Hello,
This series add support for the renameat2 system call RENAME_EXCHANGE flag (which allows to atomically replace two paths) to the vfat filesystem code.
There are many use cases for this, but we are particularly interested in making possible for vfat filesystems to be part of OSTree [0] deployments.
Currently OSTree relies on symbolic links to make the deployment updates an atomic transactional operation. But RENAME_EXCHANGE could be used [1] to achieve a similar level of robustness when using a vfat filesystem.
Patch #1 is just a preparatory patch to introduce the RENAME_EXCHANGE support in patch #2 and finally patch #3 adds some kselftests to test it.
This is a v2 that addresses issues pointed out in the first version that was posted as an RFC:
https://lore.kernel.org/lkml/20220519092343.2776414-1-javierm@redhat.com/
[0]: https://github.com/ostreedev/ostree [1]: https://github.com/ostreedev/ostree/issues/1649
Changes in v2: - Only update the new_dir inode version and timestamps if != old_dir (Alex Larsson). - Add some helper functions to avoid duplicating code (OGAWA Hirofumi). - Use braces for multi-lines blocks even if are one statement (OGAWA Hirofumi). - Mention in commit message that the operation is as transactional as possible but within the vfat limitations of not having a journal (Colin Walters). - Call sync to flush the page cache before checking the file contents (Alex Larsson). - Drop RFC prefix since the patches already got some review.
Javier Martinez Canillas (3): fat: add a vfat_rename2() and make existing .rename callback a helper fat: add renameat2 RENAME_EXCHANGE flag support selftests/filesystems: add a vfat RENAME_EXCHANGE test
MAINTAINERS | 1 + fs/fat/namei_vfat.c | 193 +++++++++++++++++- tools/testing/selftests/Makefile | 1 + .../selftests/filesystems/fat/Makefile | 7 + .../testing/selftests/filesystems/fat/config | 2 + .../filesystems/fat/rename_exchange.c | 37 ++++ .../filesystems/fat/run_fat_tests.sh | 82 ++++++++ 7 files changed, 316 insertions(+), 7 deletions(-) create mode 100644 tools/testing/selftests/filesystems/fat/Makefile create mode 100644 tools/testing/selftests/filesystems/fat/config create mode 100644 tools/testing/selftests/filesystems/fat/rename_exchange.c create mode 100755 tools/testing/selftests/filesystems/fat/run_fat_tests.sh
Add a test for the renameat2 RENAME_EXCHANGE support in vfat, but split it in a tool that just does the rename exchange and a script that is run by the kselftests framework on `make TARGETS="filesystems/fat" kselftest`.
That way the script can be easily extended to test other file operations.
The script creates a 1 MiB disk image, that is then formated with a vfat filesystem and mounted using a loop device. That way all file operations are done on an ephemeral filesystem.
Signed-off-by: Javier Martinez Canillas javierm@redhat.com ---
Changes in v2: - Call sync to flush the page cache before checking the file contents (Alex Larsson).
