[PATCH v2] add tests for drain io with multishot reqs

[Hao Xu <haoxu@linux.alibaba.com>]

Add a simple test for drain io with multishot reqs. A generic one as
well, which randomly generates sqes for testing. The later will cover
most cases.

Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
---
 src/include/liburing/io_uring.h |  15 ++
 test/Makefile                   |   2 +
 test/multicqes_drain.c          | 380 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 397 insertions(+)
 create mode 100644 test/multicqes_drain.c

diff --git a/src/include/liburing/io_uring.h b/src/include/liburing/io_uring.h
index d3d166e57be8..eed991d08655 100644
--- a/src/include/liburing/io_uring.h
+++ b/src/include/liburing/io_uring.h
@@ -165,6 +165,21 @@ enum {
 #define SPLICE_F_FD_IN_FIXED	(1U << 31) /* the last bit of __u32 */
 
 /*
+ * POLL_ADD flags. Note that since sqe->poll_events is the flag space, the
+ * command flags for POLL_ADD are stored in sqe->len.
+ *
+ * IORING_POLL_ADD_MULTI        Multishot poll. Sets IORING_CQE_F_MORE if
+ *                              the poll handler will continue to report
+ *                              CQEs on behalf of the same SQE.
+ *
+ * IORING_POLL_UPDATE           Update existing poll request, matching
+ *                              sqe->addr as the old user_data field.
+ */
+#define IORING_POLL_ADD_MULTI   (1U << 0)
+#define IORING_POLL_UPDATE_EVENTS       (1U << 1)
+#define IORING_POLL_UPDATE_USER_DATA    (1U << 2)
+
+/*
  * IO completion data structure (Completion Queue Entry)
  */
 struct io_uring_cqe {
diff --git a/test/Makefile b/test/Makefile
index 210571c22b40..5ffad0309914 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -66,6 +66,7 @@ test_targets += \
 	link-timeout \
 	link_drain \
 	madvise \
+	multicqes_drain \
 	nop \
 	nop-all-sizes \
 	open-close \
@@ -202,6 +203,7 @@ test_srcs := \
 	link.c \
 	link_drain.c \
 	madvise.c \
+	multicqes_drain.c \
 	nop-all-sizes.c \
 	nop.c \
 	open-close.c \
diff --git a/test/multicqes_drain.c b/test/multicqes_drain.c
new file mode 100644
index 000000000000..4f657e5c444a
--- /dev/null
+++ b/test/multicqes_drain.c
@@ -0,0 +1,380 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Description: generic tests for  io_uring drain io
+ *
+ * The main idea is to randomly generate different type of sqe to
+ * challenge the drain logic. There are some restrictions for the
+ * generated sqes, details in io_uring maillist:
+ * https://lore.kernel.org/io-uring/39a49b4c-27c2-1035-b250-51daeccaab9b@linux.alibaba.com/
+ *
+ */
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <sys/poll.h>
+
+#include "liburing.h"
+
+enum {
+	multi,
+	single,
+	nop,
+	cancel,
+	op_last,
+};
+
+struct sqe_info {
+	__u8 op;
+	unsigned flags;
+};
+
+#define max_entry 50
+
+/*
+ * sqe_flags: combination of sqe flags
+ * multi_sqes: record the user_data/index of all the multishot sqes
+ * cnt: how many entries there are in multi_sqes
+ * we can leverage multi_sqes array for cancellation: we randomly pick
+ * up an entry in multi_sqes when form a cancellation sqe.
+ * multi_cap: limitation of number of multishot sqes
+ */
+const unsigned sqe_flags[4] = {0, IOSQE_IO_LINK, IOSQE_IO_DRAIN,
+	IOSQE_IO_LINK | IOSQE_IO_DRAIN};
+int multi_sqes[max_entry], cnt = 0;
+int multi_cap = max_entry / 5;
+
+int write_pipe(int pipe, char *str)
+{
+	int ret;
+	do {
+		errno = 0;
+		ret = write(pipe, str, 3);
+	} while (ret == -1 && errno == EINTR);
+	return ret;
+}
+
