From 204d1a6434158ac655fc4037f29742b9b6103f0e Mon Sep 17 00:00:00 2001 From: Pankaj Gupta Date: Wed, 11 Nov 2020 06:16:57 +0100 Subject: md: add comments in md_flush_request() 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 Signed-off-by: Song Liu --- drivers/md/md.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'drivers') diff --git a/drivers/md/md.c b/drivers/md/md.c index 3992e8c5c0d6..a0998ad6388c 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; -- cgit v1.2.3