X-Git-Url: http://git.ipfire.org/?p=thirdparty%2Fmdadm.git;a=blobdiff_plain;f=sysfs.c;h=d28e21a251eba7851a27c6ba96a97f9795e10259;hp=f1c66692019a9fb970f3d1b49a54a1d9f5e0d2af;hb=36138e4e4b6c3f9db21e65ac8962bf22d4b2c274;hpb=a5062b1cb6ad51ebaa1f8b60e1cfe5408dbf17d7

diff --git a/sysfs.c b/sysfs.c
index f1c66692..d28e21a2 100644
--- a/sysfs.c
+++ b/sysfs.c
@@ -27,15 +27,15 @@
 #include	<dirent.h>
 #include	<ctype.h>
 
-int load_sys(char *path, char *buf)
+int load_sys(char *path, char *buf, int len)
 {
 	int fd = open(path, O_RDONLY);
 	int n;
 	if (fd < 0)
 		return -1;
-	n = read(fd, buf, 1024);
+	n = read(fd, buf, len);
 	close(fd);
-	if (n <0 || n >= 1024)
+	if (n <0 || n >= len)
 		return -1;
 	buf[n] = 0;
 	if (n && buf[n-1] == '\n')
@@ -57,16 +57,12 @@ void sysfs_free(struct mdinfo *sra)
 	}
 }
 
-int sysfs_open(int devnum, char *devname, char *attr)
+int sysfs_open(char *devnm, char *devname, char *attr)
 {
 	char fname[50];
 	int fd;
-	char *mdname = devnum2devname(devnum);
 
-	if (!mdname)
-		return -1;
-
-	sprintf(fname, "/sys/block/%s/md/", mdname);
+	sprintf(fname, "/sys/block/%s/md/", devnm);
 	if (devname) {
 		strcat(fname, devname);
 		strcat(fname, "/");
@@ -75,41 +71,42 @@ int sysfs_open(int devnum, char *devname, char *attr)
 	fd = open(fname, O_RDWR);
 	if (fd < 0 && errno == EACCES)
 		fd = open(fname, O_RDONLY);
-	free(mdname);
 	return fd;
 }
 
-void sysfs_init(struct mdinfo *mdi, int fd, int devnum)
+void sysfs_init_dev(struct mdinfo *mdi, unsigned long devid)
+{
+	snprintf(mdi->sys_name,
+		 sizeof(mdi->sys_name), "dev-%s", devid2kname(devid));
+}
+
+void sysfs_init(struct mdinfo *mdi, int fd, char *devnm)
 {
 	mdi->sys_name[0] = 0;
 	if (fd >= 0) {
 		mdu_version_t vers;
 		if (ioctl(fd, RAID_VERSION, &vers) != 0)
 			return;
-		devnum = fd2devnum(fd);
+		devnm = fd2devnm(fd);
 	}
-	if (devnum == NoMdDev)
+	if (devnm == NULL)
 		return;
-	fmt_devname(mdi->sys_name, devnum);
+	strcpy(mdi->sys_name, devnm);
 }
 
-
-struct mdinfo *sysfs_read(int fd, int devnum, unsigned long options)
+struct mdinfo *sysfs_read(int fd, char *devnm, unsigned long options)
 {
 	char fname[PATH_MAX];
 	char buf[PATH_MAX];
 	char *base;
 	char *dbase;
 	struct mdinfo *sra;
-	struct mdinfo *dev;
+	struct mdinfo *dev, **devp;
 	DIR *dir = NULL;
 	struct dirent *de;
 
