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.
This patch factors out a helper that can be called from sd_revalidate_disk and
cache_type_store.
Signed-off-by: Vaughan Cao <vaughan....@oracle.com>
---
drivers/scsi/sd.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index efcbcd1..e4774aa 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -132,6 +132,19 @@ static const char *sd_cache_types[] = {
"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)
@@ -175,6 +188,7 @@ cache_type_store(struct device *dev, struct
device_attribute *attr,
if (sdkp->cache_override) {
sdkp->WCE = wce;
sdkp->RCD = rcd;
+ sd_set_flush_flag(sdkp);
return count;
}
@@ -2712,7 +2726,6 @@ static int sd_revalidate_disk(struct gendisk *disk)
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"));
@@ -2758,13 +2771,7 @@ static int sd_revalidate_disk(struct gendisk *disk)
* 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);
--
1.9.0
--
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