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Commit 4d5324f7 authored by NeilBrown's avatar NeilBrown Committed by Shaohua Li
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md: always hold reconfig_mutex when calling mddev_suspend() 



Most often mddev_suspend() is called with
reconfig_mutex held.  Make this a requirement in
preparation a subsequent patch.  Also require
reconfig_mutex to be held for mddev_resume(),
partly for symmetry and partly to guarantee
no races with incr/decr of mddev->suspend.

Taking the mutex in r5c_disable_writeback_async() is
a little tricky as this is called from a work queue
via log->disable_writeback_work, and flush_work()
is called on that while holding ->reconfig_mutex.
If the work item hasn't run before flush_work()
is called, the work function will not be able to
get the mutex.

So we use mddev_trylock() inside the wait_event() call, and have that
abort when conf->log is set to NULL, which happens before
flush_work() is called.
We wait in mddev->sb_wait and ensure this is woken
when any of the conditions change.  This requires
waking mddev->sb_wait in mddev_unlock().  This is only
like to trigger extra wake_ups of threads that needn't
be woken when metadata is being written, and that
doesn't happen often enough that the cost would be
noticeable.

Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Signed-off-by: default avatarShaohua Li <shli@fb.com>
parent 230b55fa

drivers/md/dm-raid.c

+8 −2
Original line number Diff line number Diff line
@@ -3628,8 +3628,11 @@ static void raid_postsuspend(struct dm_target *ti) 
{

	struct raid_set *rs = ti->private;



	if (!test_and_set_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags))

	if (!test_and_set_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags)) {

		mddev_lock_nointr(&rs->md);

		mddev_suspend(&rs->md);

		mddev_unlock(&rs->md);

	}



	rs->md.ro = 1;

}
@@ -3886,8 +3889,11 @@ static void raid_resume(struct dm_target *ti) 
	if (!(rs->ctr_flags & RESUME_STAY_FROZEN_FLAGS))

		clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);



	if (test_and_clear_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags))

	if (test_and_clear_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags)) {

		mddev_lock_nointr(mddev);

		mddev_resume(mddev);

		mddev_unlock(mddev);

	}

}



static struct target_type raid_target = {

drivers/md/md.c

+3 −0
Original line number Diff line number Diff line
@@ -344,6 +344,7 @@ static blk_qc_t md_make_request(struct request_queue *q, struct bio *bio) 
void mddev_suspend(struct mddev *mddev)

{

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

	lockdep_assert_held(&mddev->reconfig_mutex);

	if (mddev->suspended++)

		return;

	synchronize_rcu();
@@ -357,6 +358,7 @@ EXPORT_SYMBOL_GPL(mddev_suspend); 


void mddev_resume(struct mddev *mddev)

{

	lockdep_assert_held(&mddev->reconfig_mutex);

	if (--mddev->suspended)

		return;

	wake_up(&mddev->sb_wait);
@@ -663,6 +665,7 @@ void mddev_unlock(struct mddev *mddev) 
	 */

	spin_lock(&pers_lock);

	md_wakeup_thread(mddev->thread);

	wake_up(&mddev->sb_wait);

	spin_unlock(&pers_lock);

}

EXPORT_SYMBOL_GPL(mddev_unlock);

drivers/md/raid5-cache.c

+13 −5
Original line number Diff line number Diff line
@@ -693,6 +693,8 @@ static void r5c_disable_writeback_async(struct work_struct *work) 
	struct r5l_log *log = container_of(work, struct r5l_log,

					   disable_writeback_work);

	struct mddev *mddev = log->rdev->mddev;

	struct r5conf *conf = mddev->private;

	int locked = 0;



	if (log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_THROUGH)

		return;
@@ -701,11 +703,15 @@ static void r5c_disable_writeback_async(struct work_struct *work) 


	/* wait superblock change before suspend */

	wait_event(mddev->sb_wait,

		   !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags));



		   conf->log == NULL ||

		   (!test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags) &&

		    (locked = mddev_trylock(mddev))));

	if (locked) {

		mddev_suspend(mddev);

		log->r5c_journal_mode = R5C_JOURNAL_MODE_WRITE_THROUGH;

		mddev_resume(mddev);

		mddev_unlock(mddev);

	}

}



static void r5l_submit_current_io(struct r5l_log *log)
@@ -3165,6 +3171,8 @@ void r5l_exit_log(struct r5conf *conf) 
	conf->log = NULL;

	synchronize_rcu();



	/* Ensure disable_writeback_work wakes up and exits */

	wake_up(&conf->mddev->sb_wait);

	flush_work(&log->disable_writeback_work);

	md_unregister_thread(&log->reclaim_thread);

	mempool_destroy(log->meta_pool);