-	sra = malloc(sizeof(*sra));
-	if (sra == NULL)
-		return sra;
-	memset(sra, 0, sizeof(*sra));
-	sysfs_init(sra, fd, devnum);
+	sra = xcalloc(1, sizeof(*sra));
+	sysfs_init(sra, fd, devnm);
 	if (sra->sys_name[0] == 0) {
 		free(sra);
 		return NULL;
@@ -121,7 +118,7 @@ struct mdinfo *sysfs_read(int fd, int devnum, unsigned long options)
 	sra->devs = NULL;
 	if (options & GET_VERSION) {
 		strcpy(base, "metadata_version");
-		if (load_sys(fname, buf))
+		if (load_sys(fname, buf, sizeof(buf)))
 			goto abort;
 		if (strncmp(buf, "none", 4) == 0) {
 			sra->array.major_version =
@@ -140,31 +137,31 @@ struct mdinfo *sysfs_read(int fd, int devnum, unsigned long options)
 	}
 	if (options & GET_LEVEL) {
 		strcpy(base, "level");
-		if (load_sys(fname, buf))
+		if (load_sys(fname, buf, sizeof(buf)))
 			goto abort;
 		sra->array.level = map_name(pers, buf);
 	}
 	if (options & GET_LAYOUT) {
 		strcpy(base, "layout");
-		if (load_sys(fname, buf))
+		if (load_sys(fname, buf, sizeof(buf)))
 			goto abort;
 		sra->array.layout = strtoul(buf, NULL, 0);
 	}
 	if (options & GET_DISKS) {
 		strcpy(base, "raid_disks");
-		if (load_sys(fname, buf))
+		if (load_sys(fname, buf, sizeof(buf)))
 			goto abort;
 		sra->array.raid_disks = strtoul(buf, NULL, 0);
 	}
 	if (options & GET_DEGRADED) {
 		strcpy(base, "degraded");
-		if (load_sys(fname, buf))
+		if (load_sys(fname, buf, sizeof(buf)))
 			goto abort;
 		sra->array.failed_disks = strtoul(buf, NULL, 0);
 	}
 	if (options & GET_COMPONENT) {
 		strcpy(base, "component_size");
-		if (load_sys(fname, buf))
+		if (load_sys(fname, buf, sizeof(buf)))
 			goto abort;
 		sra->component_size = strtoull(buf, NULL, 0);
 		/* sysfs reports "K", but we want sectors */
@@ -172,19 +169,21 @@ struct mdinfo *sysfs_read(int fd, int devnum, unsigned long options)
 	}
 	if (options & GET_CHUNK) {
 		strcpy(base, "chunk_size");
-		if (load_sys(fname, buf))
+		if (load_sys(fname, buf, sizeof(buf)))
 			goto abort;
 		sra->array.chunk_size = strtoul(buf, NULL, 0);
 	}
 	if (options & GET_CACHE) {
 		strcpy(base, "stripe_cache_size");
-		if (load_sys(fname, buf))
-			goto abort;
-		sra->cache_size = strtoul(buf, NULL, 0);
+		if (load_sys(fname, buf, sizeof(buf)))
+			/* Probably level doesn't support it */
+			sra->cache_size = 0;
+		else
+			sra->cache_size = strtoul(buf, NULL, 0);
 	}
 	if (options & GET_MISMATCH) {
 		strcpy(base, "mismatch_cnt");
-		if (load_sys(fname, buf))
+		if (load_sys(fname, buf, sizeof(buf)))
 			goto abort;
 		sra->mismatch_cnt = strtoul(buf, NULL, 0);
 	}
@@ -196,7 +195,7 @@ struct mdinfo *sysfs_read(int fd, int devnum, unsigned long options)
 		size_t len;
 
 		strcpy(base, "safe_mode_delay");
-		if (load_sys(fname, buf))
+		if (load_sys(fname, buf, sizeof(buf)))
 			goto abort;
 
 		/* remove a period, and count digits after it */
@@ -217,6 +216,27 @@ struct mdinfo *sysfs_read(int fd, int devnum, unsigned long options)
 		msec = (msec * 1000) / scale;
 		sra->safe_mode_delay = msec;
 	}
+	if (options & GET_BITMAP_LOCATION) {
+		strcpy(base, "bitmap/location");
+		if (load_sys(fname, buf, sizeof(buf)))
+			goto abort;
+		if (strncmp(buf, "file", 4) == 0)
+			sra->bitmap_offset = 1;
+		else if (strncmp(buf, "none", 4) == 0)
+			sra->bitmap_offset = 0;
+		else if (buf[0] == '+')
+			sra->bitmap_offset = strtol(buf+1, NULL, 10);
+		else
+			goto abort;
+	}
+
+	if (options & GET_ARRAY_STATE) {
+		strcpy(base, "array_state");
+		if (load_sys(fname, sra->sysfs_array_state,
+			     sizeof(sra->sysfs_array_state)))
+			goto abort;
+	} else
+		sra->sysfs_array_state[0] = 0;
 
 	if (! (options & GET_DEVS))
 		return sra;
@@ -228,6 +248,8 @@ struct mdinfo *sysfs_read(int fd, int devnum, unsigned long options)
 		goto abort;
 	sra->array.spare_disks = 0;
 
+	devp = &sra->devs;
+	sra->devs = NULL;
 	while ((de = readdir(dir)) != NULL) {
 		char *ep;
 		if (de->d_ino == 0 ||
@@ -237,13 +259,11 @@ struct mdinfo *sysfs_read(int fd, int devnum, unsigned long options)
 		dbase = base + strlen(base);
 		*dbase++ = '/';
 
