Re: [PATCH] block: Do not reread partition table on exclusively open device

[Yu Kuai <yukuai1@xxxxxxxxxxxxxxx>]

Hi, Christoph

在 2023/01/31 22:15, Christoph Hellwig 写道:
> It might be easier to just move the check into blkdev_get_whole,
> which also ensures that non-excluisve openers don't cause a partition
> scan while someone else has the device exclusively open.
>
> diff --git a/block/bdev.c b/block/bdev.c
> index edc110d90df404..a831b6c9c627d7 100644
> --- a/block/bdev.c
> +++ b/block/bdev.c
> @@ -666,25 +666,28 @@ static void blkdev_flush_mapping(struct block_device *bdev)
>   static int blkdev_get_whole(struct block_device *bdev, fmode_t mode)
>   {
>   	struct gendisk *disk = bdev->bd_disk;
> -	int ret;
> +	int ret = 0;
>   
> -	if (disk->fops->open) {
> +	if (disk->fops->open)
>   		ret = disk->fops->open(bdev, mode);
> -		if (ret) {
> -			/* avoid ghost partitions on a removed medium */
> -			if (ret == -ENOMEDIUM &&
> -			     test_bit(GD_NEED_PART_SCAN, &disk->state))
> -				bdev_disk_changed(disk, true);
> +
> +	if (ret) {
> +		/* avoid ghost partitions on a removed medium */
> +		if (ret != -ENOMEDIUM)
>   			return ret;
> -		}
> +	} else {
> +		if (!atomic_read(&bdev->bd_openers))
> +			set_init_blocksize(bdev);
> +		atomic_inc(&bdev->bd_openers);
>   	}
>   
> -	if (!atomic_read(&bdev->bd_openers))
> -		set_init_blocksize(bdev);
> -	if (test_bit(GD_NEED_PART_SCAN, &disk->state))
> +	/*
> +	 * Skip the partition scan if someone else has the device exclusively
> +	 * open.
> +	 */
> +	if (test_bit(GD_NEED_PART_SCAN, &disk->state) && !bdev->bd_holder)
>   		bdev_disk_changed(disk, false);

I think this is wrong here... We should at least allow the exclusively
opener to scan partition, right?

Thanks,
Kuai