linux-kernel - Re: [PATCH] block: don't set GD_NEED_PART

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Date:   Fri, 24 Mar 2023 07:59:30 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     jack@...e.cz, hch@...radead.org, axboe@...nel.dk,
        yukuai3@...wei.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com,
        yangerkun@...wei.com
Subject: Re: [PATCH] block: don't set GD_NEED_PART_SCAN if scan partition
 failed

On Wed, Mar 22, 2023 at 11:59:26AM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@...wei.com>
> 
> Currently if disk_scan_partitions() failed, GD_NEED_PART_SCAN will still
> set, and partition scan will be proceed again when blkdev_get_by_dev()
> is called. However, this will cause a problem that re-assemble partitioned
> raid device will creat partition for underlying disk.
> 
> Test procedure:
> 
> mdadm -CR /dev/md0 -l 1 -n 2 /dev/sda /dev/sdb -e 1.0
> sgdisk -n 0:0:+100MiB /dev/md0
> blockdev --rereadpt /dev/sda
> blockdev --rereadpt /dev/sdb
> mdadm -S /dev/md0
> mdadm -A /dev/md0 /dev/sda /dev/sdb
> 
> Test result: underlying disk partition and raid partition can be
> observed at the same time
> 
> Note that this can still happen in come corner cases that
> GD_NEED_PART_SCAN can be set for underlying disk while re-assemble raid
> device.

That is why I suggest to touch this flag as less as possible, maybe
replace it with one function parameter in future.

> 
> Fixes: e5cfefa97bcc ("block: fix scan partition for exclusively open device again")
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>

So far, let's move on with the fix:

Reviewed-by: Ming Lei <ming.lei@...hat.com>

Thanks,
Ming