From: Qi Zheng <zhengqi.arch@bytedance.com>
Date: Thu, 26 Sep 2024 06:46:17 +0000 (+0800)
Subject: mm: khugepaged: __collapse_huge_page_swapin() use pte_offset_map_ro_nolock()
X-Git-Tag: v6.13-rc1~99^2~189
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c85507857bb8904f8631b3a89b19aa73b1f77e48;p=thirdparty%2Fkernel%2Flinux.git

mm: khugepaged: __collapse_huge_page_swapin() use pte_offset_map_ro_nolock()

In __collapse_huge_page_swapin(), we just use the ptl for pte_same() check
in do_swap_page().  In other places, we directly use
pte_offset_map_lock(), so convert it to using pte_offset_map_ro_nolock().

Link: https://lkml.kernel.org/r/dc97a6c3cb9ea80cab30c5626eeea79959d93258.1727332572.git.zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index ed1a225dd198e..8e0d05bd3d560 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1014,7 +1014,11 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
 		};
 
 		if (!pte++) {
-			pte = pte_offset_map_nolock(mm, pmd, address, &ptl);
+			/*
+			 * Here the ptl is only used to check pte_same() in
+			 * do_swap_page(), so readonly version is enough.
+			 */
+			pte = pte_offset_map_ro_nolock(mm, pmd, address, &ptl);
 			if (!pte) {
 				mmap_read_unlock(mm);
 				result = SCAN_PMD_NULL;