On Thu, Oct 19, 2017 at 09:49:27AM +0800, Gu Jinxiang wrote:
> From: Gu JinXiang <gujx@xxxxxxxxxxxxxx>
>
> Fix bug of commit 74d46992e0d9
> ("block: replace bi_bdev with a gendisk pointer and partitions index").
>
> In this modify, use bio_dev(bio) to find dev state in function
> __btrfsic_submit_bio. But when dev_state added to hashtable, it is using
> dev_t of block_device.
>
> bio_dev(bio) returns a dev_t of part0 which is different from dev_t in
> block_device(bd_dev). bd_dev in block_device represents the exact
> partition.
> block_device.bd_dev =
> bio->bi_partno (same as block_device.bd_partno) + bio_dev(bio).
>
> When add a dev_state into hashtable it is using the exact partition's dev_t.
> So when lookup it, it should also use the exact partition's dev_t.
>
> Reproduce of this bug:
> Use MOUNT_OPTIONS="-o check_int" when run btrfs/001 in xfstest.
> Then there will be WARNING like below.
> WARNING:
> btrfs: attempt to write superblock which references block M @29523968 (sda7 /1111654400/2) which is never written!
>
> changelog:
> v1->v2: Add explanation that bio_dev(bio) is different with block_device(bd_dev).
>
> Signed-off-by: Gu JinXiang <gujx@xxxxxxxxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
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