On 8/6/22 12:40 AM, Hou Tao wrote:
From: Hou Tao <houtao1@xxxxxxxxxx>
After closing both related link fd and map fd, reading the map
iterator fd to ensure it is OK to do so.
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
.../selftests/bpf/prog_tests/bpf_iter.c | 90 +++++++++++++++++++
1 file changed, 90 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
index a33874b081b6..94c2c8df3fe4 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
@@ -28,6 +28,7 @@
#include "bpf_iter_test_kern6.skel.h"
#include "bpf_iter_bpf_link.skel.h"
#include "bpf_iter_ksym.skel.h"
+#include "bpf_iter_sockmap.skel.h"
static int duration;
@@ -67,6 +68,48 @@ static void do_dummy_read(struct bpf_program *prog)
bpf_link__destroy(link);
}
+static void do_read_map_iter_fd(struct bpf_object_skeleton **skel, struct bpf_program *prog,
+ struct bpf_map *map)
+{
+ DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
+ union bpf_iter_link_info linfo;
+ struct bpf_link *link;
+ char buf[16] = {};
+ int iter_fd, len;
+
+ memset(&linfo, 0, sizeof(linfo));
+ linfo.map.map_fd = bpf_map__fd(map);
+ opts.link_info = &linfo;
+ opts.link_info_len = sizeof(linfo);
+ link = bpf_program__attach_iter(prog, &opts);
+ if (!ASSERT_OK_PTR(link, "attach_map_iter"))
+ return;
+
+ iter_fd = bpf_iter_create(bpf_link__fd(link));
+ if (!ASSERT_GE(iter_fd, 0, "create_map_iter")) {
+ bpf_link__destroy(link);
+ return;
+ }
+
+ /* Close link and map fd prematurely */
+ bpf_link__destroy(link);
+ bpf_object__destroy_skeleton(*skel);
+ *skel = NULL;
+
+ /* Let kworker to run first */
Which kworker?
+ usleep(100);
+ /* Sock map is freed after two synchronize_rcu() calls, so wait */
+ kern_sync_rcu();
+ kern_sync_rcu();
In btf_map_in_map.c, the comment mentions two kern_sync_rcu()
is needed for 5.8 and earlier kernel. Other cases in prog_tests/
directory only has one kern_sync_rcu(). Why we need two
kern_sync_rcu() for the current kernel?
+
+ /* Read after both map fd and link fd are closed */
+ while ((len = read(iter_fd, buf, sizeof(buf))) > 0)
+ ;
+ ASSERT_GE(len, 0, "read_iterator");
+
+ close(iter_fd);
+}
+
static int read_fd_into_buffer(int fd, char *buf, int size)
{
int bufleft = size;
@@ -827,6 +870,20 @@ static void test_bpf_array_map(void)
bpf_iter_bpf_array_map__destroy(skel);
}
+static void test_bpf_array_map_iter_fd(void)
+{
+ struct bpf_iter_bpf_array_map *skel;
+
+ skel = bpf_iter_bpf_array_map__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "bpf_iter_bpf_array_map__open_and_load"))
+ return;
+
+ do_read_map_iter_fd(&skel->skeleton, skel->progs.dump_bpf_array_map,
+ skel->maps.arraymap1);
+
+ bpf_iter_bpf_array_map__destroy(skel);
+}
+
[...]
