1 files changed, 111 insertions, 0 deletions
diff --git a/tools/testing/selftests/memfd/fuse_mnt.c b/tools/testing/selftests/memfd/fuse_mnt.c
new file mode 100644
index 000000000..6936f2a00
--- /dev/null
+++ b/tools/testing/selftests/memfd/fuse_mnt.c
@@ -0,0 +1,111 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * memfd test file-system
+ * This file uses FUSE to create a dummy file-system with only one file /memfd.
+ * This file is read-only and takes 1s per read.
+ *
+ * This file-system is used by the memfd test-cases to force the kernel to pin
+ * pages during reads(). Due to the 1s delay of this file-system, this is a
+ * nice way to test race-conditions against get_user_pages() in the kernel.
+ *
+ * We use direct_io==1 to force the kernel to use direct-IO for this
+ * file-system.
+ */
+
+#define FUSE_USE_VERSION 26
+
+#include <fuse.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+static const char memfd_content[] = "memfd-example-content";
+static const char memfd_path[] = "/memfd";
+
+static int memfd_getattr(const char *path, struct stat *st)
+{
+	memset(st, 0, sizeof(*st));
+
+	if (!strcmp(path, "/")) {
+		st->st_mode = S_IFDIR | 0755;
+		st->st_nlink = 2;
+	} else if (!strcmp(path, memfd_path)) {
+		st->st_mode = S_IFREG | 0444;
+		st->st_nlink = 1;
+		st->st_size = strlen(memfd_content);
+	} else {
+		return -ENOENT;
+	}
+
+	return 0;
+}
+
+static int memfd_readdir(const char *path,
+			 void *buf,
+			 fuse_fill_dir_t filler,
+			 off_t offset,
+			 struct fuse_file_info *fi)
+{
+	if (strcmp(path, "/"))
+		return -ENOENT;
+
+	filler(buf, ".", NULL, 0);
+	filler(buf, "..", NULL, 0);
+	filler(buf, memfd_path + 1, NULL, 0);
+
+	return 0;
+}
+
+static int memfd_open(const char *path, struct fuse_file_info *fi)
+{
+	if (strcmp(path, memfd_path))
+		return -ENOENT;
+
+	if ((fi->flags & 3) != O_RDONLY)
+		return -EACCES;
+
+	/* force direct-IO */
+	fi->direct_io = 1;
+
+	return 0;
+}
+
+static int memfd_read(const char *path,
+		      char *buf,
+		      size_t size,
+		      off_t offset,
+		      struct fuse_file_info *fi)
+{
+	size_t len;
+
+	if (strcmp(path, memfd_path) != 0)
+		return -ENOENT;
+
+	sleep(1);
+
+	len = strlen(memfd_content);
+	if (offset < len) {
+		if (offset + size > len)
+			size = len - offset;
+
+		memcpy(buf, memfd_content + offset, size);
+	} else {
+		size = 0;
+	}
+
+	return size;
+}
+
+static struct fuse_operations memfd_ops = {
+	.getattr	= memfd_getattr,
+	.readdir	= memfd_readdir,
+	.open		= memfd_open,
+	.read		= memfd_read,
+};
+
+int main(int argc, char *argv[])
+{
+	return fuse_main(argc, argv, &memfd_ops, NULL);
+}