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:

quoted

From: Yu Kuai <redacted>

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 <redacted>
---
  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()'?

quoted

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