+void read_pipe(int pipe)
+{
+	char str[4] = {0};
+
+	read(pipe, &str, 3);
+}
+
+int trigger_event(int p[])
+{
+	int ret;
+	if ((ret = write_pipe(p[1], "foo")) != 3) {
+		fprintf(stderr, "bad write return %d\n", ret);
+		return 1;
+	}
+	read_pipe(p[0]);
+	return 0;
+}
+
+void io_uring_sqe_prep(int op, struct io_uring_sqe *sqe, unsigned sqe_flags, int arg)
+{
+	switch (op) {
+		case multi:
+			io_uring_prep_poll_add(sqe, arg, POLLIN);
+			sqe->len |= IORING_POLL_ADD_MULTI;
+			break;
+		case single:
+			io_uring_prep_poll_add(sqe, arg, POLLIN);
+			break;
+		case nop:
+			io_uring_prep_nop(sqe);
+			break;
+		case cancel:
+			io_uring_prep_poll_remove(sqe, (void *)(long)arg);
+			break;
+	}
+	sqe->flags = sqe_flags;
+}
+
+__u8 generate_flags(int sqe_op)
+{
+	__u8 flags = 0;
+	/*
+	 * drain sqe must be put after multishot sqes cancelled
+	 */
+	do {
+		flags = sqe_flags[rand() % 4];
+	} while ((flags & IOSQE_IO_DRAIN) && cnt);
+
+	/*
+	 * cancel req cannot have drain or link flag
+	 */
+	if (sqe_op == cancel) {
+		flags &= ~(IOSQE_IO_DRAIN | IOSQE_IO_LINK);
+	}
+	/*
+	 * avoid below case:
+	 * sqe0(multishot, link)->sqe1(nop, link)->sqe2(nop)->sqe3(cancel_sqe0)
+	 * sqe3 may excute before sqe0 so that sqe0 isn't cancelled
+	 */
+	if (sqe_op == multi)
+		flags &= ~IOSQE_IO_LINK;
+
+	return flags;
+
+}
+
+/*
+ * function to generate opcode of a sqe
+ * several restrictions here:
+ * - cancel all the previous multishot sqes as soon as possible when
+ *   we reach high watermark.
+ * - ensure there is some multishot sqe when generating a cancel sqe
+ * - ensure a cancel/multshot sqe is not in a linkchain
+ * - ensure number of multishot sqes doesn't exceed multi_cap
+ * - don't generate multishot sqes after high watermark
+ */
+int generate_opcode(int i, int pre_flags)
+{
+	int sqe_op;
+	int high_watermark = max_entry - max_entry / 5;
+	bool retry0 = false, retry1 = false, retry2 = false;
+
+	if ((i >= high_watermark) && cnt) {
+		sqe_op = cancel;
+	} else {
+		do {
+			sqe_op = rand() % op_last;
+			retry0 = (sqe_op == cancel) && (!cnt || (pre_flags & IOSQE_IO_LINK));
+			retry1 = (sqe_op == multi) && ((multi_cap - 1 < 0) || i >= high_watermark);
+			retry2 = (sqe_op == multi) && (pre_flags & IOSQE_IO_LINK);
+		} while (retry0 || retry1 || retry2);
+	}
+
+	if (sqe_op == multi)
+		multi_cap--;
+	return sqe_op;
+}
+
+inline void add_multishot_sqe(int index)
+{
+	multi_sqes[cnt++] = index;
+}
+
+int remove_multishot_sqe()
+{
+	int ret;
+
+	int rem_index = rand() % cnt;
+	ret = multi_sqes[rem_index];
+	multi_sqes[rem_index] = multi_sqes[cnt - 1];
+	cnt--;
+
+	return ret;
+}
+
+static int test_generic_drain(struct io_uring *ring)
+{
+	struct io_uring_cqe *cqe;
+	struct io_uring_sqe *sqe[max_entry];
+	struct sqe_info si[max_entry];
+	int cqe_data[max_entry << 1], cqe_res[max_entry << 1];
+	int i, j, ret, arg = 0;
+	int pipes[max_entry][2];
+	int pre_flags = 0;
+
+	for (i = 0; i < max_entry; i++) {
+		if (pipe(pipes[i]) != 0) {
+			perror("pipe");
+			return 1;
+		}
+	}
+
+	srand((unsigned)time(NULL));
+	for (i = 0; i < max_entry; i++) {
+		sqe[i] = io_uring_get_sqe(ring);
+		if (!sqe[i]) {
+			printf("get sqe failed\n");
+			goto err;
+		}
+
+		int sqe_op = generate_opcode(i, pre_flags);
+		__u8 flags = generate_flags(sqe_op);
+
+		if (sqe_op == cancel)
+			arg = remove_multishot_sqe();
+		if (sqe_op == multi || sqe_op == single)
+			arg = pipes[i][0];
+		io_uring_sqe_prep(sqe_op, sqe[i], flags, arg);
+		sqe[i]->user_data = i;
