casadm: use alru max dirty ratio

[live4thee]

This patch will enable the 'max_dirty_ratio' parameter from Open-CAS/ocf#757

With patched casadm:

$ casadm -G -n cleaning-alru -i 1
+===============================+=======+
| Parameter name                | Value |
+===============================+=======+
| Wake up time [s]              |    10 |
| Stale buffer time [s]         |   120 |
| Flush max buffers             |   256 |
| Activity threshold [ms]       |  1000 |
| Maximum dirty ratio [percent] |    75 |
+===============================+=======+

$ casadm -X -n cleaning-alru -i 1 -d 80
$ casadm -G -n cleaning-alru -i 1
+===============================+=======+
| Parameter name                | Value |
+===============================+=======+
| Wake up time [s]              |    10 |
| Stale buffer time [s]         |   120 |
| Flush max buffers             |   256 |
| Activity threshold [ms]       |  1000 |
| Maximum dirty ratio [percent] |    80 |
+===============================+=======+

The odd is, if upgrading from existing installation - the first '-G -n cleaning-alru' will report an ioctl failure. It will be OK after issuing an -X -n cleaning-alru -i 1 -d something. I guess that's due to the missing 'max_dirty_ratio' in existing metadata. If any examples that handle such issue, please guide me.

Thanks in advance.

[CAS-Linux-Jenkins]

Can one of the admins verify this patch?