sd: notify block layer when using temporary change to cache_type
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 a temporary change
of the cache_type to write through. Without this, a SYNCHRONIZE CACHE
command will still be generated. This patch factors out a helper that
can be called from sd_revalidate_disk and cache_type_store.
Signed-off-by: Vaughan Cao <vaughan.cao@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 14ec8f5..4056004 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -134,6 +134,19 @@
"write back, no read (daft)"
};
+static void sd_set_flush_flag(struct scsi_disk *sdkp)
+{
+ unsigned flush = 0;
+
+ if (sdkp->WCE) {
+ flush |= REQ_FLUSH;
+ if (sdkp->DPOFUA)
+ flush |= REQ_FUA;
+ }
+
+ blk_queue_flush(sdkp->disk->queue, flush);
+}
+
static ssize_t
cache_type_store(struct device *dev, struct device_attribute *attr,
const char *buf, size_t count)
@@ -177,6 +190,7 @@
if (sdkp->cache_override) {
sdkp->WCE = wce;
sdkp->RCD = rcd;
+ sd_set_flush_flag(sdkp);
return count;
}
@@ -2698,7 +2712,6 @@
struct scsi_disk *sdkp = scsi_disk(disk);
struct scsi_device *sdp = sdkp->device;
unsigned char *buffer;
- unsigned flush = 0;
SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp,
"sd_revalidate_disk\n"));
@@ -2744,13 +2757,7 @@
* We now have all cache related info, determine how we deal
* with flush requests.
*/
- if (sdkp->WCE) {
- flush |= REQ_FLUSH;
- if (sdkp->DPOFUA)
- flush |= REQ_FUA;
- }
-
- blk_queue_flush(sdkp->disk->queue, flush);
+ sd_set_flush_flag(sdkp);
set_capacity(disk, sdkp->capacity);
sd_config_write_same(sdkp);