io_uring: change registration/upd/rsrc tagging ABI

There are ABI moments about recently added rsrc registration/update and
tagging that might become a nuisance in the future. First,
IORING_REGISTER_RSRC[_UPD] hide different types of resources under it,
so breaks fine control over them by restrictions. It works for now, but
once those are wanted under restrictions it would require a rework.

It was also inconvenient trying to fit a new resource not supporting
all the features (e.g. dynamic update) into the interface, so better
to return to IORING_REGISTER_* top level dispatching.

Second, register/update were considered to accept a type of resource,
however that's not a good idea because there might be several ways of
registration of a single resource type, e.g. we may want to add
non-contig buffers or anything more exquisite as dma mapped memory.
So, remove IORING_RSRC_[FILE,BUFFER] out of the ABI, and place them
internally for now to limit changes.

Signed-off-by: Pavel Begunkov <[email protected]>
Link: https://lore.kernel.org/r/9b554897a7c17ad6e3becc48dfed2f7af9f423d5.1623339162.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <[email protected]>

Author: isilence

fs/io_uring.c

@@ -783,6 +783,11 @@ struct io_task_work {
 	task_work_func_t	func;
 };
 
+enum {
+	IORING_RSRC_FILE		= 0,
+	IORING_RSRC_BUFFER		= 1,
+};
+
 /*
  * NOTE! Each of the iocb union members has the file pointer
  * as the first entry in their struct definition. So you can
@@ -9911,21 +9916,21 @@ static int io_register_files_update(struct io_ring_ctx *ctx, void __user *arg,
 }
 
 static int io_register_rsrc_update(struct io_ring_ctx *ctx, void __user *arg,
-				   unsigned size)
+				   unsigned size, unsigned type)
 {
 	struct io_uring_rsrc_update2 up;
 
 	if (size != sizeof(up))
 		return -EINVAL;
 	if (copy_from_user(&up, arg, sizeof(up)))
 		return -EFAULT;
-	if (!up.nr)
+	if (!up.nr || up.resv)
 		return -EINVAL;
-	return __io_register_rsrc_update(ctx, up.type, &up, up.nr);
+	return __io_register_rsrc_update(ctx, type, &up, up.nr);
 }
 
 static int io_register_rsrc(struct io_ring_ctx *ctx, void __user *arg,
-			    unsigned int size)
+			    unsigned int size, unsigned int type)
 {
 	struct io_uring_rsrc_register rr;
 
@@ -9936,10 +9941,10 @@ static int io_register_rsrc(struct io_ring_ctx *ctx, void __user *arg,
 	memset(&rr, 0, sizeof(rr));
 	if (copy_from_user(&rr, arg, size))
 		return -EFAULT;
-	if (!rr.nr)
+	if (!rr.nr || rr.resv || rr.resv2)
 		return -EINVAL;
 
-	switch (rr.type) {
+	switch (type) {
 	case IORING_RSRC_FILE:
 		return io_sqe_files_register(ctx, u64_to_user_ptr(rr.data),
 					     rr.nr, u64_to_user_ptr(rr.tags));
@@ -9961,8 +9966,10 @@ static bool io_register_op_must_quiesce(int op)
 	case IORING_REGISTER_PROBE:
 	case IORING_REGISTER_PERSONALITY:
 	case IORING_UNREGISTER_PERSONALITY:
-	case IORING_REGISTER_RSRC:
-	case IORING_REGISTER_RSRC_UPDATE:
+	case IORING_REGISTER_FILES2:
+	case IORING_REGISTER_FILES_UPDATE2:
+	case IORING_REGISTER_BUFFERS2:
+	case IORING_REGISTER_BUFFERS_UPDATE:
 		return false;
 	default:
 		return true;
@@ -10088,11 +10095,19 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 	case IORING_REGISTER_RESTRICTIONS:
 		ret = io_register_restrictions(ctx, arg, nr_args);
 		break;
-	case IORING_REGISTER_RSRC:
-		ret = io_register_rsrc(ctx, arg, nr_args);
+	case IORING_REGISTER_FILES2:
+		ret = io_register_rsrc(ctx, arg, nr_args, IORING_RSRC_FILE);
+		break;
+	case IORING_REGISTER_FILES_UPDATE2:
+		ret = io_register_rsrc_update(ctx, arg, nr_args,
+					      IORING_RSRC_FILE);
+		break;
+	case IORING_REGISTER_BUFFERS2:
+		ret = io_register_rsrc(ctx, arg, nr_args, IORING_RSRC_BUFFER);
 		break;
-	case IORING_REGISTER_RSRC_UPDATE:
-		ret = io_register_rsrc_update(ctx, arg, nr_args);
+	case IORING_REGISTER_BUFFERS_UPDATE:
+		ret = io_register_rsrc_update(ctx, arg, nr_args,
+					      IORING_RSRC_BUFFER);
 		break;
 	default:
 		ret = -EINVAL;

include/uapi/linux/io_uring.h

@@ -298,8 +298,12 @@ enum {
 	IORING_UNREGISTER_PERSONALITY		= 10,
 	IORING_REGISTER_RESTRICTIONS		= 11,
 	IORING_REGISTER_ENABLE_RINGS		= 12,
-	IORING_REGISTER_RSRC			= 13,
-	IORING_REGISTER_RSRC_UPDATE		= 14,
+
+	/* extended with tagging */
+	IORING_REGISTER_FILES2			= 13,
+	IORING_REGISTER_FILES_UPDATE2		= 14,
+	IORING_REGISTER_BUFFERS2		= 15,
+	IORING_REGISTER_BUFFERS_UPDATE		= 16,
 
 	/* this goes last */
 	IORING_REGISTER_LAST
@@ -312,14 +316,10 @@ struct io_uring_files_update {
 	__aligned_u64 /* __s32 * */ fds;
 };
 
-enum {
-	IORING_RSRC_FILE		= 0,
-	IORING_RSRC_BUFFER		= 1,
-};
-
 struct io_uring_rsrc_register {
-	__u32 type;
 	__u32 nr;
+	__u32 resv;
+	__u64 resv2;
 	__aligned_u64 data;
 	__aligned_u64 tags;
 };
@@ -335,8 +335,8 @@ struct io_uring_rsrc_update2 {
 	__u32 resv;
 	__aligned_u64 data;
 	__aligned_u64 tags;
-	__u32 type;
 	__u32 nr;
+	__u32 resv2;
 };
 
 /* Skip updating fd indexes set to this value in the fd table */