libmount: refactor mnt_cache_read_tags()

Split the function into smaller functions to make it easier to read
and extend in the future.

Introduce a struct to hold all variants of tag names, including udev
names in the future.

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

diff --git a/libmount/src/cache.c b/libmount/src/cache.c
index a03d6d6d618eae80b950e38b101c235d000dfed2..29f08674fd98d8201387dde04758ec0c8327d130 100644 (file)
--- a/libmount/src/cache.c
+++ b/libmount/src/cache.c
@@ -72,6 +72,24 @@ struct libmnt_cache {
        struct libmnt_table     *mountinfo;
 };
 
+
+struct libmnt_cachetag {
+       const char *mnt_name;   /* tag name used by libmount */
+       const char *blk_name;   /* tag name used by libblkid */
+};
+
+static const struct libmnt_cachetag mnttags[] =
+{
+       /* mount        blkid */
+       { "LABEL",      "LABEL" },
+       { "UUID",       "UUID" },
+       { "TYPE",       "TYPE" },
+       { "PARTUUID",   "PART_ENTRY_UUID" },
+       { "PARTLABEL",  "PART_ENTRY_NAME" },
+
+       { NULL, NULL }
+};
+
 /**
  * mnt_new_cache:
  *
@@ -324,39 +342,34 @@ static char *cache_find_tag_value(struct libmnt_cache *cache,
        return NULL;
 }
 
-/**
- * mnt_cache_read_tags
- * @cache: pointer to struct libmnt_cache instance
- * @devname: path device
- *
- * Reads @devname LABEL and UUID to the @cache.
- *
- * Returns: 0 if at least one tag was added, 1 if no tag was added or
- *          negative number in case of error.
- */
-int mnt_cache_read_tags(struct libmnt_cache *cache, const char *devname)
+static bool is_device_cached(struct libmnt_cache *cache, const char *devname)
 {
-       blkid_probe pr;
-       size_t i, ntags = 0;
-       int rc;
-       const char *tags[] = { "LABEL", "UUID", "TYPE", "PARTUUID", "PARTLABEL" };
-       const char *blktags[] = { "LABEL", "UUID", "TYPE", "PART_ENTRY_UUID", "PART_ENTRY_NAME" };
-
-       if (!cache || !devname)
-               return -EINVAL;
-
-       DBG(CACHE, ul_debugobj(cache, "tags for %s requested", devname));
+       size_t i;
 
-       /* check if device is already cached */
        for (i = 0; i < cache->nents; i++) {
                struct mnt_cache_entry *e = &cache->ents[i];
                if (!(e->flag & MNT_CACHE_TAGREAD))
                        continue;
                if (strcmp(e->value, devname) == 0)
-                       /* tags have already been read */
-                       return 0;
+                       return 1; /* already in cache */
        }
 
+       return 0;
+}
+
+/* read data from libblkid into local cache */
+static int read_from_blkid(struct libmnt_cache *cache, const char *devname)
+{
+       blkid_probe pr;
+       const struct libmnt_cachetag *t;
+       size_t ntags = 0;
+       int rc;
+
+       assert(cache);
+       assert(devname);
+
+       DBG(CACHE, ul_debugobj(cache, "%s: reading from blkid", devname));
+
        pr =  blkid_new_probe_from_filename(devname);
        if (!pr)
                return -1;
@@ -373,23 +386,21 @@ int mnt_cache_read_tags(struct libmnt_cache *cache, const char *devname)
        if (rc)
                goto error;
 
-       DBG(CACHE, ul_debugobj(cache, "reading tags for: %s", devname));
-
-       for (i = 0; i < ARRAY_SIZE(tags); i++) {
+       for (t = mnttags; t && t->mnt_name; t++) {
                const char *data;
                char *dev;
 
-               if (cache_find_tag_value(cache, devname, tags[i])) {
+               if (cache_find_tag_value(cache, devname, t->mnt_name)) {
                        DBG(CACHE, ul_debugobj(cache,
-                                       "\ntag %s already cached", tags[i]));
+                                       "\ntag %s already cached", t->mnt_name));
                        continue;
                }
-               if (blkid_probe_lookup_value(pr, blktags[i], &data, NULL))
+               if (blkid_probe_lookup_value(pr, t->blk_name, &data, NULL))
                        continue;
                dev = strdup(devname);
                if (!dev)
                        goto error;
-               if (cache_add_tag(cache, tags[i], data, dev,
+               if (cache_add_tag(cache, t->mnt_name, data, dev,
                                        MNT_CACHE_TAGREAD)) {
                        free(dev);
                        goto error;
@@ -403,6 +414,30 @@ int mnt_cache_read_tags(struct libmnt_cache *cache, const char *devname)
 error:
        blkid_free_probe(pr);
        return rc < 0 ? rc : -1;
+
+}
+
+/**
+ * mnt_cache_read_tags
+ * @cache: pointer to struct libmnt_cache instance
+ * @devname: path device
+ *
+ * Reads @devname LABEL and UUID to the @cache.
+ *
+ * Returns: 0 if at least one tag was added, 1 if no tag was added or
+ *          negative number in case of error.
+ */
+int mnt_cache_read_tags(struct libmnt_cache *cache, const char *devname)
+{
+       if (!cache || !devname)
+               return -EINVAL;
+
+       DBG(CACHE, ul_debugobj(cache, "tags for %s requested", devname));
+
+       if (is_device_cached(cache, devname))
+               return 0;
+
+       return read_from_blkid(cache, devname);
 }
 
 /**