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

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

ping...
在 2021/9/13 下午9:08, Hao Xu 写道:
> 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)
>