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fs: virtiofs: add virtiofs sample
This commit adds virtiofs sample that presents use of this filesystem Signed-off-by: Jakub Michalski <[email protected]> Signed-off-by: Filip Kokosinski <[email protected]>
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‎samples/subsys/fs/virtiofs/CMakeLists.txt

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# SPDX-License-Identifier: Apache-2.0
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cmake_minimum_required(VERSION 3.20.0)
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find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
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project(virtiofs)
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target_sources(app PRIVATE src/main.c)

‎samples/subsys/fs/virtiofs/README.rst

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.. zephyr:code-sample:: virtiofs
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:name: virtiofs filesystem
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:relevant-api: file_system_api
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Use file system API over virtiofs.
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Overview
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********
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This sample app demonstrates use of Zephyr's :ref:`file system API
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<file_system_api>` over `virtiofs <https://virtio-fs.gitlab.io/>`_ by reading, creating and listing files and directories.
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In the case of virtiofs the mounted filesystem is a directory on the host.
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Requirements
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************
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This sample requires `virtiofsd <https://gitlab.com/virtio-fs/virtiofsd>`_ to run.
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Building
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********
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.. zephyr-app-commands::
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:zephyr-app: samples/subsys/fs/virtiofs
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:board: qemu_x86_64
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:goals: build
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:compact:
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Running
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*******
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Before launching QEMU the virtiofsd has to be running. The QEMU arguments are embedded using :code:`CONFIG_QEMU_EXTRA_FLAGS` and socket path is set to :code:`/tmp/vhostqemu`, so virtiofsd has to be launched using
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.. code-block::
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virtiofsd --socket-path=/tmp/vhostqemu -o source=shared_dir_path
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where :code:`shared_dir_path` is a directory that will be mounted on Zephyr side.
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Then you can launch the QEMU using:
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.. code-block::
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west build -t run
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This sample will list files and directories in the mounted filesystem and print contents of file :code:`file` in the mounted directory.
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This sample will also create some files and directories.
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You can create sample directory using :code:`prepare_sample_directory.sh`.
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Example output:
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.. code-block::
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*** Booting Zephyr OS build v4.1.0-rc1-28-gc6816316fc50 ***
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/virtiofs directory tree:
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- dir2 (type=dir)
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- b (type=file, size=3)
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- a (type=file, size=2)
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- c (type=file, size=4)
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- dir (type=dir)
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- some_file (type=file, size=0)
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- nested_dir (type=dir)
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- some_other_file (type=file, size=0)
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- file (type=file, size=27)
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/virtiofs/file content:
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this is a file on the host
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After running the sample you can check the created files:
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.. code-block:: console
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shared_dir_path$ cat file_created_by_zephyr
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hello world
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shared_dir_path$ cat second_file_created_by_zephyr
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lorem ipsum

‎samples/subsys/fs/virtiofs/boards/qemu_x86_64.overlay

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&pcie0 {
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virtio_pci: virtio_pci {
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compatible = "virtio,pci";
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vendor-id = <0x1af4>;
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device-id = <0x105a>;
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interrupts = <0xb 0x0 0x0>;
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interrupt-parent = <&intc>;
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status = "okay";
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};
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};

‎samples/subsys/fs/virtiofs/prepare_sample_directory.sh

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# Copyright (c) 2025 Antmicro <www.antmicro.com>
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# SPDX-License-Identifier: Apache-2.0
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mkdir -p dir/nested_dir
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touch dir/some_file
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touch dir/nested_dir/some_other_file
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mkdir dir2
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echo "a" > dir2/a
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echo "bb" > dir2/b
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echo "ccc" > dir2/c
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echo "this is a file on the host" > file

‎samples/subsys/fs/virtiofs/prj.conf

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CONFIG_VIRTIO=y
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CONFIG_PCIE=y
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CONFIG_FILE_SYSTEM=y
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CONFIG_FILE_SYSTEM_VIRTIOFS=y
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CONFIG_HEAP_MEM_POOL_SIZE=100000
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CONFIG_QEMU_EXTRA_FLAGS="-chardev socket,id=char0,path=/tmp/vhostqemu -device vhost-user-fs-pci,queue-size=1024,chardev=char0,tag=myfs -m 32M -object memory-backend-memfd,id=mem,size=32M,share=on -numa node,memdev=mem"

