Re: [PATCH] Btrfs: fix crash on endio of reading corrupted block

[Eric Sandeen <sandeen@redhat.com>]

On 8/19/14, 10:33 AM, Liu Bo wrote:
> The crash is
> 
> ------------[ cut here ]------------
> kernel BUG at fs/btrfs/extent_io.c:2124!
> [...]
> Workqueue: btrfs-endio normal_work_helper [btrfs]
> RIP: 0010:[<ffffffffa02d6055>]  [<ffffffffa02d6055>] end_bio_extent_readpage+0xb45/0xcd0 [btrfs]
> 
> This is in fact a regression.

It'd be helpful to identify the commit, or at least kernel release, which caused
the regression.

> It is because we forgot to increase @offset properly in reading corrupted block,
> so that the @offset remains, and this leads to checksum errors while reading
> left blocks queued up in the same bio, and then ends up with hiting the above
> BUG_ON.

So does that mean that any checksum error on this path will crash the kernel?

That sounds like this bug has exposed a more fundamental problem, no?

Thanks,
-Eric

> Reported-by: Chris Murphy <lists@colorremedies.com>
> Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
> ---
>  fs/btrfs/extent_io.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 3af4966..be41e4d 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -2602,6 +2602,7 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
>  					test_bit(BIO_UPTODATE, &bio->bi_flags);
>  				if (err)
>  					uptodate = 0;
> +				offset += len;
>  				continue;
>  			}
>  		}
>