On Tue, 2014-05-27 at 19:39 +0800, Vaughan Cao wrote:
> This is a fix for commit:
> 39c60a0948cc06139e2fbfe084f83cb7e7deae3b sd: fix array cache flushing bug causing performance problems
> We must notify the block layer via q->flush_flags after temporary change the cache_type to write through.
> If not, SYNCHRONIZE CACHE command will still be generated.
>
> Signed-off-by: Vaughan Cao <vaughan.cao@xxxxxxxxxx>
> ---
> drivers/scsi/sd.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index 6146b9d..366e48b 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -144,6 +144,7 @@ sd_store_cache_type(struct device *dev, struct device_attribute *attr,
This is a weird function name. The name in the vanilla kernel is
cache_type_store().
> struct scsi_sense_hdr sshdr;
> static const char temp[] = "temporary ";
> int len;
> + unsigned flush;
>
> if (sdp->type != TYPE_DISK)
> /* no cache control on RBC devices; theoretically they
> @@ -174,6 +175,17 @@ sd_store_cache_type(struct device *dev, struct device_attribute *attr,
> if (sdkp->cache_override) {
> sdkp->WCE = wce;
> sdkp->RCD = rcd;
> +
> + /* set flush_flags to notify the block layer */
> + flush = 0;
> + if (sdkp->WCE) {
> + flush |= REQ_FLUSH;
> + if (sdkp->DPOFUA)
> + flush |= REQ_FUA;
> + }
> +
> + blk_queue_flush(sdkp->disk->queue, flush);
> +
Is there a reason you cut and paste from sd_revalidate_disk() instead of
just calling it directly?
James
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