add user friendly command strings sd_wr_cache to enable/disable
write&read cache. user can enable both write and read cache by one of
the following commands:
echo w1r1 > cache_type
echo "write back" > cache_type
sd_wr_cache[] = {"w0r1", "w0r0", "w1r1", "w1r0"};
for sd_wr_cache 0 means disable, 1 means enable.
Encoding | WCE RCD | Write_cache Read_cache
--------------------------------------------------------------------
write through / w0r1 | 0 0 | off on
none / w0r0 | 0 1 | off off
write back / w1r1 | 1 0 | on on
write back, no read (daft) / w1r0 | 1 1 | on off
Signed-off-by: weiping zhang <zhangweip...@didichuxing.com>
---
drivers/scsi/sd.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index a028ab3..ce2fda5 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -134,10 +134,20 @@ static DEFINE_MUTEX(sd_ref_mutex);
static struct kmem_cache *sd_cdb_cache;
static mempool_t *sd_cdb_pool;
+/*
+ * Encoding | WCE RCD | Write_cache Read_cache
+ * --------------------------------------------------------------------
+ * write through / w0r1 | 0 0 | off on
+ * none / w0r0 | 0 1 | off off
+ * write back / w1r1 | 1 0 | on on
+ * write back, no read (daft) / w1r0 | 1 1 | on off
+ */
static const char *sd_cache_types[] = {
"write through", "none", "write back",
"write back, no read (daft)"
};
+/* 0:disable, 1:enable */
+static const char * const sd_wr_cache[] = {"w0r1", "w0r0", "w1r1", "w1r0"};
static void sd_set_flush_flag(struct scsi_disk *sdkp)
{
@@ -172,6 +182,10 @@ cache_type_store(struct device *dev, struct
device_attribute *attr,
* it's not worth the risk */
return -EINVAL;
+ /*
+ * for "temporary", we only change request_queue's flag, not send
+ * any command to disk, so actually disk'cache dosen't changed yet.
+ */
if (strncmp(buf, temp, sizeof(temp) - 1) == 0) {
buf += sizeof(temp) - 1;
sdkp->cache_override = 1;
@@ -180,8 +194,11 @@ cache_type_store(struct device *dev, struct
device_attribute *attr,
}
ct = sysfs_match_string(sd_cache_types, buf);
- if (ct < 0)
- return -EINVAL;
+ if (ct < 0) {
+ ct = sysfs_match_string(sd_wr_cache, buf);
+ if (ct < 0)
+ return -EINVAL;
+ }
rcd = ct & 0x01 ? 1 : 0;
wce = (ct & 0x02) && !sdkp->write_prot ? 1 : 0;
--
2.9.4
