Hi Tejun,
On 09/03/2010 02:43 AM +0900, Tejun Heo wrote:
> rq->rq_disk and bio->bi_bdev->bd_disk may differ if a request has
> passed through remapping drivers. FSEQ_DATA request incorrectly
> followed bio->bi_bdev->bd_disk ending up being issued w/ mismatching
> rq_disk. Make it follow orig_rq->rq_disk.
>
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> Reported-by: Kiyoshi Ueda <k-ueda@xxxxxxxxxxxxx>
> ---
> Kiyoshi, can you please apply this patch on top and verify that the
> problem goes away? The reason I and Mike didn't see the problem was
> because we were using REQ_FUA capable underlying device, which makes
> block layer bypass sequencing for FSEQ_DATA request.
>
> Thanks.
>
> block/blk-flush.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> Index: block/block/blk-flush.c
> ===================================================================
> --- block.orig/block/blk-flush.c
> +++ block/block/blk-flush.c
> @@ -111,6 +111,13 @@ static struct request *queue_next_fseq(s
> break;
> case QUEUE_FSEQ_DATA:
> init_request_from_bio(rq, orig_rq->bio);
> + /*
> + * orig_rq->rq_disk may be different from
> + * bio->bi_bdev->bd_disk if orig_rq got here through
> + * remapping drivers. Make sure rq->rq_disk points
> + * to the same one as orig_rq.
> + */
> + rq->rq_disk = orig_rq->rq_disk;
> rq->cmd_flags &= ~(REQ_FLUSH | REQ_FUA);
> rq->cmd_flags |= orig_rq->cmd_flags & (REQ_FLUSH | REQ_FUA);
> rq->end_io = flush_data_end_io;
Ah, I see, thank you for the quick fix!
I confirmed no panic occurs with this patch.
Tested-by: Kiyoshi Ueda <k-ueda@xxxxxxxxxxxxx>
By the way, I had been considering a block-layer interface which remaps
struct request and its bios to a block device such as:
void blk_remap_request(struct request *rq, struct block_device *bdev)
{
rq->rq_disk = bdev->bd_disk;
__rq_for_each_bio(bio, rq) {
bio->bi_bdev = bdev->bd_disk;
}
}
If there is such an interface and remapping drivers use it, then these
kind of issues may be avoided in the future.
Thanks,
Kiyoshi Ueda
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