[PATCH bpf-next v3 08/10] selftests/bpf: Test partial reads for io_uring, epoll iterators

Kumar Kartikeya Dwivedi
2021-12-01T04:24:43Z

Ensure that the output is consistent in face of partial reads that
return to userspace and then resume again later. To this end, we do
reads in 1-byte chunks, which is a bit stupid in real life, but works
well to simulate interrupted iteration. This also tests case where
seq_file buffer is consumed (after seq_printf) on interrupted read
before iterator invoked BPF prog again.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
.../selftests/bpf/prog_tests/bpf_iter.c | 33 ++++++++++++-------
1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
index cc0555c5b373..3a07fdf31874 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
@@ -73,13 +73,13 @@ static void do_dummy_read(struct bpf_program *prog)
bpf_link__destroy(link);
}

-static int read_fd_into_buffer(int fd, char *buf, int size)
+static int __read_fd_into_buffer(int fd, char *buf, int size, size_t chunks)
{
int bufleft = size;
int len;

do {
- len = read(fd, buf, bufleft);
+ len = read(fd, buf, chunks ?: bufleft);
if (len > 0) {
buf += len;
bufleft -= len;
@@ -89,6 +89,11 @@ static int read_fd_into_buffer(int fd, char *buf, int size)
return len < 0 ? len : size - bufleft;
}

+static int read_fd_into_buffer(int fd, char *buf, int size)
+{
+ return __read_fd_into_buffer(fd, buf, size, 0);
+}
+
static void test_ipv6_route(void)
{
struct bpf_iter_ipv6_route *skel;
@@ -1301,7 +1306,7 @@ static int io_uring_inode_match(int link_fd, int io_uring_fd)
return 0;
}

-void test_io_uring_buf(void)
+void test_io_uring_buf(bool partial)
{
DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
char rbuf[4096], buf[4096] = "B\n";
@@ -1375,7 +1380,7 @@ void test_io_uring_buf(void)
if (!ASSERT_GE(iter_fd, 0, "bpf_iter_create"))
goto end_close_fd;

- ret = read_fd_into_buffer(iter_fd, rbuf, sizeof(rbuf));
+ ret = __read_fd_into_buffer(iter_fd, rbuf, sizeof(rbuf), partial);
if (!ASSERT_GT(ret, 0, "read_fd_into_buffer"))
goto end_close_iter;

@@ -1396,7 +1401,7 @@ void test_io_uring_buf(void)
bpf_iter_io_uring__destroy(skel);
}

-void test_io_uring_file(void)
+void test_io_uring_file(bool partial)
{
int reg_files[] = { [0 ... 7] = -1 };
DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
@@ -1464,7 +1469,7 @@ void test_io_uring_file(void)
if (!ASSERT_OK(ret, "io_uring_register_files"))
goto end_iter_fd;

- ret = read_fd_into_buffer(iter_fd, rbuf, sizeof(rbuf));
+ ret = __read_fd_into_buffer(iter_fd, rbuf, sizeof(rbuf), partial);
if (!ASSERT_GT(ret, 0, "read_fd_into_buffer(iterator_fd, buf)"))
goto end_iter_fd;

@@ -1488,7 +1493,7 @@ void test_io_uring_file(void)
bpf_iter_io_uring__destroy(skel);
}

-void test_epoll(void)
+void test_epoll(bool partial)
{
const char *fmt = "B\npipe:%d\nsocket:%d\npipe:%d\nsocket:%d\nE\n";
DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
@@ -1554,7 +1559,7 @@ void test_epoll(void)
if (!ASSERT_GE(ret, 0, "snprintf") || !ASSERT_LT(ret, sizeof(buf), "snprintf"))
goto end_iter_fd;

- ret = read_fd_into_buffer(iter_fd, rbuf, sizeof(rbuf));
+ ret = __read_fd_into_buffer(iter_fd, rbuf, sizeof(rbuf), partial);
if (!ASSERT_GT(ret, 0, "read_fd_into_buffer"))
goto end_iter_fd;

@@ -1666,9 +1671,15 @@ void test_bpf_iter(void)
if (test__start_subtest("buf-neg-offset"))
test_buf_neg_offset();
if (test__start_subtest("io_uring_buf"))
- test_io_uring_buf();
+ test_io_uring_buf(false);
if (test__start_subtest("io_uring_file"))
- test_io_uring_file();
+ test_io_uring_file(false);
if (test__start_subtest("epoll"))
- test_epoll();
+ test_epoll(false);
+ if (test__start_subtest("io_uring_buf-partial"))
+ test_io_uring_buf(true);
+ if (test__start_subtest("io_uring_file-partial"))
+ test_io_uring_file(true);
+ if (test__start_subtest("epoll-partial"))
+ test_epoll(true);
}
--
2.34.1