[PATCH 2/3] md: add comments in md_flush_request()
From: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Date: 2020-11-11 05:17:29
Also in:
lkml
Subsystem:
software raid (multiple disks) support, the rest · Maintainers:
Song Liu, Yu Kuai, Linus Torvalds
From: Pankaj Gupta <redacted> 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 <redacted> --- 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