linux-kernel - Re: [PATCH -next v3 6/7] md: factor out a helper rdev_addable() from remove_and_add

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Message-ID: <2766d001-f618-d224-f8a9-ec38ed1dc2a7@huaweicloud.com>
Date:   Wed, 23 Aug 2023 11:04:47 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     Yu Kuai <yukuai1@...weicloud.com>, Song Liu <song@...nel.org>
Cc:     xni@...hat.com, mariusz.tkaczyk@...ux.intel.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 -next v3 6/7] md: factor out a helper rdev_addable() from
 remove_and_add_spares()

Hi,

在 2023/08/22 10:17, Yu Kuai 写道:
> Hi,
> 
> 在 2023/08/22 7:22, Song Liu 写道:
>> On Sun, Aug 20, 2023 at 2:13 AM Yu Kuai <yukuai1@...weicloud.com> wrote:
>>>
>>> From: Yu Kuai <yukuai3@...wei.com>
>>>
>>> There are no functional changes, just to make the code simpler and
>>> prepare to delay remove_and_add_spares() to md_start_sync().
>>>
>>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>>> ---
>>>   drivers/md/md.c | 28 ++++++++++++++++------------
>>>   1 file changed, 16 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>>> index 11d27c934fdd..cdc361c521d4 100644
>>> --- a/drivers/md/md.c
>>> +++ b/drivers/md/md.c
>>> @@ -9177,6 +9177,20 @@ static bool rdev_is_spare(struct md_rdev *rdev)
>>>                 !test_bit(Faulty, &rdev->flags);
>>>   }
>>>
>>> +static bool rdev_addable(struct md_rdev *rdev)
>>> +{
>>> +       if (test_bit(Candidate, &rdev->flags) || rdev->raid_disk >= 0 ||
>>> +           test_bit(Faulty, &rdev->flags))
>>> +               return false;
>>> +
>>> +       if (!test_bit(Journal, &rdev->flags) && 
>>> !md_is_rdwr(rdev->mddev) &&
>>
>> Instead of straightforward refactoring, I hope we can make these rdev_*
>> helpers more meaningful, and hopefullly reusable. For example, let's 
>> define
>> the meaning of "addable", and write the function to match that 
>> meaning. In
>> this case, I think we shouldn't check md_is_rdwr() inside rdev_addable().
>>
>> Does this make sense?
> 
> Yes, this make sense, rdev can be added to read-only array.
> 
> There are total three callers of pers->hot_add_sisk, I'll try to find if
> they have common conditions.

Unfortunately, the conditions is quite different, and It's difficult to
factor out a common helper for them to use.

In this case, !md_is_rdwr() is one of the four conditions, which means
if the array is read-only, there is a special case that rdev can't be
added to the configuration. Perhaps it's okay to keep this?

Thanks,
Kuai
> 
> Thanks,
> Kuai
> 
>>
>> Thanks,
>> Song
>>
>>
>>> +           !(rdev->saved_raid_disk >= 0 &&
>>> +             !test_bit(Bitmap_sync, &rdev->flags)))
>>> +               return false;
>>> +
>>> +       return true;
>>> +}
>>> +
>>>   static int remove_and_add_spares(struct mddev *mddev,
>>>                                   struct md_rdev *this)
>>>   {
>>> @@ -9227,20 +9241,10 @@ static int remove_and_add_spares(struct mddev 
>>> *mddev,
>>>                          continue;
>>>                  if (rdev_is_spare(rdev))
>>>                          spares++;
>>> -               if (test_bit(Candidate, &rdev->flags))
>>> +               if (!rdev_addable(rdev))
>>>                          continue;
>>> -               if (rdev->raid_disk >= 0)
>>> -                       continue;
>>> -               if (test_bit(Faulty, &rdev->flags))
>>> -                       continue;
>>> -               if (!test_bit(Journal, &rdev->flags)) {
>>> -                       if (!md_is_rdwr(mddev) &&
>>> -                           !(rdev->saved_raid_disk >= 0 &&
>>> -                             !test_bit(Bitmap_sync, &rdev->flags)))
>>> -                               continue;
>>> -
>>> +               if (!test_bit(Journal, &rdev->flags))
>>>                          rdev->recovery_offset = 0;
>>> -               }
>>>                  if (mddev->pers->hot_add_disk(mddev, rdev) == 0) {
>>>                          /* failure here is OK */
>>>                          sysfs_link_rdev(mddev, rdev);
>>> -- 
>>> 2.39.2
>>>
>> .
>>
> 
> .
>