Unverified Commit 51b4cb4f authored by Christian Brauner's avatar Christian Brauner
Browse files

block: WARN_ON_ONCE() when we remove active partitions 

The logic for disk->open_partitions is:

blkdev_get_by_*()
-> bdev_is_partition()
   -> blkdev_get_part()
      -> blkdev_get_whole() // bdev_whole->bd_openers++
      -> if (part->bd_openers == 0)
                 disk->open_partitions++
         part->bd_openers

In other words, when we first claim/open a partition we increment
disk->open_partitions and only when all part->bd_openers are closed will
disk->open_partitions be zero. That should mean that
disk->open_partitions is always > 0 as long as there's anyone that
has an open partition.

So the check for disk->open_partitions should mean that we can never
remove an active partition that has a holder and holder ops set. Assert
that in the code. The main disk isn't removed so that check doesn't work
for disk->part0 which is what we want. After all we only care about
partition not about the main disk.

Link: https://lore.kernel.org/r/20231017184823.1383356-3-hch@lst.de


Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarJens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent c30b9787

block/partitions/core.c

+17 −13
Original line number Diff line number Diff line
@@ -274,17 +274,6 @@ void drop_partition(struct block_device *part) 
	put_device(&part->bd_device);

}



static void delete_partition(struct block_device *part)

{

	/*

	 * Remove the block device from the inode hash, so that it cannot be

	 * looked up any more even when openers still hold references.

	 */

	remove_inode_hash(part->bd_inode);

	bdev_mark_dead(part, false);

	drop_partition(part);

}



static ssize_t whole_disk_show(struct device *dev,

			       struct device_attribute *attr, char *buf)

{
@@ -674,8 +663,23 @@ int bdev_disk_changed(struct gendisk *disk, bool invalidate) 
	sync_blockdev(disk->part0);

	invalidate_bdev(disk->part0);



	xa_for_each_start(&disk->part_tbl, idx, part, 1)

		delete_partition(part);

	xa_for_each_start(&disk->part_tbl, idx, part, 1) {

		/*

		 * Remove the block device from the inode hash, so that

		 * it cannot be looked up any more even when openers

		 * still hold references.

		 */

		remove_inode_hash(part->bd_inode);



		/*

		 * If @disk->open_partitions isn't elevated but there's

		 * still an active holder of that block device things

		 * are broken.

		 */

		WARN_ON_ONCE(atomic_read(&part->bd_openers));

		invalidate_bdev(part);

		drop_partition(part);

	}

	clear_bit(GD_NEED_PART_SCAN, &disk->state);



	/*