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Message-ID: <0f3c2220-f929-5b57-0c4d-3e487d3d1415@huaweicloud.com>
Date: Tue, 9 Jan 2024 16:28:32 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Song Liu <song@...nel.org>, 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
Hi,
在 2024/01/09 16:12, Song Liu 写道:
> 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);
Yes, this is good. I didn't notice the api seq_list_start_head().
> }
>
> 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);
And I will still move status_unused() to md_seq_show(), because
seq_read_iter() only handle the case that seq_printf() overflowed from
md_seq_show(), not md_seq_start/stop().
Thanks,
Kuai
> + return 0;
> + }
> +
> if (!mddev_get(mddev))
> return 0;
>
> .
>
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