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md: split MD_RECOVERY_NEEDED out of mddev_resume

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New mddev_resume() calls are added to synchronize IO with array
reconfiguration, however, this introduces a performance regression while
adding it in md_start_sync():

1) someone sets MD_RECOVERY_NEEDED first;
2) daemon thread grabs reconfig_mutex, then clears MD_RECOVERY_NEEDED and
   queues a new sync work;
3) daemon thread releases reconfig_mutex;
4) in md_start_sync
   a) check that there are spares that can be added/removed, then suspend
      the array;
   b) remove_and_add_spares may not be called, or called without really
      add/remove spares;
   c) resume the array, then set MD_RECOVERY_NEEDED again!

Loop between 2 - 4, then mddev_suspend() will be called quite often, for
consequence, normal IO will be quite slow.

Fix this problem by don't set MD_RECOVERY_NEEDED again in md_start_sync(),
hence the loop will be broken.

Fixes: bc08041b32 ("md: suspend array in md_start_sync() if array need reconfiguration")
Suggested-by: Song Liu <song@kernel.org>
Reported-by: Janpieter Sollie <janpieter.sollie@edpnet.be>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218200
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20231207020724.2797445-1-yukuai1@huaweicloud.com
This commit is contained in:
Yu Kuai 2023-12-07 10:07:24 +08:00 committed by Song Liu
parent f52f5c71f3
commit b39113349d
1 changed files with 26 additions and 4 deletions
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30
drivers/md/md.c
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@ -490,7 +490,7 @@ int mddev_suspend(struct mddev *mddev, bool interruptible)
}
EXPORT_SYMBOL_GPL(mddev_suspend);
void mddev_resume(struct mddev *mddev)
static void __mddev_resume(struct mddev *mddev, bool recovery_needed)
{
lockdep_assert_not_held(&mddev->reconfig_mutex);
@ -507,12 +507,18 @@ void mddev_resume(struct mddev *mddev)
percpu_ref_resurrect(&mddev->active_io);
wake_up(&mddev->sb_wait);
set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
if (recovery_needed)
set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
md_wakeup_thread(mddev->thread);
md_wakeup_thread(mddev->sync_thread); /* possibly kick off a reshape */
mutex_unlock(&mddev->suspend_mutex);
}
void mddev_resume(struct mddev *mddev)
{
return __mddev_resume(mddev, true);
}
EXPORT_SYMBOL_GPL(mddev_resume);
/*
@ -9389,7 +9395,15 @@ static void md_start_sync(struct work_struct *ws)
goto not_running;
}
suspend ? mddev_unlock_and_resume(mddev) : mddev_unlock(mddev);
mddev_unlock(mddev);
/*
* md_start_sync was triggered by MD_RECOVERY_NEEDED, so we should
* not set it again. Otherwise, we may cause issue like this one:
* https://bugzilla.kernel.org/show_bug.cgi?id=218200
* Therefore, use __mddev_resume(mddev, false).
*/
if (suspend)
__mddev_resume(mddev, false);
md_wakeup_thread(mddev->sync_thread);
sysfs_notify_dirent_safe(mddev->sysfs_action);
md_new_event();
@ -9401,7 +9415,15 @@ static void md_start_sync(struct work_struct *ws)
clear_bit(MD_RECOVERY_REQUESTED, &mddev->recovery);
clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
clear_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
suspend ? mddev_unlock_and_resume(mddev) : mddev_unlock(mddev);
mddev_unlock(mddev);
/*
* md_start_sync was triggered by MD_RECOVERY_NEEDED, so we should
* not set it again. Otherwise, we may cause issue like this one:
* https://bugzilla.kernel.org/show_bug.cgi?id=218200
* Therefore, use __mddev_resume(mddev, false).
*/
if (suspend)
__mddev_resume(mddev, false);
wake_up(&resync_wait);
if (test_and_clear_bit(MD_RECOVERY_RECOVER, &mddev->recovery) &&