MAINTAINERS | 1 + tools/testing/selftests/Makefile | 1 + .../selftests/filesystems/fat/Makefile | 7 ++ .../testing/selftests/filesystems/fat/config | 2 + .../filesystems/fat/rename_exchange.c | 37 +++++++++ .../filesystems/fat/run_fat_tests.sh | 82 +++++++++++++++++++ 6 files changed, 130 insertions(+) create mode 100644 tools/testing/selftests/filesystems/fat/Makefile create mode 100644 tools/testing/selftests/filesystems/fat/config create mode 100644 tools/testing/selftests/filesystems/fat/rename_exchange.c create mode 100755 tools/testing/selftests/filesystems/fat/run_fat_tests.sh
diff --git a/MAINTAINERS b/MAINTAINERS index 4fdbbd6c1984..158771bb7755 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -20841,6 +20841,7 @@ M: OGAWA Hirofumi hirofumi@mail.parknet.co.jp S: Maintained F: Documentation/filesystems/vfat.rst F: fs/fat/ +F: tools/testing/selftests/filesystems/fat/
VFIO DRIVER M: Alex Williamson alex.williamson@redhat.com diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile index 0aedcd76cf0f..fc59ad849a90 100644 --- a/tools/testing/selftests/Makefile +++ b/tools/testing/selftests/Makefile @@ -16,6 +16,7 @@ TARGETS += exec TARGETS += filesystems TARGETS += filesystems/binderfs TARGETS += filesystems/epoll +TARGETS += filesystems/fat TARGETS += firmware TARGETS += fpu TARGETS += ftrace diff --git a/tools/testing/selftests/filesystems/fat/Makefile b/tools/testing/selftests/filesystems/fat/Makefile new file mode 100644 index 000000000000..93ee73c16828 --- /dev/null +++ b/tools/testing/selftests/filesystems/fat/Makefile @@ -0,0 +1,7 @@ +# SPDX-License-Identifier: GPL-2.0 + +TEST_PROGS := run_fat_tests.sh +TEST_GEN_PROGS_EXTENDED := rename_exchange +CFLAGS += -O2 -g -Wall -I../../../../usr/include/ + +include ../../lib.mk diff --git a/tools/testing/selftests/filesystems/fat/config b/tools/testing/selftests/filesystems/fat/config new file mode 100644 index 000000000000..6cf95e787a17 --- /dev/null +++ b/tools/testing/selftests/filesystems/fat/config @@ -0,0 +1,2 @@ +CONFIG_BLK_DEV_LOOP=y +CONFIG_VFAT_FS=y diff --git a/tools/testing/selftests/filesystems/fat/rename_exchange.c b/tools/testing/selftests/filesystems/fat/rename_exchange.c new file mode 100644 index 000000000000..e488ad354fce --- /dev/null +++ b/tools/testing/selftests/filesystems/fat/rename_exchange.c @@ -0,0 +1,37 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Program that atomically exchanges two paths using + * the renameat2() system call RENAME_EXCHANGE flag. + * + * Copyright 2022 Red Hat Inc. + * Author: Javier Martinez Canillas javierm@redhat.com + */ + +#define _GNU_SOURCE +#include <fcntl.h> +#include <stdio.h> +#include <stdlib.h> + +void print_usage(const char *program) +{ + printf("Usage: %s [oldpath] [newpath]\n", program); + printf("Atomically exchange oldpath and newpath\n"); +} + +int main(int argc, char *argv[]) +{ + int ret; + + if (argc != 3) { + print_usage(argv[0]); + exit(EXIT_FAILURE); + } + + ret = renameat2(AT_FDCWD, argv[1], AT_FDCWD, argv[2], RENAME_EXCHANGE); + if (ret) { + perror("rename exchange failed"); + exit(EXIT_FAILURE); + } + + exit(EXIT_SUCCESS); +} diff --git a/tools/testing/selftests/filesystems/fat/run_fat_tests.sh b/tools/testing/selftests/filesystems/fat/run_fat_tests.sh new file mode 100755 index 000000000000..7f35dc3d15df --- /dev/null +++ b/tools/testing/selftests/filesystems/fat/run_fat_tests.sh @@ -0,0 +1,82 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# +# Run filesystem operations tests on an 1 MiB disk image that is formatted with +# a vfat filesystem and mounted in a temporary directory using a loop device. +# +# Copyright 2022 Red Hat Inc. +# Author: