From: David Vernet <void@manifault.com> To: akpm@linux-foundation.org Cc: tj@kernel.org, roman.gushchin@linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, hannes@cmpxchg.org, mhocko@kernel.org, shakeelb@google.com, kernel-team@fb.com, void@manifault.com Subject: [PATCH 5/5] cgroup: Fix racy check in alloc_pagecache_max_30M() helper function Date: Fri, 22 Apr 2022 08:57:29 -0700 [thread overview] Message-ID: <20220422155728.3055914-6-void@manifault.com> (raw) In-Reply-To: <20220422155728.3055914-1-void@manifault.com> alloc_pagecache_max_30M() in the cgroup memcg tests performs a 50MB pagecache allocation, which it expects to be capped at 30MB due to the calling process having a memory.high setting of 30MB. After the allocation, the function contains a check that verifies that MB(29) < memory.current <= MB(30). This check can actually fail non-deterministically. The testcases that use this function are test_memcg_high() and test_memcg_max(), which set memory.min and memory.max to 30MB respectively for the cgroup under test. The allocation can slightly exceed this number in both cases, and for memory.max, the process performing the allocation will not have the OOM killer invoked as it's performing a pagecache allocation. This patchset therefore updates the above check to instead use the verify_close() helper function. Signed-off-by: David Vernet <void@manifault.com> --- tools/testing/selftests/cgroup/test_memcontrol.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c index c4735fa36a3d..088850f01ae7 100644 --- a/tools/testing/selftests/cgroup/test_memcontrol.c +++ b/tools/testing/selftests/cgroup/test_memcontrol.c @@ -564,9 +564,14 @@ static int alloc_pagecache_max_30M(const char *cgroup, void *arg) { size_t size = MB(50); int ret = -1; - long current; + long current, high, max; int fd; + high = cg_read_long(cgroup, "memory.high"); + max = cg_read_long(cgroup, "memory.max"); + if (high != MB(30) && max != MB(30)) + goto cleanup; + fd = get_temp_fd(); if (fd < 0) return -1; @@ -575,7 +580,7 @@ static int alloc_pagecache_max_30M(const char *cgroup, void *arg) goto cleanup; current = cg_read_long(cgroup, "memory.current"); - if (current <= MB(29) || current > MB(30)) + if (!values_close(current, MB(30), 5)) goto cleanup; ret = 0; -- 2.30.2
WARNING: multiple messages have this Message-ID (diff)
From: David Vernet <void-gq6j2QGBifHby3iVrkZq2A@public.gmane.org> To: akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org Cc: tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, roman.gushchin-fxUVXftIFDnyG1zEObXtfA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, kernel-team-b10kYP2dOMg@public.gmane.org, void-gq6j2QGBifHby3iVrkZq2A@public.gmane.org Subject: [PATCH 5/5] cgroup: Fix racy check in alloc_pagecache_max_30M() helper function Date: Fri, 22 Apr 2022 08:57:29 -0700 [thread overview] Message-ID: <20220422155728.3055914-6-void@manifault.com> (raw) In-Reply-To: <20220422155728.3055914-1-void-gq6j2QGBifHby3iVrkZq2A@public.gmane.org> alloc_pagecache_max_30M() in the cgroup memcg tests performs a 50MB pagecache allocation, which it expects to be capped at 30MB due to the calling process having a memory.high setting of 30MB. After the allocation, the function contains a check that verifies that MB(29) < memory.current <= MB(30). This check can actually fail non-deterministically. The testcases that use this function are test_memcg_high() and test_memcg_max(), which set memory.min and memory.max to 30MB respectively for the cgroup under test. The allocation can slightly exceed this number in both cases, and for memory.max, the process performing the allocation will not have the OOM killer invoked as it's performing a pagecache allocation. This patchset therefore updates the above check to instead use the verify_close() helper function. Signed-off-by: David Vernet <void-gq6j2QGBifHby3iVrkZq2A@public.gmane.org> --- tools/testing/selftests/cgroup/test_memcontrol.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c index c4735fa36a3d..088850f01ae7 100644 --- a/tools/testing/selftests/cgroup/test_memcontrol.c +++ b/tools/testing/selftests/cgroup/test_memcontrol.c @@ -564,9 +564,14 @@ static int alloc_pagecache_max_30M(const char *cgroup, void *arg) { size_t size = MB(50); int ret = -1; - long current; + long current, high, max; int fd; + high = cg_read_long(cgroup, "memory.high"); + max = cg_read_long(cgroup, "memory.max"); + if (high != MB(30) && max != MB(30)) + goto cleanup; + fd = get_temp_fd(); if (fd < 0) return -1; @@ -575,7 +580,7 @@ static int alloc_pagecache_max_30M(const char *cgroup, void *arg) goto cleanup; current = cg_read_long(cgroup, "memory.current"); - if (current <= MB(29) || current > MB(30)) + if (!values_close(current, MB(30), 5)) goto cleanup; ret = 0; -- 2.30.2
next prev parent reply other threads:[~2022-04-22 15:58 UTC|newest] Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-04-22 15:57 [PATCH 0/5] Fix bugs in memcontroller cgroup tests David Vernet 2022-04-22 15:57 ` David Vernet 2022-04-22 15:57 ` [PATCH 1/5] cgroups: Refactor children cgroups in memcg tests David Vernet 2022-04-22 15:57 ` David Vernet 2022-04-22 23:04 ` Roman Gushchin 2022-04-22 23:04 ` Roman Gushchin 2022-04-23 11:30 ` David Vernet 2022-04-23 11:30 ` David Vernet 2022-04-23 15:19 ` Roman Gushchin 2022-04-23 15:19 ` Roman Gushchin 2022-04-23 15:33 ` David Vernet 2022-04-23 15:33 ` David Vernet 2022-04-22 15:57 ` [PATCH 2/5] cgroup: Account for memory_recursiveprot in test_memcg_low() David Vernet 2022-04-22 15:57 ` David Vernet 2022-04-22 23:06 ` Roman Gushchin 2022-04-22 23:06 ` Roman Gushchin 2022-04-23 11:33 ` David Vernet 2022-04-23 11:33 ` David Vernet 2022-04-22 15:57 ` [PATCH 3/5] cgroup: Account for memory_localevents in test_memcg_oom_group_leaf_events() David Vernet 2022-04-22 15:57 ` David Vernet 2022-04-22 23:14 ` Roman Gushchin 2022-04-22 23:14 ` Roman Gushchin 2022-04-23 11:36 ` David Vernet 2022-04-23 11:36 ` David Vernet 2022-04-22 15:57 ` [PATCH 4/5] cgroup: Removing racy check in test_memcg_sock() David Vernet 2022-04-22 15:57 ` David Vernet 2022-04-22 23:50 ` Roman Gushchin 2022-04-22 23:50 ` Roman Gushchin 2022-04-23 11:50 ` David Vernet 2022-04-23 11:50 ` David Vernet 2022-04-22 15:57 ` David Vernet [this message] 2022-04-22 15:57 ` [PATCH 5/5] cgroup: Fix racy check in alloc_pagecache_max_30M() helper function David Vernet 2022-04-22 23:56 ` Roman Gushchin 2022-04-22 23:56 ` Roman Gushchin
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