[experimental]Set cleaning policy

[rafalste]

Add RPC methods for changing cleaning policy and parameters:

• bdev_ocf_set_cleaning_alru
• bdev_ocf_set_cleaning_acp
• bdev_ocf_set_cleaning_nop

Signed-off-by: Rafal Stefanowski rafal.stefanowski@intel.com

[pep8speaks]

Hello @rafalste! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file scripts/rpc.py:

Line 348:80: E501 line too long (90 > 79 characters)
Line 349:80: E501 line too long (96 > 79 characters)
Line 350:80: E501 line too long (99 > 79 characters)
Line 352:80: E501 line too long (98 > 79 characters)
Line 355:80: E501 line too long (107 > 79 characters)
Line 357:80: E501 line too long (105 > 79 characters)
Line 358:80: E501 line too long (86 > 79 characters)
Line 360:80: E501 line too long (116 > 79 characters)
Line 362:80: E501 line too long (111 > 79 characters)
Line 369:80: E501 line too long (96 > 79 characters)
Line 371:80: E501 line too long (97 > 79 characters)
Line 374:80: E501 line too long (101 > 79 characters)
Line 376:80: E501 line too long (121 > 79 characters)
Line 383:80: E501 line too long (81 > 79 characters)

• In the file scripts/rpc/bdev.py:

Line 238:80: E501 line too long (81 > 79 characters)
Line 239:80: E501 line too long (84 > 79 characters)
Line 240:80: E501 line too long (84 > 79 characters)

[mmkayPL]

I think it might be better to set the default implicitly to 20 here (and other default values too) and not base it on defaults in OCF? In that case changing the type to uint32 would also be useful, I think.

[rafalste]

I think there are two problems with your proposed approach:

1. SPDK maintainers prefer to be as independent as possible from any hard-coded values. This way, when we change OCF defaults in the future, there will be no need to update them also in SPDK adapter.
2. Some of those parameters takes a range from 0 to some value, so the default=-1 informs of no change to that particular parameter. I think it will be much more obfuscated to handle this situation using different type of variable here.