Javier Martinez Canillas javierm@redhat.com + +set -e +set -u +set -o pipefail + +BASE_DIR="$(dirname $0)" +TMP_DIR="$(mktemp -d /tmp/fat_tests_tmp.XXXX)" +IMG_PATH="${TMP_DIR}/fat.img" +MNT_PATH="${TMP_DIR}/mnt" + +cleanup() +{ + mountpoint -q "${MNT_PATH}" && unmount_image + rm -rf "${TMP_DIR}" +} +trap cleanup SIGINT SIGTERM EXIT + +create_loopback() +{ + touch "${IMG_PATH}" + chattr +C "${IMG_PATH}" >/dev/null 2>&1 || true + + truncate -s 1M "${IMG_PATH}" + mkfs.vfat "${IMG_PATH}" >/dev/null 2>&1 +} + +mount_image() +{ + mkdir -p "${MNT_PATH}" + sudo mount -o loop "${IMG_PATH}" "${MNT_PATH}" +} + +rename_exchange_test() +{ + local rename_exchange="${BASE_DIR}/rename_exchange" + local old_path="${MNT_PATH}/old_file" + local new_path="${MNT_PATH}/new_file" + + echo old | sudo tee "${old_path}" >/dev/null 2>&1 + echo new | sudo tee "${new_path}" >/dev/null 2>&1 + sudo "${rename_exchange}" "${old_path}" "${new_path}" >/dev/null 2>&1 + sudo sync -f "${MNT_PATH}" + grep new "${old_path}" >/dev/null 2>&1 + grep old "${new_path}" >/dev/null 2>&1 +} + +rename_exchange_subdir_test() +{ + local rename_exchange="${BASE_DIR}/rename_exchange" + local dir_path="${MNT_PATH}/subdir" + local old_path="${MNT_PATH}/old_file" + local new_path="${dir_path}/new_file" + + sudo mkdir -p "${dir_path}" + echo old | sudo tee "${old_path}" >/dev/null 2>&1 + echo new | sudo tee "${new_path}" >/dev/null 2>&1 + sudo "${rename_exchange}" "${old_path}" "${new_path}" >/dev/null 2>&1 + sudo sync -f "${MNT_PATH}" + grep new "${old_path}" >/dev/null 2>&1 + grep old "${new_path}" >/dev/null 2>&1 +} + +unmount_image() +{ + sudo umount "${MNT_PATH}" &> /dev/null +} + +create_loopback +mount_image +rename_exchange_test +rename_exchange_subdir_test +unmount_image + +exit 0
On 5/24/22 12:36 PM, Javier Martinez Canillas wrote:
diff --git a/tools/testing/selftests/filesystems/fat/Makefile b/tools/testing/selftests/filesystems/fat/Makefile new file mode 100644 index 000000000000..93ee73c16828 --- /dev/null +++ b/tools/testing/selftests/filesystems/fat/Makefile @@ -0,0 +1,7 @@ +# SPDX-License-Identifier: GPL-2.0
+TEST_PROGS := run_fat_tests.sh +TEST_GEN_PROGS_EXTENDED := rename_exchange
Please create a .gitignore file and add rename_exchange to it.
+CFLAGS += -O2 -g -Wall -I../../../../usr/include/
Build may fail if kernel on which this test is being build has old headers. Always use $(KHDR_INCLUDES) instead of "-I../../../../usr/include/" to use the kernel headers from the kernel source instead of the natively installed headers.
Hello Muhammad,
Thanks a lot for your feedback.
On 5/24/22 16:54, Muhammad Usama Anjum wrote:
On 5/24/22 12:36 PM, Javier Martinez Canillas wrote:
diff --git a/tools/testing/selftests/filesystems/fat/Makefile b/tools/testing/selftests/filesystems/fat/Makefile new file mode 100644 index 000000000000..93ee73c16828 --- /dev/null +++ b/tools/testing/selftests/filesystems/fat/Makefile @@ -0,0 +1,7 @@ +# SPDX-License-Identifier: GPL-2.0
+TEST_PROGS := run_fat_tests.sh +TEST_GEN_PROGS_EXTENDED := rename_exchange
Please create a .gitignore file and add rename_exchange to it.
Sorry, you mentioned that in the first revision but I missed.
Yes, I'll do it that on v3.
+CFLAGS += -O2 -g -Wall -I../../../../usr/include/
Build may fail if kernel on which this test is being build has old headers. Always use $(KHDR_INCLUDES) instead of "-I../../../../usr/include/" to use the kernel headers from the kernel source instead of the natively installed headers.
Sure, I'll do that as well.
linux-kselftest-mirror@lists.linaro.org
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Javier Martinez Canillas -
Muhammad Usama Anjum