From: NeilBrown Date: Mon, 14 Dec 2009 01:49:50 +0000 (+1100) Subject: md/raid5: don't complete make_request on barrier until writes are scheduled X-Git-Tag: v2.6.33-rc1~284^2~20 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=729a18663a30a9c8076e3adc2b3e4c866974f935;p=pandora-kernel.git 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: NeilBrown --- diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 8c9395f2028f..c78d4835b0d6 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -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; }