-		dev = malloc(sizeof(*dev));
-		if (!dev)
-			goto abort;
+		dev = xmalloc(sizeof(*dev));
 
 		/* Always get slot, major, minor */
 		strcpy(dbase, "slot");
-		if (load_sys(fname, buf)) {
+		if (load_sys(fname, buf, sizeof(buf))) {
 			/* hmm... unable to read 'slot' maybe the device
 			 * is going away?
 			 */
@@ -261,50 +281,57 @@ struct mdinfo *sysfs_read(int fd, int devnum, unsigned long options)
 				free(dev);
 				goto abort;
 			}
-			
+
 		}
 		strcpy(dev->sys_name, de->d_name);
 		dev->disk.raid_disk = strtoul(buf, &ep, 10);
 		if (*ep) dev->disk.raid_disk = -1;
 
 		strcpy(dbase, "block/dev");
-		if (load_sys(fname, buf)) {
+		if (load_sys(fname, buf, sizeof(buf))) {
 			/* assume this is a stale reference to a hot
 			 * removed device
 			 */
 			free(dev);
 			continue;
 		}
+		sra->array.nr_disks++;
 		sscanf(buf, "%d:%d", &dev->disk.major, &dev->disk.minor);
 
 		/* special case check for block devices that can go 'offline' */
 		strcpy(dbase, "block/device/state");
-		if (load_sys(fname, buf) == 0 &&
+		if (load_sys(fname, buf, sizeof(buf)) == 0 &&
 		    strncmp(buf, "offline", 7) == 0) {
 			free(dev);
 			continue;
 		}
 
 		/* finally add this disk to the array */
-		dev->next = sra->devs;
-		sra->devs = dev;
+		*devp = dev;
+		devp = & dev->next;
+		dev->next = NULL;
 
 		if (options & GET_OFFSET) {
 			strcpy(dbase, "offset");
-			if (load_sys(fname, buf))
+			if (load_sys(fname, buf, sizeof(buf)))
 				goto abort;
 			dev->data_offset = strtoull(buf, NULL, 0);
+			strcpy(dbase, "new_offset");
+			if (load_sys(fname, buf, sizeof(buf)) == 0)
+				dev->new_data_offset = strtoull(buf, NULL, 0);
+			else
+				dev->new_data_offset = dev->data_offset;
 		}
 		if (options & GET_SIZE) {
 			strcpy(dbase, "size");
-			if (load_sys(fname, buf))
+			if (load_sys(fname, buf, sizeof(buf)))
 				goto abort;
 			dev->component_size = strtoull(buf, NULL, 0) * 2;
 		}
 		if (options & GET_STATE) {
 			dev->disk.state = 0;
 			strcpy(dbase, "state");
-			if (load_sys(fname, buf))
+			if (load_sys(fname, buf, sizeof(buf)))
 				goto abort;
 			if (strstr(buf, "in_sync"))
 				dev->disk.state |= (1<<MD_DISK_SYNC);
@@ -315,7 +342,7 @@ struct mdinfo *sysfs_read(int fd, int devnum, unsigned long options)
 		}
 		if (options & GET_ERROR) {
 			strcpy(buf, "errors");
-			if (load_sys(fname, buf))
+			if (load_sys(fname, buf, sizeof(buf)))
 				goto abort;
 			dev->errors = strtoul(buf, NULL, 0);
 		}
@@ -367,7 +394,8 @@ unsigned long long get_component_size(int fd)
 	struct stat stb;
 	char fname[50];
 	int n;
-	if (fstat(fd, &stb)) return 0;
+	if (fstat(fd, &stb))
+		return 0;
 	if (major(stb.st_rdev) != (unsigned)get_mdp_major())
 		sprintf(fname, "/sys/block/md%d/md/component_size",
 			(int)minor(stb.st_rdev));
@@ -379,7 +407,7 @@ unsigned long long get_component_size(int fd)
 		return 0;
 	n = read(fd, fname, sizeof(fname));
 	close(fd);
-	if (n == sizeof(fname))
+	if (n < 0 || n == sizeof(fname))
 		return 0;
 	fname[n] = 0;
 	return strtoull(fname, NULL, 10) * 2;
@@ -400,7 +428,7 @@ int sysfs_set_str(struct mdinfo *sra, struct mdinfo *dev,
 	n = write(fd, val, strlen(val));
 	close(fd);
 	if (n != strlen(val)) {
-		dprintf(Name ": failed to write '%s' to '%s' (%s)\n",
+		dprintf("failed to write '%s' to '%s' (%s)\n",
 			val, fname, strerror(errno));
 		return -1;
 	}
@@ -415,6 +443,14 @@ int sysfs_set_num(struct mdinfo *sra, struct mdinfo *dev,
 	return sysfs_set_str(sra, dev, name, valstr);
 }
 
