From 4b9c399bf67501183389087437313c5b08f8f776 Mon Sep 17 00:00:00 2001
From: Karel Zak <kzak@redhat.com>
Date: Thu, 10 May 2007 12:10:57 +0200
Subject: [PATCH] mount: fsprobe: use blkid cache only when really necessary

The blkid_get_cache() parses /etc/blkid.tab, it's better do it only
when we really need to resolve a spec (label or uuid).

Signed-off-by: Karel Zak <kzak@redhat.com>
---
 mount/fsprobe_blkid.c | 55 +++++++++++++++++++++++++++++++++++--------
 1 file changed, 45 insertions(+), 10 deletions(-)

diff --git a/mount/fsprobe_blkid.c b/mount/fsprobe_blkid.c
index 2dc734e5..4d288972 100644
--- a/mount/fsprobe_blkid.c
+++ b/mount/fsprobe_blkid.c
@@ -2,35 +2,55 @@
 #include <blkid/blkid.h>
 #include "fsprobe.h"
 
+#define BLKID_EMPTY_CACHE	"/dev/null"
 static blkid_cache blkid;
 
 void
-fsprobe_init(void) {
-	blkid_get_cache(&blkid, NULL);
+fsprobe_init(void)
+{
+	blkid = NULL;
 }
 
 void
-fsprobe_exit(void) {
-	blkid_put_cache(blkid);
+fsprobe_exit(void)
+{
+	if (blkid)
+		blkid_put_cache(blkid);
 }
 
 const char *
-fsprobe_get_label_by_devname(const char *devname) {
+fsprobe_get_label_by_devname(const char *devname)
+{
+	if (!blkid)
+		blkid_get_cache(&blkid, NULL);
+
 	return blkid_get_tag_value(blkid, "LABEL", devname);
 }
 
 const char *
-fsprobe_get_uuid_by_devname(const char *devname) {
+fsprobe_get_uuid_by_devname(const char *devname)
+{
+	if (!blkid)
+		blkid_get_cache(&blkid, NULL);
+
 	return blkid_get_tag_value(blkid, "UUID", devname);
 }
 
 const char *
-fsprobe_get_devname_by_uuid(const char *uuid) {
+fsprobe_get_devname_by_uuid(const char *uuid)
+{
+	if (!blkid)
+		blkid_get_cache(&blkid, NULL);
+
 	return blkid_get_devname(blkid, "UUID", uuid);
 }
 
 const char *
-fsprobe_get_devname_by_label(const char *label) {
+fsprobe_get_devname_by_label(const char *label)
+{
+	if (!blkid)
+		blkid_get_cache(&blkid, NULL);
+
 	return blkid_get_devname(blkid, "LABEL", label);
 }
 
@@ -41,7 +61,22 @@ fsprobe_known_fstype(const char *fstype)
 }
 
 const char *
-fsprobe_get_fstype_by_devname(const char *devname) {
-	return blkid_get_tag_value(blkid, "TYPE", devname);
+fsprobe_get_fstype_by_devname(const char *devname)
+{
+	blkid_cache c;
+	const char *tp;
+
+	if (blkid)
+		return blkid_get_tag_value(blkid, "TYPE", devname);
+
+	/* The cache is not initialized yet. Use empty cache rather than waste
+	 * time with /etc/blkid.tab. It seems that probe FS is faster than
+	 * parse the cache file.  -- kzak (17-May-2007)
+	 */
+	blkid_get_cache(&c, BLKID_EMPTY_CACHE);
+	tp = blkid_get_tag_value(c, "TYPE", devname);
+	blkid_put_cache(c);
+
+	return tp;
 }
 
-- 
2.39.5