+ mm-memcg-cg2-memoryswappeak-write-tests.patch added to mm-unstable branch

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

The patch titled
     Subject: mm, memcg: cg2 memory{.swap,}.peak write tests
has been added to the -mm mm-unstable branch.  Its filename is
     mm-memcg-cg2-memoryswappeak-write-tests.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memcg-cg2-memoryswappeak-write-tests.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: David Finkel <davidf@vimeo.com>
Subject: mm, memcg: cg2 memory{.swap,}.peak write tests
Date: Tue, 23 Jul 2024 19:31:49 -0400

Extend two existing tests to cover extracting memory usage through the
newly mutable memory.peak and memory.swap.peak handlers.

In particular, make sure to exercise adding and removing watchers with
overlapping lifetimes so the less-trivial logic gets tested.

Link: https://lkml.kernel.org/r/20240723233149.3226636-3-davidf@vimeo.com
Signed-off-by: David Finkel <davidf@vimeo.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/cgroup/cgroup_util.c     |   22 +
 tools/testing/selftests/cgroup/cgroup_util.h     |    2 
 tools/testing/selftests/cgroup/test_memcontrol.c |  226 ++++++++++++-
 3 files changed, 242 insertions(+), 8 deletions(-)

--- a/tools/testing/selftests/cgroup/cgroup_util.c~mm-memcg-cg2-memoryswappeak-write-tests
+++ a/tools/testing/selftests/cgroup/cgroup_util.c
@@ -141,6 +141,16 @@ long cg_read_long(const char *cgroup, co
 	return atol(buf);
 }
 
+long cg_read_long_fd(int fd)
+{
+	char buf[128];
+
+	if (pread(fd, buf, sizeof(buf), 0) <= 0)
+		return -1;
+
+	return atol(buf);
+}
+
 long cg_read_key_long(const char *cgroup, const char *control, const char *key)
 {
 	char buf[PAGE_SIZE];
@@ -183,6 +193,18 @@ int cg_write(const char *cgroup, const c
 	return ret == len ? 0 : ret;
 }
 
+/*
+ * Returns fd on success, or -1 on failure.
+ * (fd should be closed with close() as usual)
+ */
+int cg_open(const char *cgroup, const char *control, int flags)
+{
+	char path[PATH_MAX];
+
+	snprintf(path, sizeof(path), "%s/%s", cgroup, control);
+	return open(path, flags);
+}
+
 int cg_write_numeric(const char *cgroup, const char *control, long value)
 {
 	char buf[64];
--- a/tools/testing/selftests/cgroup/cgroup_util.h~mm-memcg-cg2-memoryswappeak-write-tests
+++ a/tools/testing/selftests/cgroup/cgroup_util.h
@@ -34,9 +34,11 @@ extern int cg_read_strcmp(const char *cg
 extern int cg_read_strstr(const char *cgroup, const char *control,
 			  const char *needle);
 extern long cg_read_long(const char *cgroup, const char *control);
+extern long cg_read_long_fd(int fd);
 long cg_read_key_long(const char *cgroup, const char *control, const char *key);
 extern long cg_read_lc(const char *cgroup, const char *control);
 extern int cg_write(const char *cgroup, const char *control, char *buf);
+extern int cg_open(const char *cgroup, const char *control, int flags);
 int cg_write_numeric(const char *cgroup, const char *control, long value);
 extern int cg_run(const char *cgroup,
 		  int (*fn)(const char *cgroup, void *arg),
--- a/tools/testing/selftests/cgroup/test_memcontrol.c~mm-memcg-cg2-memoryswappeak-write-tests
+++ a/tools/testing/selftests/cgroup/test_memcontrol.c
@@ -161,12 +161,12 @@ cleanup:
 /*
  * This test create a memory cgroup, allocates
  * some anonymous memory and some pagecache
- * and check memory.current and some memory.stat values.
+ * and checks memory.current, memory.peak, and some memory.stat values.
  */
-static int test_memcg_current(const char *root)
+static int test_memcg_current_peak(const char *root)
 {
 	int ret = KSFT_FAIL;
-	long current;
+	long current, peak, peak_reset;
 	char *memcg;
 
 	memcg = cg_name(root, "memcg_test");
@@ -180,15 +180,108 @@ static int test_memcg_current(const char
 	if (current != 0)
 		goto cleanup;
 
+	peak = cg_read_long(memcg, "memory.peak");
+	if (peak != 0)
+		goto cleanup;
+
 	if (cg_run(memcg, alloc_anon_50M_check, NULL))
 		goto cleanup;
 
