mm/numa: no task_numa_fault() call if page table is changed

When handling a numa page fault, task_numa_fault() should be called by a
process that restores the page table of the faulted folio to avoid
duplicated stats counting.  Commit b99a342 ("NUMA balancing: reduce
TLB flush via delaying mapping on hint page fault") restructured
do_numa_page() and do_huge_pmd_numa_page() and did not avoid
task_numa_fault() call in the second page table check after a numa
migration failure.  Fix it by making all !pte_same()/!pmd_same() return
immediately.

This issue can cause task_numa_fault() being called more than necessary
and lead to unexpected numa balancing results (It is hard to tell whether
the issue will cause positive or negative performance impact due to
duplicated numa fault counting).

Link: https://lkml.kernel.org/r/[email protected]
Fixes: b99a342 ("NUMA balancing: reduce TLB flush via delaying mapping on hint page fault")
Signed-off-by: Zi Yan <[email protected]>
Reported-by: "Huang, Ying" <[email protected]>
Closes: https://lore.kernel.org/linux-mm/[email protected]/
Cc: Baolin Wang <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Kefeng Wang <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: x-y-z

mm/huge_memory.c

@@ -1738,10 +1738,11 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
 		goto out_map;
 	}
 
-out:
+count_fault:
 	if (nid != NUMA_NO_NODE)
 		task_numa_fault(last_cpupid, nid, HPAGE_PMD_NR, flags);
 
+out:
 	return 0;
 
 out_map:
@@ -1753,7 +1754,7 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
 	set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
 	update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
 	spin_unlock(vmf->ptl);
-	goto out;
+	goto count_fault;
 }
 
 /*

mm/memory.c

@@ -5371,9 +5371,10 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
 		goto out_map;
 	}
 
-out:
+count_fault:
 	if (nid != NUMA_NO_NODE)
 		task_numa_fault(last_cpupid, nid, nr_pages, flags);
+out:
 	return 0;
 out_map:
 	/*
@@ -5387,7 +5388,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
 		numa_rebuild_single_mapping(vmf, vma, vmf->address, vmf->pte,
 					    writable);
 	pte_unmap_unlock(vmf->pte, vmf->ptl);
-	goto out;
+	goto count_fault;
 }
 
 static inline vm_fault_t create_huge_pmd(struct vm_fault *vmf)