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Message-ID: <CALTww2-YiGbw9HAA-hvEbCmWuOHpdHkx1KCBciRW9d6r=j44nQ@mail.gmail.com>
Date: Tue, 21 Nov 2023 14:34:02 +0800
From: Xiao Ni <xni@...hat.com>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: song@...nel.org, yukuai3@...wei.com, neilb@...e.de,
linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH -next 6/8] md: factor out a helper to stop sync_thread
On Tue, Nov 21, 2023 at 2:02 PM Xiao Ni <xni@...hat.com> wrote:
>
> On Fri, Nov 10, 2023 at 5:34 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
> >
> > From: Yu Kuai <yukuai3@...wei.com>
> >
> > stop_sync_thread(), md_set_readonly() and do_md_stop() are trying to
> > stop sync_thread() the same way, hence factor out a helper to make code
> > cleaner, and also prepare to use the new helper to fix problems later.
> >
> > Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> > Signed-off-by: Yu Kuai <yukuai1@...weicloud.com>
> > ---
> > drivers/md/md.c | 129 ++++++++++++++++++++++++++----------------------
> > 1 file changed, 69 insertions(+), 60 deletions(-)
> >
> > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > index c0f2bdafe46a..7252fae0c989 100644
> > --- a/drivers/md/md.c
> > +++ b/drivers/md/md.c
> > @@ -4848,29 +4848,46 @@ action_show(struct mddev *mddev, char *page)
> > return sprintf(page, "%s\n", type);
> > }
> >
> > -static int stop_sync_thread(struct mddev *mddev)
> > +static bool sync_thread_stopped(struct mddev *mddev, int *seq_ptr)
> > {
> > - int ret = 0;
> > + if (seq_ptr && *seq_ptr != atomic_read(&mddev->sync_seq))
> > + return true;
> >
> > - if (!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
> > - return 0;
> > + return (!mddev->sync_thread &&
> > + !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery));
> > +}
> >
> > - ret = mddev_lock(mddev);
> > - if (ret)
> > - return ret;
> > +/*
> > + * stop_sync_thread() - stop running sync_thread.
> > + * @mddev: the array that sync_thread belongs to.
> > + * @freeze: set true to prevent new sync_thread to start.
> > + * @interruptible: if set true, then user can interrupt while waiting for
> > + * sync_thread to be done.
> > + *
> > + * Noted that this function must be called with 'reconfig_mutex' grabbed, and
> > + * fter this function return, 'reconfig_mtuex' will be released.
> > + */
> > +static int stop_sync_thread(struct mddev *mddev, bool freeze,
> > + bool interruptible)
> > + __releases(&mddev->reconfig_mutex)
> > +{
> > + int *seq_ptr = NULL;
> > + int sync_seq;
> > + int ret = 0;
> > +
> > + if (freeze) {
> > + set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > + } else {
> > + clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > + sync_seq = atomic_read(&mddev->sync_seq);
> > + seq_ptr = &sync_seq;
> > + }
> >
> > - /*
> > - * Check again in case MD_RECOVERY_RUNNING is cleared before lock is
> > - * held.
> > - */
> > if (!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
> > mddev_unlock(mddev);
> > return 0;
> > }
> Hi Kuai
>
> It does the unlock inside this function. For me, it's not good,
> because the caller does the lock. So the caller should do the unlock
> too.
> >
> > - if (work_pending(&mddev->sync_work))
> > - flush_workqueue(md_misc_wq);
> > -
> > set_bit(MD_RECOVERY_INTR, &mddev->recovery);
> > /*
> > * Thread might be blocked waiting for metadata update which will now
> > @@ -4879,53 +4896,58 @@ static int stop_sync_thread(struct mddev *mddev)
> > md_wakeup_thread_directly(mddev->sync_thread);
> >
> > mddev_unlock(mddev);
>
> Same with above point.
>
> > - return 0;
> > + if (work_pending(&mddev->sync_work))
> > + flush_work(&mddev->sync_work);
> > +
> > + if (interruptible)
> > + ret = wait_event_interruptible(resync_wait,
> > + sync_thread_stopped(mddev, seq_ptr));
> > + else
> > + wait_event(resync_wait, sync_thread_stopped(mddev, seq_ptr));
> > +
>
> It looks like the three roles (md_set_readonly, do_md_stop and
> stop_sync_thread) need to wait for different events. We can move these
> codes out this helper function and make this helper function to be
> more common.
Or get lock again before returning this function and leave the wait here?
