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1 /******************************************************************************/
2 /* Copyright (c) Tim LaBerge <tim.laberge@quantum.com>, 2009                  */
3 /*                                                                            */
4 /* This program is free software;  you can redistribute it and/or modify      */
5 /* it under the terms of the GNU General Public License as published by       */
6 /* the Free Software Foundation; either version 2 of the License, or          */
7 /* (at your option) any later version.                                        */
8 /*                                                                            */
9 /* This program is distributed in the hope that it will be useful,            */
10 /* but WITHOUT ANY WARRANTY;  without even the implied warranty of            */
11 /* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See                  */
12 /* the GNU General Public License for more details.                           */
13 /*                                                                            */
14 /* You should have received a copy of the GNU General Public License          */
15 /* along with this program;  if not, write to the Free Software Foundation,   */
16 /* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA           */
17 /*                                                                            */
18 /******************************************************************************/
19 
20 /******************************************************************************/
21 /*                                                                            */
22 /* File:        dma_thread_diotest7.c                                         */
23 /*                                                                            */
24 /* Description: The man page for open(2) states the following:                */
25 /*   O_DIRECT (Since Linux 2.6.10). Try to minimize cache effects of the I/O  */
26 /*   to and from this file. In general this will degrade performance, but it  */
27 /*   is useful in special situations, such as when applications do their own  */
28 /*   caching. File I/O is done directly to/from user space buffers. The I/O is*/
29 /*   synchronous, that is, at the completion of a read(2) or write(2), data is*/
30 /*   guranteed to have been transferred. Under Linux 2.4 transfer sizes, and  */
31 /*   the alignment of user buffer and file  offset  must all be multiples of  */
32 /*   the logical block size of the file system.  Under Linux 2.6 alignment to */
33 /*   512-byte bound-aries suffices.                                           */
34 /*   However, it appears that data corruption may occur when a multithreaded  */
35 /*   process reads into a non-page size aligned user buffer. A test program   */
36 /*   which reliably reproduces the problem on ext3 and xfs is attached. The   */
37 /*   program creates, patterns, reads, and verify a series of files. In the   */
38 /*   read phase, a file is opened with O_DIRECT n times, where n is the       */
39 /*   number of cpu's. A single buffer large enough to contain the file is     */
40 /*   allocated and patterned with data not found in any of the files. The     */
41 /*   alignment of the buffer is controlled by a command line option. Each file*/
42 /*   is read in parallel by n threads, where n is the number of cpu's. Thread */
43 /*   0 reads the first page of data from the file into the first page of the  */
44 /*   buffer, thread 1 reads the second page of data in to the second page of  */
45 /*   the buffer, and so on.  Thread n - 1 reads the remainder of the file into*/
46 /*   the remainder of the buffer.                                             */
47 /*   After a thread reads data into the buffer, it immediately verifies that  */
48 /*   the contents of the buffer are correct. If the buffer contains corrupt   */
49 /*   data, the thread dumps the data surrounding the corruption and calls     */
50 /*   abort(). Otherwise, the thread exits.                                    */
51 /*   Crucially, before the reader threads are dispatched, another thread is   */
