This patch seemed like a good idea to me; I just checked linux-next,
and looks like nothing like this is planned to be merged. Just
thought I would send a prod-o-gram to see what the current thinking
was around adding something like this.
Thanks,
- Ted
On Tue, Nov 30, 2010 at 05:41:24PM +0100, Christoph Hellwig wrote:
> FYI, here's an updated version of my patch to not run pure flushes
> that also works on SCSI/ATA and not just virtio. I suspect the patch
> alone might not be enough, but together with a variant of Neil's
> suggestion might do the trick, with my patch taking care of the
> highend-devices and Neil's scheme of taking care of stupid SATA disks.
>
>
> Index: linux-2.6/block/blk-flush.c
> ===================================================================
> --- linux-2.6.orig/block/blk-flush.c 2010-11-30 17:27:33.108254088 +0100
> +++ linux-2.6/block/blk-flush.c 2010-11-30 17:27:38.790004333 +0100
> @@ -143,6 +143,17 @@ struct request *blk_do_flush(struct requ
> unsigned skip = 0;
>
> /*
> + * Just issue pure flushes directly.
> + */
> + if (!blk_rq_sectors(rq)) {
> + if (!do_preflush) {
> + __blk_end_request_all(rq, 0);
> + return NULL;
> + }
> + return rq;
> + }
> +
> + /*
> * Special case. If there's data but flush is not necessary,
> * the request can be issued directly.
> *
> Index: linux-2.6/drivers/scsi/scsi_lib.c
> ===================================================================
> --- linux-2.6.orig/drivers/scsi/scsi_lib.c 2010-11-30 17:27:33.120254298 +0100
> +++ linux-2.6/drivers/scsi/scsi_lib.c 2010-11-30 17:27:38.791003634 +0100
> @@ -1060,7 +1060,7 @@ int scsi_setup_blk_pc_cmnd(struct scsi_d
> * that does not transfer data, in which case they may optionally
> * submit a request without an attached bio.
> */
> - if (req->bio) {
> + if (req->bio && !(req->cmd_flags & REQ_FLUSH)) {
> int ret;
>
> BUG_ON(!req->nr_phys_segments);
--
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