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Message-ID: <8eeacd36-6f35-230c-1c93-074c63eee08f@huaweicloud.com>
Date: Mon, 13 Feb 2023 10:41:32 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Hannes Reinecke <hare@...e.de>, Yu Kuai <yukuai1@...weicloud.com>,
hch@...radead.org, jack@...e.cz, axboe@...nel.dk
Cc: 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,
在 2023/02/12 19:36, Hannes Reinecke 写道:
> On 2/12/23 10:26, 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>
>> ---
>> 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);
> Usual caveat:
> What happens if the flag is already set here?
> Wouldn't that imply that another scan is underway?
I think this is not true, currently set the state just means we're going
to scan, and if some checking failed, the state will be left. I don't
have a good idea how to fix this yet...
Thanks,
Kuai
> And wouldn't it be better to use 'test_and_set()'?
>
>
>> 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:
> Similar here.
>
> Cheers,
>
> Hannes
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