Commit cf1b6d44 authored by Yu Kuai's avatar Yu Kuai Committed by Song Liu
Browse files

md: simplify md_seq_ops 



Before this patch, the implementation is hacky and hard to understand:

1) md_seq_start set pos to 1;
2) md_seq_show found pos is 1, then print Personalities;
3) md_seq_next found pos is 1, then it update pos to the first mddev;
4) md_seq_show found pos is not 1 or 2, show mddev;
5) md_seq_next found pos is not 1 or 2, update pos to next mddev;
6) loop 4-5 until the last mddev, then md_seq_next update pos to 2;
7) md_seq_show found pos is 2, then print unused devices;
8) md_seq_next found pos is 2, stop;

This patch remove the magic value and use seq_list_start/next/stop()
directly, and move printing "Personalities" to md_seq_start(),
"unsed devices" to md_seq_stop():

1) md_seq_start print Personalities, and then set pos to first mddev;
2) md_seq_show show mddev;
3) md_seq_next update pos to next mddev;
4) loop 2-3 until the last mddev;
5) md_seq_stop print unsed devices;

Signed-off-by: default avatarYu Kuai <yukuai3@huawei.com>
Signed-off-by: default avatarSong Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230927061241.1552837-3-yukuai1@huaweicloud.com
parent 3d8d3287

drivers/md/md.c

+22 −78
Original line number Diff line number Diff line
@@ -8213,105 +8213,46 @@ static int status_resync(struct seq_file *seq, struct mddev *mddev) 
}



static void *md_seq_start(struct seq_file *seq, loff_t *pos)

	__acquires(&all_mddevs_lock)

{

	struct list_head *tmp;

	loff_t l = *pos;

	struct mddev *mddev;



	if (l == 0x10000) {

		++*pos;

		return (void *)2;

	}

	if (l > 0x10000)

		return NULL;

	if (!l--)

		/* header */

		return (void*)1;



	spin_lock(&all_mddevs_lock);

	list_for_each(tmp,&all_mddevs)

		if (!l--) {

			mddev = list_entry(tmp, struct mddev, all_mddevs);

			if (!mddev_get(mddev))

				continue;

			spin_unlock(&all_mddevs_lock);

			return mddev;

		}

	spin_unlock(&all_mddevs_lock);

	if (!l--)

		return (void*)2;/* tail */

	return NULL;

}

	struct md_personality *pers;



static void *md_seq_next(struct seq_file *seq, void *v, loff_t *pos)

{

	struct list_head *tmp;

	struct mddev *next_mddev, *mddev = v;

	struct mddev *to_put = NULL;

	seq_puts(seq, "Personalities : ");

	spin_lock(&pers_lock);

	list_for_each_entry(pers, &pers_list, list)

		seq_printf(seq, "[%s] ", pers->name);



	++*pos;

	if (v == (void*)2)

		return NULL;

	spin_unlock(&pers_lock);

	seq_puts(seq, "\n");

	seq->poll_event = atomic_read(&md_event_count);



	spin_lock(&all_mddevs_lock);

	if (v == (void*)1) {

		tmp = all_mddevs.next;

	} else {

		to_put = mddev;

		tmp = mddev->all_mddevs.next;

	}



	for (;;) {

		if (tmp == &all_mddevs) {

			next_mddev = (void*)2;

			*pos = 0x10000;

			break;

	return seq_list_start(&all_mddevs, *pos);

}

		next_mddev = list_entry(tmp, struct mddev, all_mddevs);

		if (mddev_get(next_mddev))

			break;

		mddev = next_mddev;

		tmp = mddev->all_mddevs.next;

	}

	spin_unlock(&all_mddevs_lock);



	if (to_put)

		mddev_put(to_put);

	return next_mddev;



static void *md_seq_next(struct seq_file *seq, void *v, loff_t *pos)

{

	return seq_list_next(v, &all_mddevs, pos);

}



static void md_seq_stop(struct seq_file *seq, void *v)

	__releases(&all_mddevs_lock)

{

	struct mddev *mddev = v;



	if (mddev && v != (void*)1 && v != (void*)2)

		mddev_put(mddev);

	status_unused(seq);

	spin_unlock(&all_mddevs_lock);

}



static int md_seq_show(struct seq_file *seq, void *v)

{

	struct mddev *mddev = v;

	struct mddev *mddev = list_entry(v, struct mddev, all_mddevs);

	sector_t sectors;

	struct md_rdev *rdev;



	if (v == (void*)1) {

		struct md_personality *pers;

		seq_printf(seq, "Personalities : ");

		spin_lock(&pers_lock);

		list_for_each_entry(pers, &pers_list, list)

			seq_printf(seq, "[%s] ", pers->name);



		spin_unlock(&pers_lock);

		seq_printf(seq, "\n");

		seq->poll_event = atomic_read(&md_event_count);

		return 0;

	}

	if (v == (void*)2) {

		status_unused(seq);

	if (!mddev_get(mddev))

		return 0;

	}



	spin_unlock(&all_mddevs_lock);

	spin_lock(&mddev->lock);

	if (mddev->pers || mddev->raid_disks || !list_empty(&mddev->disks)) {

		seq_printf(seq, "%s : %sactive", mdname(mddev),
@@ -8382,6 +8323,9 @@ static int md_seq_show(struct seq_file *seq, void *v) 
		seq_printf(seq, "\n");

	}

	spin_unlock(&mddev->lock);

	spin_lock(&all_mddevs_lock);

	if (atomic_dec_and_test(&mddev->active))

		__mddev_put(mddev);



	return 0;

}