fs/writeback: skip AS_NO_DATA_INTEGRITY mappings in wait_sb_inodes()

In the Linux kernel, the following vulnerability has been resolved:

fs/writeback: skip AS_NO_DATA_INTEGRITY mappings in wait_sb_inodes()

Above the while() loop in wait_sb_inodes(), we document that we must wait for all pages under writeback for data integrity. Consequently, if a mapping, like fuse, traditionally does not have data integrity semantics, there is no need to wait at all; we can simply skip these inodes.

This restores fuse back to prior behavior where syncs are no-ops. This fixes a user regression where if a system is running a faulty fuse server that does not reply to issued write requests, this causes wait_sb_inodes() to wait forever.