Add a new option to the blkid program, -l, which will more efficiently search

for a single device.

Add a new function to the blkid library, blkid_probe_all_new().

Optimize blkid_find_dev_with_tag() so that extraneous device validation are
skipped.  (Makes a difference for system with a large number of disks).

7 files changed, 114 insertions, 21 deletions

diff --git a/lib/blkid/ChangeLog b/lib/blkid/ChangeLog
index 40c7d122..d84c9037 100644
--- a/lib/blkid/ChangeLog
+++ b/lib/blkid/ChangeLog
@@ -1,5 +1,14 @@
 2005-05-07  Theodore Ts'o  <tytso@mit.edu>
 
+	* tag.c (blkid_find_dev_with_tag): If a device can't be found with
+		the specified search arguments, probe all new devices
+		before trying to verify existing devices, as a speed
+		optimization.
+
+	* devname.c (blkid_probe_all_new): New function which only probes
+		devices are not known in the blkid cache.  This takes
+		much less time than a full probe of all devices.
+
 	* cache.c, dev.c, devno.c, probe.c, probe.h: Fix gcc -Wall nits.
 
 	* blkidP.h, cache.c, dev.c, read.c, tag.c: Clean up the debugging
diff --git a/lib/blkid/blkid.h b/lib/blkid/blkid.h
index 84be589f..892b7980 100644
--- a/lib/blkid/blkid.h
+++ b/lib/blkid/blkid.h
@@ -65,6 +65,7 @@ extern char *blkid_devno_to_devname(dev_t devno);
 
 /* devname.c */
 extern int blkid_probe_all(blkid_cache cache);
+extern int blkid_probe_all_new(blkid_cache cache);
 extern blkid_dev blkid_get_dev(blkid_cache cache, const char *devname,
 			       int flags);
 
diff --git a/lib/blkid/devname.c b/lib/blkid/devname.c
index 87d5cbef..3b1ad89b 100644
--- a/lib/blkid/devname.c
+++ b/lib/blkid/devname.c
@@ -79,7 +79,7 @@ blkid_dev blkid_get_dev(blkid_cache cache, const char *devname, int flags)
  * Probe a single block device to add to the device cache.
  */
 static void probe_one(blkid_cache cache, const char *ptname,
-		      dev_t devno, int pri)
+		      dev_t devno, int pri, int only_if_new)
 {
 	blkid_dev dev = NULL;
 	struct list_head *p;
@@ -91,6 +91,8 @@ static void probe_one(blkid_cache cache, const char *ptname,
 		blkid_dev tmp = list_entry(p, struct blkid_struct_dev,
 					   bid_devs);
 		if (tmp->bid_devno == devno) {
+			if (only_if_new)
+				return;
 			dev = blkid_verify(cache, tmp);
 			break;
 		}
@@ -171,7 +173,7 @@ static dev_t lvm_get_devno(const char *lvm_device)
 	return ret;
 }
 
-static void lvm_probe_all(blkid_cache cache)
+static void lvm_probe_all(blkid_cache cache, int only_if_new)
 {
 	DIR		*vg_list;
 	struct dirent	*vg_iter;
@@ -222,7 +224,8 @@ static void lvm_probe_all(blkid_cache cache)
 			DBG(DEBUG_DEVNAME, printf("LVM dev %s: devno 0x%04X\n",
 						  lvm_device,
 						  (unsigned int) dev));
-			probe_one(cache, lvm_device, dev, BLKID_PRI_LVM);
+			probe_one(cache, lvm_device, dev, BLKID_PRI_LVM, 
+				  only_if_new);
 			free(lvm_device);
 		}
 		closedir(lv_list);
@@ -235,7 +238,7 @@ exit:
 #define PROC_EVMS_VOLUMES "/proc/evms/volumes"
 
 static int
-evms_probe_all(blkid_cache cache)
+evms_probe_all(blkid_cache cache, int only_if_new)
 {
 	char line[100];
 	int ma, mi, sz, num = 0;
@@ -253,7 +256,8 @@ evms_probe_all(blkid_cache cache)
 		DBG(DEBUG_DEVNAME, printf("Checking partition %s (%d, %d)\n",
 					  device, ma, mi));
 
