[LTP] [PATCH v2] Add mincore() test for pages cached by another process

[Xiao Yang]

On 7/28/20 2:59 PM, Shwetha Subramanian wrote:
> It tests the result of mincore when memory is mapped and cached by
> another process. A file is mapped in both parent and child
> process.Then the mapped memory is accessed in the child process. The
> results of mincore are tested in the parent process.
>
> Changes from v1
> 1. Added cleanup actions to child process
> 2. Fixed formatting issues
> 3. Expanded mem_sync() and file_setup() in setup function
> 4. Reformatted forked processes
> 5. Altered test result statements

Hi Shwetha，

Please put it after --- because the commit message doesn't need to 
include it.

>
> References:#460
>
> Signed-off-by: Shwetha Subramanian. <shwetha@zilogic.com>
> Reviewed-by:Vijay Kumar B. <vijaykumar@zilogic.com>
> ---
>   runtest/syscalls                              |   1 +
>   testcases/kernel/syscalls/mincore/.gitignore  |   1 +
>   testcases/kernel/syscalls/mincore/mincore04.c | 115 ++++++++++++++++++
>   3 files changed, 117 insertions(+)
>   create mode 100644 testcases/kernel/syscalls/mincore/mincore04.c
>
> diff --git a/runtest/syscalls b/runtest/syscalls
> index c2bfc6df3..bd3a5145a 100644
> --- a/runtest/syscalls
> +++ b/runtest/syscalls
> @@ -881,6 +881,7 @@ open_tree02 open_tree02
>   mincore01 mincore01
>   mincore02 mincore02
>   mincore03 mincore03
> +mincore04 mincore04
>   
>   madvise01 madvise01
>   madvise02 madvise02
> diff --git a/testcases/kernel/syscalls/mincore/.gitignore b/testcases/kernel/syscalls/mincore/.gitignore
> index 71c3e9864..25a5e8ab1 100644
> --- a/testcases/kernel/syscalls/mincore/.gitignore
> +++ b/testcases/kernel/syscalls/mincore/.gitignore
> @@ -1,3 +1,4 @@
>   /mincore01
>   /mincore02
>   /mincore03
> +/mincore04
> diff --git a/testcases/kernel/syscalls/mincore/mincore04.c b/testcases/kernel/syscalls/mincore/mincore04.c
> new file mode 100644
> index 000000000..284c284d5
> --- /dev/null
> +++ b/testcases/kernel/syscalls/mincore/mincore04.c
> @@ -0,0 +1,115 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) Zilogic Systems Pvt. Ltd., 2020
> + * Email: code@zilogic.com
> + */
> +
> +/*
> + * mincore04
> + * Test shows that pages mapped in one process(parent) and
> + * faulted in another(child) results in mincore(in parent) reporting
> + * that all mapped pages are resident.
> + */
> +
> +#include <unistd.h>
> +#include <sys/types.h>
> +#include <sys/mman.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <sys/wait.h>
> +#include <fcntl.h>
> +#include <stdlib.h>
> +#include "tst_test.h"
> +
> +#define NUM_PAGES 3
> +
> +static int fd;
> +static int size;
> +static void *ptr;
> +
> +static void cleanup(void)
> +{
> +	if (fd > 0)
> +		SAFE_CLOSE(fd);
> +	if (ptr)
> +		SAFE_MUNMAP(ptr, size);
> +}
> +
> +static void setup(void)
> +{
> +	int page_size, ret;
> +
> +	page_size = getpagesize();
> +	size = page_size * NUM_PAGES;
> +	fd = SAFE_OPEN("FILE", O_CREAT | O_RDWR, 0600);
> +	SAFE_FTRUNCATE(fd, size);
> +
> +	/* File pages from file creation are cleared from cache. */
> +	SAFE_FSYNC(fd);
> +	ret = posix_fadvise(fd, 0, size, POSIX_FADV_DONTNEED);
> +	if (ret == -1)
> +		tst_brk(TBROK | TERRNO, "fadvise failed");
> +}
> +
> +static void mmap_lock_file(void)
> +{
> +	ptr = SAFE_MMAP(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
> +	SAFE_MLOCK(ptr, size);
> +	TST_CHECKPOINT_WAKE(0);
> +	TST_CHECKPOINT_WAIT(1);
> +
> +	SAFE_CLOSE(fd);
> +	SAFE_MUNLOCK(ptr, size);
> +	SAFE_MUNMAP(ptr, size);
> +}
> +
> +static int count_pages_in_cache(void)
> +{
> +	int locked_pages = 0;
> +	int count, ret;
> +	unsigned char vec[NUM_PAGES];
> +
> +	TST_CHECKPOINT_WAIT(0);
> +	ptr = SAFE_MMAP(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
> +
> +	ret = mincore(ptr, size, vec);
> +	if (ret == -1)
> +		tst_brk(TBROK | TERRNO, "mincore failed");
> +	for (count = 0; count < NUM_PAGES; count++) {
> +		if (vec[count] & 1)
> +			locked_pages++;
> +	}
> +
> +	TST_CHECKPOINT_WAKE(1);

Parent and child seem to get the same virtual address by either of the 
following orders:

1) map in parent and child after fork.

2) map before fork.

I wonder if we can move SAFE_MUNMAP() to setup()?

Thanks,

Xiao Yang

> +	return locked_pages;
> +}
> +
> +static void test_mincore(void)
> +{
> +	int  locked_pages;
> +
> +	pid_t child_pid = SAFE_FORK();
> +
> +	if (child_pid == 0) {
> +		mmap_lock_file();
> +		exit(0);
> +	}
> +
> +	locked_pages = count_pages_in_cache();
> +	tst_reap_children();
> +
> +	if (locked_pages == NUM_PAGES)
> +		tst_res(TPASS, "mincore reports all %d pages locked by child process "
> +			"are resident", locked_pages);
> +	else
> +		tst_res(TFAIL, "mincore reports %d pages resident but %d pages "
> +			"locked by child process", locked_pages, NUM_PAGES);
> +}
> +
> +static struct tst_test test = {
> +	.setup = setup,
> +	.cleanup = cleanup,
> +	.forks_child = 1,
> +	.test_all = test_mincore,
> +	.needs_checkpoints = 1,
> +};