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Subject: Re: [PATCH md-6.10 3/9] md: add new helpers for sync_action
To: Xiao Ni <xni@redhat.com>, Yu Kuai <yukuai1@huaweicloud.com>
Cc: agk@redhat.com, snitzer@kernel.org, mpatocka@redhat.com, song@kernel.org,
 dm-devel@lists.linux.dev, linux-kernel@vger.kernel.org,
 linux-raid@vger.kernel.org, yi.zhang@huawei.com, yangerkun@huawei.com,
 "yukuai (C)" <yukuai3@huawei.com>
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From: Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <2d457d0f-8bb5-39cb-0b8a-0bfdde1f560f@huaweicloud.com>
Date: Tue, 14 May 2024 16:52:34 +0800
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在 2024/05/14 16:40, Xiao Ni 写道:
> On Tue, May 14, 2024 at 3:39 PM Yu Kuai <yukuai1@huaweicloud.com> wrote:
>>
>> Hi,
>>
>> 在 2024/05/14 14:52, Xiao Ni 写道:
>>> On Mon, May 13, 2024 at 5:31 PM Yu Kuai <yukuai1@huaweicloud.com> wrote:
>>>>
>>>> From: Yu Kuai <yukuai3@huawei.com>
>>>>
>>>> The new helpers will get current sync_action of the array, will be used
>>>> in later patches to make code cleaner.
>>>>
>>>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
>>>> ---
>>>>    drivers/md/md.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++
>>>>    drivers/md/md.h |  3 +++
>>>>    2 files changed, 67 insertions(+)
>>>>
>>>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>>>> index 00bbafcd27bb..48ec35342d1b 100644
>>>> --- a/drivers/md/md.c
>>>> +++ b/drivers/md/md.c
>>>> @@ -69,6 +69,16 @@
>>>>    #include "md-bitmap.h"
>>>>    #include "md-cluster.h"
>>>>
>>>> +static char *action_name[NR_SYNC_ACTIONS] = {
>>>> +       [ACTION_RESYNC]         = "resync",
>>>> +       [ACTION_RECOVER]        = "recover",
>>>> +       [ACTION_CHECK]          = "check",
>>>> +       [ACTION_REPAIR]         = "repair",
>>>> +       [ACTION_RESHAPE]        = "reshape",
>>>> +       [ACTION_FROZEN]         = "frozen",
>>>> +       [ACTION_IDLE]           = "idle",
>>>> +};
>>>> +
>>>>    /* pers_list is a list of registered personalities protected by pers_lock. */
>>>>    static LIST_HEAD(pers_list);
>>>>    static DEFINE_SPINLOCK(pers_lock);
>>>> @@ -4867,6 +4877,60 @@ metadata_store(struct mddev *mddev, const char *buf, size_t len)
>>>>    static struct md_sysfs_entry md_metadata =
>>>>    __ATTR_PREALLOC(metadata_version, S_IRUGO|S_IWUSR, metadata_show, metadata_store);
>>>>
>>>> +enum sync_action md_sync_action(struct mddev *mddev)
>>>> +{
>>>> +       unsigned long recovery = mddev->recovery;
>>>> +
>>>> +       /*
>>>> +        * frozen has the highest priority, means running sync_thread will be
>>>> +        * stopped immediately, and no new sync_thread can start.
>>>> +        */
>>>> +       if (test_bit(MD_RECOVERY_FROZEN, &recovery))
>>>> +               return ACTION_FROZEN;
>>>> +
>>>> +       /*
>>>> +        * idle means no sync_thread is running, and no new sync_thread is
>>>> +        * requested.
>>>> +        */
>>>> +       if (!test_bit(MD_RECOVERY_RUNNING, &recovery) &&
>>>> +           (!md_is_rdwr(mddev) || !test_bit(MD_RECOVERY_NEEDED, &recovery)))
>>>> +               return ACTION_IDLE;
>>>
>>> Hi Kuai
>>>
>>> Can I think the above judgement cover these two situations:
>>> 1. The array is readonly / readauto and it doesn't have
>>> MD_RECOVERY_RUNNING. Now maybe it has MD_RECOVERY_NEEDED, it means one
>>> array may want to do some sync action, but the array state is not
>>> readwrite and it can't start.
>>> 2. The array doesn't have MD_RECOVERY_RUNNING and MD_RECOVERY_NEEDED
>>>
>>>> +
>>>> +       if (test_bit(MD_RECOVERY_RESHAPE, &recovery) ||
>>>> +           mddev->reshape_position != MaxSector)
>>>> +               return ACTION_RESHAPE;
>>>> +
>>>> +       if (test_bit(MD_RECOVERY_RECOVER, &recovery))
>>>> +               return ACTION_RECOVER;
>>>> +
>>>> +       if (test_bit(MD_RECOVERY_SYNC, &recovery)) {
>>>> +               if (test_bit(MD_RECOVERY_CHECK, &recovery))
>>>> +                       return ACTION_CHECK;
>>>> +               if (test_bit(MD_RECOVERY_REQUESTED, &recovery))
>>>> +                       return ACTION_REPAIR;
>>>> +               return ACTION_RESYNC;
>>>> +       }
>>>> +
>>>> +       return ACTION_IDLE;
>>>
>>> Does it need this? I guess it's the reason in case there are other
>>> situations, right?
>>
>> Yes, we need this, because they are many places to set
>> MD_RECOVERY_NEEDED, while there are no sync action actually, this case
>> is 'idle'.
> 
> To be frank, the logic in action_show is easier to understand than the
> logic above. I have taken more than half an hour to think if the logic
> here is right or not. In action_show, it only needs to think when it's
> not idle and it's easy.
> 
> Now this patch logic needs to think in the opposite direction: when
> it's idle. And it returns ACTION_IDLE at two places which means it
> still needs to think about when it has sync action. So it's better to
> keep the original logic in action_show now. It's just my 2 cents
> point.

