Re: [PATCH v3 2/6] selftests/liveupdate: add helper functions for memfd tests

[Zhu Yanjun <yanjun.zhu@linux.dev>]

在 2026/4/4 3:24, Pratyush Yadav 写道:
> From: "Pratyush Yadav (Google)" <pratyush@kernel.org>
> 
> Add some helper functions that will be used by memfd tests. This moves
> some of the complexity out of the test itself, which results in better
> test readability and less code duplication.
> 
> Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Signed-off-by: Pratyush Yadav <ptyadav@amazon.de>
> Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
> ---
>   .../selftests/liveupdate/luo_test_utils.c     | 191 +++++++++++++++++-
>   .../selftests/liveupdate/luo_test_utils.h     |  10 +
>   2 files changed, 200 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/liveupdate/luo_test_utils.c b/tools/testing/selftests/liveupdate/luo_test_utils.c
> index 3c8721c505df..ceb918ef9813 100644
> --- a/tools/testing/selftests/liveupdate/luo_test_utils.c
> +++ b/tools/testing/selftests/liveupdate/luo_test_utils.c
> @@ -1,8 +1,12 @@
>   // SPDX-License-Identifier: GPL-2.0-only
>   
>   /*
> - * Copyright (c) 2025, Google LLC.
> + * Copyright (c) 2025-2026, Google LLC.
>    * Pasha Tatashin <pasha.tatashin@soleen.com>
> + * Pratyush Yadav (Google) <pratyush@kernel.org>
> + *
> + * Copyright (C) 2025 Amazon.com Inc. or its affiliates.
> + * Pratyush Yadav <ptyadav@amazon.de>
>    */
>   
>   #define _GNU_SOURCE
> @@ -20,9 +24,194 @@
>   #include <sys/stat.h>
>   #include <errno.h>
>   #include <stdarg.h>
> +#include <sys/vfs.h>
> +#include <linux/magic.h>
>   
>   #include "luo_test_utils.h"
>   
> +int cwd_is_tmpfs(void)
> +{
> +	struct statfs buf;
> +
> +	if (statfs(".", &buf) < 0)
> +		return -errno;
> +
> +	return buf.f_type == TMPFS_MAGIC;
> +}
> +
> +/* Read exactly specified size from fd. Any less results in error. */
> +int read_size(int fd, char *buffer, size_t size)
> +{
> +	size_t remain = size;
> +	ssize_t bytes_read;
> +
> +	while (remain) {

while (remain > 0) ?

> +		bytes_read = read(fd, buffer, remain);
> +		if (bytes_read == 0)
> +			return -ENODATA;
> +		if (bytes_read < 0) {
> +			if (errno == EINTR)
> +				continue;
> +			else
> +				return -errno;
> +		}
> +
> +		remain -= bytes_read;
> +		buffer += bytes_read;
> +	}
> +
> +	return 0;
> +}
> +
> +/* Write exactly specified size from fd. Any less results in error. */
> +int write_size(int fd, const char *buffer, size_t size)
> +{
> +	size_t remain = size;
> +	ssize_t written;
> +
> +	while (remain) {

while (remain>0) is better?

Zhu Yanjun

> +		written = write(fd, buffer, remain);
> +		if (written == 0)
> +			return -EIO;
> +		if (written < 0) {
> +			if (errno == EINTR)
> +				continue;
> +			else
> +				return -errno;
> +		}
> +
> +		remain -= written;
> +		buffer += written;
> +	}
> +
> +	return 0;
> +}
> +
> +int generate_random_data(char *buffer, size_t size)
> +{
> +	int fd, ret;
> +
> +	fd = open("/dev/urandom", O_RDONLY);
> +	if (fd < 0)
> +		return -errno;
> +
> +	ret = read_size(fd, buffer, size);
> +	close(fd);
> +	return ret;
> +}
> +
> +int save_test_data(const char *filename, const char *buffer, size_t size)
> +{
> +	int fd, ret;
> +
> +	fd = open(filename, O_RDWR | O_CREAT | O_TRUNC, 0666);
> +	if (fd < 0)
> +		return -errno;
> +
> +	ret = write_size(fd, buffer, size);
> +	fsync(fd);
> +	close(fd);
> +	return ret;
> +}
> +
> +int load_test_data(const char *filename, char *buffer, size_t size)
> +{
> +	int fd, ret;
> +
> +	fd = open(filename, O_RDONLY);
> +	if (fd < 0)
> +		return -errno;
> +
> +	ret = read_size(fd, buffer, size);
> +	close(fd);
> +	return ret;
> +}
> +
> +/* Create and initialize a memfd with random data. */
> +int create_random_memfd(const char *memfd_name, char *buffer, size_t size)
> +{
> +	int fd;
> +	int ret;
> +
> +	fd = memfd_create(memfd_name, 0);
> +	if (fd < 0)
> +		return -errno;
> +
> +	ret = generate_random_data(buffer, size);
> +	if (ret < 0) {
> +		close(fd);
> +		return ret;
> +	}
> +
> +	ret = write_size(fd, buffer, size);
> +	if (ret < 0) {
> +		close(fd);
> +		return ret;
> +	}
> +
> +	/* Reset file position to beginning */
> +	if (lseek(fd, 0, SEEK_SET) < 0) {
> +		ret = -errno;
> +		close(fd);
> +		return ret;
> +	}
> +
> +	return fd;
> +}
> +
> +/*
> + * Make sure fd contains expected data up to size. Returns 0 on success, 1 on
> + * data mismatch, -errno on error.
> + */
> +int verify_fd_content_read(int fd, const char *expected_data, size_t size)
> +{
> +	char *buffer;
> +	int ret;
> +
> +	buffer = malloc(size);
> +	if (!buffer)
> +		return -ENOMEM;
> +
> +	/* Reset file position to beginning */
> +	if (lseek(fd, 0, SEEK_SET) < 0) {
> +		ret = -errno;
> +		goto out;
> +	}
> +
> +	ret = read_size(fd, buffer, size);
> +	if (ret < 0)
> +		goto out;
> +
> +	if (memcmp(buffer, expected_data, size) != 0) {
> +		ret = 1;
> +		goto out;
> +	}
> +
> +	ret = 0;
> +
> +out:
> +	free(buffer);
> +	return ret;
> +}
> +
> +/*
> + * Verify fd content using mmap. Returns 0 on success, 1 on data mismatch,
> + * -errno on error.
> + */
> +int verify_fd_content_mmap(int fd, const char *expected_data, size_t size)
> +{
> +	char *mapped_mem;
> +	int ret;
> +
> +	mapped_mem = mmap(NULL, size, PROT_READ, MAP_SHARED, fd, 0);
> +	if (mapped_mem == MAP_FAILED)
> +		return -errno;
> +
> +	ret = memcmp(mapped_mem, expected_data, size) ? 1 : 0;
> +	munmap(mapped_mem, size);
> +	return ret;
> +}
> +
>   int luo_open_device(void)
>   {
>   	return open(LUO_DEVICE, O_RDWR);
> diff --git a/tools/testing/selftests/liveupdate/luo_test_utils.h b/tools/testing/selftests/liveupdate/luo_test_utils.h
> index 90099bf49577..a69dce2649b0 100644
> --- a/tools/testing/selftests/liveupdate/luo_test_utils.h
> +++ b/tools/testing/selftests/liveupdate/luo_test_utils.h
> @@ -35,6 +35,16 @@ void restore_and_read_stage(int state_session_fd, int token, int *stage);
>   
>   void daemonize_and_wait(void);
>   
> +int cwd_is_tmpfs(void);
> +int read_size(int fd, char *buffer, size_t size);
> +int write_size(int fd, const char *buffer, size_t size);
> +int generate_random_data(char *buffer, size_t size);
> +int save_test_data(const char *filename, const char *buffer, size_t size);
> +int load_test_data(const char *filename, char *buffer, size_t size);
> +int create_random_memfd(const char *memfd_name, char *buffer, size_t size);
> +int verify_fd_content_read(int fd, const char *expected_data, size_t size);
> +int verify_fd_content_mmap(int fd, const char *expected_data, size_t size);
> +
>   typedef void (*luo_test_stage1_fn)(int luo_fd);
>   typedef void (*luo_test_stage2_fn)(int luo_fd, int state_session_fd);
>