[LU-529] Fix Direct IO pages support in osc cache

• Type: Bug
• Resolution: Fixed
• Priority: Critical
• Severity: 3
• Assignee: Jinshan Xiong (Inactive)
• Reporter: Jinshan Xiong (Inactive)

Description

There are several problems in current clio implementation:
1. may mix caching and direct io pages, this will cause problem if OST space is running out because it may return -ENOSPC even for OBD_BRW_FROM_GRANT pages;
2. after lu-485 is committed, there may be two cl_page in cache pointing to the same file index;

we should issue different RPCs for caching and direct pages to fix these issues.