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Date: Tue, 21 Nov 2023 21:01:19 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Xiao Ni <xni@...hat.com>, Yu Kuai <yukuai1@...weicloud.com>
Cc: song@...nel.org, neilb@...e.de, linux-kernel@...r.kernel.org,
linux-raid@...r.kernel.org, yi.zhang@...wei.com,
yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH -next 6/8] md: factor out a helper to stop sync_thread
Hi,
在 2023/11/21 14:34, Xiao Ni 写道:
> 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?
>
I tried but I made code complex. 😞
I guess I'll need to drop this version and restart...
Thanks,
Kuai
> 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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