Commit 69ba1ee9 authored by Lars Ellenberg's avatar Lars Ellenberg Committed by Jens Axboe
Browse files

drbd: possibly disable discard support, if backend has discard_zeroes_data=0 



Now that we have the discard_zeroes_if_aligned setting, we should also
check it when setting up our queue parameters on the primary,
not only on the receiving side.

We announce discard support,
UNLESS

 * we are connected to a peer that does not support TRIM
   on the DRBD protocol level.  Otherwise, it would either discard, or
   do a fallback to zero-out, depending on its backend and configuration.

 * our local backend does not support discards,
   or (discard_zeroes_data=0 AND discard_zeroes_if_aligned=no).

Signed-off-by: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent dd4f699d

drivers/block/drbd/drbd_nl.c

+55 −25
Original line number Diff line number Diff line
@@ -1154,6 +1154,59 @@ static int drbd_check_al_size(struct drbd_device *device, struct disk_conf *dc) 
	return 0;

}



static void blk_queue_discard_granularity(struct request_queue *q, unsigned int granularity)

{

	q->limits.discard_granularity = granularity;

}

static void decide_on_discard_support(struct drbd_device *device,

			struct request_queue *q,

			struct request_queue *b,

			bool discard_zeroes_if_aligned)

{

	/* q = drbd device queue (device->rq_queue)

	 * b = backing device queue (device->ldev->backing_bdev->bd_disk->queue),

	 *     or NULL if diskless

	 */

	struct drbd_connection *connection = first_peer_device(device)->connection;

	bool can_do = b ? blk_queue_discard(b) : true;



	if (can_do && b && !b->limits.discard_zeroes_data && !discard_zeroes_if_aligned) {

		can_do = false;

		drbd_info(device, "discard_zeroes_data=0 and discard_zeroes_if_aligned=no: disabling discards\n");

	}

	if (can_do && connection->cstate >= C_CONNECTED && !(connection->agreed_features & FF_TRIM)) {

		can_do = false;

		drbd_info(connection, "peer DRBD too old, does not support TRIM: disabling discards\n");

	}

	if (can_do) {

		/* We don't care for the granularity, really.

		 * Stacking limits below should fix it for the local

		 * device.  Whether or not it is a suitable granularity

		 * on the remote device is not our problem, really. If

		 * you care, you need to use devices with similar

		 * topology on all peers. */

		blk_queue_discard_granularity(q, 512);

		q->limits.max_discard_sectors = DRBD_MAX_DISCARD_SECTORS;

		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);

	} else {

		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);

		blk_queue_discard_granularity(q, 0);

		q->limits.max_discard_sectors = 0;

	}

}



static void fixup_discard_if_not_supported(struct request_queue *q)

{

	/* To avoid confusion, if this queue does not support discard, clear

	 * max_discard_sectors, which is what lsblk -D reports to the user.

	 * Older kernels got this wrong in "stack limits".

	 * */

	if (!blk_queue_discard(q)) {

		blk_queue_max_discard_sectors(q, 0);

		blk_queue_discard_granularity(q, 0);

	}

}



static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backing_dev *bdev,

				   unsigned int max_bio_size)

{
@@ -1183,26 +1236,8 @@ static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backi 
	/* This is the workaround for "bio would need to, but cannot, be split" */

	blk_queue_max_segments(q, max_segments ? max_segments : BLK_MAX_SEGMENTS);

	blk_queue_segment_boundary(q, PAGE_SIZE-1);



	decide_on_discard_support(device, q, b, discard_zeroes_if_aligned);

	if (b) {

		struct drbd_connection *connection = first_peer_device(device)->connection;



		blk_queue_max_discard_sectors(q, DRBD_MAX_DISCARD_SECTORS);



		if (blk_queue_discard(b) && (b->limits.discard_zeroes_data || discard_zeroes_if_aligned) &&

		    (connection->cstate < C_CONNECTED || connection->agreed_features & FF_TRIM)) {

			/* We don't care, stacking below should fix it for the local device.

			 * Whether or not it is a suitable granularity on the remote device

			 * is not our problem, really. If you care, you need to

			 * use devices with similar topology on all peers. */

			q->limits.discard_granularity = 512;

			queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);

		} else {

			blk_queue_max_discard_sectors(q, 0);

			queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);

			q->limits.discard_granularity = 0;

		}



		blk_queue_stack_limits(q, b);



		if (q->backing_dev_info.ra_pages != b->backing_dev_info.ra_pages) {
@@ -1212,12 +1247,7 @@ static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backi 
			q->backing_dev_info.ra_pages = b->backing_dev_info.ra_pages;

		}

	}

	/* To avoid confusion, if this queue does not support discard, clear

	 * max_discard_sectors, which is what lsblk -D reports to the user.  */

	if (!blk_queue_discard(q)) {

		blk_queue_max_discard_sectors(q, 0);

		q->limits.discard_granularity = 0;

	}

	fixup_discard_if_not_supported(q);

}



void drbd_reconsider_queue_parameters(struct drbd_device *device, struct drbd_backing_dev *bdev)

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