lvmlockd: skip unnecessary lvmetad cache update

In cases where a VG is reread from disk, but the
seqno matches what is currently in lvmetad, the
metadata in lvmetad doesn't need to be updated.

diff --git a/lib/cache/lvmetad.c b/lib/cache/lvmetad.c
index 7ca5d4a649055f1046a47ade3d2f8f7436bfa83a..a68044104050cd9409817a67be24b3a542679bee 100644 (file)
--- a/lib/cache/lvmetad.c
+++ b/lib/cache/lvmetad.c
@@ -872,7 +872,7 @@ struct volume_group *lvmetad_vg_lookup(struct cmd_context *cmd, const char *vgna
 
        } else {
                log_error(INTERNAL_ERROR "VG name required (VGID not available)");
-               goto out;
+               return NULL;
        }
 
        if (_lvmetad_handle_reply(reply, "vg_lookup", diag_name, &found) && found) {
@@ -958,16 +958,14 @@ struct volume_group *lvmetad_vg_lookup(struct cmd_context *cmd, const char *vgna
                 * invalidated the cached vg.
                 */
                if (rescan) {
-                       log_debug_lvmetad("Update invalid lvmetad cache for VG %s", vgname);
-                       vg2 = lvmetad_pvscan_vg(cmd, vg);
-                       release_vg(vg);
-                       vg = vg2;
-                       if (!vg) {
+                       if (!(vg2 = lvmetad_pvscan_vg(cmd, vg))) {
                                log_debug_lvmetad("VG %s from lvmetad not found during rescan.", vgname);
                                fid = NULL;
                                goto out;
-                       } else
-                               fid = vg->fid;
+                       }
+                       release_vg(vg);
+                       vg = vg2;
+                       fid = vg2->fid;
                }
 
                dm_list_iterate_items(pvl, &vg->pvs) {
@@ -1575,6 +1573,7 @@ static struct volume_group *lvmetad_pvscan_vg(struct cmd_context *cmd, struct vo
        struct format_instance_ctx fic = { .type = 0 };
        struct _lvmetad_pvscan_baton baton;
        struct device *save_dev = NULL;
+       uint32_t save_seqno = 0;
 
        dm_list_iterate_items(pvl, &vg->pvs) {
                /* missing pv */
@@ -1622,6 +1621,9 @@ static struct volume_group *lvmetad_pvscan_vg(struct cmd_context *cmd, struct vo
                        continue;
                }
 
+               if (!save_seqno)
+                       save_seqno = baton.vg->seqno;
+
                if (!(vgmeta = export_vg_to_config_tree(baton.vg))) {
                        log_error("VG export to config tree failed");
                        release_vg(baton.vg);
@@ -1661,10 +1663,14 @@ static struct volume_group *lvmetad_pvscan_vg(struct cmd_context *cmd, struct vo
                 * but that is the field which lvmetad_vg_update() uses
                 * to send the metadata cft to lvmetad.
                 */
-               vg_ret->cft_precommitted = vgmeta_ret;
-               if (!lvmetad_vg_update(vg_ret))
-                       log_error("Failed to update lvmetad with new VG meta");
-               vg_ret->cft_precommitted = NULL;
+               if (save_seqno != vg->seqno) {
+                       log_debug_lvmetad("Update lvmetad from seqno %u to seqno %u for VG %s",
+                                         vg->seqno, save_seqno, vg->name);
+                       vg_ret->cft_precommitted = vgmeta_ret;
+                       if (!lvmetad_vg_update(vg_ret))
+                               log_error("Failed to update lvmetad with new VG meta");
+                       vg_ret->cft_precommitted = NULL;
+               }
                dm_config_destroy(vgmeta_ret);
        }
 out: