linux-kernel - Re: [PATCH -next RFC 2/3] block: factor out the setting of GD_NEED_PART

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Date:   Fri, 17 Feb 2023 09:44:09 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     Jan Kara <jack@...e.cz>, Yu Kuai <yukuai1@...weicloud.com>
Cc:     hch@...radead.org, axboe@...nel.dk, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com,
        yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH -next RFC 2/3] block: factor out the setting of
 GD_NEED_PART_SCAN

Hi, jan!

在 2023/02/16 21:17, Jan Kara 写道:
> On Sun 12-02-23 17:26:40, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@...wei.com>
>>
>> In order to prevent scan partition for a device that is opened
>> exclusively by someone else, new conditions will be added to
>> disk_scan_partitions() in the next patch. Hence if device is opened
>> exclusively between bdev_add() and disk_scan_partitions(), the first
>> partition scan will fail unexpected. This patch factor out the setting
>> of GD_NEED_PART_SCAN to prevent the problem.
>>
>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> 
> I'd rather leave the setting of GD_NEED_PART_SCAN in disk_scan_partitions()
> to keep it self-contained. On top of that we can set GD_NEED_PART_SCAN in
> device_add_disk() to ensure initial partition scan but we should probably
> also make sure flags like GD_SUPPRESS_PART_SCAN or GENHD_FL_NO_PART are not
> set to avoid unwanted partition scanning.

Thanks for the suggestion, I'll remove this patch and do that in patch 3
in the next version.

Thanks,
Kuai
> 
> 								Honza
> 
>> ---
>>   block/genhd.c | 2 +-
>>   block/ioctl.c | 1 +
>>   2 files changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/block/genhd.c b/block/genhd.c
>> index 075d8da284f5..c0d1220bd798 100644
>> --- a/block/genhd.c
>> +++ b/block/genhd.c
>> @@ -367,7 +367,6 @@ int disk_scan_partitions(struct gendisk *disk, fmode_t mode)
>>   	if (disk->open_partitions)
>>   		return -EBUSY;
>>   
>> -	set_bit(GD_NEED_PART_SCAN, &disk->state);
>>   	bdev = blkdev_get_by_dev(disk_devt(disk), mode, NULL);
>>   	if (IS_ERR(bdev))
>>   		return PTR_ERR(bdev);
>> @@ -493,6 +492,7 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
>>   		if (ret)
>>   			goto out_unregister_bdi;
>>   
>> +		set_bit(GD_NEED_PART_SCAN, &disk->state);
>>   		bdev_add(disk->part0, ddev->devt);
>>   		if (get_capacity(disk))
>>   			disk_scan_partitions(disk, FMODE_READ);
>> diff --git a/block/ioctl.c b/block/ioctl.c
>> index 6dd49d877584..0eefcdb936a0 100644
>> --- a/block/ioctl.c
>> +++ b/block/ioctl.c
>> @@ -528,6 +528,7 @@ static int blkdev_common_ioctl(struct block_device *bdev, fmode_t mode,
>>   			return -EACCES;
>>   		if (bdev_is_partition(bdev))
>>   			return -EINVAL;
>> +		set_bit(GD_NEED_PART_SCAN, &bdev->bd_disk->state);
>>   		return disk_scan_partitions(bdev->bd_disk, mode & ~FMODE_EXCL);
>>   	case BLKTRACESTART:
>>   	case BLKTRACESTOP:
>> -- 
>> 2.31.1
>>