Attachment 314573 Details for Bug 459337 – second testcase

second testcase

testcase-read-snapshot-vs-write-origin-2.c (text/plain), 6.76 KB, created by Mikuláš Patočka on 2008-08-19 21:05:55 UTC

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Creator: Mikuláš Patočka

Created: 2008-08-19 21:05:55 UTC

Size: 6.76 KB

patch

obsolete

>#define _XOPEN_SOURCE 500
>#define _GNU_SOURCE
>#include <stdio.h>
>#include <stdlib.h>
>#include <unistd.h>
>#include <fcntl.h>
>#include <string.h>
>#include <errno.h>
>#include <malloc.h>
>#include <pthread.h>
>#include <asm/unistd.h>
>
>/*
> * A testcase for a race-condition in dm-snapshots.
> *
> * Change "VG" symbol to a volume group name that you are using.
> * The group should be on real disk with NCQ disabled.
> * No virtualization, no network disks, no ramdisk, no pagecache-backed loopback
> * (dm-loop is OK)
> * Use a CFQ disk scheduler on the physical device.
> *
> * You may tune the parameters with this #defines, if you have too fast disk,
> * try increasing number of threads.
> *
> * How does it work:
> *	It creates 10MB logical volume, fills it with a pattern and creates
> *	snapshot.
> *	Then, it spawns 10 threads, and synchronizes them so that the main
> *	thread simultaneously starts writing to the main volume and 10 helper
> *	threads start reading the snapshot.
> *	All the threads run in lockstep, operating on the same block
> *	simultaneously (note the unusual use of 3 rw-locks for maintaining the
> *	lockstep).
> *	The reader threads have much lower I/O priority than the main writing
> *	thread, so that their reads will be submitted, but will eventually wait
> *	until the main thread does its relocate and write. The readers will then
> *	read from the old overwritten area and signal an error.
> */
>
>#define VG		"vg1"
>#define LV		"test_lv"
>#define LV_SNAP		"test_snap"
>#define MEGABYTES	"12"
>#define SNAP_MEGABYTES	"16"
>#define THREADS		10
>#define BS		4096
>#define ORIG_PATTERN	'p'
>#define NEW_PATTERN	'n'
>
>enum {
>	IOPRIO_CLASS_NONE,
>	IOPRIO_CLASS_RT,
>	IOPRIO_CLASS_BE,
>	IOPRIO_CLASS_IDLE,
>};
>
>enum {
>	IOPRIO_WHO_PROCESS = 1,
>	IOPRIO_WHO_PGRP,
>	IOPRIO_WHO_USER,
>};
>
>#define IOPRIO_CLASS_SHIFT	13
>
>static inline int ioprio_set(int which, int who, int ioprio)
>{
>	return syscall(__NR_ioprio_set, which, who, ioprio);
>}
>
>static inline int ioprio_get(int which, int who)
>{
>	return syscall(__NR_ioprio_get, which, who);
>}
>
>#define PRIO_READER	((IOPRIO_CLASS_IDLE << IOPRIO_CLASS_SHIFT) | 0xff)
>#define PRIO_WRITER	(IOPRIO_CLASS_RT << IOPRIO_CLASS_SHIFT)
>
>static void do_cmd(char *cmd, int ign_err)
>{
>	int r;
>	fprintf(stderr, "* %s\n", cmd);
>	r = system(cmd);
>	if (r) {
>		if (r == -1) {
>			perror("system");
>		} else {
>			if (ign_err) return;
>			fprintf(stderr, "return code %x\n", r);
>		}
>		exit(1);
>	}
>}
>
>static char pattern[BS];
>
>static int h_orig, h_snap;
>static int n;
>static long long test_of;
>static pthread_rwlock_t rw_lock_1;
>static pthread_rwlock_t rw_lock_2;
>static pthread_rwlock_t rw_lock_3;
>static volatile int started = 0;
>
>static void pthread_error(int r)
>{
>	fprintf(stderr, "pthread_error: %s\n", strerror(r));
>	exit(1);
>}
>
>static void *test_read(void *of)
>{
>	int r;
>	char *t = memalign(BS, BS);
>	if (!t) perror("memalign"), exit(1);
>	if ((r = pread(h_snap, t, BS, *(long long *)of)) != BS) {
>		fprintf(stderr, "can't read (%d): %s\n", r, strerror(errno));
>		exit(1);
>	}
>	if (memcmp(pattern, t, BS)) {
>		int i;
>		for (i = 0; i < BS; i++) if (t[i] != pattern[i]) break;
>		fprintf(stderr, "!!!! SNAPSHOT VOLUME DAMAGE AT BLOCK OFFSET %llX, BYTE OFFSET %X: %02x != %02x\n", *(long long *)of, i, (unsigned char)t[i], (unsigned char)pattern[i]);
>		exit(2);
>	}
>	free(t);
>	return NULL;
>}
>
>static void *test_thread(void *_)
>{
