Commit 7c13edc8 authored by NeilBrown's avatar NeilBrown
Browse files

md: incorporate new plugging into raid5. 



In raid5 plugging is used for 2 things:
 1/ collecting writes that require a bitmap update
 2/ collecting writes in the hope that we can create full
    stripes - or at least more-full.

We now release these different sets of stripes when plug_cnt
is zero.

Also in make_request, we call mddev_check_plug to hopefully increase
plug_cnt, and wake up the thread at the end if plugging wasn't
achieved for some reason.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 97658cdd

drivers/md/raid5.c

+16 −7
Original line number Diff line number Diff line
@@ -27,12 +27,12 @@ 
 *

 * We group bitmap updates into batches.  Each batch has a number.

 * We may write out several batches at once, but that isn't very important.

 * conf->bm_write is the number of the last batch successfully written.

 * conf->bm_flush is the number of the last batch that was closed to

 * conf->seq_write is the number of the last batch successfully written.

 * conf->seq_flush is the number of the last batch that was closed to

 *    new additions.

 * When we discover that we will need to write to any block in a stripe

 * (in add_stripe_bio) we update the in-memory bitmap and record in sh->bm_seq

 * the number of the batch it will be in. This is bm_flush+1.

 * the number of the batch it will be in. This is seq_flush+1.

 * When we are ready to do a write, if that batch hasn't been written yet,

 *   we plug the array and queue the stripe for later.

 * When an unplug happens, we increment bm_flush, thus closing the current
@@ -459,7 +459,7 @@ get_active_stripe(raid5_conf_t *conf, sector_t sector, 
						     < (conf->max_nr_stripes *3/4)

						     || !conf->inactive_blocked),

						    conf->device_lock,

						    md_wakeup_thread(conf->mddev->thread));

						    );

				conf->inactive_blocked = 0;

			} else

				init_stripe(sh, sector, previous);
@@ -3927,6 +3927,7 @@ static int make_request(mddev_t *mddev, struct bio * bi) 
	struct stripe_head *sh;

	const int rw = bio_data_dir(bi);

	int remaining;

	int plugged;



	if (unlikely(bi->bi_rw & REQ_FLUSH)) {

		md_flush_request(mddev, bi);
@@ -3945,6 +3946,7 @@ static int make_request(mddev_t *mddev, struct bio * bi) 
	bi->bi_next = NULL;

	bi->bi_phys_segments = 1;	/* over-loaded to count active stripes */



	plugged = mddev_check_plugged(mddev);

	for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {

		DEFINE_WAIT(w);

		int disks, data_disks;
@@ -4059,6 +4061,9 @@ static int make_request(mddev_t *mddev, struct bio * bi) 
		}

			

	}

	if (!plugged)

		md_wakeup_thread(mddev->thread);



	spin_lock_irq(&conf->device_lock);

	remaining = raid5_dec_bi_phys_segments(bi);

	spin_unlock_irq(&conf->device_lock);
@@ -4472,14 +4477,18 @@ static void raid5d(mddev_t *mddev) 
	while (1) {

		struct bio *bio;



		if (conf->seq_flush != conf->seq_write) {

			int seq = conf->seq_flush;

		if (atomic_read(&mddev->plug_cnt) == 0 &&

		    !list_empty(&conf->bitmap_list)) {

			/* Now is a good time to flush some bitmap updates */

			conf->seq_flush++;

			spin_unlock_irq(&conf->device_lock);

			bitmap_unplug(mddev->bitmap);

			spin_lock_irq(&conf->device_lock);

			conf->seq_write = seq;

			conf->seq_write = conf->seq_flush;

			activate_bit_delay(conf);

		}

		if (atomic_read(&mddev->plug_cnt) == 0)

			raid5_activate_delayed(conf);



		while ((bio = remove_bio_from_retry(conf))) {

			int ok;

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