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

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

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

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,
> +};