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    Subject[RFC v3 23/24] lockd: replace kthread freezing with auto fs freezing
    Date
    The kernel power management now supports allowing the VFS
    to handle filesystem freezing freezes and thawing. Take advantage
    of that and remove the kthread freezing. This is needed so that we
    properly really stop IO in flight without races after userspace
    has been frozen. Without this we rely on kthread freezing and
    its semantics are loose and error prone.

    The filesystem therefore is in charge of properly dealing with
    quiescing of the filesystem through its callbacks if it thinks
    it knows better than how the VFS handles it.

    The following Coccinelle rule was used as to remove the now superflous
    freezer calls:

    spatch --sp-file fs-freeze-cleanup.cocci --in-place --timeout 120 --dir fs/lockd --jobs 12 --use-gitgrep

    @ remove_set_freezable @
    expression time;
    statement S, S2;
    expression task, current;
    @@

    (
    - set_freezable();
    |
    - if (try_to_freeze())
    - continue;
    |
    - try_to_freeze();
    |
    - freezable_schedule();
    + schedule();
    |
    - freezable_schedule_timeout(time);
    + schedule_timeout(time);
    |
    - if (freezing(task)) { S }
    |
    - if (freezing(task)) { S }
    - else
    { S2 }
    |
    - freezing(current)
    )

    @ remove_wq_freezable @
    expression WQ_E, WQ_ARG1, WQ_ARG2, WQ_ARG3, WQ_ARG4;
    identifier fs_wq_fn;
    @@

    (
    WQ_E = alloc_workqueue(WQ_ARG1,
    - WQ_ARG2 | WQ_FREEZABLE,
    + WQ_ARG2,
    ...);
    |
    WQ_E = alloc_workqueue(WQ_ARG1,
    - WQ_ARG2 | WQ_FREEZABLE | WQ_ARG3,
    + WQ_ARG2 | WQ_ARG3,
    ...);
    |
    WQ_E = alloc_workqueue(WQ_ARG1,
    - WQ_ARG2 | WQ_ARG3 | WQ_FREEZABLE,
    + WQ_ARG2 | WQ_ARG3,
    ...);
    |
    WQ_E = alloc_workqueue(WQ_ARG1,
    - WQ_ARG2 | WQ_ARG3 | WQ_FREEZABLE | WQ_ARG4,
    + WQ_ARG2 | WQ_ARG3 | WQ_ARG4,
    ...);
    |
    WQ_E =
    - WQ_ARG1 | WQ_FREEZABLE
    + WQ_ARG1
    |
    WQ_E =
    - WQ_ARG1 | WQ_FREEZABLE | WQ_ARG3
    + WQ_ARG1 | WQ_ARG3
    |
    fs_wq_fn(
    - WQ_FREEZABLE | WQ_ARG2 | WQ_ARG3
    + WQ_ARG2 | WQ_ARG3
    )
    |
    fs_wq_fn(
    - WQ_FREEZABLE | WQ_ARG2
    + WQ_ARG2
    )
    |
    fs_wq_fn(
    - WQ_FREEZABLE
    + 0
    )
    )

    @ add_auto_flag @
    expression E1;
    identifier fs_type;
    @@

    struct file_system_type fs_type = {
    .fs_flags = E1
    + | FS_AUTOFREEZE
    ,
    };

    Generated-by: Coccinelle SmPL
    Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
    ---
    fs/lockd/clntproc.c | 1 -
    fs/lockd/svc.c | 3 ---
    2 files changed, 4 deletions(-)

    diff --git a/fs/lockd/clntproc.c b/fs/lockd/clntproc.c
    index e875a3571c41..996f5b4d5d17 100644
    --- a/fs/lockd/clntproc.c
    +++ b/fs/lockd/clntproc.c
    @@ -247,7 +247,6 @@ static int nlm_wait_on_grace(wait_queue_head_t *queue)
    prepare_to_wait(queue, &wait, TASK_INTERRUPTIBLE);
    if (!signalled ()) {
    schedule_timeout(NLMCLNT_GRACE_WAIT);
    - try_to_freeze();
    if (!signalled ())
    status = 0;
    }
    diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
    index e56d85335599..bfccbd6f20ed 100644
    --- a/fs/lockd/svc.c
    +++ b/fs/lockd/svc.c
    @@ -135,9 +135,6 @@ lockd(void *vrqstp)
    struct net *net = &init_net;
    struct lockd_net *ln = net_generic(net, lockd_net_id);

    - /* try_to_freeze() is called from svc_recv() */
    - set_freezable();
    -
    /* Allow SIGKILL to tell lockd to drop all of its locks */
    allow_signal(SIGKILL);

    --
    2.35.1

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