Hi All,
I noticed that the sysfs file cache_type is not is sync with the information in the mode page. If we change the WCE attribute in the mode page (sdparm --set=WCE /dev/sda and sdparm --clear=WCE /dev/sda) it does not reflect this in the sysfs file.
$ cat /sys/block/sda/device/scsi_disk/6\:0\:0\:0/cache_type
write back
$ sdparm --clear=WCE /dev/sda
/dev/sda: TOSHIBA AL13SEB600 0101
$ cat /sys/block/sda/device/scsi_disk/6\:0\:0\:0/cache_type
write back
Ideally cache_type should have changed to 'write through' or 'none'. I have a small one line change that can fix this one. This patch applies against the latest branch "linux-3.15-rc8".
Few things to note:
1. revalidate_disk() also reads a whole bunch of other things from the mode page and I don't know if this will have any side effects. This call is made on store_cache_type as well, so I think it should be OK.
2. This is extra work which is not needed in most cases (mode pages hardly change). Is there an event that we can subscribe to when the modpages change?
Please review.
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index efcbcd1..5b65ccc 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -256,6 +256,7 @@ static ssize_t
cache_type_show(struct device *dev, struct device_attribute *attr, char *buf)
{
struct scsi_disk *sdkp = to_scsi_disk(dev);
+ revalidate_disk(sdkp->disk);
int ct = sdkp->RCD + 2*sdkp->WCE;
return snprintf(buf, 40, "%s\n", sd_cache_types[ct]);
Thanks,
Vishwanath
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