volume_id: clear probing result before probing and do not probe a second time, if...

On Thu, Nov 20, 2008 at 14:17, Karel Zak <kzak@redhat.com> wrote:
>  I see the patch (volume_id_probe_filesystem()) and a few things come
>  to mind:
>
>  - shouldn't be the relevant parts (label, uuid, version, ...) of
>    the "struct volume_id" zeroized when you found a signature and
>    before you call the next probing function?
>
>  - it seems as overkill to use two for()s and probe two times for all
>    filesystems. What about to store the first result and re-use it?
>
>  - .. or at least never use the second for() when the fist for() found
>    nothing ;-)

diff --git a/extras/volume_id/lib/volume_id.c b/extras/volume_id/lib/volume_id.c
index aaa15e1e75fe8375c1391005f1cd335ce4588856..a93ade6427363176b68010cc9f18f57021380cf5 100644 (file)
--- a/extras/volume_id/lib/volume_id.c
+++ b/extras/volume_id/lib/volume_id.c
@@ -383,6 +383,18 @@ found:
        return 0;
 }
 
+static void volume_id_reset_result(struct volume_id *id)
+{
+       id->label_raw_len = 0;
+       id->label[0] = '\0';
+       id->uuid_raw_len = 0;
+       id->uuid[0] = '\0';
+       id->usage_id = VOLUME_ID_UNUSED;
+       id->usage = NULL;
+       id->type = NULL;
+       id->type_version[0] = '\0';
+}
+
 /**
  * volume_id_probe_filesystem:
  * @id: Probing context.
@@ -423,25 +435,41 @@ int volume_id_probe_filesystem(struct volume_id *id, uint64_t off, uint64_t size
        if (size > 1440 * 1024) {
                int found = 0;
                int force_unique_result = 0;
+               int first_match = -1;
 
+               volume_id_reset_result(id);
                for (i = 0; i < ARRAY_SIZE(prober_filesystem); i++) {
                        int match;
 
                        match = (prober_filesystem[i].prober(id, off, size) == 0);
                        if (match) {
-                               info("signature '%s' detected\n", id->type);
+                               info("signature '%s' %i detected\n", id->type, i);
                                if (id->force_unique_result)
                                        force_unique_result = 1;
                                if (found && force_unique_result) {
                                        info("conflicting signatures found, skip results\n");
                                        return -1;
                                }
-                               found = 1;
+                               found++;
+                               if (first_match < 0)
+                                       first_match = i;
                        }
                }
+               if (found < 1)
+                       return -1;
+               if (found == 1)
+                       goto found;
+               if (found > 1) {
+                       volume_id_reset_result(id);
+                       info("re-read first match metadata %i\n", first_match);
+                       if (prober_filesystem[first_match].prober(id, off, size) == 0)
+                               goto found;
+                       return -1;
+               }
        }
 
        /* return the first match */
+       volume_id_reset_result(id);
        for (i = 0; i < ARRAY_SIZE(prober_filesystem); i++) {
                if (prober_filesystem[i].prober(id, off, size) == 0) {
                        info("signature '%s' detected\n", id->type);