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From:   Mauricio Faria de Oliveira <mfo@canonical.com>
To:     Jan Kara <jack@suse.cz>
Cc:     linux-ext4@vger.kernel.org,
        dann frazier <dann.frazier@canonical.com>,
        Mauricio Faria de Oliveira <mauricio.foliveira@gmail.com>,
        Jan Kara <jack@suse.com>
Subject: [RFC PATCH v2/TEST CASE]
Date:   Sun,  9 Aug 2020 22:02:10 -0300
Message-Id: <20200810010210.3305322-8-mfo@canonical.com>
In-Reply-To: <20200810010210.3305322-1-mfo@canonical.com>
References: <20200810010210.3305322-1-mfo@canonical.com>
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#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <sys/mman.h>

int main() {
	int fd, rc;
	char *addr;
	const int PAGE_SIZE = sysconf(_SC_PAGESIZE);

	rc = unlink("file");
	if (rc < 0 && errno != ENOENT ) {
		perror("unlink");
		return 1;
	}

	fd = open("file", O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
	if (fd < 0) {
		perror("open");
		return 1;
	}

	addr = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	if (addr < 0) {
		perror("mmap");
		return 1;
	}

	rc = pwrite(fd, "a", 1, 0);
	if (rc < 0) {
		perror("pwrite");
		close(fd);
		return 1;
	}

	addr[0] = 'B';
	addr[1] = 'U';
	addr[2] = 'G';

	while (1) {
		printf("Press enter to change buffer contents\n");
		getchar();
		addr[3]++;
		printf("Buffer contents changed\n");
	}

	// This is not reached.
	rc = munmap(addr, PAGE_SIZE);
	if (rc < 0) {
		perror("munmap");
		return 1;
	}

	close(fd);
	return 0;
}