Re: [PATCH v7 8/8] selftests/cgroup: test_zswap: wait for asynchronous writeback

["Michal Koutný" <mkoutny@suse.com>]

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On Fri, Apr 24, 2026 at 12:00:59PM +0800, Li Wang <li.wang@linux.dev> wrote:
> @@ -345,7 +366,10 @@ static int test_zswap_writeback_one(const char *cgroup, bool wb)
>  		return -1;
>  
>  	/* Verify that zswap writeback occurred only if writeback was enabled */
> -	zswpwb_after = get_cg_wb_count(cgroup);
> +	if (wb)
> +		zswpwb_after = wait_for_writeback(cgroup, 5000);

We should have something like
	cg_read_key_long_poll(cgroup,
	                      "memory.stat",
			      "zswpwb",
			      0,
			      500,
	                      DEFAULT_WAIT_INTERVAL_US);
for this.

Although this also needs further change like (and respective adjustment):

diff --git a/tools/testing/selftests/cgroup/lib/cgroup_util.c b/tools/testing/selftests/cgroup/lib/cgroup_util.c
index a7b3380d88d77..c0511853db9c6 100644
--- a/tools/testing/selftests/cgroup/lib/cgroup_util.c
+++ b/tools/testing/selftests/cgroup/lib/cgroup_util.c
@@ -188,8 +188,8 @@ long cg_read_key_long(const char *cgroup, const char *control, const char *key)
 }

 long cg_read_key_long_poll(const char *cgroup, const char *control,
-                          const char *key, long expected, int retries,
-                          useconds_t wait_interval_us)
+                          const char *key, enum exp_op expected_op, long expected,
+                          int retries, useconds_t wait_interval_us)
 {
        long val = -1;
        int i;
@@ -199,7 +199,9 @@ long cg_read_key_long_poll(const char *cgroup, const char *control,
                if (val < 0)
                        return val;

-               if (val == expected)
+               if (expected_op == EXP_EQUAL && val == expected)
+                       break;
+               if (expected_op == EXP_GT && val > expected)
                        break;

                usleep(wait_interval_us);
diff --git a/tools/testing/selftests/cgroup/lib/include/cgroup_util.h b/tools/testing/selftests/cgroup/lib/include/cgroup_util.h
index 567b1082974c5..3e9bfb66cf5a9 100644
--- a/tools/testing/selftests/cgroup/lib/include/cgroup_util.h
+++ b/tools/testing/selftests/cgroup/lib/include/cgroup_util.h
@@ -19,6 +19,11 @@

 #define DEFAULT_WAIT_INTERVAL_US (100 * 1000) /* 100 ms */

+enum exp_op {
+       EXP_EQUAL,
+       EXP_GT,
+};
+
 /*
  * Checks if two given values differ by less than err% of their sum.
  */
@@ -69,8 +74,8 @@ 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);
 long cg_read_key_long_poll(const char *cgroup, const char *control,
-                          const char *key, long expected, int retries,
-                          useconds_t wait_interval_us);
+                          const char *key, enum exp_op expected_op, long expected,
+                          int retries, useconds_t wait_interval_us);
 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);

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