[dm-devel] [PATCH] dm-bufio: adjust the reserved buffer for dm-verify-target.

Greg KH greg at kroah.com
Wed Aug 8 05:25:14 UTC 2018

On Wed, Aug 08, 2018 at 01:07:03PM +0800, xiao jin wrote:
> We hit the BUG() report at include/linux/scatterlist.h:144!
> The callback is as bellow:
>   => verity_work
>   => verity_hash_for_block
>   => verity_verify_level
>   => verity_hash
>   => verity_hash_update
>   => sg_init_one
>   => sg_set_buf
> More debug shows the root cause. When creating dufio client it
> uses the __vmalloc() to allocate the buffer data for the reserved
> dm_buffer. The buffer that allocated by the __vmalloc() is invalid
> according to the __virt_addr_valid().
> Mostly the reserved dm_buffer is not touched. But occasionally
> it might fail to allocate the dm_buffer data when we try to
> allocate in the __alloc_buffer_wait_no_callback(). Then it has
> to take the reserved dm_buffer for usage. Finally it reports the
> BUG() as virt_addr_valid() detects the buffer data address is invalid.
> The patch is to adjust the reserved buffer for dm-verity-target. We
> allocated two dm_buffers into the reserved buffers list when creating
> the buffer interface. The first dm_buffer in the reserved buffer list
> is allocated by the __vmalloc(), it's not used after that. The second
> dm_buffer in the reserved buffer list is allocated by the
> __get_free_pages() which can be consumed after that.
> Signed-off-by: xiao jin <jin.xiao at intel.com>
> ---
>  drivers/md/dm-bufio.c         | 4 ++--
>  drivers/md/dm-verity-target.c | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)


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