+int sysfs_set_num_signed(struct mdinfo *sra, struct mdinfo *dev,
+			 char *name, long long val)
+{
+	char valstr[50];
+	sprintf(valstr, "%lli", val);
+	return sysfs_set_str(sra, dev, name, valstr);
+}
+
 int sysfs_uevent(struct mdinfo *sra, char *event)
 {
 	char fname[50];
@@ -428,8 +464,13 @@ int sysfs_uevent(struct mdinfo *sra, char *event)
 		return -1;
 	n = write(fd, event, strlen(event));
 	close(fd);
+	if (n != (int)strlen(event)) {
+		dprintf("failed to write '%s' to '%s' (%s)\n",
+			event, fname, strerror(errno));
+		return -1;
+	}
 	return 0;
-}	
+}
 
 int sysfs_attribute_available(struct mdinfo *sra, struct mdinfo *dev, char *name)
 {
@@ -464,8 +505,8 @@ int sysfs_fd_get_ll(int fd, unsigned long long *val)
 
 	lseek(fd, 0, 0);
 	n = read(fd, buf, sizeof(buf));
-	if (n <= 0)
-		return -1;
+	if (n <= 0 || n == sizeof(buf))
+		return -2;
 	buf[n] = 0;
 	*val = strtoull(buf, &ep, 0);
 	if (ep == buf || (*ep != 0 && *ep != '\n' && *ep != ' '))
@@ -487,13 +528,56 @@ int sysfs_get_ll(struct mdinfo *sra, struct mdinfo *dev,
 	return n;
 }
 
+int sysfs_fd_get_two(int fd, unsigned long long *v1, unsigned long long *v2)
+{
+	/* two numbers in this sysfs file, either
+	 *  NNN (NNN)
+	 * or
+	 *  NNN / NNN
+	 */
+	char buf[80];
+	int n;
+	char *ep, *ep2;
+
+	lseek(fd, 0, 0);
+	n = read(fd, buf, sizeof(buf));
+	if (n <= 0 || n == sizeof(buf))
+		return -2;
+	buf[n] = 0;
+	*v1 = strtoull(buf, &ep, 0);
+	if (ep == buf || (*ep != 0 && *ep != '\n' && *ep != ' '))
+		return -1;
+	while (*ep == ' ' || *ep == '/' || *ep == '(')
+		ep++;
+	*v2 = strtoull(ep, &ep2, 0);
+	if (ep2 == ep || (*ep2 != 0 && *ep2 != '\n' && *ep2 != ' ' && *ep2 != ')')) {
+		*v2 = *v1;
+		return 1;
+	}
+	return 2;
+}
+
+int sysfs_get_two(struct mdinfo *sra, struct mdinfo *dev,
+		  char *name, unsigned long long *v1, unsigned long long *v2)
+{
+	int n;
+	int fd;
+
+	fd = sysfs_get_fd(sra, dev, name);
+	if (fd < 0)
+		return -1;
+	n = sysfs_fd_get_two(fd, v1, v2);
+	close(fd);
+	return n;
+}
+
 int sysfs_fd_get_str(int fd, char *val, int size)
 {
 	int n;
 
 	lseek(fd, 0, 0);
 	n = read(fd, val, size);
-	if (n <= 0)
+	if (n <= 0 || n == size)
 		return -1;
 	val[n] = 0;
 	return n;
@@ -536,13 +620,25 @@ int sysfs_set_array(struct mdinfo *info, int vers)
 	ver[0] = 0;
 	if (info->array.major_version == -1 &&
 	    info->array.minor_version == -2) {
+		char buf[1024];
+
 		strcat(strcpy(ver, "external:"), info->text_version);
 
