According to the comment above CFS_ALLOC_HIGH, the flag allows allocator to return memory in the highmen zone:
/* allow to return page beyond KVM. It has to be mapped into KVM by

• cfs_page_map(); */

But cfs_alloc_flags_to_gfp() converts it to __GFP_HIGH, which according to kernel header:
#define __GFP_HIGH 0x20 /* Should access emergency pools? */

I think __GFP_HIGHMEM should be used instead. Also it makes sense to rename CFS_ALLOC_HIGH to CFS_ALLOC_HIGHMEM to avoid further confusion.