+		si[i].op = sqe_op;
+		si[i].flags = flags;
+		pre_flags = flags;
+		if (sqe_op == multi)
+			add_multishot_sqe(i);
+	}
+
+	ret = io_uring_submit(ring);
+	if (ret < 0) {
+		printf("sqe submit failed\n");
+		goto err;
+	} else if (ret < max_entry) {
+		printf("Submitted only %d\n", ret);
+		goto err;
+	}
+
+	sleep(4);
+	// TODO: randomize event triggerring order
+	for (i = 0; i < max_entry; i++) {
+		if (si[i].op != multi && si[i].op != single)
+			continue;
+
+		if (trigger_event(pipes[i]))
+			goto err;
+	}
+	sleep(5);
+	i = 0;
+	while (!io_uring_peek_cqe(ring, &cqe)) {
+		cqe_data[i] = cqe->user_data;
+		cqe_res[i++] = cqe->res;
+		io_uring_cqe_seen(ring, cqe);
+	}
+
+	/*
+	 * compl_bits is a bit map to record completions.
+	 * eg. sqe[0], sqe[1], sqe[2] fully completed
+	 * then compl_bits is 000...00111b
+	 * 
+	 */
+	unsigned long long compl_bits = 0;
+	for (j = 0; j < i; j++) {
+		int index = cqe_data[j];
+		if ((si[index].flags & IOSQE_IO_DRAIN) && index) {
+			if ((~compl_bits) & ((1ULL << index) - 1)) {
+				printf("drain failed\n");
+				goto err;
+			}
+		}
+		/*
+		 * for multishot sqes, record them only when it is cancelled
+		 */
+		if ((si[index].op != multi) || (cqe_res[j] == -ECANCELED))
+			compl_bits |= (1ULL << index);
+	}
+
+	return 0;
+err:
+	return 1;
+}
+
+static int test_simple_drain(struct io_uring *ring)
+{
+	struct io_uring_cqe *cqe;
+	struct io_uring_sqe *sqe[2];
+	int i, ret;
+	int pipe1[2], pipe2[2];
+
+	if (pipe(pipe1) != 0 || pipe(pipe2) != 0) {
+		perror("pipe");
+		return 1;
+	}
+
+	for (i = 0; i < 2; i++) {
+		sqe[i] = io_uring_get_sqe(ring);
+		if (!sqe[i]) {
+			printf("get sqe failed\n");
+			goto err;
+		}
+	}
+
+	io_uring_prep_poll_add(sqe[0], pipe1[0], POLLIN);
+	sqe[0]->len |= IORING_POLL_ADD_MULTI;
+	sqe[0]->user_data = 0;
+	io_uring_prep_poll_add(sqe[1], pipe2[0], POLLIN);
+	sqe[1]->user_data = 1;
+
+	ret = io_uring_submit(ring);
+	if (ret < 0) {
+		printf("sqe submit failed\n");
+		goto err;
+	} else if (ret < 2) {
+		printf("Submitted only %d\n", ret);
+		goto err;
+	}
+
+	for (i = 0; i < 2; i++) {
+		if (trigger_event(pipe1))
+			goto err;
+	}
+	if (trigger_event(pipe2))
+			goto err;
+
+	for (i = 0; i < 2; i++) {
+		sqe[i] = io_uring_get_sqe(ring);
+		if (!sqe[i]) {
+			printf("get sqe failed\n");
+			goto err;
+		}
+	}
+
+	io_uring_prep_poll_remove(sqe[0], 0);
+	sqe[0]->user_data = 2;
+	io_uring_prep_nop(sqe[1]);
+	sqe[1]->flags |= IOSQE_IO_DRAIN;
+	sqe[1]->user_data = 3;
+
+	ret = io_uring_submit(ring);
+	if (ret < 0) {
+		printf("sqe submit failed\n");
+		goto err;
+	} else if (ret < 2) {
+		printf("Submitted only %d\n", ret);
+		goto err;
+	}
+
+
+	for (i = 0; i < 6; i++) {
+		ret = io_uring_wait_cqe(ring, &cqe);
+		if (ret < 0) {
+			printf("wait completion %d\n", ret);
+			goto err;
+		}
+		io_uring_cqe_seen(ring, cqe);
+		if ((i == 5) && (cqe->user_data != 3))
+			goto err;
+	}
+
+	return 0;
+err:
+	return 1;
+}
+
+int main(int argc, char *argv[])
+{
+	struct io_uring ring;
+	int i, ret;
+
+	if (argc > 1)
+		return 0;
+
+	ret = io_uring_queue_init(1024, &ring, 0);
+	if (ret) {
+		printf("ring setup failed\n");
+		return 1;
+	}
+
+	for (i = 0; i < 5; i++) {
+		ret = test_simple_drain(&ring);
+		if (ret) {
+			fprintf(stderr, "test_simple_drain failed\n");
+			break;
+		}
+	}
+
+	for (i = 0; i < 5; i++) {
+		ret = test_generic_drain(&ring);
+		if (ret) {
+			fprintf(stderr, "test_generic_drain failed\n");
+			break;
+		}
+	}
+	return ret;
+}
-- 
1.8.3.1