linux-kernel - Re: [PATCH v7 4/4] mm/vmscan: avoid split lazyfree THP during shrink_folio

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20240613072858.16512-1-ioworker0@gmail.com>
Date: Thu, 13 Jun 2024 15:28:58 +0800
From: Lance Yang <ioworker0@...il.com>
To: akpm@...ux-foundation.org
Cc: ioworker0@...il.com,
	21cnbao@...il.com,
	baolin.wang@...ux.alibaba.com,
	david@...hat.com,
	fengwei.yin@...el.com,
	libang.li@...group.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	maskray@...gle.com,
	mhocko@...e.com,
	minchan@...nel.org,
	peterx@...hat.com,
	ryan.roberts@....com,
	shy828301@...il.com,
	sj@...nel.org,
	songmuchun@...edance.com,
	wangkefeng.wang@...wei.com,
	willy@...radead.org,
	xiehuan09@...il.com,
	ziy@...dia.com,
	zokeefe@...gle.com
Subject: Re: [PATCH v7 4/4] mm/vmscan: avoid split lazyfree THP during shrink_folio_list()

Hi Andrew,

I'd like to fix the bug[1] I mentioned previously. Could you please fold the
following changes into this patch? 

[1] https://lore.kernel.org/linux-mm/20240613065521.15960-1-ioworker0@gmail.com/

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f409ea9fcc18..425374ae06ed 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2707,10 +2707,8 @@ static bool __discard_anon_folio_pmd_locked(struct vm_area_struct *vma,
 	if (unlikely(page_folio(page) != folio))
 		return false;
 
-	if (folio_test_dirty(folio) || pmd_dirty(orig_pmd)) {
-		folio_set_swapbacked(folio);
+	if (folio_test_dirty(folio) || pmd_dirty(orig_pmd))
 		return false;
-	}
 
 	orig_pmd = pmdp_huge_clear_flush(vma, addr, pmdp);
 
@@ -2737,10 +2735,8 @@ static bool __discard_anon_folio_pmd_locked(struct vm_area_struct *vma,
 	 *
 	 * The only folio refs must be one from isolation plus the rmap(s).
 	 */
-	if (folio_test_dirty(folio) || pmd_dirty(orig_pmd))
-		folio_set_swapbacked(folio);
-
-	if (folio_test_swapbacked(folio) || ref_count != map_count + 1) {
+	if (folio_test_dirty(folio) || pmd_dirty(orig_pmd) ||
+	    ref_count != map_count + 1) {
 		set_pmd_at(mm, addr, pmdp, orig_pmd);
 		return false;
 	}
diff --git a/mm/rmap.c b/mm/rmap.c
index b9e5943c8349..393e2c11c44c 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1824,12 +1824,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
 			 */
 			if (unlikely(folio_test_swapbacked(folio) !=
 					folio_test_swapcache(folio))) {
-				/*
-				 * unmap_huge_pmd_locked() will unmark a
-				 * PMD-mapped folio as lazyfree if the folio or
-				 * its PMD was redirtied.
-				 */
-				WARN_ON_ONCE(!pmd_mapped);
+				WARN_ON_ONCE(1);
 				goto walk_done_err;
 			}
 
-- 

Thanks,
Lance