On 2010-07-13 09:50, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
> Issuing a blkdev_issue_flush() on an unconfigured loop device causes a panic
> q->make_request_fn is not configured. This can occur when trying to mount the
> unconfigured loop device as an XFS filesystem. There are no guards that catch
> the bio before the request function is called because we don't add a payload
> the bio. Instead, manually check this case as soon as we have a pointer to the
> queue to flush.
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> block/blk-barrier.c | 9 +++++++++
> 1 files changed, 9 insertions(+), 0 deletions(-)
> diff --git a/block/blk-barrier.c b/block/blk-barrier.c
> index 0d710c9..0fd766e 100644
> --- a/block/blk-barrier.c
> +++ b/block/blk-barrier.c
> @@ -319,6 +319,15 @@ int blkdev_issue_flush(struct block_device *bdev, gfp_t
> if (!q)
> return -ENXIO;
> + /*
> + * some block devices may not have their queue correctly set up here
> + * (e.g. loop device without a backing file) and so issuing a flush
> + * here will panic. Ensure there is a request function before issuing
> + * the barrier.
> + */
> + if (!q->make_request_fn)
> + return -ENXIO;
> bio = bio_alloc(gfp_mask, 0);
> bio->bi_end_io = bio_end_empty_barrier;
> bio->bi_bdev = bdev;
This may appear ugly, but I think the patch is fine since there's not
much we can do about the loop crap (outside of changing how you do
setup/configure of it).
I'll apply this, thanks.