[PATCH v3 01/25] io_uring/kbuf: refactor io_buf_pbuf_register() logic into generic helpers

[Joanne Koong <joannelkoong@gmail.com>]

Refactor the logic in io_register_pbuf_ring() into generic helpers:
- io_validate_buf_reg(): Validate user input and buffer registration
  parameters
- io_alloc_new_buffer_list(): Allocate and initialize a new buffer
  list for the given buffer group ID
- io_setup_pbuf_ring(): Sets up the physical buffer ring region and
  handles memory mapping for provided buffer rings

This is a preparatory change for upcoming kernel-managed buffer ring
support which will need to reuse some of these helpers.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 io_uring/kbuf.c | 123 ++++++++++++++++++++++++++++++++----------------
 1 file changed, 82 insertions(+), 41 deletions(-)

diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index 796d131107dd..100367bb510b 100644
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -596,55 +596,71 @@ int io_manage_buffers_legacy(struct io_kiocb *req, unsigned int issue_flags)
 	return IOU_COMPLETE;
 }
 
-int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
+static int io_validate_buf_reg(struct io_uring_buf_reg *reg,
+			       unsigned int permitted_flags)
 {
-	struct io_uring_buf_reg reg;
-	struct io_buffer_list *bl;
-	struct io_uring_region_desc rd;
-	struct io_uring_buf_ring *br;
-	unsigned long mmap_offset;
-	unsigned long ring_size;
-	int ret;
-
-	lockdep_assert_held(&ctx->uring_lock);
-
-	if (copy_from_user(&reg, arg, sizeof(reg)))
-		return -EFAULT;
-	if (!mem_is_zero(reg.resv, sizeof(reg.resv)))
+	if (!mem_is_zero(reg->resv, sizeof(reg->resv)))
 		return -EINVAL;
-	if (reg.flags & ~(IOU_PBUF_RING_MMAP | IOU_PBUF_RING_INC))
+	if (reg->flags & ~permitted_flags)
 		return -EINVAL;
-	if (!is_power_of_2(reg.ring_entries))
+	if (!is_power_of_2(reg->ring_entries))
 		return -EINVAL;
 	/* cannot disambiguate full vs empty due to head/tail size */
-	if (reg.ring_entries >= 65536)
+	if (reg->ring_entries >= 65536)
 		return -EINVAL;
+	return 0;
+}
 
-	bl = io_buffer_get_list(ctx, reg.bgid);
-	if (bl) {
+static int io_alloc_new_buffer_list(struct io_ring_ctx *ctx,
+				    struct io_uring_buf_reg *reg,
+				    struct io_buffer_list **bl)
+{
+	struct io_buffer_list *list;
+
+	list = io_buffer_get_list(ctx, reg->bgid);
+	if (list) {
 		/* if mapped buffer ring OR classic exists, don't allow */
-		if (bl->flags & IOBL_BUF_RING || !list_empty(&bl->buf_list))
+		if (list->flags & IOBL_BUF_RING || !list_empty(&list->buf_list))
 			return -EEXIST;
-		io_destroy_bl(ctx, bl);
+		io_destroy_bl(ctx, list);
 	}
 
-	bl = kzalloc(sizeof(*bl), GFP_KERNEL_ACCOUNT);
-	if (!bl)
+	list = kzalloc(sizeof(*list), GFP_KERNEL_ACCOUNT);
+	if (!list)
 		return -ENOMEM;
 
-	mmap_offset = (unsigned long)reg.bgid << IORING_OFF_PBUF_SHIFT;
-	ring_size = flex_array_size(br, bufs, reg.ring_entries);
+	list->nr_entries = reg->ring_entries;
+	list->mask = reg->ring_entries - 1;
+	list->flags = IOBL_BUF_RING;
+
+	*bl = list;
+
+	return 0;
+}
+
+static int io_setup_pbuf_ring(struct io_ring_ctx *ctx,
+			      struct io_uring_buf_reg *reg,
+			      struct io_buffer_list *bl)
+{
+	struct io_uring_region_desc rd;
+	unsigned long mmap_offset;
+	unsigned long ring_size;
+	int ret;
+
+	mmap_offset = (unsigned long)reg->bgid << IORING_OFF_PBUF_SHIFT;
+	ring_size = flex_array_size(bl->buf_ring, bufs, reg->ring_entries);
 
 	memset(&rd, 0, sizeof(rd));
 	rd.size = PAGE_ALIGN(ring_size);
-	if (!(reg.flags & IOU_PBUF_RING_MMAP)) {
-		rd.user_addr = reg.ring_addr;
+	if (!(reg->flags & IOU_PBUF_RING_MMAP)) {
+		rd.user_addr = reg->ring_addr;
 		rd.flags |= IORING_MEM_REGION_TYPE_USER;
 	}
+
 	ret = io_create_region(ctx, &bl->region, &rd, mmap_offset);
 	if (ret)
-		goto fail;
-	br = io_region_get_ptr(&bl->region);
+		return ret;
+	bl->buf_ring = io_region_get_ptr(&bl->region);
 
 #ifdef SHM_COLOUR
 	/*
@@ -656,25 +672,50 @@ int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
 	 * should use IOU_PBUF_RING_MMAP instead, and liburing will handle
 	 * this transparently.
 	 */
-	if (!(reg.flags & IOU_PBUF_RING_MMAP) &&
-	    ((reg.ring_addr | (unsigned long)br) & (SHM_COLOUR - 1))) {
-		ret = -EINVAL;
-		goto fail;
+	if (!(reg->flags & IOU_PBUF_RING_MMAP) &&
+	    ((reg->ring_addr | (unsigned long)bl->buf_ring) &
+	     (SHM_COLOUR - 1))) {
+		io_free_region(ctx->user, &bl->region);
+		return -EINVAL;
 	}
 #endif
 
-	bl->nr_entries = reg.ring_entries;
-	bl->mask = reg.ring_entries - 1;
-	bl->flags |= IOBL_BUF_RING;
-	bl->buf_ring = br;
+	return 0;
+}
+
+int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
+{
+	unsigned int permitted_flags;
+	struct io_uring_buf_reg reg;
+	struct io_buffer_list *bl;
+	int ret;
+
+	lockdep_assert_held(&ctx->uring_lock);
+
+	if (copy_from_user(&reg, arg, sizeof(reg)))
+		return -EFAULT;
+
+	permitted_flags = IOU_PBUF_RING_MMAP | IOU_PBUF_RING_INC;
+	ret = io_validate_buf_reg(&reg, permitted_flags);
+	if (ret)
+		return ret;
+
+	ret = io_alloc_new_buffer_list(ctx, &reg, &bl);
+	if (ret)
+		return ret;
+
+	ret = io_setup_pbuf_ring(ctx, &reg, bl);
+	if (ret) {
+		kfree(bl);
+		return ret;
+	}
+
 	if (reg.flags & IOU_PBUF_RING_INC)
 		bl->flags |= IOBL_INC;
+
 	io_buffer_add_list(ctx, bl, reg.bgid);
+
 	return 0;
-fail:
-	io_free_region(ctx->user, &bl->region);
-	kfree(bl);
-	return ret;
 }
 
 int io_unregister_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
-- 
2.47.3