+ selftests-test_zswap-add-test-for-hierarchical-zswapwriteback.patch added to mm-unstable branch

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

The patch titled
     Subject: selftests: test_zswap: add test for hierarchical zswap.writeback
has been added to the -mm mm-unstable branch.  Its filename is
     selftests-test_zswap-add-test-for-hierarchical-zswapwriteback.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-test_zswap-add-test-for-hierarchical-zswapwriteback.patch

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

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 via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: Mike Yuan <me@yhndnzj.com>
Subject: selftests: test_zswap: add test for hierarchical zswap.writeback
Date: Fri, 16 Aug 2024 14:44:19 +0000

Ensure that zswap.writeback check goes up the cgroup tree.

Link: https://lkml.kernel.org/r/20240816144344.18135-2-me@yhndnzj.com
Signed-off-by: Mike Yuan <me@yhndnzj.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/cgroup/test_zswap.c |   69 ++++++++++++------
 1 file changed, 48 insertions(+), 21 deletions(-)

--- a/tools/testing/selftests/cgroup/test_zswap.c~selftests-test_zswap-add-test-for-hierarchical-zswapwriteback
+++ a/tools/testing/selftests/cgroup/test_zswap.c
@@ -263,15 +263,13 @@ out:
 static int attempt_writeback(const char *cgroup, void *arg)
 {
 	long pagesize = sysconf(_SC_PAGESIZE);
-	char *test_group = arg;
 	size_t memsize = MB(4);
 	char buf[pagesize];
 	long zswap_usage;
-	bool wb_enabled;
+	bool wb_enabled = *(bool *) arg;
 	int ret = -1;
 	char *mem;
 
-	wb_enabled = cg_read_long(test_group, "memory.zswap.writeback");
 	mem = (char *)malloc(memsize);
 	if (!mem)
 		return ret;
@@ -288,12 +286,12 @@ static int attempt_writeback(const char
 		memcpy(&mem[i], buf, pagesize);
 
 	/* Try and reclaim allocated memory */
-	if (cg_write_numeric(test_group, "memory.reclaim", memsize)) {
+	if (cg_write_numeric(cgroup, "memory.reclaim", memsize)) {
 		ksft_print_msg("Failed to reclaim all of the requested memory\n");
 		goto out;
 	}
 
-	zswap_usage = cg_read_long(test_group, "memory.zswap.current");
+	zswap_usage = cg_read_long(cgroup, "memory.zswap.current");
 
 	/* zswpin */
 	for (int i = 0; i < memsize; i += pagesize) {
@@ -303,7 +301,7 @@ static int attempt_writeback(const char
 		}
 	}
 
-	if (cg_write_numeric(test_group, "memory.zswap.max", zswap_usage/2))
+	if (cg_write_numeric(cgroup, "memory.zswap.max", zswap_usage/2))
 		goto out;
 
 	/*
@@ -312,7 +310,7 @@ static int attempt_writeback(const char
 	 * If writeback is disabled, memory reclaim will fail as zswap is limited and
 	 * it can't writeback to swap.
 	 */
-	ret = cg_write_numeric(test_group, "memory.reclaim", memsize);
+	ret = cg_write_numeric(cgroup, "memory.reclaim", memsize);
 	if (!wb_enabled)
 		ret = (ret == -EAGAIN) ? 0 : -1;
 
@@ -321,12 +319,38 @@ out:
 	return ret;
 }
 
+static int test_zswap_writeback_one(const char *cgroup, bool wb)
+{
+	long zswpwb_before, zswpwb_after;
+
+	zswpwb_before = get_cg_wb_count(cgroup);
+	if (zswpwb_before != 0) {
+		ksft_print_msg("zswpwb_before = %ld instead of 0\n", zswpwb_before);
+		return -1;
+	}
+
+	if (cg_run(cgroup, attempt_writeback, (void *) &wb))
+		return -1;
+
+	/* Verify that zswap writeback occurred only if writeback was enabled */
+	zswpwb_after = get_cg_wb_count(cgroup);
+	if (zswpwb_after < 0)
+		return -1;
+
+	if (wb != !!zswpwb_after) {
+		ksft_print_msg("zswpwb_after is %ld while wb is %s",
+				zswpwb_after, wb ? "enabled" : "disabled");
+		return -1;
+	}
+
+	return 0;
+}
+
 /* Test to verify the zswap writeback path */
 static int test_zswap_writeback(const char *root, bool wb)
 {
-	long zswpwb_before, zswpwb_after;
 	int ret = KSFT_FAIL;
-	char *test_group;
+	char *test_group, *test_group_child = NULL;
 
 	test_group = cg_name(root, "zswap_writeback_test");
 	if (!test_group)
@@ -336,29 +360,32 @@ static int test_zswap_writeback(const ch
 	if (cg_write(test_group, "memory.zswap.writeback", wb ? "1" : "0"))
 		goto out;
 
-	zswpwb_before = get_cg_wb_count(test_group);
-	if (zswpwb_before != 0) {
-		ksft_print_msg("zswpwb_before = %ld instead of 0\n", zswpwb_before);
+	if (test_zswap_writeback_one(test_group, wb))
 		goto out;
-	}
 
-	if (cg_run(test_group, attempt_writeback, (void *) test_group))
+	if (cg_write(test_group, "memory.zswap.max", "max"))
+		goto out;
+	if (cg_write(test_group, "cgroup.subtree_control", "+memory"))
 		goto out;
 
-	/* Verify that zswap writeback occurred only if writeback was enabled */
-	zswpwb_after = get_cg_wb_count(test_group);
-	if (zswpwb_after < 0)
+	test_group_child = cg_name(test_group, "zswap_writeback_test_child");
+	if (!test_group_child)
+		goto out;
+	if (cg_create(test_group_child))
+		goto out;
+	if (cg_write(test_group_child, "memory.zswap.writeback", "1"))
 		goto out;
 
-	if (wb != !!zswpwb_after) {
-		ksft_print_msg("zswpwb_after is %ld while wb is %s",
-				zswpwb_after, wb ? "enabled" : "disabled");
+	if (test_zswap_writeback_one(test_group_child, wb))
 		goto out;
-	}
 
 	ret = KSFT_PASS;
 
 out:
+	if (test_group_child) {
+		cg_destroy(test_group_child);
+		free(test_group_child);
+	}
 	cg_destroy(test_group);
 	free(test_group);
 	return ret;
_

Patches currently in -mm which might be from me@yhndnzj.com are

mm-memcontrol-respect-zswapwriteback-setting-from-parent-cg-too.patch
selftests-test_zswap-add-test-for-hierarchical-zswapwriteback.patch