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Commit 380207d0 authored by Philipp Reisner's avatar Philipp Reisner
Browse files

drbd: Load balancing of read requests 



New config option for the disk secition "read-balancing", with
the values: prefer-local, prefer-remote, round-robin, when-congested-remote.

Signed-off-by: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
parent d10b4ea3

drivers/block/drbd/drbd_int.h

+1 −0
Original line number Diff line number Diff line
@@ -698,6 +698,7 @@ enum { 
	AHEAD_TO_SYNC_SOURCE,   /* Ahead -> SyncSource queued */

	B_RS_H_DONE,		/* Before resync handler done (already executed) */

	DISCARD_MY_DATA,	/* discard_my_data flag per volume */

	READ_BALANCE_RR,

};



struct drbd_bitmap; /* opaque for drbd_conf */

drivers/block/drbd/drbd_receiver.c

+1 −1
Original line number Diff line number Diff line
@@ -4974,7 +4974,7 @@ static int got_NegDReply(struct drbd_tconn *tconn, struct packet_info *pi) 


	update_peer_seq(mdev, be32_to_cpu(p->seq_num));



	dev_err(DEV, "Got NegDReply; Sector %llus, len %u; Fail original request.\n",

	dev_err(DEV, "Got NegDReply; Sector %llus, len %u.\n",

	    (unsigned long long)sector, be32_to_cpu(p->blksize));



	return validate_req_change_req_state(mdev, p->block_id, sector,

drivers/block/drbd/drbd_req.c

+56 −1
Original line number Diff line number Diff line
@@ -563,6 +563,11 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what, 
		if (req->rq_state & RQ_NET_SENT && req->rq_state & RQ_WRITE)

			atomic_sub(req->i.size >> 9, &mdev->ap_in_flight);



		if (!(req->rq_state & RQ_WRITE) &&

		    mdev->state.disk == D_UP_TO_DATE &&

		    !IS_ERR_OR_NULL(req->private_bio))

			goto goto_read_retry_local;



		/* if it is still queued, we may not complete it here.

		 * it will be canceled soon. */

		if (!(req->rq_state & RQ_NET_QUEUED))
@@ -625,10 +630,22 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what, 
		req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);



		req->rq_state |= RQ_NET_DONE;



		if (!(req->rq_state & RQ_WRITE) &&

		    mdev->state.disk == D_UP_TO_DATE &&

		    !IS_ERR_OR_NULL(req->private_bio))

			goto goto_read_retry_local;



		_req_may_be_done_not_susp(req, m);

		/* else: done by HANDED_OVER_TO_NETWORK */

		break;



	goto_read_retry_local:

		req->rq_state |= RQ_LOCAL_PENDING;

		req->private_bio->bi_bdev = mdev->ldev->backing_bdev;

		generic_make_request(req->private_bio);

		break;



	case FAIL_FROZEN_DISK_IO:

		if (!(req->rq_state & RQ_LOCAL_COMPLETED))

			break;
@@ -689,6 +706,11 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what, 
		dec_ap_pending(mdev);

		req->rq_state &= ~RQ_NET_PENDING;

		req->rq_state |= (RQ_NET_OK|RQ_NET_DONE);

		if (!IS_ERR_OR_NULL(req->private_bio)) {

			bio_put(req->private_bio);

			req->private_bio = NULL;

			put_ldev(mdev);

		}

		_req_may_be_done_not_susp(req, m);

		break;

	};
@@ -723,6 +745,35 @@ static bool drbd_may_do_local_read(struct drbd_conf *mdev, sector_t sector, int 
	return drbd_bm_count_bits(mdev, sbnr, ebnr) == 0;

}



static bool remote_due_to_read_balancing(struct drbd_conf *mdev)

{

	enum drbd_read_balancing rbm;

	struct backing_dev_info *bdi;



	if (mdev->state.pdsk < D_UP_TO_DATE)

		return false;



	rcu_read_lock();

	rbm = rcu_dereference(mdev->ldev->disk_conf)->read_balancing;

	rcu_read_unlock();



	switch (rbm) {

	case RB_CONGESTED_REMOTE:

		bdi = &mdev->ldev->backing_bdev->bd_disk->queue->backing_dev_info;

		return bdi_read_congested(bdi);

	case RB_LEAST_PENDING:

		return atomic_read(&mdev->local_cnt) >

			atomic_read(&mdev->ap_pending_cnt) + atomic_read(&mdev->rs_pending_cnt);

	case RB_ROUND_ROBIN:

		return test_and_change_bit(READ_BALANCE_RR, &mdev->flags);

	case RB_PREFER_REMOTE:

		return true;

	case RB_PREFER_LOCAL:

	default:

		return false;

	}

}



/*

 * complete_conflicting_writes  -  wait for any conflicting write requests

 *
@@ -790,6 +841,10 @@ int __drbd_make_request(struct drbd_conf *mdev, struct bio *bio, unsigned long s 
				bio_put(req->private_bio);

				req->private_bio = NULL;

				put_ldev(mdev);

			} else if (remote_due_to_read_balancing(mdev)) {

				/* Keep the private bio in case we need it

				   for a local retry */

				local = 0;

			}

		}

		remote = !local && mdev->state.pdsk >= D_UP_TO_DATE;
@@ -1017,7 +1072,7 @@ fail_free_complete: 
	if (req->rq_state & RQ_IN_ACT_LOG)

		drbd_al_complete_io(mdev, &req->i);

fail_and_free_req:

	if (local) {

	if (!IS_ERR_OR_NULL(req->private_bio)) {

		bio_put(req->private_bio);

		req->private_bio = NULL;

		put_ldev(mdev);

include/linux/drbd.h

+8 −0
Original line number Diff line number Diff line
@@ -102,6 +102,14 @@ enum drbd_on_congestion { 
	OC_DISCONNECT,

};



enum drbd_read_balancing {

	RB_PREFER_LOCAL,

	RB_PREFER_REMOTE,

	RB_ROUND_ROBIN,

	RB_LEAST_PENDING,

	RB_CONGESTED_REMOTE,

};



/* KEEP the order, do not delete or insert. Only append. */

enum drbd_ret_code {

	ERR_CODE_BASE		= 100,

include/linux/drbd_genl.h

+1 −0
Original line number Diff line number Diff line
@@ -129,6 +129,7 @@ GENL_struct(DRBD_NLA_DISK_CONF, 3, disk_conf, 
	__flg_field_def(18, DRBD_GENLA_F_MANDATORY,	disk_drain, DRBD_DISK_DRAIN_DEF)

	__flg_field_def(19, DRBD_GENLA_F_MANDATORY,	md_flushes, DRBD_MD_FLUSHES_DEF)

	__u32_field_def(20,	DRBD_GENLA_F_MANDATORY,	disk_timeout, DRBD_DISK_TIMEOUT_DEF)

	__u32_field_def(21,	0 /* OPTIONAL */,       read_balancing, DRBD_READ_BALANCING_DEF)

)



GENL_struct(DRBD_NLA_RESOURCE_OPTS, 4, res_opts,