52 /*   started which calls fork()/msleep() in a loop until all reads are compl- */
53 /*   eted. The child created by fork() does nothing but call exit(0). A comm- */
54 /*   and line option controls whether the buffer is aligned.  In the case wh- */
55 /*   ere the buffer is aligned on a page boundary, all is well. In the case   */
56 /*   where the buffer is aligned on a page + 512 byte offset, corruption is   */
57 /*   seen frequently.                                                         */
58 /*   I believe that what is happening is that in the direct IO path, because  */
59 /*   the user's buffer is not aligned, some user pages are being mapped twice.*/
60 /*   When a fork() happens in between the calls to map the page, the page will*/
61 /*   be marked as COW. When the second map happens (via get_user_pages()), a  */
62 /*   new physical page will be allocated and copied. Thus, there is a race    */
63 /*   between the completion of the first read from disk (and write to the user*/
64 /*   page) and get_user_pages() mapping the page for the second time. If the  */
65 /*   write does not complete before the page is copied, the user will see     */
66 /*   stale data in the first 512 bytes of this page of their buffer. Indeed,  */
67 /*   this is corruption most frequently seen. (It's also possible for the race*/
68 /*   to be lost the other way, so that the last 3584 bytes of the page are    */
69 /*   stale.)                                                                  */
70 /*   The attached program (which is a heavily modified version of a program   */
71 /*   provided by a customer seeing this problem) reliably reproduces the pro- */
72 /*   blem on any multicore linux machine on both ext3 and xfs, although any   */
73 /*   filesystem using the generic blockdev_direct_IO() routine is probably    */
74 /*   vulnerable. I've seen a few threads that mention the potential for this  */
75 /*   kind of problem, but no definitive solution or workaround (other than    */
76 /*   "Don't do that").                                                        */
77 /*   http://marc.info/?l=linux-mm&m=122668235304637&w=2                       */
78 /*                                                                            */
79 /* Total Tests: 1                                                             */
80 /*                                                                            */
81 /* Test Name:   dma_thread_diotest7                                           */
82 /*                                                                            */
83 /* Author:      Tim LaBerge <tim.laberge@quantum.com>                         */
84 /*                                                                            */
85 /* History:     Reported - Jan 07 2009 - Li Zefan <lizf@cn.fujitsu.com>       */
86 /*              Ported   - Jan 23 2009 - Subrata <subrata@linux.vnet.ibm.com> */
87 /*                                                                            */
88 /******************************************************************************/
89 
90 #define _GNU_SOURCE 1
91 
92 #include <stdio.h>
93 #include <stdint.h>
94 #include <stdlib.h>
95 #include <fcntl.h>
96 #include <unistd.h>
97 #include <memory.h>
98 #include <pthread.h>
99 #include <getopt.h>
100 #include <errno.h>
101 #include <sys/types.h>
102 #include <sys/wait.h>
103 #include <sys/mount.h>
104 
105 #include "test.h"
106 #include "safe_macros.h"
107 
108 #define FILESIZE	(12*1024*1024)
109 #define READSIZE	(1024*1024)
110 
111 #define MNT_POINT	"mntpoint"
112 #define FILE_BASEPATH   MNT_POINT "/_dma_thread_test_%.04d.tmp"
113 #define DIR_MODE	(S_IRUSR|S_IWUSR|S_IXUSR|S_IRGRP| \
114 			 S_IXGRP|S_IROTH|S_IXOTH)
115 #define FILECOUNT	100
116 #define PATTERN		(0xfa)
117 #define PAGE_SIZE	getpagesize()
118 #define MIN_WORKERS	2
119 #define MAX_WORKERS	(READSIZE/PAGE_SIZE)
120 
121 char *TCID = "dma_thread_diotest";
122 int TST_TOTAL = 1;
123 
124 static void setup(void);
125 static void dma_thread_diotest_verify(void);
126 static void cleanup(void);
127 static void help(void);
128 
129 static unsigned char *buffer;
130 
131 static char *align_str;
132 static int align;
133 static char *workers_str;
134 static int workers;