+		/* meta version might already be set if we are setting
+		 * new geometry for a reshape.  In that case we don't
+		 * want to over-write the 'readonly' flag that is
+		 * stored in the metadata version.  So read the current
+		 * version first, and preserve the flag
+		 */
+		if (sysfs_get_str(info, NULL, "metadata_version",
+				  buf, 1024) > 0)
+			if (strlen(buf) >= 9 && buf[9] == '-')
+				ver[9] = '-';
+
 		if ((vers % 100) < 2 ||
 		    sysfs_set_str(info, NULL, "metadata_version",
 				  ver) < 0) {
-			fprintf(stderr, Name ": This kernel does not "
-				"support external metadata.\n");
+			pr_err("This kernel does not support external metadata.\n");
 			return 1;
 		}
 	}
@@ -562,9 +658,7 @@ int sysfs_set_array(struct mdinfo *info, int vers)
 		rc = sysfs_set_num(info, NULL, "array_size",
 				   info->custom_array_size/2);
 		if (rc && errno == ENOENT) {
-			fprintf(stderr, Name ": This kernel does not "
-				"have the md/array_size attribute, "
-				"the array may be larger than expected\n");
+			pr_err("This kernel does not have the md/array_size attribute, the array may be larger than expected\n");
 			rc = 0;
 		}
 		rv |= rc;
@@ -600,13 +694,7 @@ int sysfs_add_disk(struct mdinfo *sra, struct mdinfo *sd, int resume)
 		return rv;
 
 	memset(nm, 0, sizeof(nm));
-	sprintf(dv, "/sys/dev/block/%d:%d", sd->disk.major, sd->disk.minor);
-	rv = readlink(dv, nm, sizeof(nm));
-	if (rv <= 0)
-		return -1;
-	nm[rv] = '\0';
-	dname = strrchr(nm, '/');
-	if (dname) dname++;
+	dname = devid2kname(makedev(sd->disk.major, sd->disk.minor));
 	strcpy(sd->sys_name, "dev-");
 	strcpy(sd->sys_name+4, dname);
 
@@ -642,7 +730,7 @@ int sysfs_disk_to_sg(int fd)
 	struct stat st;
 	char path[256];
 	char sg_path[256];
-	char sg_major_minor[8];
+	char sg_major_minor[10];
 	char *c;
 	DIR *dir;
 	struct dirent *de;
@@ -677,7 +765,7 @@ int sysfs_disk_to_sg(int fd)
 
 	rv = read(fd, sg_major_minor, sizeof(sg_major_minor));
 	close(fd);
-	if (rv < 0)
+	if (rv < 0 || rv == sizeof(sg_major_minor))
 		return -1;
 	else
 		sg_major_minor[rv - 1] = '\0';
@@ -704,9 +792,9 @@ int sysfs_disk_to_scsi_id(int fd, __u32 *id)
 	/* from an open block device, try to retrieve it scsi_id */
 	struct stat st;
 	char path[256];
-	char *c1, *c2;
 	DIR *dir;
 	struct dirent *de;
+	int host, bus, target, lun;
 
 	if (fstat(fd, &st))
 		return 1;
@@ -718,61 +806,52 @@ int sysfs_disk_to_scsi_id(int fd, __u32 *id)
 	if (!dir)
 		return 1;
 
-	de = readdir(dir);
-	while (de) {
-		if (strchr(de->d_name, ':'))
+	for (de = readdir(dir); de; de = readdir(dir)) {
+		int count;
+
+		if (de->d_type != DT_DIR)
+			continue;
+
+		count = sscanf(de->d_name, "%d:%d:%d:%d", &host, &bus, &target, &lun);
+		if (count == 4)
 			break;
-		de = readdir(dir);
 	}
 	closedir(dir);
 
 	if (!de)
 		return 1;
 
-	c1 = de->d_name;
-	c2 = strchr(c1, ':');
-	*c2 = '\0';
-	*id = strtol(c1, NULL, 10) << 24; /* host */
-	c1 = c2 + 1;
-	c2 = strchr(c1, ':');
-	*c2 = '\0';
-	*id |= strtol(c1, NULL, 10) << 16; /* bus */
-	c1 = c2 + 1;
-	c2 = strchr(c1, ':');
-	*c2 = '\0';
-	*id |= strtol(c1, NULL, 10) << 8; /* target */
-	c1 = c2 + 1;
-	*id |= strtol(c1, NULL, 10); /* lun */
-
+	*id = (host << 24) | (bus << 16) | (target << 8) | (lun << 0);
 	return 0;
 }
 
