From: Karel Zak <kzak@redhat.com>
Date: Thu, 26 May 2016 10:02:12 +0000 (+0200)
Subject: libblkid: store only canonical devnames to the cache
X-Git-Tag: v2.29-rc1~219
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=924c93d9df118338fd54cd73b4a45ccddc4ac103;p=thirdparty%2Futil-linux.git

libblkid: store only canonical devnames to the cache

Let's try to use symlink:

 # ls -la /dev/block/8\:1
 # lrwxrwxrwx 1 root root 7 May 25 16:42 /dev/block/8:1 -> ../sda1

 # blkid /dev/block/8:1
 /dev/block/8:3: LABEL="HOME" UUID="196972ad-3b13-4bba-ac54-4cb3f7b409a4" TYPE="ext4" PARTUUID="6073277f-87bc-43ff-bcfd-724c4484a63a"

unfortunately the symlink is stored to the cache:

 <device DEVNO="0x0803" TIME="1464253300.715279" LABEL="HOME" UUID="196972ad-3b13-4bba-ac54-4cb3f7b409a4" TYPE="ext4" PARTUUID="6073277f-87bc-43ff-bcfd-724c4484a63a">/dev/block/8:3</device>

next time if you ask for LABEL=HOME the answer will be /dev/block/8:3
rather than /dev/sda3.

It seems better to canonicalize the paths we store to the cache.

Unfortunately if you ask for /dev/block/8:3 then you probably expect
that blkid_dev_devname() returns the same path. This patch introduces
dev->bid_xname, this is the path used by application (and never stored
in the cache).

Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1332779
Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/libblkid/src/blkidP.h b/libblkid/src/blkidP.h
index e298b41dd1..68204233d2 100644
--- a/libblkid/src/blkidP.h
+++ b/libblkid/src/blkidP.h
@@ -42,7 +42,8 @@ struct blkid_struct_dev
 	struct list_head	bid_devs;	/* All devices in the cache */
 	struct list_head	bid_tags;	/* All tags for this device */
 	blkid_cache		bid_cache;	/* Dev belongs to this cache */
-	char			*bid_name;	/* Device inode pathname */
+	char			*bid_name;	/* Device real pathn (as used in cache) */
+	char			*bid_xname;	/* Device path as used by application (maybe symlink..) */
 	char			*bid_type;	/* Preferred device TYPE */
 	int			bid_pri;	/* Device priority */
 	dev_t			bid_devno;	/* Device major/minor number */
diff --git a/libblkid/src/dev.c b/libblkid/src/dev.c
index f35895da98..b5ad0f1150 100644
--- a/libblkid/src/dev.c
+++ b/libblkid/src/dev.c
@@ -58,16 +58,23 @@ void blkid_free_dev(blkid_dev dev)
 					   bit_tags);
 		blkid_free_tag(tag);
 	}
+	free(dev->bid_xname);
 	free(dev->bid_name);
 	free(dev);
 }
 
 /*
- * Given a blkid device, return its name
+ * Given a blkid device, return its name. The function returns the name
+ * previously used for blkid_get_dev(). This name does not have to be canonical
+ * (real path) name, but for example symlink.
  */
 const char *blkid_dev_devname(blkid_dev dev)
 {
-	return dev ? dev->bid_name : NULL;
+	if (!dev)
+		return NULL;
+	if (dev->bid_xname)
+		return dev->bid_xname;
+	return dev->bid_name;
 }
 
 void blkid_debug_dump_dev(blkid_dev dev)
diff --git a/libblkid/src/devname.c b/libblkid/src/devname.c
index dbbe5b54d7..2e5f4f1514 100644
--- a/libblkid/src/devname.c
+++ b/libblkid/src/devname.c
@@ -50,28 +50,55 @@ blkid_dev blkid_get_dev(blkid_cache cache, const char *devname, int flags)
 {
 	blkid_dev dev = NULL, tmp;
 	struct list_head *p, *pnext;
+	char *cn = NULL;
 
 	if (!cache || !devname)
 		return NULL;
 
+	/* search by name */
 	list_for_each(p, &cache->bic_devs) {
 		tmp = list_entry(p, struct blkid_struct_dev, bid_devs);
 		if (strcmp(tmp->bid_name, devname))
 			continue;
-
-		DBG(DEVNAME, ul_debug("found devname %s in cache", tmp->bid_name));
 		dev = tmp;
 		break;
 	}
 
+	/* try canonicalize the name */
+	if (!dev && (cn = canonicalize_path(devname))) {
+		if (strcmp(cn, devname) != 0) {
+			DBG(DEVNAME, ul_debug("search cannonical %s", cn));
+			list_for_each(p, &cache->bic_devs) {
+				tmp = list_entry(p, struct blkid_struct_dev, bid_devs);
+				if (strcmp(tmp->bid_name, cn))
+					continue;
+				dev = tmp;
+
+				/* update name returned by blkid_dev_devname() */
+				free(dev->bid_xname);
+				dev->bid_xname = strdup(devname);
+				break;
+			}
+		} else {
+			free(cn);
+			cn = NULL;
+		}
+	}
+
 	if (!dev && (flags & BLKID_DEV_CREATE)) {
 		if (access(devname, F_OK) < 0)
-			return NULL;
+			goto done;
 		dev = blkid_new_dev();
 		if (!dev)
-			return NULL;
+			goto done;
 		dev->bid_time = INT_MIN;
-		dev->bid_name = strdup(devname);
+		if (cn) {
+			dev->bid_name = cn;
+			dev->bid_xname = strdup(devname);
+			cn = NULL;	/* see free() below */
+		} else
+			dev->bid_name = strdup(devname);
+
 		dev->bid_cache = cache;
 		list_add_tail(&dev->bid_devs, &cache->bic_devs);
 		cache->bic_flags |= BLKID_BIC_FL_CHANGED;
@@ -80,7 +107,7 @@ blkid_dev blkid_get_dev(blkid_cache cache, const char *devname, int flags)
 	if (flags & BLKID_DEV_VERIFY) {
 		dev = blkid_verify(cache, dev);
 		if (!dev || !(dev->bid_flags & BLKID_BID_FL_VERIFIED))
-			return dev;
+			goto done;
 		/*
 		 * If the device is verified, then search the blkid
 		 * cache for any entries that match on the type, uuid,
@@ -111,6 +138,10 @@ blkid_dev blkid_get_dev(blkid_cache cache, const char *devname, int flags)
 				blkid_free_dev(dev2);
 		}
 	}
+done:
+	if (dev)
+		DBG(DEVNAME, ul_debug("%s requested, found %s in cache", devname, dev->bid_name));
+	free(cn);
 	return dev;
 }