‎samples/subsys/fs/virtiofs/sample.yaml

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sample:
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name: virtio filesystem sample
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common:
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tags:
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- filesystem
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- virtio
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tests:
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sample.filesystem.virtiofs:
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build_only: true
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filter: CONFIG_DT_HAS_VIRTIO_PCI_ENABLED

‎samples/subsys/fs/virtiofs/src/main.c

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/*
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* Copyright (c) 2025 Antmicro <www.antmicro.com>
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <stdio.h>
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#include <string.h>
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#include <zephyr/device.h>
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#include <zephyr/fs/fs.h>
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#include <zephyr/fs/virtiofs.h>
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#include <zephyr/kernel.h>
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#define VIRTIO_DEV DEVICE_DT_GET(DT_NODELABEL(virtio_pci))
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#define MOUNT_POINT "/virtiofs"
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struct virtiofs_fs_data fs_data;
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static struct fs_mount_t mp = {
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.type = FS_VIRTIOFS,
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.fs_data = &fs_data,
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.flags = 0,
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.storage_dev = (void *)VIRTIO_DEV,
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.mnt_point = MOUNT_POINT,
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};
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void dirtree(const char *path, int indent)
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{
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struct fs_dir_t dir;
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fs_dir_t_init(&dir);
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if (fs_opendir(&dir, path) == 0) {
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while (1) {
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struct fs_dirent entry;
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if (fs_readdir(&dir, &entry) == 0) {
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if (entry.name[0] == '\0') {
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break;
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}
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if (entry.type == FS_DIR_ENTRY_DIR) {
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printf("%*s- %s (type=dir)\n", indent * 2, "", entry.name);
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char *subdir_path = k_malloc(
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strlen(path) + strlen(entry.name) + 2
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);
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if (subdir_path == NULL) {
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printf("failed to allocate subdir path\n");
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continue;
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}
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strcpy(subdir_path, path);
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strcat(subdir_path, "/");
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strcat(subdir_path, entry.name);
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dirtree(subdir_path, indent + 1);
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k_free(subdir_path);
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} else {
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printf(
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"%*s- %s (type=file, size=%lu)\n",
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indent * 2, "", entry.name, entry.size
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);
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}
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} else {
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printf("failed to readdir %s\n", path);
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break;
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}
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};
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fs_closedir(&dir);
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} else {
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printf("failed to opendir %s\n", path);
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}
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}
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void create_file(const char *path, const char *content)
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{
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struct fs_file_t file;
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fs_file_t_init(&file);
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if (fs_open(&file, path, FS_O_CREATE | FS_O_WRITE) == 0) {
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fs_write(&file, content, strlen(content) + 1);
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} else {
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printf("failed to create %s\n", path);
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}
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fs_close(&file);
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}
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void print_file(const char *path)
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{
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struct fs_file_t file;
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fs_file_t_init(&file);
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if (fs_open(&file, path, FS_O_READ) == 0) {
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char buf[256] = "\0";
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int read_c = fs_read(&file, buf, sizeof(buf));
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if (read_c >= 0) {
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buf[read_c] = 0;
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printf(
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"%s content:\n"
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"%s\n",
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path, buf
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);
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} else {
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printf("failed to read from %s\n", path);
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}
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fs_close(&file);
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} else {
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printf("failed to open %s\n", path);
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}
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}
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int main(void)
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{
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if (fs_mount(&mp) == 0) {
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printf("%s directory tree:\n", MOUNT_POINT);
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dirtree(MOUNT_POINT, 0);
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printf("\n");
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print_file(MOUNT_POINT"/file");
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create_file("/virtiofs/file_created_by_zephyr", "hello world\n");
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create_file("/virtiofs/second_file_created_by_zephyr", "lorem ipsum\n");
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fs_mkdir("/virtiofs/dir_created_by_zephyr");
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} else {
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printf("failed to mount %s\n", MOUNT_POINT);
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}
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return 0;
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}

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