From: David Hildenbrand <david@redhat.com>
Date: Fri, 4 Jul 2025 10:25:06 +0000 (+0200)
Subject: mm/zsmalloc: stop using __ClearPageMovable()
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a109262734c527296f0a945825f568c78dc804f2;p=thirdparty%2Flinux.git

mm/zsmalloc: stop using __ClearPageMovable()

Instead, let's check in the callbacks if the page was already destroyed,
which can be checked by looking at zpdesc->zspage (see reset_zpdesc()).

If we detect that the page was destroyed:

(1) Fail isolation, just like the migration core would

(2) Fake migration success just like the migration core would

In the putback case there is nothing to do, as we don't do anything just
like the migration core would do.

In the future, we should look into not letting these pages get destroyed
while they are isolated -- and instead delaying that to the
putback/migration call.  Add a TODO for that.

Link: https://lkml.kernel.org/r/20250704102524.326966-13-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Eugenio Pé rez <eperezma@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Jerrin Shaji George <jerrin.shaji-george@broadcom.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mathew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: xu xin <xu.xin16@zte.com.cn>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 626f09fb27138..b12250e219bb7 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -877,7 +877,6 @@ static void reset_zpdesc(struct zpdesc *zpdesc)
 {
 	struct page *page = zpdesc_page(zpdesc);
 
-	__ClearPageMovable(page);
 	ClearPagePrivate(page);
 	zpdesc->zspage = NULL;
 	zpdesc->next = NULL;
@@ -1716,10 +1715,11 @@ static void replace_sub_page(struct size_class *class, struct zspage *zspage,
 static bool zs_page_isolate(struct page *page, isolate_mode_t mode)
 {
 	/*
-	 * Page is locked so zspage couldn't be destroyed. For detail, look at
-	 * lock_zspage in free_zspage.
+	 * Page is locked so zspage can't be destroyed concurrently
+	 * (see free_zspage()). But if the page was already destroyed
+	 * (see reset_zpdesc()), refuse isolation here.
 	 */
-	return true;
+	return page_zpdesc(page)->zspage;
 }
 
 static int zs_page_migrate(struct page *newpage, struct page *page,
@@ -1737,6 +1737,16 @@ static int zs_page_migrate(struct page *newpage, struct page *page,
 	unsigned long old_obj, new_obj;
 	unsigned int obj_idx;
 
+	/*
+	 * TODO: nothing prevents a zspage from getting destroyed while
+	 * it is isolated for migration, as the page lock is temporarily
+	 * dropped after zs_page_isolate() succeeded: we should rework that
+	 * and defer destroying such pages once they are un-isolated (putback)
+	 * instead.
+	 */
+	if (!zpdesc->zspage)
+		return MIGRATEPAGE_SUCCESS;
+
 	/* The page is locked, so this pointer must remain valid */
 	zspage = get_zspage(zpdesc);
 	pool = zspage->pool;