-		probe_one(cache, device, makedev(ma, mi), BLKID_PRI_EVMS);
+		probe_one(cache, device, makedev(ma, mi), BLKID_PRI_EVMS,
+			  only_if_new);
 		num++;
 	}
 	fclose(procpt);
@@ -263,7 +267,7 @@ evms_probe_all(blkid_cache cache)
 /*
  * Read the device data for all available block devices in the system.
  */
-int blkid_probe_all(blkid_cache cache)
+static int probe_all(blkid_cache cache, int only_if_new)
 {
 	FILE *proc;
 	char line[1024];
@@ -286,9 +290,9 @@ int blkid_probe_all(blkid_cache cache)
 		return 0;
 
 	blkid_read_cache(cache);
-	evms_probe_all(cache);
+	evms_probe_all(cache, only_if_new);
 #ifdef VG_DIR
-	lvm_probe_all(cache);
+	lvm_probe_all(cache, only_if_new);
 #endif
 
 	proc = fopen(PROC_PARTITIONS, "r");
@@ -325,7 +329,8 @@ int blkid_probe_all(blkid_cache cache)
 				   ptname, (unsigned int) devs[which]));
 
 			if (sz > 1)
-				probe_one(cache, ptname, devs[which], 0);
+				probe_one(cache, ptname, devs[which], 0, 
+					  only_if_new);
 			lens[which] = 0;
 			lens[last] = 0;
 		} else if (lens[last] && strncmp(ptnames[last], ptname,
@@ -333,23 +338,44 @@ int blkid_probe_all(blkid_cache cache)
 			DBG(DEBUG_DEVNAME,
 			    printf("whole dev %s, devno 0x%04X\n",
 				   ptnames[last], (unsigned int) devs[last]));
-			probe_one(cache, ptnames[last], devs[last], 0);
+			probe_one(cache, ptnames[last], devs[last], 0,
+				  only_if_new);
 			lens[last] = 0;
 		}
 	}
 
 	/* Handle the last device if it wasn't partitioned */
 	if (lens[which])
-		probe_one(cache, ptname, devs[which], 0);
+		probe_one(cache, ptname, devs[which], 0, only_if_new);
 
 	fclose(proc);
+	blkid_flush_cache(cache);
+	return 0;
+}
 
+int blkid_probe_all(blkid_cache cache)
+{
+	int ret;
+
+	DBG(DEBUG_PROBE, printf("Begin blkid_probe_all()\n"));
+	ret = probe_all(cache, 0);
 	cache->bic_time = time(0);
 	cache->bic_flags |= BLKID_BIC_FL_PROBED;
-	blkid_flush_cache(cache);
-	return 0;
+	DBG(DEBUG_PROBE, printf("End blkid_probe_all()\n"));
+	return ret;
 }
 
+int blkid_probe_all_new(blkid_cache cache)
+{
+	int ret;
+
+	DBG(DEBUG_PROBE, printf("Begin blkid_probe_all_new()\n"));
+	ret = probe_all(cache, 1);
+	DBG(DEBUG_PROBE, printf("End blkid_probe_all_new()\n"));
+	return ret;
+}
+
+
 #ifdef TEST_PROGRAM
 int main(int argc, char **argv)
 {
diff --git a/lib/blkid/tag.c b/lib/blkid/tag.c
index 9470ac01..9bca2c6a 100644
--- a/lib/blkid/tag.c
+++ b/lib/blkid/tag.c
@@ -316,9 +316,6 @@ extern void blkid_tag_iterate_end(blkid_tag_iterate iter)
  * type/value pair.  If there is more than one device that matches the
  * search specification, it returns the one with the highest priority
  * value.  This allows us to give preference to EVMS or LVM devices.
- *
- * XXX there should also be an interface which uses an iterator so we
- * can get all of the devices which match a type/value search parameter.
  */
 extern blkid_dev blkid_find_dev_with_tag(blkid_cache cache,
 					 const char *type,
@@ -328,6 +325,7 @@ extern blkid_dev blkid_find_dev_with_tag(blkid_cache cache,
 	blkid_dev	dev;
 	int		pri;
 	struct list_head *p;
+	int		probe_new = 0;
 
 	if (!cache || !type || !value)
 		return NULL;
@@ -359,6 +357,13 @@ try_again:
 			goto try_again;
 	}
 
+	if (!dev && !probe_new) {
+		if (blkid_probe_all_new(cache) < 0)
+			return NULL;
+		probe_new++;
+		goto try_again;
+	}
+
 	if (!dev && !(cache->bic_flags & BLKID_BIC_FL_PROBED)) {
 		if (blkid_probe_all(cache) < 0)
 			return NULL;
diff --git a/misc/ChangeLog b/misc/ChangeLog
index b0b87f6d..67dec48f 100644
--- a/misc/ChangeLog
+++ b/misc/ChangeLog
@@ -4,6 +4,10 @@
 		blkid_dev_has_tag().  Remove compare_search_type() since
 		it has been obseleted by blkid_dev_has_tag().
 
