check if @scrubs_running=@scrubs_paused condition inside wait_event()
is not an atomic operation which means we may inc/dec @scrub_running/
paused at any time. Let's wake up @scrub_pause_wait as much as we can
to let commit transaction blocked less.
An example below:
Thread1 Thread2
|->scrub_blocked_if_needed() |->scrub_pending_trans_workers_inc
|->increase @scrub_paused
|->increase @scrub_running
|->wake up scrub_pause_wait list
|->scrub blocked
|->increase @scrub_paused
Thread3 is commiting transaction which is blocked at btrfs_scrub_pause().
So after Thread2 increase @scrub_paused, we meet the condition
@scrub_paused=@scrub_running, but transaction will be still blocked until
another calling to wake up @scrub_pause_wait.
Signed-off-by: Wang Shilong <wangsl.f...@cn.fujitsu.com>
Signed-off-by: Miao Xie <mi...@cn.fujitsu.com>
---
fs/btrfs/scrub.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index f2f8803..682ec3fc 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -315,6 +315,16 @@ static void scrub_pending_trans_workers_inc(struct
scrub_ctx *sctx)
atomic_inc(&fs_info->scrubs_running);
atomic_inc(&fs_info->scrubs_paused);
mutex_unlock(&fs_info->scrub_lock);
+
+ /*
+ * check if @scrubs_running=@scrubs_paused condition
+ * inside wait_event() is not an atomic operation.
+ * which means we may inc/dec @scrub_running/paused
+ * at any time. Let's wake up @scrub_pause_wait as
+ * much as we can to let commit transaction blocked less.
+ */
+ wake_up(&fs_info->scrub_pause_wait);
+
atomic_inc(&sctx->workers_pending);
}
--
1.8.3.1
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