io_uring/msg_ring: Pass custom flags to the cqe

This patch adds a new flag (IORING_MSG_RING_FLAGS_PASS) in the message
ring operations (IORING_OP_MSG_RING). This new flag enables the sender
to specify custom flags, which will be copied over to cqe->flags in the
receiving ring.  These custom flags should be specified using the
sqe->file_index field.

This mechanism provides additional flexibility when sending messages
between rings.

Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20230103160507.617416-1-leitao@debian.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 2780bce62fafe63354a58df610d7c912efc870c3..636a4c2c129445a8c8cb0e8738f4d65a8c327a10 100644 (file)
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -347,6 +347,8 @@ enum {
  *                             applicable for IORING_MSG_DATA, obviously.
  */
 #define IORING_MSG_RING_CQE_SKIP       (1U << 0)
+/* Pass through the flags from sqe->file_index to cqe->flags */
+#define IORING_MSG_RING_FLAGS_PASS     (1U << 1)
 
 /*
  * IO completion data structure (Completion Queue Entry)

diff --git a/io_uring/msg_ring.c b/io_uring/msg_ring.c
index 15602a136821b510a8201f90daf541b0c9188e08..27992bda1ffafdb51080c0220f432f09f82fe7e7 100644 (file)
--- a/io_uring/msg_ring.c
+++ b/io_uring/msg_ring.c
@@ -13,6 +13,11 @@
 #include "filetable.h"
 #include "msg_ring.h"
 
+
+/* All valid masks for MSG_RING */
+#define IORING_MSG_RING_MASK           (IORING_MSG_RING_CQE_SKIP | \
+                                       IORING_MSG_RING_FLAGS_PASS)
+
 struct io_msg {
        struct file                     *file;
        struct file                     *src_file;
@@ -21,7 +26,10 @@ struct io_msg {
        u32 len;
        u32 cmd;
        u32 src_fd;
-       u32 dst_fd;
+       union {
+               u32 dst_fd;
+               u32 cqe_flags;
+       };
        u32 flags;
 };
 
@@ -114,9 +122,12 @@ static int io_msg_ring_data(struct io_kiocb *req, unsigned int issue_flags)
 {
        struct io_ring_ctx *target_ctx = req->file->private_data;
        struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
+       u32 flags = 0;
        int ret;
 
-       if (msg->src_fd || msg->dst_fd || msg->flags)
+       if (msg->src_fd || msg->flags & ~IORING_MSG_RING_FLAGS_PASS)
+               return -EINVAL;
+       if (!(msg->flags & IORING_MSG_RING_FLAGS_PASS) && msg->dst_fd)
                return -EINVAL;
        if (target_ctx->flags & IORING_SETUP_R_DISABLED)
                return -EBADFD;
@@ -124,15 +135,18 @@ static int io_msg_ring_data(struct io_kiocb *req, unsigned int issue_flags)
        if (io_msg_need_remote(target_ctx))
                return io_msg_exec_remote(req, io_msg_tw_complete);
 
+       if (msg->flags & IORING_MSG_RING_FLAGS_PASS)
+               flags = msg->cqe_flags;
+
        ret = -EOVERFLOW;
        if (target_ctx->flags & IORING_SETUP_IOPOLL) {
                if (unlikely(io_double_lock_ctx(target_ctx, issue_flags)))
                        return -EAGAIN;
-               if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, 0))
+               if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, flags))
                        ret = 0;
                io_double_unlock_ctx(target_ctx);
        } else {
-               if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, 0))
+               if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, flags))
                        ret = 0;
        }
        return ret;
@@ -241,7 +255,7 @@ int io_msg_ring_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
        msg->src_fd = READ_ONCE(sqe->addr3);
        msg->dst_fd = READ_ONCE(sqe->file_index);
        msg->flags = READ_ONCE(sqe->msg_ring_flags);
-       if (msg->flags & ~IORING_MSG_RING_CQE_SKIP)
+       if (msg->flags & ~IORING_MSG_RING_MASK)
                return -EINVAL;
 
        return 0;