Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Muchun Song <songmuchun@bytedance.com>
To:     akpm@linux-foundation.org, zi.yan@cs.rutgers.edu,
        kirill.shutemov@linux.intel.com, rientjes@google.com,
        lars.persson@axis.com, mike.kravetz@oracle.com, ziy@nvidia.com
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        duanxiongchun@bytedance.com, fam.zheng@bytedance.com,
        Muchun Song <songmuchun@bytedance.com>
Subject: [PATCH v5 1/7] mm: thp: fix wrong cache flush in remove_migration_pmd()
Date:   Thu, 10 Feb 2022 20:30:52 +0800
Message-Id: <20220210123058.79206-2-songmuchun@bytedance.com>
In-Reply-To: <20220210123058.79206-1-songmuchun@bytedance.com>
References: <20220210123058.79206-1-songmuchun@bytedance.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The flush_cache_range() is supposed to be justified only if the page
is already placed in process page table, and that is done right after
flush_cache_range(). So using this interface is wrong. And there is
no need to invalite cache since it was non-present before in
remove_migration_pmd(). So just to remove it.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
---
 mm/huge_memory.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f58524394dc1..45ede45b11f5 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3207,7 +3207,6 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
 	if (pmd_swp_uffd_wp(*pvmw->pmd))
 		pmde = pmd_wrprotect(pmd_mkuffd_wp(pmde));
 
-	flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
 	if (PageAnon(new))
 		page_add_anon_rmap(new, vma, mmun_start, true);
 	else
@@ -3215,6 +3214,8 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
 	set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
 	if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
 		mlock_vma_page(new);
+
+	/* No need to invalidate - it was non-present before */
 	update_mmu_cache_pmd(vma, address, pvmw->pmd);
 }
 #endif
-- 
2.11.0