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    Subject[PATCH 3.12 103/118] NFSv4 wait on recovery for async session errors
    Date
    3.12-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Andy Adamson <andros@netapp.com>

    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@netapp.com>
    Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/nfs/nfs4proc.c | 3 +--
    1 file changed, 1 insertion(+), 2 deletions(-)

    --- a/fs/nfs/nfs4proc.c
    +++ b/fs/nfs/nfs4proc.c
    @@ -4752,8 +4752,7 @@ nfs4_async_handle_error(struct rpc_task
    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);



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