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Commit 729a1866 authored by NeilBrown's avatar NeilBrown
Browse files

md/raid5: don't complete make_request on barrier until writes are scheduled 



The post-barrier-flush is sent by md as soon as make_request on the
barrier write completes.  For raid5, the data might not be in the
per-device queues yet.  So for barrier requests, wait for any
pre-reading to be done so that the request will be in the per-device
queues.

We use the 'preread_active' count to check that nothing is still in
the preread phase, and delay the decrement of this count until after
write requests have been submitted to the underlying devices.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent a2826aa9

drivers/md/raid5.c

+39 −12
Original line number Diff line number Diff line
@@ -2947,6 +2947,7 @@ static void handle_stripe5(struct stripe_head *sh) 
	struct r5dev *dev;

	mdk_rdev_t *blocked_rdev = NULL;

	int prexor;

	int dec_preread_active = 0;



	memset(&s, 0, sizeof(s));

	pr_debug("handling stripe %llu, state=%#lx cnt=%d, pd_idx=%d check:%d "
@@ -3096,12 +3097,8 @@ static void handle_stripe5(struct stripe_head *sh) 
					set_bit(STRIPE_INSYNC, &sh->state);

			}

		}

		if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {

			atomic_dec(&conf->preread_active_stripes);

			if (atomic_read(&conf->preread_active_stripes) <

				IO_THRESHOLD)

				md_wakeup_thread(conf->mddev->thread);

		}

		if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state))

			dec_preread_active = 1;

	}



	/* Now to consider new write requests and what else, if anything
@@ -3208,6 +3205,16 @@ static void handle_stripe5(struct stripe_head *sh) 


	ops_run_io(sh, &s);



	if (dec_preread_active) {

		/* We delay this until after ops_run_io so that if make_request

		 * is waiting on a barrier, it won't continue until the writes

		 * have actually been submitted.

		 */

		atomic_dec(&conf->preread_active_stripes);

		if (atomic_read(&conf->preread_active_stripes) <

		    IO_THRESHOLD)

			md_wakeup_thread(conf->mddev->thread);

	}

	return_io(return_bi);

}
@@ -3221,6 +3228,7 @@ static void handle_stripe6(struct stripe_head *sh) 
	struct r6_state r6s;

	struct r5dev *dev, *pdev, *qdev;

	mdk_rdev_t *blocked_rdev = NULL;

	int dec_preread_active = 0;



	pr_debug("handling stripe %llu, state=%#lx cnt=%d, "

		"pd_idx=%d, qd_idx=%d\n, check:%d, reconstruct:%d\n",
@@ -3379,12 +3387,8 @@ static void handle_stripe6(struct stripe_head *sh) 
					set_bit(STRIPE_INSYNC, &sh->state);

			}

		}

		if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {

			atomic_dec(&conf->preread_active_stripes);

			if (atomic_read(&conf->preread_active_stripes) <

				IO_THRESHOLD)

				md_wakeup_thread(conf->mddev->thread);

		}

		if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state))

			dec_preread_active = 1;

	}



	/* Now to consider new write requests and what else, if anything
@@ -3493,6 +3497,18 @@ static void handle_stripe6(struct stripe_head *sh) 


	ops_run_io(sh, &s);





	if (dec_preread_active) {

		/* We delay this until after ops_run_io so that if make_request

		 * is waiting on a barrier, it won't continue until the writes

		 * have actually been submitted.

		 */

		atomic_dec(&conf->preread_active_stripes);

		if (atomic_read(&conf->preread_active_stripes) <

		    IO_THRESHOLD)

			md_wakeup_thread(conf->mddev->thread);

	}



	return_io(return_bi);

}
@@ -3995,6 +4011,9 @@ static int make_request(struct request_queue *q, struct bio * bi) 
			finish_wait(&conf->wait_for_overlap, &w);

			set_bit(STRIPE_HANDLE, &sh->state);

			clear_bit(STRIPE_DELAYED, &sh->state);

			if (mddev->barrier && 

			    !test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))

				atomic_inc(&conf->preread_active_stripes);

			release_stripe(sh);

		} else {

			/* cannot get stripe for read-ahead, just give-up */
@@ -4014,6 +4033,14 @@ static int make_request(struct request_queue *q, struct bio * bi) 


		bio_endio(bi, 0);

	}



	if (mddev->barrier) {

		/* We need to wait for the stripes to all be handled.

		 * So: wait for preread_active_stripes to drop to 0.

		 */

		wait_event(mddev->thread->wqueue,

			   atomic_read(&conf->preread_active_stripes) == 0);

	}

	return 0;

}