linux-kernel - [PATCH v2 3/6] mm/huge_memory.c: rework the function do_huge_pmd_numa

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Date:   Tue, 16 Mar 2021 08:40:04 -0400
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <ziy@...dia.com>, <willy@...radead.org>,
        <william.kucharski@...cle.com>, <vbabka@...e.cz>,
        <peterx@...hat.com>, <yulei.kernel@...il.com>, <walken@...gle.com>,
        <aneesh.kumar@...ux.ibm.com>, <rcampbell@...dia.com>,
        <thomas_os@...pmail.org>, <yang.shi@...ux.alibaba.com>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH v2 3/6] 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.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/huge_memory.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index caad9942c693..57a1b72e03c8 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1462,12 +1462,6 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
 	 */
 	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 vm_fault *vmf, pmd_t pmd)
 		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;
 	}
 
 	/*
-- 
2.19.1