Question about blkdev_issue_zeroout()

[Daeho Jeong <daeho43@xxxxxxxxx>]

Hi guys,

When I looked into blkdev_issue_zeroout(), I found something that I
cannot understand there. In my understanding, all the submitted bio
will stay in the plug list during plugging. But, I found
submit_bio_wait() calling during the plugging. I guess the below
submit_bio_wait() might wait forever in the lower kernel version like
4.14, because of plugging. If I am wrong, plz, correct me.

     >>>  blk_start_plug(&plug); <<<
        if (try_write_zeroes) {
                ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects,
                                                  gfp_mask, &bio, flags);
        } else if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
                ret = __blkdev_issue_zero_pages(bdev, sector, nr_sects,
                                                gfp_mask, &bio);
        } else {
                /* No zeroing offload support */
                ret = -EOPNOTSUPP;
        }
        if (ret == 0 && bio) {
                ret = submit_bio_wait(bio);
                bio_put(bio);
        }
      >>> blk_finish_plug(&plug); <<<