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Commit 19f843aa authored by Lars Ellenberg's avatar Lars Ellenberg Committed by Philipp Reisner
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drbd: bitmap keep track of changes vs on-disk bitmap 



When we set or clear bits in a bitmap page,
also set a flag in the page->private pointer.

This allows us to skip writes of unchanged pages.

Signed-off-by: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
parent 95a0f10c

drivers/block/drbd/drbd_actlog.c

+29 −103
Original line number Diff line number Diff line
@@ -262,6 +262,33 @@ void drbd_al_complete_io(struct drbd_conf *mdev, sector_t sector) 
	spin_unlock_irqrestore(&mdev->al_lock, flags);

}



#if (PAGE_SHIFT + 3) < (AL_EXTENT_SHIFT - BM_BLOCK_SHIFT)

/* Currently BM_BLOCK_SHIFT, BM_EXT_SHIFT and AL_EXTENT_SHIFT

 * are still coupled, or assume too much about their relation.

 * Code below will not work if this is violated.

 * Will be cleaned up with some followup patch.

 */

# error FIXME

#endif



static unsigned int al_extent_to_bm_page(unsigned int al_enr)

{

	return al_enr >>

		/* bit to page */

		((PAGE_SHIFT + 3) -

		/* al extent number to bit */

		 (AL_EXTENT_SHIFT - BM_BLOCK_SHIFT));

}



static unsigned int rs_extent_to_bm_page(unsigned int rs_enr)

{

	return rs_enr >>

		/* bit to page */

		((PAGE_SHIFT + 3) -

		/* al extent number to bit */

		 (BM_EXT_SHIFT - BM_BLOCK_SHIFT));

}



int

w_al_write_transaction(struct drbd_conf *mdev, struct drbd_work *w, int unused)

{
@@ -289,7 +316,7 @@ w_al_write_transaction(struct drbd_conf *mdev, struct drbd_work *w, int unused) 
	 * For now, we must not write the transaction,

	 * if we cannot write out the bitmap of the evicted extent. */

	if (mdev->state.conn < C_CONNECTED && evicted != LC_FREE)

		drbd_bm_write_sect(mdev, evicted/AL_EXT_PER_BM_SECT);

		drbd_bm_write_page(mdev, al_extent_to_bm_page(evicted));



	/* The bitmap write may have failed, causing a state change. */

	if (mdev->state.disk < D_INCONSISTENT) {
@@ -635,105 +662,6 @@ static int atodb_prepare_unless_covered(struct drbd_conf *mdev, 
	return err;

}



/**

 * drbd_al_to_on_disk_bm() -  * Writes bitmap parts covered by active AL extents

 * @mdev:	DRBD device.

 *

 * Called when we detach (unconfigure) local storage,

 * or when we go from R_PRIMARY to R_SECONDARY role.

 */

void drbd_al_to_on_disk_bm(struct drbd_conf *mdev)

{

	int i, nr_elements;

	unsigned int enr;

	struct bio **bios;

	struct drbd_atodb_wait wc;



	ERR_IF (!get_ldev_if_state(mdev, D_ATTACHING))

		return; /* sorry, I don't have any act_log etc... */



	wait_event(mdev->al_wait, lc_try_lock(mdev->act_log));



	nr_elements = mdev->act_log->nr_elements;



	/* GFP_KERNEL, we are not in anyone's write-out path */

	bios = kzalloc(sizeof(struct bio *) * nr_elements, GFP_KERNEL);

	if (!bios)

		goto submit_one_by_one;



	atomic_set(&wc.count, 0);

	init_completion(&wc.io_done);

	wc.mdev = mdev;

	wc.error = 0;



	for (i = 0; i < nr_elements; i++) {

		enr = lc_element_by_index(mdev->act_log, i)->lc_number;

		if (enr == LC_FREE)

			continue;

		/* next statement also does atomic_inc wc.count and local_cnt */

		if (atodb_prepare_unless_covered(mdev, bios,

						enr/AL_EXT_PER_BM_SECT,

						&wc))

			goto free_bios_submit_one_by_one;

	}



	/* unnecessary optimization? */

	lc_unlock(mdev->act_log);

	wake_up(&mdev->al_wait);



	/* all prepared, submit them */

	for (i = 0; i < nr_elements; i++) {

		if (bios[i] == NULL)

			break;

		if (drbd_insert_fault(mdev, DRBD_FAULT_MD_WR)) {

			bios[i]->bi_rw = WRITE;

			bio_endio(bios[i], -EIO);

		} else {

			submit_bio(WRITE, bios[i]);

		}

	}



	/* always (try to) flush bitmap to stable storage */

	drbd_md_flush(mdev);



	/* In case we did not submit a single IO do not wait for

	 * them to complete. ( Because we would wait forever here. )

	 *

	 * In case we had IOs and they are already complete, there

	 * is not point in waiting anyways.

	 * Therefore this if () ... */

	if (atomic_read(&wc.count))

		wait_for_completion(&wc.io_done);



	put_ldev(mdev);



	kfree(bios);

	return;



 free_bios_submit_one_by_one:

	/* free everything by calling the endio callback directly. */

	for (i = 0; i < nr_elements && bios[i]; i++)

		bio_endio(bios[i], 0);



	kfree(bios);



 submit_one_by_one:

	dev_warn(DEV, "Using the slow drbd_al_to_on_disk_bm()\n");



	for (i = 0; i < mdev->act_log->nr_elements; i++) {

		enr = lc_element_by_index(mdev->act_log, i)->lc_number;

		if (enr == LC_FREE)

			continue;

		/* Really slow: if we have al-extents 16..19 active,

		 * sector 4 will be written four times! Synchronous! */

		drbd_bm_write_sect(mdev, enr/AL_EXT_PER_BM_SECT);

	}



	lc_unlock(mdev->act_log);

	wake_up(&mdev->al_wait);

	put_ldev(mdev);

}



/**

 * drbd_al_apply_to_bm() - Sets the bitmap to diry(1) where covered ba active AL extents

 * @mdev:	DRBD device.
@@ -813,7 +741,7 @@ static int w_update_odbm(struct drbd_conf *mdev, struct drbd_work *w, int unused 
		return 1;

	}



	drbd_bm_write_sect(mdev, udw->enr);

	drbd_bm_write_page(mdev, rs_extent_to_bm_page(udw->enr));

	put_ldev(mdev);



	kfree(udw);
@@ -893,7 +821,6 @@ static void drbd_try_clear_on_disk_bm(struct drbd_conf *mdev, sector_t sector, 
				dev_warn(DEV, "Kicking resync_lru element enr=%u "

				     "out with rs_failed=%d\n",

				     ext->lce.lc_number, ext->rs_failed);

				set_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags);

			}

			ext->rs_left = rs_left;

			ext->rs_failed = success ? 0 : count;
@@ -912,7 +839,6 @@ static void drbd_try_clear_on_disk_bm(struct drbd_conf *mdev, sector_t sector, 
				drbd_queue_work_front(&mdev->data.work, &udw->w);

			} else {

				dev_warn(DEV, "Could not kmalloc an udw\n");

				set_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags);

			}

		}

	} else {