On Thu, Jan 02, 2014 at 01:21:21AM +0900, Roman Pen wrote:
> From: Roman Peniaev <r.peni...@gmail.com>
>
> mtd_blkdevs is device with volatile cache (writeback buffer), so it should
> support
> REQ_FLUSH to do explicit flush.
>
> Without this patch 'sync' does not guarantee that writeback buffer will be
> flushed
> on disk in case of power off, e.g.:
>
> $ cp some_file /mnt
> $ sync
>
> ### POWER OFF
>
> In case of this sequence writeback buffer will not be flushed on disk.
>
> This patch fixes this behaviour and explicitly reports to block layer that
> flush
> requests are being supported.
>
> Signed-off-by: Roman Peniaev <r.peni...@gmail.com>
> CC: David Woodhouse <dw...@infradead.org>
> CC: linux-...@lists.infradead.org
> CC: linux-kernel@vger.kernel.org
> ---
> drivers/mtd/mtd_blkdevs.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
> index 5073cbc..feafe5c 100644
> --- a/drivers/mtd/mtd_blkdevs.c
> +++ b/drivers/mtd/mtd_blkdevs.c
> @@ -89,6 +89,12 @@ static int do_blktrans_request(struct mtd_blktrans_ops *tr,
> if (req->cmd_type != REQ_TYPE_FS)
> return -EIO;
>
> + if (req->cmd_flags & REQ_FLUSH) {
> + if (tr->flush)
> + return tr->flush(dev);
> + return 0;
> + }
> +
> if (blk_rq_pos(req) + blk_rq_cur_sectors(req) >
> get_capacity(req->rq_disk))
> return -EIO;
> @@ -409,6 +415,8 @@ int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
> if (!new->rq)
> goto error3;
>
> + blk_queue_flush(new->rq, REQ_FLUSH);
How about only registering the flush command if we support it? So:
if (tr->flush)
blk_queue_flush(new->rq, REQ_FLUSH);
Then you can probably also change the earlier hunk to the following, no?
if (req->cmd_flags & REQ_FLUSH)
return tr->flush(dev);
> +
> new->rq->queuedata = new;
> blk_queue_logical_block_size(new->rq, tr->blksize);
>
Brian
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