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Commit e3555d85 authored by Philipp Reisner's avatar Philipp Reisner
Browse files

drbd: Implemented priority inheritance for resync requests 



We only issue resync requests if there is no significant application IO
going on. = Application IO has higher priority than resnyc IO.

If application IO can not be started because the resync process locked
an resync_lru entry, start the IO operations necessary to release the
lock ASAP.

Signed-off-by: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
parent 59817f4f

drivers/block/drbd/drbd_actlog.c

+2 −2
Original line number Diff line number Diff line
@@ -182,6 +182,7 @@ static struct lc_element *_al_get(struct drbd_conf *mdev, unsigned int enr) 
	if (unlikely(tmp != NULL)) {

		struct bm_extent  *bm_ext = lc_entry(tmp, struct bm_extent, lce);

		if (test_bit(BME_NO_WRITES, &bm_ext->flags)) {

			set_bit(BME_PRIORITY, &bm_ext->flags);

			spin_unlock_irq(&mdev->al_lock);

			return NULL;

		}
@@ -1297,8 +1298,7 @@ void drbd_rs_complete_io(struct drbd_conf *mdev, sector_t sector) 
	}



	if (lc_put(mdev->resync, &bm_ext->lce) == 0) {

		clear_bit(BME_LOCKED, &bm_ext->flags);

		clear_bit(BME_NO_WRITES, &bm_ext->flags);

		bm_ext->flags = 0; /* clear BME_LOCKED, BME_NO_WRITES and BME_PRIORITY */

		mdev->resync_locked--;

		wake_up(&mdev->al_wait);

	}

drivers/block/drbd/drbd_int.h

+2 −1
Original line number Diff line number Diff line
@@ -1326,6 +1326,7 @@ struct bm_extent { 


#define BME_NO_WRITES  0  /* bm_extent.flags: no more requests on this one! */

#define BME_LOCKED     1  /* bm_extent.flags: syncer active on this one. */

#define BME_PRIORITY   2  /* finish resync IO on this extent ASAP! App IO waiting! */



/* drbd_bitmap.c */

/*
@@ -1552,7 +1553,7 @@ extern int w_start_resync(struct drbd_conf *, struct drbd_work *, int); 
extern void resync_timer_fn(unsigned long data);



/* drbd_receiver.c */

extern int drbd_rs_should_slow_down(struct drbd_conf *mdev);

extern int drbd_rs_should_slow_down(struct drbd_conf *mdev, sector_t sector);

extern int drbd_submit_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e,

		const unsigned rw, const int fault_type);

extern int drbd_release_ee(struct drbd_conf *mdev, struct list_head *list);

drivers/block/drbd/drbd_receiver.c

+18 −4
Original line number Diff line number Diff line
@@ -1862,10 +1862,11 @@ static int receive_Data(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned 
 * The current sync rate used here uses only the most recent two step marks,

 * to have a short time average so we can react faster.

 */

int drbd_rs_should_slow_down(struct drbd_conf *mdev)

int drbd_rs_should_slow_down(struct drbd_conf *mdev, sector_t sector)

{

	struct gendisk *disk = mdev->ldev->backing_bdev->bd_contains->bd_disk;

	unsigned long db, dt, dbdt;

	struct lc_element *tmp;

	int curr_events;

	int throttle = 0;
@@ -1873,9 +1874,22 @@ int drbd_rs_should_slow_down(struct drbd_conf *mdev) 
	if (mdev->sync_conf.c_min_rate == 0)

		return 0;



	spin_lock_irq(&mdev->al_lock);

	tmp = lc_find(mdev->resync, BM_SECT_TO_EXT(sector));

	if (tmp) {

		struct bm_extent *bm_ext = lc_entry(tmp, struct bm_extent, lce);

		if (test_bit(BME_PRIORITY, &bm_ext->flags)) {

			spin_unlock_irq(&mdev->al_lock);

			return 0;

		}

		/* Do not slow down if app IO is already waiting for this extent */

	}

	spin_unlock_irq(&mdev->al_lock);



	curr_events = (int)part_stat_read(&disk->part0, sectors[0]) +

		      (int)part_stat_read(&disk->part0, sectors[1]) -

			atomic_read(&mdev->rs_sect_ev);



	if (!mdev->rs_last_events || curr_events - mdev->rs_last_events > 64) {

		unsigned long rs_left;

		int i;
@@ -2060,9 +2074,9 @@ static int receive_DataRequest(struct drbd_conf *mdev, enum drbd_packets cmd, un 
	 * we would also throttle its application reads.

	 * In that case, throttling is done on the SyncTarget only.

	 */

	if (mdev->state.peer != R_PRIMARY && drbd_rs_should_slow_down(mdev))

		msleep(100);

	if (drbd_rs_begin_io(mdev, e->sector))

	if (mdev->state.peer != R_PRIMARY && drbd_rs_should_slow_down(mdev, sector))

		schedule_timeout_uninterruptible(HZ/10);

	if (drbd_rs_begin_io(mdev, sector))

		goto out_free_e;



submit_for_resync:

drivers/block/drbd/drbd_worker.c

+5 −13
Original line number Diff line number Diff line
@@ -355,7 +355,7 @@ static int read_for_csum(struct drbd_conf *mdev, sector_t sector, int size) 
	if (!get_ldev(mdev))

		return -EIO;



	if (drbd_rs_should_slow_down(mdev))

	if (drbd_rs_should_slow_down(mdev, sector))

		goto defer;



	/* GFP_TRY, because if there is no memory available right now, this may
@@ -503,16 +503,6 @@ int drbd_rs_number_requests(struct drbd_conf *mdev) 
		number = SLEEP_TIME * mdev->c_sync_rate  / ((BM_BLOCK_SIZE / 1024) * HZ);

	}



	/* Throttle resync on lower level disk activity, which may also be

	 * caused by application IO on Primary/SyncTarget.

	 * Keep this after the call to drbd_rs_controller, as that assumes

	 * to be called as precisely as possible every SLEEP_TIME,

	 * and would be confused otherwise. */

	if (number && drbd_rs_should_slow_down(mdev)) {

		mdev->c_sync_rate = 1;

		number = 0;

	}



	/* ignore the amount of pending requests, the resync controller should

	 * throttle down to incoming reply rate soon enough anyways. */

	return number;
@@ -594,7 +584,8 @@ int w_make_resync_request(struct drbd_conf *mdev, 


		sector = BM_BIT_TO_SECT(bit);



		if (drbd_try_rs_begin_io(mdev, sector)) {

		if (drbd_rs_should_slow_down(mdev, sector) ||

		    drbd_try_rs_begin_io(mdev, sector)) {

			mdev->bm_resync_fo = bit;

			goto requeue;

		}
@@ -719,7 +710,8 @@ static int w_make_ov_request(struct drbd_conf *mdev, struct drbd_work *w, int ca 


		size = BM_BLOCK_SIZE;



		if (drbd_try_rs_begin_io(mdev, sector)) {

		if (drbd_rs_should_slow_down(mdev, sector) ||

		    drbd_try_rs_begin_io(mdev, sector)) {

			mdev->ov_position = sector;

			goto requeue;

		}