Merge tag 'mm-hotfixes-stable-2022-05-27' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull hotfixes from Andrew Morton:
 "Six hotfixes.

  The page_table_check one from Miaohe Lin is considered a minor thing
  so it isn't marked for -stable. The remainder address pre-5.19 issues
  and are cc:stable"

* tag 'mm-hotfixes-stable-2022-05-27' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
  mm/page_table_check: fix accessing unmapped ptep
  kexec_file: drop weak attribute from arch_kexec_apply_relocations[_add]
  mm/page_alloc: always attempt to allocate at least one page during bulk allocation
  hugetlb: fix huge_pmd_unshare address update
  zsmalloc: fix races between asynchronous zspage free and page migration
  Revert "mm/cma.c: remove redundant cma_mutex lock"

1 files changed, 33 insertions, 4 deletions

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 9152fbde33b5..5d5fc04385b8 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1718,11 +1718,40 @@ static enum fullness_group putback_zspage(struct size_class *class,
  */
 static void lock_zspage(struct zspage *zspage)
 {
-	struct page *page = get_first_page(zspage);
+	struct page *curr_page, *page;
 
-	do {
-		lock_page(page);
-	} while ((page = get_next_page(page)) != NULL);
+	/*
+	 * Pages we haven't locked yet can be migrated off the list while we're
+	 * trying to lock them, so we need to be careful and only attempt to
+	 * lock each page under migrate_read_lock(). Otherwise, the page we lock
+	 * may no longer belong to the zspage. This means that we may wait for
+	 * the wrong page to unlock, so we must take a reference to the page
+	 * prior to waiting for it to unlock outside migrate_read_lock().
+	 */
+	while (1) {
+		migrate_read_lock(zspage);
+		page = get_first_page(zspage);
+		if (trylock_page(page))
+			break;
+		get_page(page);
+		migrate_read_unlock(zspage);
+		wait_on_page_locked(page);
+		put_page(page);
+	}
+
+	curr_page = page;
+	while ((page = get_next_page(curr_page))) {
+		if (trylock_page(page)) {
+			curr_page = page;
+		} else {
+			get_page(page);
+			migrate_read_unlock(zspage);
+			wait_on_page_locked(page);
+			put_page(page);
+			migrate_read_lock(zspage);
+		}
+	}
+	migrate_read_unlock(zspage);
 }
 
 static int zs_init_fs_context(struct fs_context *fc)