linux-kernel - Re: [PATCH 3/5] md: make sure md_do_sync() will set MD_RECOVERY

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Date: Wed, 24 Jan 2024 11:14:21 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Xiao Ni <xni@...hat.com>, Yu Kuai <yukuai1@...weicloud.com>
Cc: mpatocka@...hat.com, dm-devel@...ts.linux.dev, msnitzer@...hat.com,
 heinzm@...hat.com, song@...nel.org, 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 3/5] md: make sure md_do_sync() will set MD_RECOVERY_DONE

Hi,

在 2024/01/24 10:58, Xiao Ni 写道:
> Hi all
> 
> MD_RECOVERY_WAIT was introduced in d5d885fd5. From this patch,
> MD_RECOVERY_WAIT only has one usage during creating raid device.
> resync job needs to wait until pers->start finishes(The only place
> which is checked). If we remove it from md_do_sync, will it break the
> logic? Or we don't need this flag anymore? If so can we remove this
> flag?
> 
> dm-raid uses this bit in patch 644e2537f (dm raid: fix stripe adding
> reshape deadlock). It's the reason why md_do_sync can't set
> MD_RECOVERY_DONE. Now we stop sync thread asynchronously, can we
> revert this patch?

I made some changes that will be sent for v2 that sync_thread is frozen
from dm suspend to resume, so I think the flag can be removed, and I
actually tried that, howver, dm-raid tests failed because ext4 is
corrupted. Anyway, let's focus on dm-raid regression for now and we can
try to remove this flag later.

Thanks,
Kuai

> 
> Best Regards
> Xiao
> 
> On Sat, Jan 20, 2024 at 6:41 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
>>
>> From: Yu Kuai <yukuai3@...wei.com>
>>
>> stop_sync_thread() will interrupt md_do_sync(), and md_do_sync() must
>> set MD_RECOVERY_DONE, so that follow up md_check_recovery() will
>> unregister sync_thread, clear MD_RECOVERY_RUNNING and wake up
>> stop_sync_thread().
>>
>> Before this patch, if MD_RECOVERY_WAIT is set or the array is read-only,
>> md_do_sync() will return without setting MD_RECOVERY_DONE, hence use
>> stop_sync_thread() directly will hang because md_check_recovery() can't
>> clear MD_RECOVERY_RUNNING, which is possible for dm-raid.
>>
>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>> ---
>>   drivers/md/md.c | 10 ++++++----
>>   1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>> index 6906d023f1d6..ba45c7be3dbe 100644
>> --- a/drivers/md/md.c
>> +++ b/drivers/md/md.c
>> @@ -8788,12 +8788,13 @@ void md_do_sync(struct md_thread *thread)
>>          int ret;
>>
>>          /* just incase thread restarts... */
>> -       if (test_bit(MD_RECOVERY_DONE, &mddev->recovery) ||
>> -           test_bit(MD_RECOVERY_WAIT, &mddev->recovery))
>> +       if (test_bit(MD_RECOVERY_DONE, &mddev->recovery))
>>                  return;
>> -       if (!md_is_rdwr(mddev)) {/* never try to sync a read-only array */
>> +
>> +       if (test_bit(MD_RECOVERY_WAIT, &mddev->recovery) ||
>> +           !md_is_rdwr(mddev)) {/* never try to sync a read-only array */
>>                  set_bit(MD_RECOVERY_INTR, &mddev->recovery);
>> -               return;
>> +               goto out;
>>          }
>>
>>          if (mddev_is_clustered(mddev)) {
>> @@ -9171,6 +9172,7 @@ void md_do_sync(struct md_thread *thread)
>>                                                  mddev->array_sectors);
>>          }
>>
>> +out:
>>          spin_lock(&mddev->lock);
>>          if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
>>                  /* We completed so min/max setting can be forgotten if used. */
>> --
>> 2.39.2
>>
>>
> 
> .
>