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Message-ID: <CAPhsuW6Ekxu9kaxvi673MCr=nBCS78D613zuH6Kcg5Y4Hs=jDw@mail.gmail.com>
Date: Tue, 9 Jan 2024 00:12:30 -0800
From: Song Liu <song@...nel.org>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: mariusz.tkaczyk@...ux.intel.com, xni@...hat.com,
linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org, yi.zhang@...wei.com,
yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v3 2/2] md: simplify md_seq_ops
On Mon, Jan 8, 2024 at 11:48 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
>
> Hi,
>
> 在 2024/01/09 9:21, Yu Kuai 写道:
> > Hi,
> >
> > 在 2024/01/09 7:38, Song Liu 写道:
> >> On Tue, Sep 26, 2023 at 11:19 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
[...]
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index e351e6c51cc7..289d3d89e73d 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -8135,6 +8135,19 @@ static void status_unused(struct seq_file *seq)
> seq_printf(seq, "\n");
> }
>
> +static void status_personalities(struct seq_file *seq)
> +{
> + struct md_personality *pers;
> +
> + 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");
> +}
> +
> static int status_resync(struct seq_file *seq, struct mddev *mddev)
> {
> sector_t max_sectors, resync, res;
> @@ -8273,43 +8286,53 @@ static int status_resync(struct seq_file *seq,
> struct mddev *mddev)
> return 1;
> }
>
> +#define MDDEV_NONE (void *)1
> +
> static void *md_seq_start(struct seq_file *seq, loff_t *pos)
> __acquires(&all_mddevs_lock)
> {
> - struct md_personality *pers;
> -
> - 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);
>
> - return seq_list_start(&all_mddevs, *pos);
> + if (!list_empty(&all_mddevs))
> + return seq_list_start(&all_mddevs, *pos);
> + else if (*pos == 0)
> + return MDDEV_NONE;
> + else
> + return NULL;
> }
>
> static void *md_seq_next(struct seq_file *seq, void *v, loff_t *pos)
> {
> + if (v == MDDEV_NONE) {
> + ++*pos;
> + return NULL;
> + }
> +
> return seq_list_next(v, &all_mddevs, pos);
> }
>
> static void md_seq_stop(struct seq_file *seq, void *v)
> __releases(&all_mddevs_lock)
> {
> - status_unused(seq);
> spin_unlock(&all_mddevs_lock);
> }
> static int md_seq_show(struct seq_file *seq, void *v)
> {
> - struct mddev *mddev = list_entry(v, struct mddev, all_mddevs);
> + struct mddev *mddev;
> sector_t sectors;
> struct md_rdev *rdev;
>
> + if (v == MDDEV_NONE) {
> + status_personalities(seq);
> + status_unused(seq);
> + return 0;
> + }
> +
> + mddev = list_entry(v, struct mddev, all_mddevs);
> + if (mddev == list_first_entry(&all_mddevs, struct mddev,
> all_mddevs))
> + status_personalities(seq);
> if (!mddev_get(mddev))
> return 0;
>
> @@ -8385,6 +8408,10 @@ static int md_seq_show(struct seq_file *seq, void *v)
> }
> spin_unlock(&mddev->lock);
> spin_lock(&all_mddevs_lock);
> +
> + if (mddev == list_last_entry(&all_mddevs, struct mddev, all_mddevs))
> + status_unused(seq);
> +
> if (atomic_dec_and_test(&mddev->active))
> __mddev_put(mddev);
>
I think something like the following is the right way to do this.
Thanks,
Song
diff --git i/drivers/md/md.c w/drivers/md/md.c
index 38a6767c65b1..14044febe009 100644
--- i/drivers/md/md.c
+++ w/drivers/md/md.c
@@ -8215,20 +8215,8 @@ 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 md_personality *pers;
-
- 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);
-
- return seq_list_start(&all_mddevs, *pos);
+ return seq_list_start_head(&all_mddevs, *pos);
}
static void *md_seq_next(struct seq_file *seq, void *v, loff_t *pos)
@@ -8243,12 +8231,31 @@ static void md_seq_stop(struct seq_file *seq, void *v)
spin_unlock(&all_mddevs_lock);
}
+static void md_seq_print_header(struct seq_file *seq)
+{
+ struct md_personality *pers;
+
+ 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);
+}
+
static int md_seq_show(struct seq_file *seq, void *v)
{
struct mddev *mddev = list_entry(v, struct mddev, all_mddevs);
sector_t sectors;
struct md_rdev *rdev;
+ if (v == &all_mddevs) {
+ md_seq_print_header(seq);
+ return 0;
+ }
+
if (!mddev_get(mddev))
return 0;
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