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md: add comments in md_flush_request()

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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@cloud.ionos.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
This commit is contained in:
Pankaj Gupta 2020-11-11 06:16:57 +01:00 committed by Song Liu
parent 81ba3c2462
commit 204d1a6434
1 changed files with 4 additions and 0 deletions
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4
drivers/md/md.c
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@ -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;