linux-kernel - Re: [BUG REPORT] Kernel panic on 3.9.0-rc7-4-gbb33db7

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Message-ID: <20130419055754.GA9691@mtj.dyndns.org>
Date:	Thu, 18 Apr 2013 22:57:54 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Wanlong Gao <gaowanlong@...fujitsu.com>
Cc:	Jens Axboe <axboe@...nel.dk>, Steven Rostedt <rostedt@...dmis.org>,
	namhyung@...il.com, agk@...hat.com, dm-devel@...hat.com,
	neilb@...e.de, LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Chris Mason <chris.mason@...ionio.com>,
	linux-btrfs@...r.kernel.org
Subject: Re: [BUG REPORT] Kernel panic on 3.9.0-rc7-4-gbb33db7

(cc'ing btrfs people)

On Fri, Apr 19, 2013 at 11:33:20AM +0800, Wanlong Gao wrote:
> RIP: 0010:[<ffffffff812484d3>]  [<ffffffff812484d3>] ftrace_raw_event_block_bio_complete+0x73/0xf0
...
>  [<ffffffff811b6c10>] bio_endio+0x80/0x90
>  [<ffffffffa0790d26>] btrfs_end_bio+0xf6/0x190 [btrfs]
>  [<ffffffff811b6bcd>] bio_endio+0x3d/0x90
>  [<ffffffff81249873>] req_bio_endio+0xa3/0xe0

Ugh....

In fs/btrfs/volumes.c

  static void bbio_error(struct btrfs_bio *bbio, struct bio *bio, u64 logical)
  {
	...
		bio->bi_bdev = (struct block_device *)
			       	       (unsigned long)bbio->mirror_num;
	...
  }

  static void btrfs_end_bio(struct bio *bio, int err)
  {
	...
		bio->bi_bdev = (struct block_device *)
					(unsigned long)bbio->mirror_num;
									
	...
  }

In fs/btrfs/extent_io.c

  static void end_bio_extent_readpage(struct bio *bio, int err)
  {
	int mirror;
	...
		mirror = (int)(unsigned long)bio->bi_bdev;
	...
  }

Ewweeeeeeeeeeeeeeeeeehh........

No wonder this thing crashes.  Chris, can't the original bio carry
bbio in bi_private and let end_bio_extent_readpage() free the bbio
instead of abusing bi_bdev like this?

-- 
tejun
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