Commit 714d2015 authored by Yu Kuai's avatar Yu Kuai Committed by Song Liu
Browse files

md: add new helpers to suspend/resume array 



Advantages for new apis:
 - reconfig_mutex is not required;
 - the weird logical that suspend array hold 'reconfig_mutex' for
   mddev_check_recovery() to update superblock is not needed;
 - the specail handling, 'pers->prepare_suspend', for raid456 is not
   needed;
 - It's safe to be called at any time once mddev is allocated, and it's
   designed to be used from slow path where array configuration is changed;
 - the new helpers is designed to be called before mddev_lock(), hence
   it support to be interrupted by user as well.

Signed-off-by: default avatarYu Kuai <yukuai3@huawei.com>
Signed-off-by: default avatarSong Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20231010151958.145896-5-yukuai1@huaweicloud.com
parent 2e82248b

drivers/md/md.c

+100 −2
Original line number Diff line number Diff line
@@ -443,12 +443,22 @@ void mddev_suspend(struct mddev *mddev) 
			lockdep_is_held(&mddev->reconfig_mutex));



	WARN_ON_ONCE(thread && current == thread->tsk);

	if (mddev->suspended++)



	/* can't concurrent with __mddev_suspend() and __mddev_resume() */

	mutex_lock(&mddev->suspend_mutex);

	if (mddev->suspended++) {

		mutex_unlock(&mddev->suspend_mutex);

		return;

	}



	wake_up(&mddev->sb_wait);

	set_bit(MD_ALLOW_SB_UPDATE, &mddev->flags);

	percpu_ref_kill(&mddev->active_io);



	/*

	 * TODO: cleanup 'pers->prepare_suspend after all callers are replaced

	 * by __mddev_suspend().

	 */

	if (mddev->pers && mddev->pers->prepare_suspend)

		mddev->pers->prepare_suspend(mddev);
@@ -459,14 +469,21 @@ void mddev_suspend(struct mddev *mddev) 
	del_timer_sync(&mddev->safemode_timer);

	/* restrict memory reclaim I/O during raid array is suspend */

	mddev->noio_flag = memalloc_noio_save();



	mutex_unlock(&mddev->suspend_mutex);

}

EXPORT_SYMBOL_GPL(mddev_suspend);



void mddev_resume(struct mddev *mddev)

{

	lockdep_assert_held(&mddev->reconfig_mutex);

	if (--mddev->suspended)



	/* can't concurrent with __mddev_suspend() and __mddev_resume() */

	mutex_lock(&mddev->suspend_mutex);

	if (--mddev->suspended) {

		mutex_unlock(&mddev->suspend_mutex);

		return;

	}



	/* entred the memalloc scope from mddev_suspend() */

	memalloc_noio_restore(mddev->noio_flag);
@@ -477,9 +494,89 @@ void mddev_resume(struct mddev *mddev) 
	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);

}

EXPORT_SYMBOL_GPL(mddev_resume);



int __mddev_suspend(struct mddev *mddev, bool interruptible)

{

	int err = 0;



	/*

	 * hold reconfig_mutex to wait for normal io will deadlock, because

	 * other context can't update super_block, and normal io can rely on

	 * updating super_block.

	 */

	lockdep_assert_not_held(&mddev->reconfig_mutex);



	if (interruptible)

		err = mutex_lock_interruptible(&mddev->suspend_mutex);

	else

		mutex_lock(&mddev->suspend_mutex);

	if (err)

		return err;



	if (mddev->suspended) {

		WRITE_ONCE(mddev->suspended, mddev->suspended + 1);

		mutex_unlock(&mddev->suspend_mutex);

		return 0;

	}



	percpu_ref_kill(&mddev->active_io);

	if (interruptible)

		err = wait_event_interruptible(mddev->sb_wait,

				percpu_ref_is_zero(&mddev->active_io));

	else

		wait_event(mddev->sb_wait,

				percpu_ref_is_zero(&mddev->active_io));

	if (err) {

		percpu_ref_resurrect(&mddev->active_io);

		mutex_unlock(&mddev->suspend_mutex);

		return err;

	}



	/*

	 * For raid456, io might be waiting for reshape to make progress,

	 * allow new reshape to start while waiting for io to be done to

	 * prevent deadlock.

	 */

	WRITE_ONCE(mddev->suspended, mddev->suspended + 1);



	del_timer_sync(&mddev->safemode_timer);

	/* restrict memory reclaim I/O during raid array is suspend */

	mddev->noio_flag = memalloc_noio_save();



	mutex_unlock(&mddev->suspend_mutex);

	return 0;

}

EXPORT_SYMBOL_GPL(__mddev_suspend);



void __mddev_resume(struct mddev *mddev)

{

	lockdep_assert_not_held(&mddev->reconfig_mutex);



	mutex_lock(&mddev->suspend_mutex);

	WRITE_ONCE(mddev->suspended, mddev->suspended - 1);

	if (mddev->suspended) {

		mutex_unlock(&mddev->suspend_mutex);

		return;

	}



	/* entred the memalloc scope from __mddev_suspend() */

	memalloc_noio_restore(mddev->noio_flag);



	percpu_ref_resurrect(&mddev->active_io);

	wake_up(&mddev->sb_wait);



	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);

}

EXPORT_SYMBOL_GPL(__mddev_resume);



/*

 * Generic flush handling for md

 */
@@ -672,6 +769,7 @@ int mddev_init(struct mddev *mddev) 
	mutex_init(&mddev->open_mutex);

	mutex_init(&mddev->reconfig_mutex);

	mutex_init(&mddev->sync_mutex);

	mutex_init(&mddev->suspend_mutex);

	mutex_init(&mddev->bitmap_info.mutex);

	INIT_LIST_HEAD(&mddev->disks);

	INIT_LIST_HEAD(&mddev->all_mddevs);

drivers/md/md.h

+3 −0
Original line number Diff line number Diff line
@@ -316,6 +316,7 @@ struct mddev { 
	unsigned long			sb_flags;



	int				suspended;

	struct mutex			suspend_mutex;

	struct percpu_ref		active_io;

	int				ro;

	int				sysfs_active; /* set when sysfs deletes
@@ -811,6 +812,8 @@ extern void md_rdev_clear(struct md_rdev *rdev); 
extern void md_handle_request(struct mddev *mddev, struct bio *bio);

extern void mddev_suspend(struct mddev *mddev);

extern void mddev_resume(struct mddev *mddev);

extern int __mddev_suspend(struct mddev *mddev, bool interruptible);

extern void __mddev_resume(struct mddev *mddev);



extern void md_reload_sb(struct mddev *mddev, int raid_disk);

extern void md_update_sb(struct mddev *mddev, int force);