Commit fef9c61f authored by NeilBrown's avatar NeilBrown
Browse files

md/raid5: change reshape-progress measurement to cope with reshaping backwards. 



When reducing the number of devices in a raid4/5/6, the reshape
process has to start at the end of the array and work down to the
beginning.  So we need to handle expand_progress and expand_lo
differently.

This patch renames "expand_progress" and "expand_lo" to avoid the
implication that anything is getting bigger (expand->reshape) and
every place they are used, we make sure that they are used the right
way depending on whether delta_disks is positive or negative.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent cea9c228

drivers/md/raid5.c

+61 −33
Original line number Diff line number Diff line
@@ -3593,24 +3593,28 @@ static int make_request(struct request_queue *q, struct bio * bi) 
	retry:

		previous = 0;

		prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);

		if (likely(conf->expand_progress == MaxSector))

		if (likely(conf->reshape_progress == MaxSector))

			disks = conf->raid_disks;

		else {

			/* spinlock is needed as expand_progress may be

			/* spinlock is needed as reshape_progress may be

			 * 64bit on a 32bit platform, and so it might be

			 * possible to see a half-updated value

			 * Ofcourse expand_progress could change after

			 * Ofcourse reshape_progress could change after

			 * the lock is dropped, so once we get a reference

			 * to the stripe that we think it is, we will have

			 * to check again.

			 */

			spin_lock_irq(&conf->device_lock);

			disks = conf->raid_disks;

			if (logical_sector >= conf->expand_progress) {

			if (mddev->delta_disks < 0

			    ? logical_sector < conf->reshape_progress

			    : logical_sector >= conf->reshape_progress) {

				disks = conf->previous_raid_disks;

				previous = 1;

			} else {

				if (logical_sector >= conf->expand_lo) {

				if (mddev->delta_disks < 0

				    ? logical_sector < conf->reshape_safe

				    : logical_sector >= conf->reshape_safe) {

					spin_unlock_irq(&conf->device_lock);

					schedule();

					goto retry;
@@ -3630,7 +3634,7 @@ static int make_request(struct request_queue *q, struct bio * bi) 
		sh = get_active_stripe(conf, new_sector, previous,

				       (bi->bi_rw&RWA_MASK));

		if (sh) {

			if (unlikely(conf->expand_progress != MaxSector)) {

			if (unlikely(conf->reshape_progress != MaxSector)) {

				/* expansion might have moved on while waiting for a

				 * stripe, so we must do the range check again.

				 * Expansion could still move past after this
@@ -3641,8 +3645,10 @@ static int make_request(struct request_queue *q, struct bio * bi) 
				 */

				int must_retry = 0;

				spin_lock_irq(&conf->device_lock);

				if (logical_sector <  conf->expand_progress &&

				    disks == conf->previous_raid_disks)

				if ((mddev->delta_disks < 0

				     ? logical_sector >= conf->reshape_progress

				     : logical_sector < conf->reshape_progress)

				    && disks == conf->previous_raid_disks)

					/* mismatch, need to try again */

					must_retry = 1;

				spin_unlock_irq(&conf->device_lock);
@@ -3720,42 +3726,58 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped 
	int dd_idx;

	sector_t writepos, safepos, gap;



	if (sector_nr == 0 &&

	    conf->expand_progress != 0) {

		/* restarting in the middle, skip the initial sectors */

		sector_nr = conf->expand_progress;

	if (sector_nr == 0) {

		/* If restarting in the middle, skip the initial sectors */

		if (mddev->delta_disks < 0 &&

		    conf->reshape_progress < raid5_size(mddev, 0, 0)) {

			sector_nr = raid5_size(mddev, 0, 0)

				- conf->reshape_progress;

		} else if (mddev->delta_disks > 0 &&

			   conf->reshape_progress > 0)

			sector_nr = conf->reshape_progress;

		sector_div(sector_nr, new_data_disks);

		if (sector_nr) {

			*skipped = 1;

			return sector_nr;

		}

	}



	/* we update the metadata when there is more than 3Meg

	 * in the block range (that is rather arbitrary, should

	 * probably be time based) or when the data about to be

	 * copied would over-write the source of the data at

	 * the front of the range.

	 * i.e. one new_stripe forward from expand_progress new_maps

	 * to after where expand_lo old_maps to

	 * i.e. one new_stripe along from reshape_progress new_maps

	 * to after where reshape_safe old_maps to

	 */

	writepos = conf->expand_progress +

		conf->chunk_size/512*(new_data_disks);

	writepos = conf->reshape_progress;

	sector_div(writepos, new_data_disks);

	safepos = conf->expand_lo;

	safepos = conf->reshape_safe;

	sector_div(safepos, data_disks);

	gap = conf->expand_progress - conf->expand_lo;

	if (mddev->delta_disks < 0) {

		writepos -= conf->chunk_size/512;

		safepos += conf->chunk_size/512;

		gap = conf->reshape_safe - conf->reshape_progress;

	} else {

		writepos += conf->chunk_size/512;

		safepos -= conf->chunk_size/512;

		gap = conf->reshape_progress - conf->reshape_safe;

