[patch 024/143] mm/huge_memory.c: rework the function do_huge_pmd_numa_page() slightly

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From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Subject: mm/huge_memory.c: rework the function do_huge_pmd_numa_page() slightly

The current code that checks if migrating misplaced transhuge page is
needed is pretty hard to follow.  Rework it and add a comment to make its
logic more clear and improve readability.

Link: https://lkml.kernel.org/r/20210318122722.13135-4-linmiaohe@xxxxxxxxxx
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: Thomas Hellstrm (Intel) <thomas_os@xxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx>
Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
Cc: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Cc: yuleixzhang <yulei.kernel@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/huge_memory.c |   11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

--- a/mm/huge_memory.c~mm-huge_memoryc-rework-the-function-do_huge_pmd_numa_page-slightly
+++ a/mm/huge_memory.c
@@ -1462,12 +1462,6 @@ vm_fault_t do_huge_pmd_numa_page(struct
 	 */
 	page_locked = trylock_page(page);
 	target_nid = mpol_misplaced(page, vma, haddr);
-	if (target_nid == NUMA_NO_NODE) {
-		/* If the page was locked, there are no parallel migrations */
-		if (page_locked)
-			goto clear_pmdnuma;
-	}
-
 	/* Migration could have started since the pmd_trans_migrating check */
 	if (!page_locked) {
 		page_nid = NUMA_NO_NODE;
@@ -1476,6 +1470,11 @@ vm_fault_t do_huge_pmd_numa_page(struct
 		spin_unlock(vmf->ptl);
 		put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE);
 		goto out;
+	} else if (target_nid == NUMA_NO_NODE) {
+		/* There are no parallel migrations and page is in the right
+		 * node. Clear the numa hinting info in this pmd.
+		 */
+		goto clear_pmdnuma;
 	}
 
 	/*
_



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