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authorLi Nan <linan122@huawei.com>2023-02-22 07:09:59 +0300
committerSong Liu <song@kernel.org>2023-04-14 08:20:23 +0300
commit72c215ed8731c88b2d7e09afc51fffc207ae47b8 (patch)
tree9375aef8ed4fd561a2fec7a7ecb37c36ea737b5e
parentbb4c19e030f45c5416f1eb4daa94fbaf7165e9ea (diff)
downloadlinux-72c215ed8731c88b2d7e09afc51fffc207ae47b8.tar.xz
md/raid10: fix task hung in raid10d
commit fe630de009d0 ("md/raid10: avoid deadlock on recovery.") allowed normal io and sync io to exist at the same time. Task hung will occur as below: T1 T2 T3 T4 raid10d handle_read_error allow_barrier conf->nr_pending-- -> 0 //submit sync io raid10_sync_request raise_barrier ->will not be blocked ... //submit to drivers raid10_read_request wait_barrier conf->nr_pending++ -> 1 //retry read fail raid10_end_read_request reschedule_retry add to retry_list conf->nr_queued++ -> 1 //sync io fail end_sync_read __end_sync_read reschedule_retry add to retry_list conf->nr_queued++ -> 2 ... handle_read_error get form retry_list conf->nr_queued-- freeze_array wait nr_pending == nr_queued+1 ->1 ->2 //task hung retry read and sync io will be added to retry_list(nr_queued->2) if they fails. raid10d() called handle_read_error() and hung in freeze_array(). nr_queued will not decrease because raid10d is blocked, nr_pending will not increase because conf->barrier is not released. Fix it by moving allow_barrier() after raid10_read_request(). raise_barrier() will wait for nr_waiting to become 0. Therefore, sync io and regular io will not be issued at the same time. Also remove the check of nr_queued in stop_waiting_barrier. It can be 0 but don't need to be blocking. Remove the check for MD_RECOVERY_RUNNING as the check is redundent. Fixes: fe630de009d0 ("md/raid10: avoid deadlock on recovery.") Signed-off-by: Li Nan <linan122@huawei.com> Signed-off-by: Song Liu <song@kernel.org> Link: https://lore.kernel.org/r/20230222041000.3341651-2-linan666@huaweicloud.com
-rw-r--r--drivers/md/raid10.c18
1 files changed, 13 insertions, 5 deletions
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 6c66357f92f5..db9ee3b637d6 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -995,11 +995,15 @@ static bool stop_waiting_barrier(struct r10conf *conf)
(!bio_list_empty(&bio_list[0]) || !bio_list_empty(&bio_list[1])))
return true;
- /* move on if recovery thread is blocked by us */
- if (conf->mddev->thread->tsk == current &&
- test_bit(MD_RECOVERY_RUNNING, &conf->mddev->recovery) &&
- conf->nr_queued > 0)
+ /*
+ * move on if io is issued from raid10d(), nr_pending is not released
+ * from original io(see handle_read_error()). All raise barrier is
+ * blocked until this io is done.
+ */
+ if (conf->mddev->thread->tsk == current) {
+ WARN_ON_ONCE(atomic_read(&conf->nr_pending) == 0);
return true;
+ }
return false;
}
@@ -2978,9 +2982,13 @@ static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)
md_error(mddev, rdev);
rdev_dec_pending(rdev, mddev);
- allow_barrier(conf);
r10_bio->state = 0;
raid10_read_request(mddev, r10_bio->master_bio, r10_bio);
+ /*
+ * allow_barrier after re-submit to ensure no sync io
+ * can be issued while regular io pending.
+ */
+ allow_barrier(conf);
}
static void handle_write_completed(struct r10conf *conf, struct r10bio *r10_bio)