Hi,

but the logical is exactlly the same as action_show(), and there are
no functional changes. I just remove the local variable and return
early, because I think code is cleaner this way...

action_show:

char *type = "idle"

if (test_bit() || xxx) {

  if (xxx)
   type ="reshape"
  else if(xxx)
   type ="resync/check/repair"
  else if(xxx)
   type = "recover"
  else if (xxx)
   type = "reshape"
  -> else is idle
}
-> else is idle

The above two place are corresponding to the new code to return
ACTION_IDLE.

Thanks,
Kuai

> 
> Best Regards
> Xiao
> 
>>
>> Thanks,
>> Kuai
>>
>>>
>>> Regards
>>> Xiao
>>>
>>>> +}
>>>> +
>>>> +enum sync_action md_sync_action_by_name(char *page)
>>>> +{
>>>> +       enum sync_action action;
>>>> +
>>>> +       for (action = 0; action < NR_SYNC_ACTIONS; ++action) {
>>>> +               if (cmd_match(page, action_name[action]))
>>>> +                       return action;
>>>> +       }
>>>> +
>>>> +       return NR_SYNC_ACTIONS;
>>>> +}
>>>> +
>>>> +char *md_sync_action_name(enum sync_action action)
>>>> +{
>>>> +       return action_name[action];
>>>> +}
>>>> +
>>>>    static ssize_t
>>>>    action_show(struct mddev *mddev, char *page)
>>>>    {
>>>> diff --git a/drivers/md/md.h b/drivers/md/md.h
>>>> index 2edad966f90a..72ca7a796df5 100644
>>>> --- a/drivers/md/md.h
>>>> +++ b/drivers/md/md.h
>>>> @@ -864,6 +864,9 @@ extern void md_unregister_thread(struct mddev *mddev, struct md_thread __rcu **t
>>>>    extern void md_wakeup_thread(struct md_thread __rcu *thread);
>>>>    extern void md_check_recovery(struct mddev *mddev);
>>>>    extern void md_reap_sync_thread(struct mddev *mddev);
>>>> +extern enum sync_action md_sync_action(struct mddev *mddev);
>>>> +extern enum sync_action md_sync_action_by_name(char *page);
>>>> +extern char *md_sync_action_name(enum sync_action action);
>>>>    extern bool md_write_start(struct mddev *mddev, struct bio *bi);
>>>>    extern void md_write_inc(struct mddev *mddev, struct bio *bi);
>>>>    extern void md_write_end(struct mddev *mddev);
>>>> --
>>>> 2.39.2
>>>>
>>>
>>> .
>>>
>>
>>
> 
> .
>