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From:   Miaohe Lin <linmiaohe@huawei.com>
To:     <akpm@linux-foundation.org>
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        <william.kucharski@oracle.com>, <vbabka@suse.cz>,
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        <linmiaohe@huawei.com>
Subject: [PATCH v3 3/6] mm/huge_memory.c: rework the function do_huge_pmd_numa_page() slightly
Date:   Thu, 18 Mar 2021 08:27:19 -0400
Message-ID: <20210318122722.13135-4-linmiaohe@huawei.com>
In-Reply-To: <20210318122722.13135-1-linmiaohe@huawei.com>
References: <20210318122722.13135-1-linmiaohe@huawei.com>
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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@huawei.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 01b96c638e73..23964adf5db2 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