Regards
Xiao
>
> Best Regards
> Xiao
>
>
> > + return ret;
> > }
> >
> > static int idle_sync_thread(struct mddev *mddev)
> > {
> > int ret;
> > - int sync_seq = atomic_read(&mddev->sync_seq);
> > bool flag;
> >
> > ret = mutex_lock_interruptible(&mddev->sync_mutex);
> > if (ret)
> > return ret;
> >
> > - flag = test_and_clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > - ret = stop_sync_thread(mddev);
> > + flag = test_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > + ret = mddev_lock(mddev);
> > if (ret)
> > - goto out;
> > + goto unlock;
> >
> > - ret = wait_event_interruptible(resync_wait,
> > - sync_seq != atomic_read(&mddev->sync_seq) ||
> > - !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery));
> > -out:
> > + ret = stop_sync_thread(mddev, false, true);
> > if (ret && flag)
> > set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > +unlock:
> > mutex_unlock(&mddev->sync_mutex);
> > return ret;
> > }
> >
> > static int frozen_sync_thread(struct mddev *mddev)
> > {
> > - int ret = mutex_lock_interruptible(&mddev->sync_mutex);
> > + int ret;
> > bool flag;
> >
> > + ret = mutex_lock_interruptible(&mddev->sync_mutex);
> > if (ret)
> > return ret;
> >
> > - flag = test_and_set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > - ret = stop_sync_thread(mddev);
> > + flag = test_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > + ret = mddev_lock(mddev);
> > if (ret)
> > - goto out;
> > + goto unlock;
> >
> > - ret = wait_event_interruptible(resync_wait,
> > - mddev->sync_thread == NULL &&
> > - !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery));
> > -out:
> > + ret = stop_sync_thread(mddev, true, true);
> > if (ret && !flag)
> > clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > +unlock:
> > mutex_unlock(&mddev->sync_mutex);
> > return ret;
> > }
> > @@ -6397,22 +6419,10 @@ static int md_set_readonly(struct mddev *mddev, struct block_device *bdev)
> > if (mddev->external && test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags))
> > return -EBUSY;
> >
> > - if (!test_bit(MD_RECOVERY_FROZEN, &mddev->recovery)) {
> > + if (!test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
> > did_freeze = 1;
> > - set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > - }
> > - if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
> > - set_bit(MD_RECOVERY_INTR, &mddev->recovery);
> >
> > - /*
> > - * Thread might be blocked waiting for metadata update which will now
> > - * never happen
> > - */
> > - md_wakeup_thread_directly(mddev->sync_thread);
> > -
> > - mddev_unlock(mddev);
> > - wait_event(resync_wait, !test_bit(MD_RECOVERY_RUNNING,
> > - &mddev->recovery));
> > + stop_sync_thread(mddev, true, false);
> > wait_event(mddev->sb_wait,
> > !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags));
> > mddev_lock_nointr(mddev);
> > @@ -6421,6 +6431,10 @@ static int md_set_readonly(struct mddev *mddev, struct block_device *bdev)
> > if ((mddev->pers && atomic_read(&mddev->openers) > !!bdev) ||
> > mddev->sync_thread ||
> > test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
> > + /*
> > + * This could happen if user change array state through
> > + * ioctl/sysfs while reconfig_mutex is released.
> > + */
> > pr_warn("md: %s still in use.\n",mdname(mddev));
> > err = -EBUSY;
> > goto out;
> > @@ -6457,30 +6471,25 @@ static int do_md_stop(struct mddev *mddev, int mode,
> > struct md_rdev *rdev;
> > int did_freeze = 0;
> >
> > - if (!test_bit(MD_RECOVERY_FROZEN, &mddev->recovery)) {
> > + if (!test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
> > did_freeze = 1;
> > +
> > + if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
> > + stop_sync_thread(mddev, true, false);
> > + mddev_lock_nointr(mddev);
> > + } else {
> > set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > }
> > - if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
> > - set_bit(MD_RECOVERY_INTR, &mddev->recovery);
> > -
> > - /*
> > - * Thread might be blocked waiting for metadata update which will now
> > - * never happen
> > - */
> > - md_wakeup_thread_directly(mddev->sync_thread);
> > -
> > - mddev_unlock(mddev);
> > - wait_event(resync_wait, (mddev->sync_thread == NULL &&
> > - !test_bit(MD_RECOVERY_RUNNING,
> > - &mddev->recovery)));
> > - mddev_lock_nointr(mddev);
> >
> > mutex_lock(&mddev->open_mutex);
> > if ((mddev->pers && atomic_read(&mddev->openers) > !!bdev) ||
> > mddev->sysfs_active ||
> > mddev->sync_thread ||
> > test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
> > + /*
> > + * This could happen if user change array state through
> > + * ioctl/sysfs while reconfig_mutex is released.
> > + */
> > pr_warn("md: %s still in use.\n",mdname(mddev));
> > mutex_unlock(&mddev->open_mutex);
> > if (did_freeze) {
> > --
> > 2.39.2
> >
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