Not the best code organization, but no real harm done. Look at the
front of md_write_start:
void md_write_start(struct mddev *mddev, struct bio *bi)
{
int did_change = 0;
if (bio_data_dir(bi) != WRITE)
return;
So writes fall thru really quickly.
Doug
On Mon, Nov 28, 2016 at 3:41 PM, Robert LeBlanc <robert@xxxxxxxxxxxxx> wrote:
> I'm looking through the code and am wondering why this is at the start
> of raid1_make_request. It seems that it is only needed for WRITE and
> would unnecessarily delay READ requests waiting for the superblock.
> Would it make more sense to put this at the start of the WRITE branch?
> What am I missing?
>
> 1057 /*
> 1058 * Register the new request and wait if the
> reconstruction
> 1059 * thread has put up a bar for new requests.
> 1060 * Continue immediately if no resync is active currently.
> 1061 */
> 1062
> 1063 md_write_start(mddev, bio); /* wait on superblock update
> early */
> 1064
> 1065 if (bio_data_dir(bio) == WRITE &&
> 1066 ((bio_end_sector(bio) > mddev->suspend_lo &&
> 1067 bio->bi_iter.bi_sector < mddev->suspend_hi) ||
> 1068 (mddev_is_clustered(mddev) &&
> 1069 md_cluster_ops->area_resyncing(mddev, WRITE,
> 1070 bio->bi_iter.bi_sector,
> bio_end_sector(bio))))) {
> 1071 /* As the suspend_* range is controlled by
> 1072 * userspace, we want an interruptible
> 1073 * wait.
> 1074 */
> 1075 DEFINE_WAIT(w);
> 1076 for (;;) {
> 1077 flush_signals(current);
> 1078 prepare_to_wait(&conf->wait_barrier,
> 1079 &w, TASK_INTERRUPTIBLE);
> 1080 if (bio_end_sector(bio) <=
> mddev->suspend_lo ||
> 1081 bio->bi_iter.bi_sector >=
> mddev->suspend_hi ||
> 1082 (mddev_is_clustered(mddev) &&
> 1083
> !md_cluster_ops->area_resyncing(mddev, WRITE,
> 1084 bio->bi_iter.bi_sector,
> bio_end_sector(bio))))
> 1085 break;
> 1086 schedule();
> 1087 }
> 1088 finish_wait(&conf->wait_barrier, &w);
> 1089 }
> 1090
> 1091 start_next_window = wait_barrier(conf, bio);
> 1092
> 1093 bitmap = mddev->bitmap;
> 1094
>
> Thanks
>
> ----------------
> Robert LeBlanc
> PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
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--
Doug Dumitru
EasyCo LLC
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