[PATCH] io_uring: add more uring info to fdinfo for debug

Hao Xu
2021-09-13T13:09:12Z

Developers may need some uring info to help themselves debug and address
issues, these info includes sqring/cqring head/tail and the detail
sqe/cqe info, which is very useful when it stucks.

Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
---
fs/io_uring.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 55 insertions(+), 4 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index f795ad281038..ac048592a3e8 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9950,8 +9950,48 @@ static int io_uring_show_cred(struct seq_file *m, unsigned int id,
static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
{
struct io_sq_data *sq = NULL;
+ struct io_overflow_cqe *ocqe;
+ struct io_rings *r = ctx->rings;
+ unsigned int sq_mask = ctx->sq_entries - 1, cq_mask = ctx->cq_entries - 1;
+ unsigned int cached_sq_head = ctx->cached_sq_head;
+ unsigned int cached_cq_tail = ctx->cached_cq_tail;
+ unsigned int sq_head = READ_ONCE(r->sq.head);
+ unsigned int sq_tail = READ_ONCE(r->sq.tail);
+ unsigned int cq_head = READ_ONCE(r->cq.head);
+ unsigned int cq_tail = READ_ONCE(r->cq.tail);
bool has_lock;
- int i;
+ unsigned int i;
+
+ /*
+ * we may get imprecise sqe and cqe info if uring is actively running
+ * since we get cached_sq_head and cached_cq_tail without uring_lock
+ * and sq_tail and cq_head are changed by userspace. But it's ok since
+ * we usually use these info when it is stuck.
+ */
+ seq_printf(m, "SqHead:\t%u\n", sq_head & sq_mask);
+ seq_printf(m, "SqTail:\t%u\n", sq_tail & sq_mask);
+ seq_printf(m, "CachedSqHead:\t%u\n", cached_sq_head & sq_mask);
+ seq_printf(m, "CqHead:\t%u\n", cq_head & cq_mask);
+ seq_printf(m, "CqTail:\t%u\n", cq_tail & cq_mask);
+ seq_printf(m, "CachedCqTail:\t%u\n", cached_cq_tail & cq_mask);
+ seq_printf(m, "SQEs:\t%u\n", sq_tail - cached_sq_head);
+ for (i = cached_sq_head; i < sq_tail; i++) {
+ unsigned int sq_idx = READ_ONCE(ctx->sq_array[i & sq_mask]);
+
+ if (likely(sq_idx <= sq_mask)) {
+ struct io_uring_sqe *sqe = &ctx->sq_sqes[sq_idx];
+
+ seq_printf(m, "%5u: opcode:%d, fd:%d, flags:%x, user_data:%llu\n",
+ sq_idx, sqe->opcode, sqe->fd, sqe->flags, sqe->user_data);
+ }
+ }
+ seq_printf(m, "CQEs:\t%u\n", cached_cq_tail - cq_head);
+ for (i = cq_head; i < cached_cq_tail; i++) {
+ struct io_uring_cqe *cqe = &r->cqes[i & cq_mask];
+
+ seq_printf(m, "%5u: user_data:%llu, res:%d, flag:%x\n",
+ i & cq_mask, cqe->user_data, cqe->res, cqe->flags);
+ }

/*
* Avoid ABBA deadlock between the seq lock and the io_uring mutex,
@@ -9993,7 +10033,10 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
xa_for_each(&ctx->personalities, index, cred)
io_uring_show_cred(m, index, cred);
}
- seq_printf(m, "PollList:\n");
+ if (has_lock)
+ mutex_unlock(&ctx->uring_lock);
+
+ seq_puts(m, "PollList:\n");
spin_lock(&ctx->completion_lock);
for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) {
struct hlist_head *list = &ctx->cancel_hash[i];
@@ -10003,9 +10046,17 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
seq_printf(m, " op=%d, task_works=%d\n", req->opcode,
req->task->task_works != NULL);
}
+
+ seq_puts(m, "CqOverflowList:\n");
+ list_for_each_entry(ocqe, &ctx->cq_overflow_list, list) {
+ struct io_uring_cqe *cqe = &ocqe->cqe;
+
+ seq_printf(m, " user_data=%llu, res=%d, flags=%x\n",
+ cqe->user_data, cqe->res, cqe->flags);
+
+ }
+
spin_unlock(&ctx->completion_lock);
- if (has_lock)
- mutex_unlock(&ctx->uring_lock);
}

static void io_uring_show_fdinfo(struct seq_file *m, struct file *f)
--
2.24.4