	}



	if (writepos >= safepos ||

	if ((mddev->delta_disks < 0

	     ? writepos < safepos

	     : writepos > safepos) ||

	    gap > (new_data_disks)*3000*2 /*3Meg*/) {

		/* Cannot proceed until we've updated the superblock... */

		wait_event(conf->wait_for_overlap,

			   atomic_read(&conf->reshape_stripes)==0);

		mddev->reshape_position = conf->expand_progress;

		mddev->reshape_position = conf->reshape_progress;

		set_bit(MD_CHANGE_DEVS, &mddev->flags);

		md_wakeup_thread(mddev->thread);

		wait_event(mddev->sb_wait, mddev->flags == 0 ||

			   kthread_should_stop());

		spin_lock_irq(&conf->device_lock);

		conf->expand_lo = mddev->reshape_position;

		conf->reshape_safe = mddev->reshape_position;

		spin_unlock_irq(&conf->device_lock);

		wake_up(&conf->wait_for_overlap);

	}
@@ -3792,7 +3814,10 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped 
		release_stripe(sh);

	}

	spin_lock_irq(&conf->device_lock);

	conf->expand_progress = (sector_nr + i) * new_data_disks;

	if (mddev->delta_disks < 0)

		conf->reshape_progress -= i * new_data_disks;

	else

		conf->reshape_progress += i * new_data_disks;

	spin_unlock_irq(&conf->device_lock);

	/* Ok, those stripe are ready. We can start scheduling

	 * reads on the source stripes.
@@ -3823,14 +3848,14 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped 
		/* Cannot proceed until we've updated the superblock... */

		wait_event(conf->wait_for_overlap,

			   atomic_read(&conf->reshape_stripes) == 0);

		mddev->reshape_position = conf->expand_progress;

		mddev->reshape_position = conf->reshape_progress;

		set_bit(MD_CHANGE_DEVS, &mddev->flags);

		md_wakeup_thread(mddev->thread);

		wait_event(mddev->sb_wait,

			   !test_bit(MD_CHANGE_DEVS, &mddev->flags)

			   || kthread_should_stop());

		spin_lock_irq(&conf->device_lock);

		conf->expand_lo = mddev->reshape_position;

		conf->reshape_safe = mddev->reshape_position;

		spin_unlock_irq(&conf->device_lock);

		wake_up(&conf->wait_for_overlap);

	}
@@ -4283,7 +4308,7 @@ static raid5_conf_t *setup_conf(mddev_t *mddev) 
		conf->max_degraded = 1;

	conf->algorithm = mddev->new_layout;

	conf->max_nr_stripes = NR_STRIPES;

	conf->expand_progress = mddev->reshape_position;

	conf->reshape_progress = mddev->reshape_position;



	memory = conf->max_nr_stripes * (sizeof(struct stripe_head) +

		 conf->raid_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
@@ -4441,9 +4466,9 @@ static int run(mddev_t *mddev) 


	print_raid5_conf(conf);



	if (conf->expand_progress != MaxSector) {

	if (conf->reshape_progress != MaxSector) {

		printk("...ok start reshape thread\n");

		conf->expand_lo = conf->expand_progress;

		conf->reshape_safe = conf->reshape_progress;

		atomic_set(&conf->reshape_stripes, 0);

		clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);

		clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
@@ -4782,8 +4807,11 @@ static int raid5_start_reshape(mddev_t *mddev) 
	spin_lock_irq(&conf->device_lock);

	conf->previous_raid_disks = conf->raid_disks;

	conf->raid_disks += mddev->delta_disks;

	conf->expand_progress = 0;

	conf->expand_lo = 0;

	if (mddev->delta_disks < 0)

		conf->reshape_progress = raid5_size(mddev, 0, 0);

	else

		conf->reshape_progress = 0;

	conf->reshape_safe = conf->reshape_progress;

	spin_unlock_irq(&conf->device_lock);



	/* Add some new drives, as many as will fit.
@@ -4825,7 +4853,7 @@ static int raid5_start_reshape(mddev_t *mddev) 
		mddev->recovery = 0;

		spin_lock_irq(&conf->device_lock);

		mddev->raid_disks = conf->raid_disks = conf->previous_raid_disks;

		conf->expand_progress = MaxSector;

		conf->reshape_progress = MaxSector;

		spin_unlock_irq(&conf->device_lock);

		return -EAGAIN;

	}
@@ -4842,7 +4870,7 @@ static void end_reshape(raid5_conf_t *conf) 


		spin_lock_irq(&conf->device_lock);

		conf->previous_raid_disks = conf->raid_disks;

		conf->expand_progress = MaxSector;

		conf->reshape_progress = MaxSector;

		spin_unlock_irq(&conf->device_lock);



		/* read-ahead size must cover two whole stripes, which is

drivers/md/raid5.h

+10 −5
Original line number Diff line number Diff line
@@ -337,11 +337,16 @@ struct raid5_private_data { 
	int			raid_disks;

	int			max_nr_stripes;



	/* used during an expand */

	sector_t		expand_progress;	/* MaxSector when no expand happening */

	sector_t		expand_lo; /* from here up to expand_progress it out-of-bounds

					    * as we haven't flushed the metadata yet

	/* reshape_progress is the leading edge of a 'reshape'

	 * It has value MaxSector when no reshape is happening

	 * If delta_disks < 0, it is the last sector we started work on,

	 * else is it the next sector to work on.

	 */

	sector_t		reshape_progress;

	/* reshape_safe is the trailing edge of a reshape.  We know that

	 * before (or after) this address, all reshape has completed.

	 */

	sector_t		reshape_safe;

	int			previous_raid_disks;



	struct list_head	handle_list; /* stripes needing handling */

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