io_uring: uniform SCM accounting

Channel all SCM accounting through io_sqe_file_register(), so we do it
uniformely for updates and initial registration and can kill duplicated
code. Registration might be slightly slower in some case, but first we
skip most of SCM accounting now so it's not a problem. Moreover, it's
nicer for an empty set registration as we don't even try to allocate
skb for them anymore.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/6c9afbeb22812777d0c43e52353b63db5b87ed1e.1649334991.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -8663,48 +8663,6 @@ static int __io_sqe_files_scm(struct io_ring_ctx *ctx, int nr, int offset)
 
 	return 0;
 }
-
-/*
- * If UNIX sockets are enabled, fd passing can cause a reference cycle which
- * causes regular reference counting to break down. We rely on the UNIX
- * garbage collection to take care of this problem for us.
- */
-static int io_sqe_files_scm(struct io_ring_ctx *ctx)
-{
-	unsigned left, total;
-	int ret = 0;
-
-	total = 0;
-	left = ctx->nr_user_files;
-	while (left) {
-		unsigned this_files = min_t(unsigned, left, SCM_MAX_FD);
-
-		ret = __io_sqe_files_scm(ctx, this_files, total);
-		if (ret)
-			break;
-		left -= this_files;
-		total += this_files;
-	}
-
-	if (!ret)
-		return 0;
-
-	while (total < ctx->nr_user_files) {
-		struct file *file = io_file_from_index(ctx, total);
-
-		if (file)
-			fput(file);
-		io_fixed_file_slot(&ctx->file_table, total)->file_ptr = 0;
-		total++;
-	}
-
-	return ret;
-}
-#else
-static int io_sqe_files_scm(struct io_ring_ctx *ctx)
-{
-	return 0;
-}
 #endif
 
 static void io_rsrc_file_put(struct io_ring_ctx *ctx, struct io_rsrc_put *prsrc)
@@ -8825,6 +8783,9 @@ static void io_rsrc_put_work(struct work_struct *work)
 	}
 }
 
+static int io_sqe_file_register(struct io_ring_ctx *ctx, struct file *file,
+				int index);
+
 static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,
 				 unsigned nr_args, u64 __user *tags)
 {
@@ -8849,27 +8810,31 @@ static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,
 	if (ret)
 		return ret;
 
-	ret = -ENOMEM;
-	if (!io_alloc_file_tables(&ctx->file_table, nr_args))
-		goto out_free;
+	if (!io_alloc_file_tables(&ctx->file_table, nr_args)) {
+		io_rsrc_data_free(ctx->file_data);
+		ctx->file_data = NULL;
+		return -ENOMEM;
+	}
 
 	for (i = 0; i < nr_args; i++, ctx->nr_user_files++) {
+		struct io_fixed_file *file_slot;
+
 		if (copy_from_user(&fd, &fds[i], sizeof(fd))) {
 			ret = -EFAULT;
-			goto out_fput;
+			goto fail;
 		}
 		/* allow sparse sets */
 		if (fd == -1) {
 			ret = -EINVAL;
 			if (unlikely(*io_get_tag_slot(ctx->file_data, i)))
-				goto out_fput;
+				goto fail;
 			continue;
 		}
 
 		file = fget(fd);
 		ret = -EBADF;
 		if (unlikely(!file))
-			goto out_fput;
+			goto fail;
 
 		/*
 		 * Don't allow io_uring instances to be registered. If UNIX
@@ -8880,30 +8845,22 @@ static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,
 		 */
 		if (file->f_op == &io_uring_fops) {
 			fput(file);
-			goto out_fput;
+			goto fail;
+		}
+		file_slot = io_fixed_file_slot(&ctx->file_table, i);
+		io_fixed_file_set(file_slot, file);
+		ret = io_sqe_file_register(ctx, file, i);
+		if (ret) {
+			file_slot->file_ptr = 0;
+			fput(file);
+			goto fail;
 		}
-		io_fixed_file_set(io_fixed_file_slot(&ctx->file_table, i), file);
-	}
-
-	ret = io_sqe_files_scm(ctx);
-	if (ret) {
-		__io_sqe_files_unregister(ctx);
-		return ret;
 	}
 
 	io_rsrc_node_switch(ctx, NULL);
-	return ret;
-out_fput:
-	for (i = 0; i < ctx->nr_user_files; i++) {
-		file = io_file_from_index(ctx, i);
-		if (file)
-			fput(file);
-	}
-	io_free_file_tables(&ctx->file_table);
-	ctx->nr_user_files = 0;
-out_free:
-	io_rsrc_data_free(ctx->file_data);
-	ctx->file_data = NULL;
+	return 0;
+fail:
+	__io_sqe_files_unregister(ctx);
 	return ret;
 }