vm_phys: Add a vm_phys_seg_paddr_to_vm_page() helper

[markj]

Summary

No functional change intended.

Suggested by: alc

[alc]

Despite the long name, it's still two characters shorter than the original code. :-)

[dougm]

sys/vm/vm_phys.c

941

This could be applied at vm_page.c:787, if it were visible there.

978

If could be used here, if the fields of vm_phys_fictitious_seg were reordered.

[markj]

sys/vm/vm_phys.c

941

I made the function externally visible.

978

I think I'd prefer to leave this case as it is. If there were more instances of this pattern, I'd be more inclined to take the suggestion.

[markj]

Incorporate one of Doug's suggestions.