-
-int sysfs_unique_holder(int devnum, long rdev)
+int sysfs_unique_holder(char *devnm, long rdev)
 {
-	/* Check that devnum is a holder of rdev,
+	/* Check that devnm is a holder of rdev,
 	 * and is the only holder.
 	 * we should be locked against races by
-	 * an O_EXCL on devnum
+	 * an O_EXCL on devnm
+	 * Return values:
+	 *  0 - not unique, not even a holder
+	 *  1 - unique, this is the only holder.
+	 *  2/3 - not unique, there is another holder
+	 * -1 - error, cannot find the holders
 	 */
 	DIR *dir;
 	struct dirent *de;
 	char dirname[100];
 	char l;
-	int found = 0;
+	int ret = 0;
 	sprintf(dirname, "/sys/dev/block/%d:%d/holders",
 		major(rdev), minor(rdev));
 	dir = opendir(dirname);
-	errno = ENOENT;
 	if (!dir)
-		return 0;
+		return -1;
 	l = strlen(dirname);
 	while ((de = readdir(dir)) != NULL) {
-		char buf[10];
+		char buf[100];
+		char *sl;
 		int n;
-		int mj, mn;
-		char c;
-		int fd;
 
 		if (de->d_ino == 0)
 			continue;
@@ -780,41 +859,28 @@ int sysfs_unique_holder(int devnum, long rdev)
 			continue;
 		strcpy(dirname+l, "/");
 		strcat(dirname+l, de->d_name);
-		strcat(dirname+l, "/dev");
-		fd = open(dirname, O_RDONLY);
-		if (fd < 0) {
-			errno = ENOENT;
-			break;
-		}
-		n = read(fd, buf, sizeof(buf)-1);
-		close(fd);
+		n = readlink(dirname, buf, sizeof(buf)-1);
+		if (n <= 0)
+			continue;
 		buf[n] = 0;
-		if (sscanf(buf, "%d:%d%c", &mj, &mn, &c) != 3 ||
-		    c != '\n') {
-			errno = ENOENT;
-			break;
-		}
-		if (mj != MD_MAJOR)
-			mn = -1-(mn>>6);
+		sl = strrchr(buf, '/');
+		if (!sl)
+			continue;
+		sl++;
 
-		if (devnum != mn) {
-			errno = EEXIST;
-			break;
-		}
-		found = 1;
+		if (strcmp(devnm, sl) == 0)
+			ret |= 1;
+		else
+			ret |= 2;
 	}
 	closedir(dir);
-	if (de)
-		return 0;
-	else
-		return found;
+	return ret;
 }
 
 int sysfs_freeze_array(struct mdinfo *sra)
 {
 	/* Try to freeze resync/rebuild on this array/container.
 	 * Return -1 if the array is busy,
-	 * return -2 container cannot be frozen,
 	 * return 0 if this kernel doesn't support 'frozen'
 	 * return 1 if it worked.
 	 */
@@ -824,10 +890,44 @@ int sysfs_freeze_array(struct mdinfo *sra)
 		return 1; /* no sync_action == frozen */
 	if (sysfs_get_str(sra, NULL, "sync_action", buf, 20) <= 0)
 		return 0;
-	if (strcmp(buf, "idle\n") != 0 &&
-	    strcmp(buf, "frozen\n") != 0)
+	if (strcmp(buf, "frozen\n") == 0)
+		/* Already frozen */
+		return 0;
+	if (strcmp(buf, "idle\n") != 0 && strcmp(buf, "recover\n") != 0)
 		return -1;
 	if (sysfs_set_str(sra, NULL, "sync_action", "frozen") < 0)
 		return 0;
 	return 1;
 }
+
+int sysfs_wait(int fd, int *msec)
+{
+	/* Wait up to '*msec' for fd to have an exception condition.
+	 * if msec == NULL, wait indefinitely.
+	 */
+	fd_set fds;
+	int n;
+	FD_ZERO(&fds);
+	FD_SET(fd, &fds);
+	if (msec == NULL)
+		n = select(fd+1, NULL, NULL, &fds, NULL);
+	else if (*msec < 0)
+		n = 0;
+	else {
+		struct timeval start, end, tv;
+		gettimeofday(&start, NULL);
+		if (*msec < 1000) {
+			tv.tv_sec = 0;
+			tv.tv_usec = (*msec)*1000;
+		} else {
+			tv.tv_sec = (*msec)/1000;
+			tv.tv_usec = 0;
+		}
+		n = select(fd+1, NULL, NULL, &fds, &tv);
+		gettimeofday(&end, NULL);
+		end.tv_sec -= start.tv_sec;
+		*msec -= (end.tv_sec * 1000 + end.tv_usec/1000
+			  - start.tv_usec/1000) + 1;
+	}
+	return n;
+}