[RFC 14/16] io_uring: extract io_create_mem_region

[Pavel Begunkov <asml.silence@gmail.com>]

Extract a helper function for creating a memory region but that can be
used at setup and not only in io_uring_register(). Specifically, it
doesn't check IORING_SETUP_R_DISABLED.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/io_uring.h |  3 +++
 io_uring/register.c | 43 +++++++++++++++++++++++++------------------
 2 files changed, 28 insertions(+), 18 deletions(-)

diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index ed57ab4161db..20f6ca4696c1 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -200,6 +200,9 @@ void io_queue_next(struct io_kiocb *req);
 void io_task_refs_refill(struct io_uring_task *tctx);
 bool __io_alloc_req_refill(struct io_ring_ctx *ctx);
 
+int io_create_mem_region(struct io_ring_ctx *ctx,
+			 struct io_uring_mem_region_reg *reg);
+
 void io_activate_pollwq(struct io_ring_ctx *ctx);
 
 static inline void io_lockdep_assert_cq_locked(struct io_ring_ctx *ctx)
diff --git a/io_uring/register.c b/io_uring/register.c
index b43a121e2974..425529a30dd9 100644
--- a/io_uring/register.c
+++ b/io_uring/register.c
@@ -572,10 +572,9 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 	return ret;
 }
 
-static int io_register_mem_region(struct io_ring_ctx *ctx, void __user *uarg)
+int io_create_mem_region(struct io_ring_ctx *ctx,
+			 struct io_uring_mem_region_reg *reg)
 {
-	struct io_uring_mem_region_reg __user *reg_uptr = uarg;
-	struct io_uring_mem_region_reg reg;
 	struct io_uring_region_desc __user *rd_uptr;
 	struct io_uring_region_desc rd;
 	struct io_mapped_region region = {};
@@ -583,23 +582,12 @@ static int io_register_mem_region(struct io_ring_ctx *ctx, void __user *uarg)
 
 	if (io_region_is_set(&ctx->param_region))
 		return -EBUSY;
-	if (copy_from_user(&reg, reg_uptr, sizeof(reg)))
-		return -EFAULT;
-	rd_uptr = u64_to_user_ptr(reg.region_uptr);
+	rd_uptr = u64_to_user_ptr(reg->region_uptr);
 	if (copy_from_user(&rd, rd_uptr, sizeof(rd)))
 		return -EFAULT;
-	if (memchr_inv(&reg.__resv, 0, sizeof(reg.__resv)))
+	if (memchr_inv(&reg->__resv, 0, sizeof(reg->__resv)))
 		return -EINVAL;
-	if (reg.flags & ~IORING_MEM_REGION_REG_WAIT_ARG)
-		return -EINVAL;
-
-	/*
-	 * This ensures there are no waiters. Waiters are unlocked and it's
-	 * hard to synchronise with them, especially if we need to initialise
-	 * the region.
-	 */
-	if ((reg.flags & IORING_MEM_REGION_REG_WAIT_ARG) &&
-	    !(ctx->flags & IORING_SETUP_R_DISABLED))
+	if (reg->flags & ~IORING_MEM_REGION_REG_WAIT_ARG)
 		return -EINVAL;
 
 	ret = io_create_region(ctx, &region, &rd, IORING_MAP_OFF_PARAM_REGION);
@@ -610,7 +598,7 @@ static int io_register_mem_region(struct io_ring_ctx *ctx, void __user *uarg)
 		return -EFAULT;
 	}
 
-	if (reg.flags & IORING_MEM_REGION_REG_WAIT_ARG) {
+	if (reg->flags & IORING_MEM_REGION_REG_WAIT_ARG) {
 		ctx->cq_wait_arg = io_region_get_ptr(&region);
 		ctx->cq_wait_size = rd.size;
 	}
@@ -619,6 +607,25 @@ static int io_register_mem_region(struct io_ring_ctx *ctx, void __user *uarg)
 	return 0;
 }
 
+static int io_register_mem_region(struct io_ring_ctx *ctx, void __user *uarg)
+{
+	struct io_uring_mem_region_reg __user *reg_uptr = uarg;
+	struct io_uring_mem_region_reg reg;
+
+	if (copy_from_user(&reg, reg_uptr, sizeof(reg)))
+		return -EFAULT;
+	/*
+	 * This ensures there are no waiters. Waiters are unlocked and it's
+	 * hard to synchronise with them, especially if we need to initialise
+	 * the region.
+	 */
+	if ((reg.flags & IORING_MEM_REGION_REG_WAIT_ARG) &&
+	    !(ctx->flags & IORING_SETUP_R_DISABLED))
+		return -EINVAL;
+
+	return io_create_mem_region(ctx, &reg);
+}
+
 static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 			       void __user *arg, unsigned nr_args)
 	__releases(ctx->uring_lock)
-- 
2.49.0