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Subject: Re: [PATCH -next 0/2] block: fix scan partition for exclusively open
 device again
To:     Yu Kuai <yukuai1@huaweicloud.com>, Ming Lei <ming.lei@redhat.com>
Cc:     jack@suse.cz, hare@suse.de, hch@infradead.org, axboe@kernel.dk,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        yi.zhang@huawei.com, yangerkun@huawei.com,
        Changhui Zhong <czhong@redhat.com>,
        "yukuai (C)" <yukuai3@huawei.com>
References: <20230217022200.3092987-1-yukuai1@huaweicloud.com>
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 <ZBpbGKxPQcs9NYst@ovpn-8-18.pek2.redhat.com>
 <5facd7c1-fa90-99ff-bd08-cdf67fe6c1ab@huaweicloud.com>
From:   Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <a8505ded-dadd-9096-4b13-31512a2c703e@huaweicloud.com>
Date:   Wed, 22 Mar 2023 10:15:30 +0800
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Hi,

在 2023/03/22 10:02, Yu Kuai 写道:
> Hi,
> 
> 在 2023/03/22 9:34, Ming Lei 写道:
>> On Wed, Mar 22, 2023 at 09:26:07AM +0800, Yu Kuai wrote:
>>> Hi,
>>>
>>> 在 2023/03/21 19:43, Ming Lei 写道:
>>>> On Fri, Feb 17, 2023 at 10:21:58AM +0800, Yu Kuai wrote:
>>>>> From: Yu Kuai <yukuai3@huawei.com>
>>>>>
>>>>> Changes from RFC:
>>>>>    - remove the patch to factor out GD_NEED_PART_SCAN
>>>>>
>>>>> Yu Kuai (2):
>>>>>     block: Revert "block: Do not reread partition table on exclusively
>>>>>       open device"
>>>>>     block: fix scan partition for exclusively open device again
>>>>
>>>> Hi Yu kuai,
>>>>
>>>> Looks the original issue starts to re-appear now with the two patches:
>>>>
>>>> https://lore.kernel.org/linux-block/20221130135344.2ul4cyfstfs3znxg@quack3/ 
>>>>
>>>>
>>>> And underlying disk partition and raid partition can be observed at the
>>>> same time.
>>>>
>>>> Can you take a look?
>>> Yes, thanks for the report. I realize that sda1 adn sdb1 is created
>>> while raid open sda and sdb excl, and I think this problem should exist
>>> before this patchset.
>>
>> Looks not reproduced before applying your two patches, that is exactly 
>> what Jan
>> tried to fix with 36369f46e917 ("block: Do not reread partition table 
>> on exclusively open device").
> 
> Hi, Ming
> 
> I just tried your test with this patchset reverted, and I can still
> reporduce the problem myself.

Oops, I forgot to revert the first patch. It's right the problem can't
be reporduced.
> 
> raid only open this device excl, and disk_scan_partitions is not called:
> 
> md_import_device
>   blkdev_get_by_devo
> 
> I need to add some debuginfo to figure out how GD_NEED_PART_SCAN is set
> for sda after raid is stopped. And this should explain why sda1 is
> created.

I found how GD_NEED_PART_SCAN is set now, in patch 2, this is set before
bd_prepare_to_claim, so preciously faild part scan will still set this
bit, and following patch shold fix this problem:

diff --git a/block/genhd.c b/block/genhd.c
index 08bb1a9ec22c..2487c9452b94 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -368,7 +368,6 @@ int disk_scan_partitions(struct gendisk *disk, 
fmode_t mode)
         if (disk->open_partitions)
                 return -EBUSY;

-       set_bit(GD_NEED_PART_SCAN, &disk->state);
         /*
          * If the device is opened exclusively by current thread 
already, it's
          * safe to scan partitons, otherwise, use bd_prepare_to_claim() to
@@ -381,6 +380,7 @@ int disk_scan_partitions(struct gendisk *disk, 
fmode_t mode)
                         return ret;
         }

+       set_bit(GD_NEED_PART_SCAN, &disk->state);
         bdev = blkdev_get_by_dev(disk_devt(disk), mode & ~FMODE_EXCL, 
NULL);
         if (IS_ERR(bdev))
                 ret =  PTR_ERR(bdev);

> 
> Thanks,
> Kuai
>>
>> The issue is reported by Changhui's block regression test.
>>
>>
>> Thanks,
>> Ming
>>
>>
>> .
>>
> 
> 
> .
>