>	int r;
>	//fprintf(stderr, "start\n");
>	if ((r = ioprio_set(IOPRIO_WHO_PROCESS, 0, PRIO_READER))) perror("ioprio_set"), exit(1);
>	if ((r = pthread_rwlock_rdlock(&rw_lock_2))) pthread_error(r);
>	started = 1;
>	if ((r = ioprio_get(IOPRIO_WHO_PROCESS, 0)) != PRIO_READER) {
>		if (r == -1) perror("ioprio_get");
>		else fprintf(stderr, "reader priority not set: %x\n", r);
>		exit(1);
>	}
>	again:
>	if ((r = pthread_rwlock_rdlock(&rw_lock_1))) pthread_error(r);
>	if ((r = pthread_rwlock_unlock(&rw_lock_2))) pthread_error(r);
>	if (test_of == -1) {
>		if ((r = pthread_rwlock_unlock(&rw_lock_1))) pthread_error(r);
>		//fprintf(stderr, "return\n");
>		return NULL;
>	}
>	//fprintf(stderr, "test(%lld)\n", test_of);
>	test_read(&test_of);
>	if ((r = pthread_rwlock_rdlock(&rw_lock_3))) pthread_error(r);
>	if ((r = pthread_rwlock_unlock(&rw_lock_1))) pthread_error(r);
>	if ((r = pthread_rwlock_rdlock(&rw_lock_2))) pthread_error(r);
>	if ((r = pthread_rwlock_unlock(&rw_lock_3))) pthread_error(r);
>	goto again;
>}
>
>int main(void)
>{
>	int i, j, r;
>	char *np;
>	pthread_t thr[THREADS];
>
>	memset(pattern, ORIG_PATTERN, sizeof pattern);
>
>	do_cmd("lvremove -f "VG"/"LV_SNAP"", 1);
>	do_cmd("lvremove -f "VG"/"LV"", 1);
>	do_cmd("lvcreate -L "MEGABYTES" -n "LV" "VG"", 0);
>
>	h_orig = open("/dev/mapper/"VG"-"LV"", O_RDWR);
>	if (h_orig < 0) perror("open orig"), exit(1);
>	n = 0;
>	while (write(h_orig, pattern, BS) == BS) {
>		n++;
>		fprintf(stderr, "creating %llx...\r", (long long)n * BS);
>	}
>	if (fsync(h_orig)) perror("fsync"), exit(1);
>	fprintf(stderr,"\n");
>	lseek(h_orig, 0, SEEK_SET);
>	close(h_orig);
>
>	do_cmd("lvcreate -L "SNAP_MEGABYTES" -n "LV_SNAP" -s "VG"/"LV"", 0);
>
>	h_orig = open("/dev/mapper/"VG"-"LV"", O_RDWR | O_DIRECT);
>	if (h_orig < 0) perror("open orig"), exit(1);
>
>	h_snap = open("/dev/mapper/"VG"-"LV_SNAP"", O_RDONLY | O_DIRECT);
>	if (h_snap < 0) perror("open snap"), exit(1);
>
>	if ((r = pthread_rwlock_init(&rw_lock_1, NULL))) pthread_error(r);
>	if ((r = pthread_rwlock_init(&rw_lock_2, NULL))) pthread_error(r);
>	if ((r = pthread_rwlock_init(&rw_lock_3, NULL))) pthread_error(r);
>	if ((r = pthread_rwlock_wrlock(&rw_lock_1))) pthread_error(r);
>	if ((r = pthread_rwlock_wrlock(&rw_lock_3))) pthread_error(r);
>
>	if ((r = ioprio_set(IOPRIO_WHO_PROCESS, 0, PRIO_WRITER))) perror("ioprio_set"), exit(1);
>
>	for (j = 0; j < THREADS; j++) {
>		if ((r = pthread_create(&thr[j], NULL, test_thread, NULL))) pthread_error(r);
>	}
>	while (!started) usleep(1000);
>
>	if ((r = ioprio_get(IOPRIO_WHO_PROCESS, 0)) != PRIO_WRITER) {
>		if (r == -1) perror("ioprio_get");
>		else fprintf(stderr, "writer priority not set: %x\n", r);
>		exit(1);
>	}
>
>	np = memalign(BS, BS);
>	if (!np) perror("memalign"), exit(1);
>	memset(np, NEW_PATTERN, BS);
>	for (i = 0; i < n; i++) {
>		test_of = (off_t)i * BS;
>		fprintf(stderr, "testing %llx...\r", test_of);
>		if ((r = pthread_rwlock_unlock(&rw_lock_1))) pthread_error(r);
>		if (pwrite(h_orig, np, BS, test_of) != BS) {
>			fprintf(stderr, "can't write (%d): %s\n", r, strerror(errno));
>			exit(1);
>		}
>		if ((r = pthread_rwlock_wrlock(&rw_lock_2))) pthread_error(r);
>		if ((r = pthread_rwlock_unlock(&rw_lock_3))) pthread_error(r);
>		if ((r = pthread_rwlock_wrlock(&rw_lock_1))) pthread_error(r);
>		if ((r = pthread_rwlock_unlock(&rw_lock_2))) pthread_error(r);
>		if ((r = pthread_rwlock_wrlock(&rw_lock_3))) pthread_error(r);
>	}
>	fprintf(stderr,"\n");
>
>	test_of = -1;
>	if ((r = pthread_rwlock_unlock(&rw_lock_1))) pthread_error(r);
>
>	for (j = 0; j < THREADS; j++) {
>		if ((r = pthread_join(thr[j], NULL))) pthread_error(r);
>	}
>
>	fprintf(stderr, "TEST PASSED OK.\n");
>
>	return 0;
>}

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Attachments on bug 459337: 314570 | 314571 | 314572 | 314573