libmount: add mnt_cache_find_tag_value()

Signed-off-by: Karel Zak <kzak@redhat.com>

5 files changed, 43 insertions, 5 deletions

diff --git a/shlibs/mount/src/cache.c b/shlibs/mount/src/cache.c
index b9d89f438..62d514d89 100644
--- a/shlibs/mount/src/cache.c
+++ b/shlibs/mount/src/cache.c
@@ -220,7 +220,7 @@ const char *mnt_cache_find_tag(mnt_cache *cache,
  *
  * Reads @devname LABEL and UUID to the @cache.
  *
- * Returns: 1 if at least on tag was added, 0 no tag was added or
+ * Returns: 0 if at least on tag was added, 1 if no tag was added or
  *          -1 in case of error.
  */
 int mnt_cache_read_tags(mnt_cache *cache, const char *devname)
@@ -289,7 +289,7 @@ int mnt_cache_read_tags(mnt_cache *cache, const char *devname)
 		ntags++;
 	}
 
-	return ntags ? 1 : 0;
+	return ntags ? 0 : 1;
 error:
 	blkid_free_probe(pr);
 	close(fd);
@@ -318,6 +318,37 @@ int mnt_cache_device_has_tag(mnt_cache *cache, const char *devname,
 }
 
 /**
+ * mnt_cache_find_tag_value:
+ * @cache: cache for results
+ * @devname: device name
+ * @token: tag name ("LABEL" or "UUID")
+ *
+ * Returns: LABEL or UUID for the @devname or NULL in case of error.
+ */
+char *mnt_cache_find_tag_value(mnt_cache *cache,
+		const char *devname, const char *token)
+{
+	int i;
+
+	if (!cache || !devname || !token)
+		return NULL;
+
+	if (mnt_cache_read_tags(cache, devname) != 0)
+		return NULL;
+
+	for (i = 0; i < cache->nents; i++) {
+		struct mnt_cache_entry *e = &cache->ents[i];
+		if (!(e->flag & MNT_CACHE_ISTAG))
+			continue;
+		if (strcmp(e->real, devname) == 0 &&	/* dev name */
+		    strcmp(token, e->native) == 0)	/* tag name */
+			return e->native + strlen(token) + 1;	/* tag value */
+	}
+
+	return NULL;
+}
+
+/**
  * mnt_resolve_path:
  * @path: "native" path
  * @cache: cache for results or NULL
diff --git a/shlibs/mount/src/fs.c b/shlibs/mount/src/fs.c
index ae97b6542..aa38998b9 100644
--- a/shlibs/mount/src/fs.c
+++ b/shlibs/mount/src/fs.c
@@ -574,7 +574,7 @@ int mnt_fs_match_source(mnt_fs *fs, const char *source, mnt_cache *cache)
 		return 0;
 
 	/* read @source's tags to the cache */
-	if (mnt_cache_read_tags(cache, cn) < 1) {
+	if (mnt_cache_read_tags(cache, cn) < 0) {
 		if (errno == EACCES) {
 			/* we don't have permissions to read TAGs from
 			 * @source, but can translate @fs tag to devname.
diff --git a/shlibs/mount/src/mount.h.in b/shlibs/mount/src/mount.h.in
index 4e918b833..7d13e7061 100644
--- a/shlibs/mount/src/mount.h.in
+++ b/shlibs/mount/src/mount.h.in
@@ -123,6 +123,10 @@ extern const char *mnt_cache_find_tag(mnt_cache *cache,
 extern int mnt_cache_read_tags(mnt_cache *cache, const char *devname);
 extern int mnt_cache_device_has_tag(mnt_cache *cache, const char *devname,
                                 const char *token, const char *value);
+
+extern char *mnt_cache_find_tag_value(mnt_cache *cache,
+				const char *devname, const char *token);
+
 extern char *mnt_resolve_path(const char *path, mnt_cache *cache);
 extern char *mnt_resolve_tag(const char *token, const char *value, mnt_cache *cache);
 extern char *mnt_resolve_spec(const char *spec, mnt_cache *cache);
diff --git a/shlibs/mount/src/mount.sym b/shlibs/mount/src/mount.sym
index 5df37796a..358d7b73e 100644
--- a/shlibs/mount/src/mount.sym
+++ b/shlibs/mount/src/mount.sym
@@ -8,6 +8,7 @@ global:
 	mnt_cache_device_has_tag;
 	mnt_cache_find_path;
 	mnt_cache_find_tag;
+	mnt_cache_find_tag_value;
 	mnt_cache_read_tags;
 	mnt_fprintf_line;
 	mnt_free_cache;
diff --git a/shlibs/mount/src/tab.c b/shlibs/mount/src/tab.c
index 98c56602b..176a7d5a7 100644
--- a/shlibs/mount/src/tab.c
+++ b/shlibs/mount/src/tab.c
@@ -519,9 +519,11 @@ mnt_fs *mnt_tab_find_srcpath(mnt_tab *tb, const char *path, int direction)
 
 	/* evaluated tag */
 	if (ntags) {
+		int rc = mnt_cache_read_tags(tb->cache, cn);
+
 		mnt_reset_iter(&itr, direction);
 
-		if (mnt_cache_read_tags(tb->cache, cn) > 0) {
+		if (rc == 0) {
 			/* @path's TAGs are in the cache */
 			while(mnt_tab_next_fs(tb, &itr, &fs) == 0) {
 				const char *t, *v;
@@ -532,7 +534,7 @@ mnt_fs *mnt_tab_find_srcpath(mnt_tab *tb, const char *path, int direction)
 				if (mnt_cache_device_has_tag(tb->cache, cn, t, v))
 					return fs;
 			}
-		} else if (errno == EACCES) {
+		} else if (rc < 0 && errno == EACCES) {
 			/* @path is unaccessible, try evaluate all TAGs in @tb
 			 * by udev symlinks -- this could be expensive on systems
 			 * with huge fstab/mtab */