135 static char *device;
136 static int mount_flag;
137 static option_t options[] = {
138 	{"a:", NULL, &align_str},
139 	{"w:", NULL, &workers_str},
140 	{NULL, NULL, NULL}
141 };
142 
143 static volatile int done;
144 static volatile int tst_result;
145 
146 typedef struct {
147 	pthread_t tid;
148 	int worker_number;
149 	int fd;
150 	int offset;
151 	int length;
152 	int pattern;
153 	unsigned char *buffer;
154 } worker_t;
155 static worker_t *worker;
156 
worker_thread(void * arg)157 static void *worker_thread(void *arg)
158 {
159 	int i, k;
160 	int nread;
161 	worker_t *worker = (worker_t *)arg;
162 	int offset = worker->offset;
163 	int fd = worker->fd;
164 	unsigned char *buffer = worker->buffer;
165 	int pattern = worker->pattern;
166 	int length = worker->length;
167 
168 	if (lseek(fd, offset, SEEK_SET) < 0) {
169 		fprintf(stderr, "Failed to lseek to %d on fd %d: %s.\n",
170 			offset, fd, strerror(errno));
171 		return (void *) 1;
172 	}
173 
174 	nread = read(fd, buffer, length);
175 	if (nread == -1 || nread != length) {
176 		fprintf(stderr, "read failed in worker thread%d: %s",
177 			worker->worker_number, strerror(errno));
178 		return (void *) 1;
179 	}
180 
181 	/* Corruption check */
182 	for (i = 0; i < length; i++) {
183 		if (buffer[i] != pattern) {
184 			printf("Bad data at 0x%.06x: %p, \n", i, buffer + i);
185 			printf("Data dump starting at 0x%.06x:\n", i - 8);
186 			printf("Expect 0x%x followed by 0x%x:\n",
187 			       pattern, PATTERN);
188 
189 			for (k = 0; k < 16; k++) {
190 				printf("%02x ", buffer[i - 8 + k]);
191 				if (k == 7) {
192 					printf("\n");
193 				}
194 			}
195 
196 			printf("\n");
197 			tst_result = 1;
198 			return NULL;
199 		}
200 	}
201 
202 	return NULL;
203 }
204 
fork_thread(void * arg)205 static void *fork_thread(void *arg)
206 {
207 	pid_t pid;
208 
209 	(void) arg;
210 
211 	while (!done) {
212 		pid = tst_fork();
213 		if (pid == 0) {
214 			exit(0);
215 		} else if (pid < 0) {
216 			fprintf(stderr, "Failed to fork child: %s.\n",
217 				strerror(errno));
218 			return (void *) 1;
219 		}
220 		waitpid(pid, NULL, 0);
221 		usleep(100);
222 	}
223 
224 	return NULL;
225 }
226 
main(int argc,char * argv[])227 int main(int argc, char *argv[])
228 {
229 	int i, lc;
230 
231 	workers = sysconf(_SC_NPROCESSORS_ONLN);
232 	if (workers > MAX_WORKERS)
233 		workers = MAX_WORKERS;
234 	tst_parse_opts(argc, argv, options, help);
235 
236 	setup();
237 
238 	for (lc = 0; TEST_LOOPING(lc); lc++) {
239 		tst_count = 0;
240 
241 		for (i = 0; i < TST_TOTAL; i++)
242 			dma_thread_diotest_verify();
243 	}
244 
245 	cleanup();
246 	tst_exit();
247 }
248 
dma_thread_diotest_verify(void)249 static void dma_thread_diotest_verify(void)
250 {
251 	int n, j, offset, rc;
252 	void *retval;
253 	char filename[PATH_MAX];
254 	pthread_t fork_tid;
255 
256 	tst_result = 0;
257 
258 	for (n = 1; n <= FILECOUNT; n++) {
259 		snprintf(filename, sizeof(filename), FILE_BASEPATH, n);
260 		for (j = 0; j < workers; j++) {
261 			worker[j].fd = SAFE_OPEN(cleanup, filename,
262 						 O_RDONLY | O_DIRECT);
263 			worker[j].pattern = n;
264 		}
265 
266 		tst_resm(TINFO, "Reading file %d.", n);
267 
268 		for (offset = 0; offset < FILESIZE; offset += READSIZE) {
269 			memset(buffer, PATTERN, READSIZE + align);
270 			for (j = 0; j < workers; j++) {
271 				worker[j].offset = offset + j * PAGE_SIZE;
272 				worker[j].buffer =
273 				    buffer + align + j * PAGE_SIZE;
274 				worker[j].length = PAGE_SIZE;
275 			}
276 			/* The final worker reads whatever is left over. */
277 			worker[workers - 1].length =
278 			    READSIZE - PAGE_SIZE * (workers - 1);
279 
280 			done = 0;
281 
282 			rc = pthread_create(&fork_tid, NULL, fork_thread, NULL);
283 			if (rc != 0) {
284 				tst_brkm(TBROK, cleanup, "pthread_create "
285 					 "failed: %s", strerror(rc));
286 			}
287 
288 			for (j = 0; j < workers; j++) {
289 				rc = pthread_create(&worker[j].tid, NULL,
290 						    worker_thread, worker + j);
291 				if (rc != 0) {
292 					tst_brkm(TBROK, cleanup, "Can't create"
293 						 "worker thread %d: %s",
294 						 j, strerror(rc));
295 				}
296 			}
297 
298 			for (j = 0; j < workers; j++) {
299 				rc = pthread_join(worker[j].tid, &retval);
