Commit 3bfa35cc authored by Zi Yan's avatar Zi Yan Committed by Wen Zhiwei
Browse files

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

stable inclusion
from stable-v6.6.48
commit 19b4397c4a15093b8f50ead50164641392f16f77
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAWEBV

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=19b4397c4a15093b8f50ead50164641392f16f77

--------------------------------

commit 40b760cfd44566bca791c80e0720d70d75382b84 upstream.

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 b99a342d ("NUMA balancing: reduce
TLB flush via delaying mapping on hint page fault") restructured
do_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() 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/20240809145906.1513458-2-ziy@nvidia.com


Fixes: b99a342d ("NUMA balancing: reduce TLB flush via delaying mapping on hint page fault")
Signed-off-by: default avatarZi Yan <ziy@nvidia.com>
Reported-by: default avatar"Huang, Ying" <ying.huang@intel.com>
Closes: https://lore.kernel.org/linux-mm/87zfqfw0yw.fsf@yhuang6-desk2.ccr.corp.intel.com/


Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Yang Shi <shy828301@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Conflicts:
 mm/memory.c
Signed-off-by: default avatarWen Zhiwei <wenzhiwei@kylinos.cn>
parent 1d21ce27

mm/memory.c

+16 −17
Original line number Diff line number Diff line
@@ -5286,7 +5286,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf) 


	if (unlikely(!pte_same(old_pte, vmf->orig_pte))) {

		pte_unmap_unlock(vmf->pte, vmf->ptl);

		goto out;

		return 0;

	}



	pte = pte_modify(old_pte, vma->vm_page_prot);
@@ -5346,23 +5346,19 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf) 
	if (migrate_misplaced_folio(folio, vma, target_nid)) {

		nid = target_nid;

		flags |= TNF_MIGRATED;

	} else {

		task_numa_fault(last_cpupid, nid, 1, flags);

		return 0;

	}



	flags |= TNF_MIGRATE_FAIL;

	vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, 

			               vmf->address, &vmf->ptl);

	if (unlikely(!vmf->pte))

			goto out;

		return 0;

	if (unlikely(!pte_same(ptep_get(vmf->pte), vmf->orig_pte))) {

		pte_unmap_unlock(vmf->pte, vmf->ptl);

			goto out;

		}

		goto out_map;

	}



out:

	if (nid != NUMA_NO_NODE)

		task_numa_fault(last_cpupid, nid, nr_pages, flags);

		return 0;

	}

out_map:

	/*

	 * Make it present again, depending on how arch implements
@@ -5375,7 +5371,10 @@ 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;



	if (nid != NUMA_NO_NODE)

		task_numa_fault(last_cpupid, nid, 1, flags);

	return 0;

}



static inline vm_fault_t create_huge_pmd(struct vm_fault *vmf)