+ selftests-cgroup-fix-alloc_anon_noexit-instantly-freeing-memory.patch added to -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: selftests: cgroup: fix alloc_anon_noexit() instantly freeing memory
has been added to the -mm tree.  Its filename is
     selftests-cgroup-fix-alloc_anon_noexit-instantly-freeing-memory.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/selftests-cgroup-fix-alloc_anon_noexit-instantly-freeing-memory.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/selftests-cgroup-fix-alloc_anon_noexit-instantly-freeing-memory.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: Yosry Ahmed <yosryahmed@google.com>
Subject: selftests: cgroup: fix alloc_anon_noexit() instantly freeing memory

Currently, alloc_anon_noexit() calls alloc_anon() which instantly frees
the allocated memory. alloc_anon_noexit() is usually used with
cg_run_nowait() to run a process in the background that allocates
memory. It makes sense for the background process to keep the memory
allocated and not instantly free it (otherwise there is no point of
running it in the background).

Link: https://lkml.kernel.org/r/20220425190040.2475377-4-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Chen Wandun <chenwandun@huawei.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Michal Koutn" <mkoutny@suse.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Vaibhav Jain <vaibhav@linux.ibm.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/cgroup/test_memcontrol.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/tools/testing/selftests/cgroup/test_memcontrol.c~selftests-cgroup-fix-alloc_anon_noexit-instantly-freeing-memory
+++ a/tools/testing/selftests/cgroup/test_memcontrol.c
@@ -214,13 +214,17 @@ static int alloc_pagecache_50M_noexit(co
 static int alloc_anon_noexit(const char *cgroup, void *arg)
 {
 	int ppid = getppid();
+	size_t size = (unsigned long)arg;
+	char *buf, *ptr;
 
-	if (alloc_anon(cgroup, arg))
-		return -1;
+	buf = malloc(size);
+	for (ptr = buf; ptr < buf + size; ptr += PAGE_SIZE)
+		*ptr = 0;
 
 	while (getppid() == ppid)
 		sleep(1);
 
+	free(buf);
 	return 0;
 }
 
_

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

selftests-cgroup-return-errno-from-cg_read-cg_write-on-failure.patch
selftests-cgroup-fix-alloc_anon_noexit-instantly-freeing-memory.patch
selftests-cgroup-add-a-selftest-for-memoryreclaim.patch