From: Pankaj Gupta <pankaj.gupta@xxxxxxxxxxxxxxx>
Request coalescing logic is dependent on flush time
update in other context. This patch adds comments
to understand the code flow better.
Signed-off-by: Pankaj Gupta <pankaj.gupta@xxxxxxxxxxxxxxx>
---
drivers/md/md.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 167c80f98533..a330e61876e0 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -662,10 +662,14 @@ bool md_flush_request(struct mddev *mddev, struct bio *bio)
{
ktime_t req_start = ktime_get_boottime();
spin_lock_irq(&mddev->lock);
+ /* flush requests wait until ongoing flush completes,
+ * hence coalescing all the pending requests.
+ */
wait_event_lock_irq(mddev->sb_wait,
!mddev->flush_bio ||
ktime_after(mddev->prev_flush_start, req_start),
mddev->lock);
+ /* new request after previous flush is completed */
if (!ktime_after(mddev->prev_flush_start, req_start)) {
WARN_ON(mddev->flush_bio);
mddev->flush_bio = bio;
--
2.20.1
