2023-02-12 09:03:09

by Yu Kuai

Subject: [PATCH -next RFC 2/3] block: factor out the setting of GD_NEED_PART_SCAN

From: Yu Kuai <[email protected]>

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 <[email protected]>
---
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

2023-02-12 11:36:59

by Hannes Reinecke

Subject: Re: [PATCH -next RFC 2/3] block: factor out the setting of GD_NEED_PART_SCAN

On 2/12/23 10:26, Yu Kuai wrote:
> From: Yu Kuai <[email protected]>
>
> 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 <[email protected]>
> ---
> 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?
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
--
Dr. Hannes Reinecke Kernel Storage Architect
[email protected] +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

2023-02-13 02:41:44

by Yu Kuai

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 <[email protected]>
>>
>> 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 <[email protected]>
>> ---
>>   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

2023-02-16 13:17:54

by Jan Kara

Subject: Re: [PATCH -next RFC 2/3] block: factor out the setting of GD_NEED_PART_SCAN

On Sun 12-02-23 17:26:40, Yu Kuai wrote:
> From: Yu Kuai <[email protected]>
>
> 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 <[email protected]>

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.

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
>
--
Jan Kara <[email protected]>
SUSE Labs, CR

2023-02-17 01:44:18

by Yu Kuai

Subject: Re: [PATCH -next RFC 2/3] block: factor out the setting of GD_NEED_PART_SCAN

Hi, jan!

?? 2023/02/16 21:17, Jan Kara д??:
> On Sun 12-02-23 17:26:40, Yu Kuai wrote:
>> From: Yu Kuai <[email protected]>
>>
>> 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 <[email protected]>
>
> 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
>>