+	peak = cg_read_long(memcg, "memory.peak");
+	if (peak < MB(50))
+		goto cleanup;
+
+	/*
+	 * We'll open a few FDs for the same memory.peak file to exercise the free-path
+	 * We need at least three to be closed in a different order than writes occurred to test
+	 * the linked-list handling.
+	 */
+	int peak_fd = cg_open(memcg, "memory.peak", O_RDWR | O_APPEND | O_CLOEXEC);
+
+	if (peak_fd == -1)
+		goto cleanup;
+
+	bool fd2_closed = false, fd3_closed = false, fd4_closed = false;
+	int peak_fd2 = cg_open(memcg, "memory.peak", O_RDWR | O_APPEND | O_CLOEXEC);
+
+	if (peak_fd2 == -1)
+		goto cleanup;
+
+	int peak_fd3 = cg_open(memcg, "memory.peak", O_RDWR | O_APPEND | O_CLOEXEC);
+
+	if (peak_fd3 == -1)
+		goto cleanup;
+
+	static const char reset_string[] = "reset\n";
+
+	peak_reset = write(peak_fd, reset_string, sizeof(reset_string));
+	if (peak_reset != sizeof(reset_string))
+		goto cleanup;
+
+	peak_reset = write(peak_fd2, reset_string, sizeof(reset_string));
+	if (peak_reset != sizeof(reset_string))
+		goto cleanup;
+
+	peak_reset = write(peak_fd3, reset_string, sizeof(reset_string));
+	if (peak_reset != sizeof(reset_string))
+		goto cleanup;
+
+	/* Make sure a completely independent read isn't affected by our  FD-local reset above*/
+	peak = cg_read_long(memcg, "memory.peak");
+	if (peak < MB(50))
+		goto cleanup;
+
+	fd2_closed = true;
+	if (close(peak_fd2))
+		goto cleanup;
+
+	int peak_fd4 = cg_open(memcg, "memory.peak", O_RDWR | O_APPEND | O_CLOEXEC);
+
+	if (peak_fd4 == -1)
+		goto cleanup;
+
+	peak_reset = write(peak_fd4, reset_string, sizeof(reset_string));
+	if (peak_reset != sizeof(reset_string))
+		goto cleanup;
+
+	peak = cg_read_long_fd(peak_fd);
+	if (peak > MB(30) || peak < 0)
+		goto cleanup;
+
 	if (cg_run(memcg, alloc_pagecache_50M_check, NULL))
 		goto cleanup;
 
+	peak = cg_read_long(memcg, "memory.peak");
+	if (peak < MB(50))
+		goto cleanup;
+
+	/* Make sure everything is back to normal */
+	peak = cg_read_long_fd(peak_fd);
+	if (peak < MB(50))
+		goto cleanup;
+
+	peak = cg_read_long_fd(peak_fd4);
+	if (peak < MB(50))
+		goto cleanup;
+
+	fd3_closed = true;
+	if (close(peak_fd3))
+		goto cleanup;
+
+	fd4_closed = true;
+	if (close(peak_fd4))
+		goto cleanup;
+
 	ret = KSFT_PASS;
 
 cleanup:
+	close(peak_fd);
+	if (!fd2_closed)
+		close(peak_fd2);
+	if (!fd3_closed)
+		close(peak_fd3);
+	if (!fd4_closed)
+		close(peak_fd4);
 	cg_destroy(memcg);
 	free(memcg);
 
@@ -817,13 +910,16 @@ cleanup:
 
 /*
  * This test checks that memory.swap.max limits the amount of
- * anonymous memory which can be swapped out.
+ * anonymous memory which can be swapped out. Additionally, it verifies that
+ * memory.swap.peak reflects the high watermark and can be reset.
  */
-static int test_memcg_swap_max(const char *root)
+static int test_memcg_swap_max_peak(const char *root)
 {
 	int ret = KSFT_FAIL;
 	char *memcg;
-	long max;
+	long max, peak;
+
+	static const char reset_string[] = "reset\n";
 
 	if (!is_swap_enabled())
 		return KSFT_SKIP;
@@ -840,6 +936,45 @@ static int test_memcg_swap_max(const cha
 		goto cleanup;
 	}
 
+	int swap_peak_fd = cg_open(memcg, "memory.swap.peak",
+				   O_RDWR | O_APPEND | O_CLOEXEC);
+
+	if (swap_peak_fd == -1)
+		goto cleanup;
+
+	int mem_peak_fd = cg_open(memcg, "memory.peak", O_RDWR | O_APPEND | O_CLOEXEC);
+
+	if (mem_peak_fd == -1)
+		goto cleanup;
+
+	if (cg_read_long(memcg, "memory.swap.peak"))
+		goto cleanup;
+
+	if (cg_read_long_fd(swap_peak_fd))
+		goto cleanup;
+
+	/* switch the swap and mem fds into local-peak tracking mode*/
+	int peak_reset = write(swap_peak_fd, reset_string, sizeof(reset_string));
+
+	if (peak_reset != sizeof(reset_string))
+		goto cleanup;
+
+	if (cg_read_long_fd(swap_peak_fd))
+		goto cleanup;
+
+	if (cg_read_long(memcg, "memory.peak"))
+		goto cleanup;
+
+	if (cg_read_long_fd(mem_peak_fd))
+		goto cleanup;
+
+	peak_reset = write(mem_peak_fd, reset_string, sizeof(reset_string));
+	if (peak_reset != sizeof(reset_string))
+		goto cleanup;
+
+	if (cg_read_long_fd(mem_peak_fd))
+		goto cleanup;
+
 	if (cg_read_strcmp(memcg, "memory.max", "max\n"))
 		goto cleanup;
 