+	* blkid.c (main): Add a new flag, -l, which will use a more
+		efficient method to find the device that matches a
+		particular tag specifier.
+
 2005-05-06  Theodore Ts'o  <tytso@mit.edu>
 
 	* blkid.c (main): Use an int instead of an char to store the
diff --git a/misc/blkid.8.in b/misc/blkid.8.in
index 0f6f7c80..f1effe1a 100644
--- a/misc/blkid.8.in
+++ b/misc/blkid.8.in
@@ -11,7 +11,7 @@ blkid \- command\-line utility to locate/print block device attributes
 .SH SYNOPSIS
 .B blkid 
 [
-.B \-hv
+.B \-hlv
 ]
 [
 [
@@ -63,6 +63,32 @@ scanned but not necessarily available at this time), specify
 .B \-h
 Display a usage message and exit.
 .TP
+.B \-l
+Lookup the device that matches the search parameter specified using
+the 
+.B \-t
+option, assuming that there is only one matching the search parameter.  
+For a system with a large number of disks, this will be more 
+efficient by avoiding the need to revalidate devices unless absolutely 
+necessary.  If this option is not specified, 
+.B blkid
+will use a less efficient approach, which allows 
+.B blkid
+to print all of the devices that match the search parameter.
+.IP
+This option is best used for tag searches such as 
+.I LABEL=data_vol
+or
+.IR UUID=e280469a-d06f-4c0b-b068-44f3b576029e .
+If you want 
+.B blkid
+to print all of the ext3 filesystems using a search parameter 
+such as
+.IR TYPE=ext3 ,
+then this option should 
+.I not
+be used.
+.TP
 .B \-o 
 Display 
 .BR blkid 's
@@ -117,7 +143,7 @@ instead of writing it to the default cache file
 If you don't want to save the cache to the default file, specify
 .IR /dev/null.
 If not specified it will be the same file as that given by the
-.B -c
+.B \-c
 option.
 .TP
 .I <device>
diff --git a/misc/blkid.c b/misc/blkid.c
index 44dd7d67..256f4f14 100644
--- a/misc/blkid.c
+++ b/misc/blkid.c
@@ -37,12 +37,13 @@ static void usage(int error)
 
 	print_version(out);
 	fprintf(out,
-		"usage:\t%s [-c <file>] [-h] [-o format] "
+		"usage:\t%s [-c <file>] [-hl] [-o format] "
 		"[-s <tag>] [-t <token>]\n    [-v] [-w <file>] [dev ...]\n"
 		"\t-c\tcache file (default: /etc/blkid.tab, /dev/null = none)\n"
 		"\t-h\tprint this usage message and exit\n"
 		"\t-s\tshow specified tag(s) (default show all tags)\n"
 		"\t-t\tfind device with a specific token (NAME=value pair)\n"
+		"\t-l\tlookup the the first device with arguments specified by -t\n"
 		"\t-v\tprint version and exit\n"
 		"\t-w\twrite cache to different file (/dev/null = no write)\n"
 		"\tdev\tspecify device(s) to probe (default: all devices)\n",
@@ -101,9 +102,10 @@ int main(int argc, char **argv)
 	int err = 4;
 	unsigned int i;
 	int output_format = 0;
+	int lookup = 0;
 	int c;
 
-	while ((c = getopt (argc, argv, "c:f:ho:s:t:w:v")) != EOF)
+	while ((c = getopt (argc, argv, "c:f:hlo:s:t:w:v")) != EOF)
 		switch (c) {
 		case 'c':
 			if (optarg && !*optarg)
@@ -113,6 +115,9 @@ int main(int argc, char **argv)
 			if (!write)
 				write = read;
 			break;
+		case 'l':
+			lookup++;
+			break;
 		case 'o':
 			if (!strcmp(optarg, "value"))
 				output_format = OUTPUT_VALUE_ONLY;
@@ -172,8 +177,25 @@ int main(int argc, char **argv)
 		goto exit;
 
 	err = 2;
+	if (lookup) {
+		blkid_dev dev;
+
+		if (!search_type) {
+			fprintf(stderr, "The lookup option requires a "
+				"search type specified using -t\n");
+			exit(1);
+		}
+		/* Load any additional devices not in the cache */
+		for (i = 0; i < numdev; i++)
+			blkid_get_dev(cache, devices[i], BLKID_DEV_NORMAL);
+
+		if ((dev = blkid_find_dev_with_tag(cache, search_type,
+						   search_value))) {
+			print_tags(dev, show, numtag, output_format);
+			err = 0;
+		}
 	/* If we didn't specify a single device, show all available devices */
-	if (!numdev) {
+	} else if (!numdev) {
 		blkid_dev_iterate	iter;
 		blkid_dev		dev;