300 				if (rc != 0) {
301 					tst_brkm(TBROK, cleanup, "Failed to "
302 						 "join worker thread %d: %s.",
303 						 j, strerror(rc));
304 				}
305 				if ((intptr_t)retval != 0) {
306 					tst_brkm(TBROK, cleanup, "there is"
307 						 "some errors in worker[%d],"
308 						 "return value: %ld",
309 						 j, (intptr_t)retval);
310 				}
311 			}
312 
313 			/* Let the fork thread know it's ok to exit */
314 			done = 1;
315 
316 			rc = pthread_join(fork_tid, &retval);
317 			if (rc != 0) {
318 				tst_brkm(TBROK, cleanup,
319 					 "Failed to join fork thread: %s.",
320 					 strerror(rc));
321 			}
322 			if ((intptr_t)retval != 0) {
323 				tst_brkm(TBROK, cleanup,
324 					 "fork() failed in fork thread:"
325 					 "return value: %ld", (intptr_t)retval);
326 			}
327 		}
328 
329 		/* Close the fd's for the next file. */
330 		for (j = 0; j < workers; j++)
331 			SAFE_CLOSE(cleanup, worker[j].fd);
332 		if (tst_result)
333 			break;
334 	}
335 
336 	if (tst_result)
337 		tst_resm(TFAIL, "data corruption is detected");
338 	else
339 		tst_resm(TPASS, "data corruption is not detected");
340 }
341 
setup(void)342 static void setup(void)
343 {
344 	char filename[PATH_MAX];
345 	int n, j, fd, directflag = 1;
346 	long type;
347 
348 	if (align_str) {
349 		align = atoi(align_str);
350 		if (align < 0 || align > PAGE_SIZE)
351 			tst_brkm(TCONF, NULL, "Bad alignment %d.", align);
352 	}
353 	tst_resm(TINFO, "using alignment %d", align);
354 
355 	if (workers_str) {
356 		workers = atoi(workers_str);
357 		if (workers < MIN_WORKERS || workers > MAX_WORKERS) {
358 			tst_brkm(TCONF, NULL, "Worker count %d not between "
359 				 "%d and %d, inclusive",
360 				 workers, MIN_WORKERS, MAX_WORKERS);
361 		}
362 	}
363 	tst_resm(TINFO, "using %d workers.", workers);
364 
365 	tst_sig(FORK, DEF_HANDLER, NULL);
366 	tst_require_root();
367 
368 	TEST_PAUSE;
369 
370 	tst_tmpdir();
371 
372 	/*
373 	 * Some file systems may not implement the O_DIRECT flag and open() will
374 	 * fail with EINVAL if it is used. So add this check for current
375 	 * filesystem current directory is in, if not supported, we choose to
376 	 * have this test in LTP_BIG_DEV and mkfs it as ext3.
377 	 */
378 	fd = open("testfile", O_CREAT | O_DIRECT, 0644);
379 	if (fd < 0 && errno == EINVAL) {
380 		type = tst_fs_type(NULL, ".");
381 		tst_resm(TINFO, "O_DIRECT flag is not supported on %s "
382 			 "filesystem", tst_fs_type_name(type));
383 		directflag = 0;
384 	} else if (fd > 0) {
385 		SAFE_CLOSE(NULL, fd);
386 	}
387 
388 	SAFE_MKDIR(cleanup, MNT_POINT, DIR_MODE);
389 
390 	/*
391 	 * verify whether the current directory has enough free space,
392 	 * if it is not satisfied, we will use the LTP_BIG_DEV, which
393 	 * will be exported by runltp with "-z" option.
394 	 */
395 	if (!directflag || !tst_fs_has_free(NULL, ".", 1300, TST_MB)) {
396 		device = getenv("LTP_BIG_DEV");
397 		if (device == NULL) {
398 			tst_brkm(TCONF, NULL,
399 				 "you must specify a big blockdevice(>1.3G)");
400 		} else {
401 			tst_mkfs(NULL, device, "ext3", NULL, NULL);
402 		}
403 
404 		SAFE_MOUNT(NULL, device, MNT_POINT, "ext3", 0, NULL);
405 		mount_flag = 1;
406 	}
407 
408 	worker = SAFE_MALLOC(cleanup, workers * sizeof(worker_t));
409 
410 	for (j = 0; j < workers; j++)
411 		worker[j].worker_number = j;
412 
413 	for (n = 1; n <= FILECOUNT; n++) {
414 		snprintf(filename, sizeof(filename), FILE_BASEPATH, n);
415 
416 		if (tst_fill_file(filename, n, FILESIZE, 1)) {
417 			tst_brkm(TBROK, cleanup, "failed to create file: %s",
418 				 filename);
419 		}
420 	}
421 
422 	if (posix_memalign((void **)&buffer, PAGE_SIZE, READSIZE + align) != 0)
423 		tst_brkm(TBROK, cleanup, "call posix_memalign failed");
424 }
425 
cleanup(void)426 static void cleanup(void)
427 {
428 	free(buffer);
429 
430 	if (mount_flag && tst_umount(MNT_POINT) < 0)
431 		tst_resm(TWARN | TERRNO, "umount device:%s failed", device);
432 
433 	free(worker);
434 
435 	tst_rmdir();
436 }
437 
help(void)438 static void help(void)
439 {
440 	printf("-a align read buffer to offset <alignment>.\n");
441 	printf("-w number of worker threads, 2 (default) to %d,"
442 	       " defaults to number of cores.\n", MAX_WORKERS);
443 }
444