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Commit 16d997b7 authored by NeilBrown's avatar NeilBrown Committed by Shaohua Li
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md/raid5: simplfy delaying of writes while metadata is updated. 



If a device fails during a write, we must ensure the failure is
recorded in the metadata before the completion of the write is
acknowleged.

Commit c3cce6cd ("md/raid5: ensure device failure recorded before
write request returns.")  added code for this, but it was
unnecessarily complicated.  We already had similar functionality for
handling updates to the bad-block-list, thanks to Commit de393cde
("md: make it easier to wait for bad blocks to be acknowledged.")

So revert most of the former commit, and instead avoid collecting
completed writes if MD_CHANGE_PENDING is set.  raid5d() will then flush
the metadata and retry the stripe_head.
As this change can leave a stripe_head ready for handling immediately
after handle_active_stripes() returns, we change raid5_do_work() to
pause when MD_CHANGE_PENDING is set, so that it doesn't spin.

We check MD_CHANGE_PENDING *after* analyse_stripe() as it could be set
asynchronously.  After analyse_stripe(), we have collected stable data
about the state of devices, which will be used to make decisions.

Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Signed-off-by: default avatarShaohua Li <shli@fb.com>
parent 49728050

drivers/md/raid5.c

+8 −23
Original line number Diff line number Diff line
@@ -4691,7 +4691,8 @@ static void handle_stripe(struct stripe_head *sh) 
	if (test_bit(STRIPE_LOG_TRAPPED, &sh->state))

		goto finish;



	if (s.handle_bad_blocks) {

	if (s.handle_bad_blocks ||

	    test_bit(MD_SB_CHANGE_PENDING, &conf->mddev->sb_flags)) {

		set_bit(STRIPE_HANDLE, &sh->state);

		goto finish;

	}
@@ -5021,15 +5022,8 @@ static void handle_stripe(struct stripe_head *sh) 
			md_wakeup_thread(conf->mddev->thread);

	}



	if (!bio_list_empty(&s.return_bi)) {

		if (test_bit(MD_SB_CHANGE_PENDING, &conf->mddev->sb_flags)) {

			spin_lock_irq(&conf->device_lock);

			bio_list_merge(&conf->return_bi, &s.return_bi);

			spin_unlock_irq(&conf->device_lock);

			md_wakeup_thread(conf->mddev->thread);

		} else

	if (!bio_list_empty(&s.return_bi))

		return_io(&s.return_bi);

	}



	clear_bit_unlock(STRIPE_ACTIVE, &sh->state);

}
@@ -6226,6 +6220,7 @@ static void raid5_do_work(struct work_struct *work) 
	struct r5worker *worker = container_of(work, struct r5worker, work);

	struct r5worker_group *group = worker->group;

	struct r5conf *conf = group->conf;

	struct mddev *mddev = conf->mddev;

	int group_id = group - conf->worker_groups;

	int handled;

	struct blk_plug plug;
@@ -6246,6 +6241,9 @@ static void raid5_do_work(struct work_struct *work) 
		if (!batch_size && !released)

			break;

		handled += batch_size;

		wait_event_lock_irq(mddev->sb_wait,

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

			conf->device_lock);

	}

	pr_debug("%d stripes handled\n", handled);
@@ -6273,18 +6271,6 @@ static void raid5d(struct md_thread *thread) 


	md_check_recovery(mddev);



	if (!bio_list_empty(&conf->return_bi) &&

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

		struct bio_list tmp = BIO_EMPTY_LIST;

		spin_lock_irq(&conf->device_lock);

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

			bio_list_merge(&tmp, &conf->return_bi);

			bio_list_init(&conf->return_bi);

		}

		spin_unlock_irq(&conf->device_lock);

		return_io(&tmp);

	}



	blk_start_plug(&plug);

	handled = 0;

	spin_lock_irq(&conf->device_lock);
@@ -6936,7 +6922,6 @@ static struct r5conf *setup_conf(struct mddev *mddev) 
	INIT_LIST_HEAD(&conf->hold_list);

	INIT_LIST_HEAD(&conf->delayed_list);

	INIT_LIST_HEAD(&conf->bitmap_list);

	bio_list_init(&conf->return_bi);

	init_llist_head(&conf->released_stripes);

	atomic_set(&conf->active_stripes, 0);

	atomic_set(&conf->preread_active_stripes, 0);

drivers/md/raid5.h

+0 −3
Original line number Diff line number Diff line
@@ -638,9 +638,6 @@ struct r5conf { 
	int			skip_copy; /* Don't copy data from bio to stripe cache */

	struct list_head	*last_hold; /* detect hold_list promotions */



	/* bios to have bi_end_io called after metadata is synced */

	struct bio_list		return_bi;



	atomic_t		reshape_stripes; /* stripes with pending writes for reshape */

	/* unfortunately we need two cache names as we temporarily have

	 * two caches.