernel: 4.12.32.53-ma D 0000000000000000     0  3393      2 0x00000000
kernel: ffff88013995fb60 0000000000000046 ffff880138cc5400 ffff88013a9df140
kernel: ffff8800000265c0 ffffffff8116eef0 ffff88013fc10080 0000000300000001
kernel: ffff88013a4ad058 ffff88013995ffd8 000000000000fbc8 ffff88013a4ad058
kernel: Call Trace:
kernel: [<ffffffff8116eef0>] ? cache_alloc_refill+0x1c0/0x240
kernel: [<ffffffffa0358110>] ? rpc_wait_bit_killable+0x0/0xa0 [sunrpc]
kernel: [<ffffffffa0358152>] rpc_wait_bit_killable+0x42/0xa0 [sunrpc]
kernel: [<ffffffff8152914f>] __wait_on_bit+0x5f/0x90
kernel: [<ffffffffa0358110>] ? rpc_wait_bit_killable+0x0/0xa0 [sunrpc]
kernel: [<ffffffff815291f8>] out_of_line_wait_on_bit+0x78/0x90
kernel: [<ffffffff8109b520>] ? wake_bit_function+0x0/0x50
kernel: [<ffffffffa035810d>] __rpc_wait_for_completion_task+0x2d/0x30 [sunrpc]
kernel: [<ffffffffa040d44c>] nfs4_run_open_task+0x11c/0x160 [nfs]
kernel: [<ffffffffa04114e7>] nfs4_open_recover_helper+0x87/0x120 [nfs]
kernel: [<ffffffffa0411646>] nfs4_open_recover+0xc6/0x150 [nfs]
kernel: [<ffffffffa040cc6f>] ? nfs4_open_recoverdata_alloc+0x2f/0x60 [nfs]
kernel: [<ffffffffa0414e1a>] nfs4_open_delegation_recall+0x6a/0xa0 [nfs]
kernel: [<ffffffffa0424020>] nfs_end_delegation_return+0x120/0x2e0 [nfs]
kernel: [<ffffffff8109580f>] ? queue_work+0x1f/0x30
kernel: [<ffffffffa0424347>] nfs_client_return_marked_delegations+0xd7/0x110 [nfs]
kernel: [<ffffffffa04225d8>] nfs4_run_state_manager+0x548/0x620 [nfs]
kernel: [<ffffffffa0422090>] ? nfs4_run_state_manager+0x0/0x620 [nfs]
kernel: [<ffffffff8109b0f6>] kthread+0x96/0xa0
kernel: [<ffffffff8100c20a>] child_rip+0xa/0x20
kernel: [<ffffffff8109b060>] ? kthread+0x0/0xa0
kernel: [<ffffffff8100c200>] ? child_rip+0x0/0x20

The state manager can not therefore process the DELEGRETURN session errors.
Change the async handler to wait for recovery on session errors.

Signed-off-by: Andy Adamson <andros at netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust at netapp.com>
[ Andy Adamson: backport to <=3.12 ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/nfs/nfs4proc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index ef31b6b..4568c7a 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -3975,8 +3975,7 @@ nfs4_async_handle_error(struct rpc_task *task, const struct nfs_server *server,
 			dprintk("%s ERROR %d, Reset session\n", __func__,
 				task->tk_status);
 			nfs4_schedule_session_recovery(clp->cl_session, task->tk_status);
-			task->tk_status = 0;
-			return -EAGAIN;
+			goto wait_on_recovery;
 #endif /* CONFIG_NFS_V4_1 */
 		case -NFS4ERR_DELAY:
 			nfs_inc_server_stats(server, NFSIOS_DELAY);
--
1.8.3.2