[lvm-devel] [PATCH] Fix vg_write/vg_commit to not reset position in metadata ring buffer on vgrename

[Peter Rajnoha]

We should write metadata into next position in the ring buffer while calling vgrename.
At this code level (_vg_write_raw), we're not able to determine if this is a rename
or not. If yes, then accompanying VG structure passed here has a new name set,
not the old one.

When looking for a location where to put metadata next, we're given a NULL value because
of failed VG name comparison (in _find_vg_rlocn) between the name in existing metadata
and metadata we're just about to write.

This resets the position in the ring buffer, overwriting any existing metadata
(and also incorrectly updates the cache to "orphan" afterwards).

This patch just adds old_name item in struct volume_group that we can check and use
if necessary and detect renames at lower layers as well.

Peter

 lib/format_text/format-text.c    |   17 +++++++++++++----
 lib/metadata/metadata-exported.h |    1 +
 lib/metadata/metadata.c          |    2 ++
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/lib/format_text/format-text.c b/lib/format_text/format-text.c
index ad4db34..4856d07 100644
--- a/lib/format_text/format-text.c
+++ b/lib/format_text/format-text.c
@@ -380,6 +380,10 @@ static struct raw_locn *_find_vg_rlocn(struct device_area *dev_area,
 	} else
 		*precommitted = 0;
 
+	/* Do not check non-existent metadata. */
+	if (!rlocn->offset && !rlocn->size)
+		return NULL;
+
 	/* FIXME Loop through rlocns two-at-a-time.  List null-terminated. */
 	/* FIXME Ignore if checksum incorrect!!! */
 	if (!dev_read(dev_area->dev, dev_area->start + rlocn->offset,
@@ -387,9 +391,11 @@ static struct raw_locn *_find_vg_rlocn(struct device_area *dev_area,
 		goto_bad;
 
 	if (!strncmp(vgnamebuf, vgname, len = strlen(vgname)) &&
-	    (isspace(vgnamebuf[len]) || vgnamebuf[len] == '{')) {
+	    (isspace(vgnamebuf[len]) || vgnamebuf[len] == '{'))
 		return rlocn;
-	}
+	else
+		log_debug("Volume group name found in metadata does "
+			  "not match expected name %s.", vgname);
 
       bad:
 	if ((info = info_from_pvid(dev_area->dev->pvid, 0)))
@@ -542,7 +548,8 @@ static int _vg_write_raw(struct format_instance *fid, struct volume_group *vg,
 	if (!(mdah = _raw_read_mda_header(fid->fmt, &mdac->area)))
 		goto_out;
 
-	rlocn = _find_vg_rlocn(&mdac->area, mdah, vg->name, &noprecommit);
+	rlocn = _find_vg_rlocn(&mdac->area, mdah,
+			vg->old_name ? vg->old_name : vg->name, &noprecommit);
 	mdac->rlocn.offset = _next_rlocn_offset(rlocn, mdah);
 
 	if (!fidtc->raw_metadata_buf &&
@@ -647,7 +654,9 @@ static int _vg_commit_raw_rlocn(struct format_instance *fid,
 	if (!(mdah = _raw_read_mda_header(fid->fmt, &mdac->area)))
 		goto_out;
 
-	if (!(rlocn = _find_vg_rlocn(&mdac->area, mdah, vg->name, &noprecommit))) {
+	if (!(rlocn = _find_vg_rlocn(&mdac->area, mdah,
+				     vg->old_name ? vg->old_name : vg->name,
+				     &noprecommit))) {
 		mdah->raw_locns[0].offset = 0;
 		mdah->raw_locns[0].size = 0;
 		mdah->raw_locns[0].checksum = 0;
diff --git a/lib/metadata/metadata-exported.h b/lib/metadata/metadata-exported.h
index 2f1405f..855ab47 100644
--- a/lib/metadata/metadata-exported.h
+++ b/lib/metadata/metadata-exported.h
@@ -216,6 +216,7 @@ struct volume_group {
 
 	struct id id;
 	char *name;
+	char *old_name;
 	char *system_id;
 
 	uint32_t extent_size;
diff --git a/lib/metadata/metadata.c b/lib/metadata/metadata.c
index 020e897..867e004 100644
--- a/lib/metadata/metadata.c
+++ b/lib/metadata/metadata.c
@@ -437,6 +437,8 @@ int vg_rename(struct cmd_context *cmd, struct volume_group *vg,
 	struct dm_pool *mem = vg->vgmem;
 	struct pv_list *pvl;
 
+	vg->old_name = vg->name;
+
 	if (!(vg->name = dm_pool_strdup(mem, new_name))) {
 		log_error("vg->name allocation failed for '%s'", new_name);
 		return 0;