Re: btrfs bio linked list corruption.

From: Chris Mason
Date: Tue Oct 11 2016 - 12:25:50 EST




On 10/11/2016 10:45 AM, Dave Jones wrote:
> This is from Linus' current tree, with Al's iovec fixups on top.
>
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 3673 at lib/list_debug.c:33 __list_add+0x89/0xb0
> list_add corruption. prev->next should be next (ffffe8ffff806648), but was ffffc9000067fcd8. (prev=ffff880503878b80).
> CPU: 1 PID: 3673 Comm: trinity-c0 Not tainted 4.8.0-think+ #13
> ffffc90000d87458 ffffffff8d32007c ffffc90000d874a8 0000000000000000
> ffffc90000d87498 ffffffff8d07a6c1 0000002100000246 ffff88050388e880
> ffff880503878b80 ffffe8ffff806648 ffffe8ffffc06600 ffff880502808008
> Call Trace:
> [<ffffffff8d32007c>] dump_stack+0x4f/0x73
> [<ffffffff8d07a6c1>] __warn+0xc1/0xe0
> [<ffffffff8d07a73a>] warn_slowpath_fmt+0x5a/0x80
> [<ffffffff8d33e689>] __list_add+0x89/0xb0
> [<ffffffff8d30a1c8>] blk_sq_make_request+0x2f8/0x350

/*
* A task plug currently exists. Since this is completely lockless,
* utilize that to temporarily store requests until the task is
* either done or scheduled away.
*/
plug = current->plug;
if (plug) {
blk_mq_bio_to_request(rq, bio);
if (!request_count)
trace_block_plug(q);

blk_mq_put_ctx(data.ctx);

if (request_count >= BLK_MAX_REQUEST_COUNT) {
blk_flush_plug_list(plug, false);
trace_block_plug(q);
}

list_add_tail(&rq->queuelist, &plug->mq_list);
^^^^^^^^^^^^^^^^^^^^^^

Dave, is this where we're crashing? This seems strange.

-chris