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Message-Id: <20230927061241.1552837-3-yukuai1@huaweicloud.com>
Date: Wed, 27 Sep 2023 14:12:41 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: mariusz.tkaczyk@...ux.intel.com, xni@...hat.com, song@...nel.org
Cc: linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
yukuai3@...wei.com, yukuai1@...weicloud.com, yi.zhang@...wei.com,
yangerkun@...wei.com
Subject: [PATCH v3 2/2] md: simplify md_seq_ops
From: Yu Kuai <yukuai3@...wei.com>
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: Yu Kuai <yukuai3@...wei.com>
---
drivers/md/md.c | 100 +++++++++++-------------------------------------
1 file changed, 22 insertions(+), 78 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 73782cafad4e..0b83a406e797 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -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;
+ struct md_personality *pers;
- if (l == 0x10000) {
- ++*pos;
- return (void *)2;
- }
- if (l > 0x10000)
- return NULL;
- if (!l--)
- /* header */
- return (void*)1;
+ seq_puts(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_puts(seq, "\n");
+ seq->poll_event = atomic_read(&md_event_count);
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;
+
+ return seq_list_start(&all_mddevs, *pos);
}
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;
-
- ++*pos;
- if (v == (void*)2)
- return NULL;
-
- 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;
- }
- 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;
-
+ 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);
+ if (!mddev_get(mddev))
return 0;
- }
- if (v == (void*)2) {
- status_unused(seq);
- 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;
}
--
2.39.2
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