linux-kernel - [PATCH 09/12] hugetlb_vmemmap: Optimistically set Optimized flag

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Message-ID: <20230825190436.55045-10-mike.kravetz@oracle.com>
Date:   Fri, 25 Aug 2023 12:04:29 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Muchun Song <songmuchun@...edance.com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        David Rientjes <rientjes@...gle.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        Xiongchun Duan <duanxiongchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: [PATCH 09/12] hugetlb_vmemmap: Optimistically set Optimized flag

At the beginning of hugetlb_vmemmap_optimize, optimistically set
the HPageVmemmapOptimized flag in the head page.  Clear the flag
if the operation fails.

No change in behavior.  However, this will become important in
subsequent patches where we batch delay TLB flushing.  We need to
make sure the content in the old and new vmemmap pages are the same.

Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
---
 mm/hugetlb_vmemmap.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index e390170c0887..500a118915ff 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -566,7 +566,9 @@ static void __hugetlb_vmemmap_optimize(const struct hstate *h,
 	if (!vmemmap_should_optimize(h, head))
 		return;
 
+	/* Optimistically assume success */
 	static_branch_inc(&hugetlb_optimize_vmemmap_key);
+	SetHPageVmemmapOptimized(head);
 
 	vmemmap_end	= vmemmap_start + hugetlb_vmemmap_size(h);
 	vmemmap_reuse	= vmemmap_start;
@@ -577,10 +579,10 @@ static void __hugetlb_vmemmap_optimize(const struct hstate *h,
 	 * to the page which @vmemmap_reuse is mapped to, then free the pages
 	 * which the range [@vmemmap_start, @vmemmap_end] is mapped to.
 	 */
-	if (vmemmap_remap_free(vmemmap_start, vmemmap_end, vmemmap_reuse, bulk_pages))
+	if (vmemmap_remap_free(vmemmap_start, vmemmap_end, vmemmap_reuse, bulk_pages)) {
 		static_branch_dec(&hugetlb_optimize_vmemmap_key);
-	else
-		SetHPageVmemmapOptimized(head);
+		ClearHPageVmemmapOptimized(head);
+	}
 }
 
 /**
-- 
2.41.0