Commit 7eaf7e8e authored by Shaohua Li's avatar Shaohua Li Committed by NeilBrown
Browse files

raid5: remove unnecessary bitmap write optimization 



Neil pointed out the bitmap write optimization in handle_stripe_clean_event()
is unnecessary, because the chance one stripe gets written twice in the mean
time is rare. We can always do a bitmap_startwrite when a write request is
added to a stripe and bitmap_endwrite after write request is done.  Delete the
optimization. With it, we can delete some cases of device_lock.

Signed-off-by: default avatarShaohua Li <shli@fusionio.com>
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent e7836bd6

drivers/md/raid5.c

+9 −12
Original line number Diff line number Diff line
@@ -2357,7 +2357,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in 
	spin_lock_irq(&conf->device_lock);

	if (forwrite) {

		bip = &sh->dev[dd_idx].towrite;

		if (*bip == NULL && sh->dev[dd_idx].written == NULL)

		if (*bip == NULL)

			firstwrite = 1;

	} else

		bip = &sh->dev[dd_idx].toread;
@@ -2458,6 +2458,7 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh, 
		/* fail all writes first */

		bi = sh->dev[i].towrite;

		sh->dev[i].towrite = NULL;

		spin_unlock_irq(&conf->device_lock);

		if (bi) {

			s->to_write--;

			bitmap_end = 1;
@@ -2477,6 +2478,10 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh, 
			}

			bi = nextbi;

		}

		if (bitmap_end)

			bitmap_endwrite(conf->mddev->bitmap, sh->sector,

				STRIPE_SECTORS, 0, 0);

		bitmap_end = 0;

		/* and fail all 'written' */

		bi = sh->dev[i].written;

		sh->dev[i].written = NULL;
@@ -2516,7 +2521,6 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh, 
				bi = nextbi;

			}

		}

		spin_unlock_irq(&conf->device_lock);

		if (bitmap_end)

			bitmap_endwrite(conf->mddev->bitmap, sh->sector,

					STRIPE_SECTORS, 0, 0);
@@ -2720,9 +2724,7 @@ static void handle_stripe_clean_event(struct r5conf *conf, 
				test_bit(R5_UPTODATE, &dev->flags)) {

				/* We can return any write requests */

				struct bio *wbi, *wbi2;

				int bitmap_end = 0;

				pr_debug("Return write for disc %d\n", i);

				spin_lock_irq(&conf->device_lock);

				wbi = dev->written;

				dev->written = NULL;

				while (wbi && wbi->bi_sector <
@@ -2735,12 +2737,7 @@ static void handle_stripe_clean_event(struct r5conf *conf, 
					}

					wbi = wbi2;

				}

				if (dev->towrite == NULL)

					bitmap_end = 1;

				spin_unlock_irq(&conf->device_lock);

				if (bitmap_end)

					bitmap_endwrite(conf->mddev->bitmap,

							sh->sector,

				bitmap_endwrite(conf->mddev->bitmap, sh->sector,

						STRIPE_SECTORS,

					 !test_bit(STRIPE_DEGRADED, &sh->state),

						0);

CRA Git | Maintained and supported by SUSTech CRA and CCSE