@@ -862,6 +997,61 @@ static int test_memcg_swap_max(const cha
 	if (cg_read_key_long(memcg, "memory.events", "oom_kill ") != 1)
 		goto cleanup;
 
+	peak = cg_read_long(memcg, "memory.peak");
+	if (peak < MB(29))
+		goto cleanup;
+
+	peak = cg_read_long(memcg, "memory.swap.peak");
+	if (peak < MB(29))
+		goto cleanup;
+
+	peak = cg_read_long_fd(mem_peak_fd);
+	if (peak < MB(29))
+		goto cleanup;
+
+	peak = cg_read_long_fd(swap_peak_fd);
+	if (peak < MB(29))
+		goto cleanup;
+
+	/*
+	 * open, reset and close the peak swap on another FD to make sure
+	 * multiple extant fds don't corrupt the linked-list
+	 */
+	peak_reset = cg_write(memcg, "memory.swap.peak", (char *)reset_string);
+	if (peak_reset)
+		goto cleanup;
+
+	peak_reset = cg_write(memcg, "memory.peak", (char *)reset_string);
+	if (peak_reset)
+		goto cleanup;
+
+	/* actually reset on the fds */
+	peak_reset = write(swap_peak_fd, reset_string, sizeof(reset_string));
+	if (peak_reset != sizeof(reset_string))
+		goto cleanup;
+
+	peak_reset = write(mem_peak_fd, reset_string, sizeof(reset_string));
+	if (peak_reset != sizeof(reset_string))
+		goto cleanup;
+
+	peak = cg_read_long_fd(swap_peak_fd);
+	if (peak > MB(10))
+		goto cleanup;
+
+	/*
+	 * The cgroup is now empty, but there may be a page or two associated
+	 * with the open FD accounted to it.
+	 */
+	peak = cg_read_long_fd(mem_peak_fd);
+	if (peak > MB(1))
+		goto cleanup;
+
+	if (cg_read_long(memcg, "memory.peak") < MB(29))
+		goto cleanup;
+
+	if (cg_read_long(memcg, "memory.swap.peak") < MB(29))
+		goto cleanup;
+
 	if (cg_run(memcg, alloc_anon_50M_check_swap, (void *)MB(30)))
 		goto cleanup;
 
@@ -869,9 +1059,29 @@ static int test_memcg_swap_max(const cha
 	if (max <= 0)
 		goto cleanup;
 
+	peak = cg_read_long(memcg, "memory.peak");
+	if (peak < MB(29))
+		goto cleanup;
+
+	peak = cg_read_long(memcg, "memory.swap.peak");
+	if (peak < MB(29))
+		goto cleanup;
+
+	peak = cg_read_long_fd(mem_peak_fd);
+	if (peak < MB(29))
+		goto cleanup;
+
+	peak = cg_read_long_fd(swap_peak_fd);
+	if (peak < MB(19))
+		goto cleanup;
+
 	ret = KSFT_PASS;
 
 cleanup:
+	if (close(mem_peak_fd))
+		ret = KSFT_FAIL;
+	if (close(swap_peak_fd))
+		ret = KSFT_FAIL;
 	cg_destroy(memcg);
 	free(memcg);
 
@@ -1295,7 +1505,7 @@ struct memcg_test {
 	const char *name;
 } tests[] = {
 	T(test_memcg_subtree_control),
-	T(test_memcg_current),
+	T(test_memcg_current_peak),
 	T(test_memcg_min),
 	T(test_memcg_low),
 	T(test_memcg_high),
@@ -1303,7 +1513,7 @@ struct memcg_test {
 	T(test_memcg_max),
 	T(test_memcg_reclaim),
 	T(test_memcg_oom_events),
-	T(test_memcg_swap_max),
+	T(test_memcg_swap_max_peak),
 	T(test_memcg_sock),
 	T(test_memcg_oom_group_leaf_events),
 	T(test_memcg_oom_group_parent_events),
_

Patches currently in -mm which might be from davidf@vimeo.com are

mm-memcg-cg2-memoryswappeak-write-handlers.patch
mm-memcg-cg2-memoryswappeak-write-tests.patch