io-wq: add io_wq_cancel_pid() to cancel based on a specific pid

Add a helper that allows the caller to cancel work based on what mm
it belongs to. This allows io_uring to cancel work from a given
task or thread when it exits.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io-wq.c

@@ -1029,6 +1029,35 @@ enum io_wq_cancel io_wq_cancel_work(struct io_wq *wq, struct io_wq_work *cwork)
 	return ret;
 }
 
+static bool io_wq_pid_match(struct io_wq_work *work, void *data)
+{
+	pid_t pid = (pid_t) (unsigned long) data;
+
+	if (work)
+		return work->task_pid == pid;
+	return false;
+}
+
+enum io_wq_cancel io_wq_cancel_pid(struct io_wq *wq, pid_t pid)
+{
+	struct work_match match = {
+		.fn	= io_wq_pid_match,
+		.data	= (void *) (unsigned long) pid
+	};
+	enum io_wq_cancel ret = IO_WQ_CANCEL_NOTFOUND;
+	int node;
+
+	for_each_node(node) {
+		struct io_wqe *wqe = wq->wqes[node];
+
+		ret = io_wqe_cancel_work(wqe, &match);
+		if (ret != IO_WQ_CANCEL_NOTFOUND)
+			break;
+	}
+
+	return ret;
+}
+
 struct io_wq_flush_data {
 	struct io_wq_work work;
 	struct completion done;

fs/io-wq.h

@@ -76,6 +76,7 @@ struct io_wq_work {
 	const struct cred *creds;
 	struct fs_struct *fs;
 	unsigned flags;
+	pid_t task_pid;
 };
 
 #define INIT_IO_WORK(work, _func)			\
@@ -109,6 +110,7 @@ void io_wq_flush(struct io_wq *wq);
 
 void io_wq_cancel_all(struct io_wq *wq);
 enum io_wq_cancel io_wq_cancel_work(struct io_wq *wq, struct io_wq_work *cwork);
+enum io_wq_cancel io_wq_cancel_pid(struct io_wq *wq, pid_t pid);
 
 typedef bool (work_cancel_fn)(struct io_wq_work *, void *);