[merged mm-stable] selftests-cgroup-test_zswap-fix-implicit-unsigned-promotion-bug-in-test_no_kmem_bypass.patch removed from -mm tree

[merged mm-stable] selftests-cgroup-test_zswap-fix-implicit-unsigned-promotion-bug-in-test_no_kmem_bypass.patch removed from -mm tree

[Andrew Morton]

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The quilt patch titled
     Subject: selftests/cgroup: test_zswap: fix implicit unsigned promotion bug in test_no_kmem_bypass
has been removed from the -mm tree.  Its filename was
     selftests-cgroup-test_zswap-fix-implicit-unsigned-promotion-bug-in-test_no_kmem_bypass.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Wilson Felipe Pereira <wfelipe@google.com>
Subject: selftests/cgroup: test_zswap: fix implicit unsigned promotion bug in test_no_kmem_bypass
Date: Fri, 28 Aug 2026 03:37:32 +0000

In test_no_kmem_bypass(), delta (stored_pages * page_size - zswapped) is
checked against stored_pages * page_size / 4 to verify that the pages
pushed to zswap belong to the test memory cgroup.

Due to slight stat update timing differences, delta can evaluate to a
small negative number (e.g.  -5MB out of 1GB).  Because delta is declared
as a signed int and stored_pages is an unsigned size_t, C's usual
arithmetic conversions implicitly promote a negative delta to a large
unsigned 64-bit integer, causing `delta < stored_pages * page_size / 4` to
falsely evaluate to 0 and fail the test.

Fix this by declaring zswapped and delta as signed long long and comparing
against a signed threshold, ensuring negative deltas correctly evaluate to
true.

Link: https://lore.kernel.org/20260828033741.2184560-3-wfelipe@google.com
Fixes: a549f9f31561a ("selftests: cgroup: add test_zswap with no kmem bypass test")
Signed-off-by: Wilson Felipe Pereira <wfelipe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Koutný <mkoutny@suse.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
---

 tools/testing/selftests/cgroup/test_zswap.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/tools/testing/selftests/cgroup/test_zswap.c~selftests-cgroup-test_zswap-fix-implicit-unsigned-promotion-bug-in-test_no_kmem_bypass
+++ a/tools/testing/selftests/cgroup/test_zswap.c
@@ -654,11 +654,14 @@ static int test_no_kmem_bypass(const cha
 			break;
 		/* If memory was pushed to zswap, verify it belongs to memcg */
 		if (stored_pages > stored_pages_threshold) {
-			int zswapped = cg_read_key_long(test_group, "memory.stat", "zswapped ");
-			int delta = stored_pages * page_size - zswapped;
-			int result_ok = delta < stored_pages * page_size / 4;
+			long zswapped = cg_read_key_long(
+				test_group, "memory.stat", "zswapped ");
+			long long delta =
+				(long long)stored_pages * page_size - zswapped;
+			long long max_delta =
+				(long long)stored_pages * page_size / 4;
 
-			ret = result_ok ? KSFT_PASS : KSFT_FAIL;
+			ret = (delta < max_delta) ? KSFT_PASS : KSFT_FAIL;
 			break;
 		}
 	}
_

Patches currently in -mm which might be from wfelipe@google.com are

mm-zswap-convert-zswap_store_page-and-zswap_compress-to-take-a-folio.patch
init-main-fix-off-by-one-in-argv_init-cleanup.patch
init-main-fix-false-positive-kernel-panic-on-environment-variable-overwrite.patch