io_uring: add fully sparse buffer registration

Honour IORING_RSRC_REGISTER_SPARSE not only for direct files but fixed
buffers as well. It makes the rsrc API more consistent.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/66f429e4912fe39fb3318217ff33a2853d4544be.1652879898.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 7b27afd..a210a2c 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -10134,12 +10134,17 @@ static int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
        }
 
        for (i = 0; i < nr_args; i++, ctx->nr_user_bufs++) {
-               ret = io_copy_iov(ctx, &iov, arg, i);
-               if (ret)
-                       break;
-               ret = io_buffer_validate(&iov);
-               if (ret)
-                       break;
+               if (arg) {
+                       ret = io_copy_iov(ctx, &iov, arg, i);
+                       if (ret)
+                               break;
+                       ret = io_buffer_validate(&iov);
+                       if (ret)
+                               break;
+               } else {
+                       memset(&iov, 0, sizeof(iov));
+               }
+
                if (!iov.iov_base && *io_get_tag_slot(data, i)) {
                        ret = -EINVAL;
                        break;
@@ -11986,7 +11991,7 @@ static __cold int io_register_rsrc(struct io_ring_ctx *ctx, void __user *arg,
                return io_sqe_files_register(ctx, u64_to_user_ptr(rr.data),
                                             rr.nr, u64_to_user_ptr(rr.tags));
        case IORING_RSRC_BUFFER:
-               if (rr.flags & IORING_RSRC_REGISTER_SPARSE)
+               if (rr.flags & IORING_RSRC_REGISTER_SPARSE && rr.data)
                        break;
                return io_sqe_buffers_register(ctx, u64_to_user_ptr(rr.data),
                                               rr.nr, u64_to_user_ptr(rr.tags));
@@ -12224,6 +12229,9 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 
        switch (opcode) {
        case IORING_REGISTER_BUFFERS:
+               ret = -EFAULT;
+               if (!arg)
+                       break;
                ret = io_sqe_buffers_register(ctx, arg, nr_args, NULL);
                break;
        case IORING_UNREGISTER_BUFFERS: