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Commit b578d55f authored by NeilBrown's avatar NeilBrown Committed by Linus Torvalds
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[PATCH] md: Only checkpoint expansion progress occasionally 



Instead of checkpointing at each stripe, only checkpoint when a new write
would overwrite uncheckpointed data.  Block any write to the uncheckpointed
area.  Arbitrarily checkpoint at least every 3Meg.

Signed-off-by: default avatarNeil Brown <neilb@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent f6705578

drivers/md/raid5.c

+42 −11
Original line number Diff line number Diff line
@@ -1764,6 +1764,7 @@ static int make_request(request_queue_t *q, struct bio * bi) 
		int disks;



	retry:

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

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

			disks = conf->raid_disks;

		else {
@@ -1771,6 +1772,13 @@ static int make_request(request_queue_t *q, struct bio * bi) 
			disks = conf->raid_disks;

			if (logical_sector >= conf->expand_progress)

				disks = conf->previous_raid_disks;

			else {

				if (logical_sector >= conf->expand_lo) {

					spin_unlock_irq(&conf->device_lock);

					schedule();

					goto retry;

				}

			}

			spin_unlock_irq(&conf->device_lock);

		}

 		new_sector = raid5_compute_sector(logical_sector, disks, disks - 1,
@@ -1779,7 +1787,6 @@ static int make_request(request_queue_t *q, struct bio * bi) 
			(unsigned long long)new_sector, 

			(unsigned long long)logical_sector);



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

		sh = get_active_stripe(conf, new_sector, disks, pd_idx, (bi->bi_rw&RWA_MASK));

		if (sh) {

			if (unlikely(conf->expand_progress != MaxSector)) {
@@ -1877,6 +1884,7 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i 
		 */

		int i;

		int dd_idx;

		sector_t writepos, safepos, gap;



		if (sector_nr == 0 &&

		    conf->expand_progress != 0) {
@@ -1887,15 +1895,36 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i 
			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

		 */

		writepos = conf->expand_progress +

			conf->chunk_size/512*(conf->raid_disks-1);

		sector_div(writepos, conf->raid_disks-1);

		safepos = conf->expand_lo;

		sector_div(safepos, conf->previous_raid_disks-1);

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



		if (writepos >= safepos ||

		    gap > (conf->raid_disks-1)*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->sb_dirty = 1;

			md_wakeup_thread(mddev->thread);

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

				   kthread_should_stop());

			spin_lock_irq(&conf->device_lock);

			conf->expand_lo = mddev->reshape_position;

			spin_unlock_irq(&conf->device_lock);

			wake_up(&conf->wait_for_overlap);

		}



		for (i=0; i < conf->chunk_size/512; i+= STRIPE_SECTORS) {

			int j;
@@ -2322,6 +2351,7 @@ static int run(mddev_t *mddev) 


	if (conf->expand_progress != MaxSector) {

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

		conf->expand_lo = conf->expand_progress;

		atomic_set(&conf->reshape_stripes, 0);

		clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);

		clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
@@ -2610,6 +2640,7 @@ static int raid5_reshape(mddev_t *mddev, int raid_disks) 
	conf->previous_raid_disks = conf->raid_disks;

	conf->raid_disks = raid_disks;

	conf->expand_progress = 0;

	conf->expand_lo = 0;

	spin_unlock_irq(&conf->device_lock);



	/* Add some new drives, as many as will fit.

include/linux/raid/raid5.h

+3 −0
Original line number Diff line number Diff line
@@ -217,6 +217,9 @@ struct raid5_private_data { 


	/* 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

					    */

	int			previous_raid_disks;



	struct list_head	handle_list; /* stripes needing handling */