ceph: invalidate dirty pages after forced umount
ceph: invalidate dirty pages after forced umount

After forced umount, ceph_writepages_start() skips flushing dirty
pages. To make sure inode's reference count get dropped to zero,
we need to invalidate dirty pages.

Signed-off-by: Yan, Zheng <5a3288024fcad83740d827e0862f4c1e6f28e7bf@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs