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 <neilb@suse.de>
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 8c9395f..c78d4835 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2947,6 +2947,7 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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;
}