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Date:   Wed, 8 Aug 2018 07:25:14 +0200
From:   Greg KH <greg@...ah.com>
To:     xiao jin <jin.xiao@...el.com>
Cc:     agk@...hat.com, snitzer@...hat.com, dm-devel@...hat.com,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        yanmin.zhang@...el.com
Subject: Re: [PATCH] dm-bufio: adjust the reserved buffer for
 dm-verify-target.

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@...el.com>
> ---
>  drivers/md/dm-bufio.c         | 4 ++--
>  drivers/md/dm-verity-target.c | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>

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