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Message-ID: <CALTww2-ivzhRRMYBoVSZ32uRUPL8Lii=z3SHGbMijsximdn=7A@mail.gmail.com>
Date: Tue, 21 Nov 2023 14:02:39 +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 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.
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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