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lvmetad: Fix a race in metadata update.

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The idea is to avoid a period when an existing VG is not mapped to either the
old or the new name. (Note that the brief "blackout" was present even if the
name did not actually change.) We instead allow a brief overlap of a VG existing
under both names, i.e. a query for a VG might succeed but before a lock is
acquired the VG disappears.
This commit is contained in:
Petr Rockai 2013-01-16 11:09:37 +01:00
parent 6fc596ca90
commit 15fdd5c90d
1 changed files with 10 additions and 8 deletions
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18
daemons/lvmetad/lvmetad-core.c
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@ -454,7 +454,8 @@ static response vg_lookup(lvmetad_state *s, request r)
DEBUGLOG(s, "vg_lookup: updated uuid = %s, name = %s", uuid, name);
if (!uuid)
/* Check the name here. */
if (!uuid || !name)
return reply_unknown("VG not found");
cft = lock_vg(s, uuid);
@ -682,16 +683,14 @@ static int update_metadata(lvmetad_state *s, const char *name, const char *_vgid
lock_vgid_to_metadata(s);
old = dm_hash_lookup(s->vgid_to_metadata, _vgid);
oldname = dm_hash_lookup(s->vgid_to_vgname, _vgid);
unlock_vgid_to_metadata(s);
lock_vg(s, _vgid);
seq = dm_config_find_int(metadata, "metadata/seqno", -1);
if (old) {
if (old)
haveseq = dm_config_find_int(old->root, "metadata/seqno", -1);
oldname = dm_hash_lookup(s->vgid_to_vgname, _vgid);
assert(oldname);
}
if (seq < 0)
goto out;
@ -743,7 +742,7 @@ static int update_metadata(lvmetad_state *s, const char *name, const char *_vgid
if (haveseq >= 0 && haveseq < seq) {
INFO(s, "Updating metadata for %s at %d to %d", _vgid, haveseq, seq);
/* temporarily orphan all of our PVs */
remove_metadata(s, vgid, 1);
update_pvid_to_vgid(s, old, "#orphan", 0);
}
lock_vgid_to_metadata(s);
@ -753,14 +752,17 @@ static int update_metadata(lvmetad_state *s, const char *name, const char *_vgid
dm_hash_insert(s->vgid_to_metadata, vgid, cft) &&
dm_hash_insert(s->vgid_to_vgname, vgid, cfgname) &&
dm_hash_insert(s->vgname_to_vgid, name, (void*) vgid)) ? 1 : 0;
if (retval && oldname && strcmp(name, oldname))
dm_hash_remove(s->vgname_to_vgid, oldname);
unlock_vgid_to_metadata(s);
if (retval)
/* FIXME: What should happen when update fails */
retval = update_pvid_to_vgid(s, cft, vgid, 1);
unlock_pvid_to_vgid(s);
out:
out: /* FIXME: We should probably abort() on partial failures. */
if (!retval && cft)
dm_config_destroy(cft);
unlock_vg(s, _vgid);