[PATCH v2 05/18] io_uring/memmap: account memory before pinning

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

Move memory accounting before page pinning. It shouldn't even try to pin
pages if it's not allowed, and accounting is also relatively
inexpensive. It also give a better code structure as we do generic
accounting and then can branch for different mapping types.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/memmap.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/io_uring/memmap.c b/io_uring/memmap.c
index f76bee5a861a..cc5f6f69ee6c 100644
--- a/io_uring/memmap.c
+++ b/io_uring/memmap.c
@@ -243,17 +243,21 @@ int io_create_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr,
 	if (check_add_overflow(reg->user_addr, reg->size, &end))
 		return -EOVERFLOW;
 
-	pages = io_pin_pages(reg->user_addr, reg->size, &nr_pages);
-	if (IS_ERR(pages))
-		return PTR_ERR(pages);
-
+	nr_pages = reg->size >> PAGE_SHIFT;
 	if (ctx->user) {
 		ret = __io_account_mem(ctx->user, nr_pages);
 		if (ret)
-			goto out_free;
+			return ret;
 		pages_accounted = nr_pages;
 	}
 
+	pages = io_pin_pages(reg->user_addr, reg->size, &nr_pages);
+	if (IS_ERR(pages)) {
+		ret = PTR_ERR(pages);
+		pages = NULL;
+		goto out_free;
+	}
+
 	vptr = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL);
 	if (!vptr) {
 		ret = -ENOMEM;
@@ -268,7 +272,8 @@ int io_create_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr,
 out_free:
 	if (pages_accounted)
 		__io_unaccount_mem(ctx->user, pages_accounted);
-	io_pages_free(&pages, nr_pages);
+	if (pages)
+		io_pages_free(&pages, nr_pages);
 	return ret;
 }
 
-- 
2.46.0