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,
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);
+
return count;
}
--
1.9.0
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