dio_append.c revision 4548c6cf9bcdd96d8303caa4130ab638b61f8a30 
1
2/*
3 * Copyright (c) 2004 Daniel McNeil <daniel@osdl.org>
4 *               2004 Open Source Development Lab
5 *   This program is free software;  you can redistribute it and/or modify
6 *   it under the terms of the GNU General Public License as published by
7 *   the Free Software Foundation; either version 2 of the License, or
8 *   (at your option) any later version.
9 *
10 *   This program is distributed in the hope that it will be useful,
11 *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
12 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
13 *   the GNU General Public License for more details.
14 *
15 *   You should have received a copy of the GNU General Public License
16 *   along with this program;  if not, write to the Free Software
17 *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
18 *
19 * Module: .c
20 */
21
22/*
23 * Change History:
24 *
25 * 2/2004  Marty Ridgeway (mridge@us.ibm.com) Changes to adapt to LTP
26 *
27 */
28/*
29 * dio_append - append zeroed data to a file using O_DIRECT while
30 *	a 2nd process is doing buffered reads and check if the buffer
31 *	reads always see zero.
32 */
33#define _GNU_SOURCE
34
35#include <stdlib.h>
36#include <sys/types.h>
37#include <signal.h>
38#include <fcntl.h>
39#include <stdio.h>
40#include <unistd.h>
41#include <memory.h>
42#include <limits.h>
43#define NUM_CHILDREN 8
44
45char *check_zero(unsigned char *buf, int size)
46{
47	unsigned char *p;
48
49	p = buf;
50
51	while (size > 0) {
52		if (*buf != 0) {
53			fprintf(stderr, "non zero buffer at buf[%d] => 0x%02x,%02x,%02x,%02x\n",
54				buf - p, (unsigned int)buf[0],
55				size > 1 ? (unsigned int)buf[1] : 0,
56				size > 2 ? (unsigned int)buf[2] : 0,
57				size > 3 ? (unsigned int)buf[3] : 0);
58			fprintf(stderr, "buf %p, p %p\n", buf, p);
59			return buf;
60		}
61		buf++;
62		size--;
63	}
64	return 0;	/* all zeros */
65}
66
67int read_eof(char *filename)
68{
69	int fd;
70	int i;
71	int r;
72	char buf[4096];
73
74	while ((fd = open(filename, O_RDONLY)) < 0) {
75		sleep(1);	/* wait for file to be created */
76	}
77
78	for (i = 0 ; i < 1000000; i++) {
79		off_t offset;
80		char *bufoff;
81
82		offset = lseek(fd, SEEK_END, 0);
83		r = read(fd, buf, 4096);
84		if (r > 0) {
85			if ((bufoff = check_zero(buf, r))) {
86				fprintf(stderr, "non-zero read at offset %p\n",
87					offset + bufoff);
88				exit(1);
89			}
90		}
91	}
92  return 0;
93}
94
95void dio_append(char *filename)
96{
97	int fd;
98	void *bufptr;
99	int i;
100	int w;
101
102	fd = open(filename, O_DIRECT|O_WRONLY|O_CREAT, 0666);
103
104	if (fd < 0) {
105		perror("cannot create file");
106		return;
107	}
108
109	if (posix_memalign(&bufptr, 4096, 64*1024)) {
110		perror("cannot malloc aligned memory");
111		return;
112	}
113
114	memset(bufptr, 0, 64*1024);
115	for (i = 0; i < 1000; i++) {
116		if ((w = write(fd, bufptr, 64*1024)) != 64*1024) {
117			fprintf(stderr, "write %d returned %d\n", i, w);
118		}
119	}
120}
121
122int main(int argc, char **argv)
123{
124	char filename[PATH_MAX];
125	int pid[NUM_CHILDREN];
126	int num_children = 1;
127	int i;
128
129	snprintf(filename, sizeof(filename), "%s/aiodio/file",
130		getenv("TMP") ? getenv("TMP") : "/tmp");
131
132	printf("Begin dio_append test...\n");
133
134	for (i = 0; i < num_children; i++) {
135		if ((pid[i] = fork()) == 0) {
136			/* child */
137			return read_eof(filename);
138		} else if (pid[i] < 0) {
139			/* error */
140			perror("fork error");
141			break;
142		} else {
143			/* Parent */
144			continue;
145		}
146	}
147
148	/*
149	 * Parent appends to end of file using direct i/o
150	 */
151
152	dio_append(filename);
153
154	for (i = 0; i < num_children; i++) {
155		kill(pid[i], SIGTERM);
156	}
157  return 0;
158}
159