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vgcreate: improve checks for existing global lock

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This tries harder to avoid creating duplicate global locks in
sanlock VGs by refusing to create a new sanlock VG with a
global lock if other sanlock VGs exist that may have a gl.
This commit is contained in:
David Teigland 2015-07-24 10:06:58 -05:00
parent e593213b87
commit 772b54a08b
4 changed files with 50 additions and 16 deletions
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6
daemons/lvmlockd/lvmlockd-core.c
View File

@ -3341,12 +3341,6 @@ static void client_send_result(struct client *cl, struct action *act)
* or if lockspaces exist, but not one with the global lock.
* Given this detail, it may be able to procede without
* the lock.
*
* FIXME: it would also help the caller to know if there
* are other sanlock VGs that have not been started.
* If there are, then one of them might have a global
* lock enabled. In that case, vgcreate may not want
* to create a new sanlock vg with gl enabled.
*/
pthread_mutex_lock(&lockspaces_mutex);
if (list_empty(&lockspaces))

13
lib/cache/lvmcache.c vendored
View File

@ -2345,3 +2345,16 @@ int lvmcache_lookup_mda(struct lvmcache_vgsummary *vgsummary)
return 0;
}
int lvmcache_contains_lock_type_sanlock(struct cmd_context *cmd)
{
struct lvmcache_vginfo *vginfo;
dm_list_iterate_items(vginfo, &_vginfos) {
if (vginfo->lock_type && !strcmp(vginfo->lock_type, "sanlock"))
return 1;
}
return 0;
}

2
lib/cache/lvmcache.h vendored
View File

@ -188,4 +188,6 @@ int lvmcache_found_duplicate_pvs(void);
void lvmcache_set_preferred_duplicates(const char *vgid);
int lvmcache_contains_lock_type_sanlock(struct cmd_context *cmd);
#endif

45
lib/locking/lvmlockd.c
View File

@ -1177,23 +1177,48 @@ int lockd_gl_create(struct cmd_context *cmd, const char *def_mode, const char *v
* skip acquiring the global lock when creating this initial
* VG, and enable the global lock in this VG.
*
* Here we assume that this is an initial bootstrap condition
* based on the fact that lvmlockd has seen no lockd VGs.
* (A commmand line option could be added to allow the user
* to make this initial bootstrap condition explicit.)
* This initial bootstrap condition is identified based on
* two things:
*
* That assumption might be wrong. It is possible that a global
* lock does exist in a VG that has not yet been seen. If that
* VG appears after this creates a new VG with a new enabled
* global lock, then there will be two VGs containing enabled
* global locks, and one will need to be disabled by the user.
* 1. No sanlock VGs have been started in lvmlockd, causing
* lvmlockd to return NO_GL_LS/NO_LOCKSPACES.
*
* 2. No sanlock VGs are seen in lvmcache after the disk
* scan performed in lvmetad_validate_global_cache().
*
* If both of those are true, we go ahead and create this new
* VG which will have the global lock enabled. However, this
* has a shortcoming: another sanlock VG may exist that hasn't
* appeared to the system yet. If that VG has its global lock
* enabled, then when it appears later, duplicate global locks
* will be seen, and a warning will indicate that one of them
* should be disabled.
*
* The two bootstrap conditions have another shortcoming to the
* opposite effect: other sanlock VGs may be visible to the
* system, but none of them have a global lock enabled.
* In that case, it would make sense to create this new VG with
* an enabled global lock. (FIXME: we could detect that none
* of the existing sanlock VGs have a gl enabled and allow this
* vgcreate to go ahead.) Enabling the global lock in one of
* the existing sanlock VGs is currently the simplest solution.
*/
if ((lockd_flags & LD_RF_NO_GL_LS) &&
(lockd_flags & LD_RF_NO_LOCKSPACES) &&
!strcmp(vg_lock_type, "sanlock")) {
log_print_unless_silent("Enabling sanlock global lock");
lvmetad_validate_global_cache(cmd, 1);
/*
* lvmcache holds provisional VG lock_type info because
* lvmetad_validate_global_cache did a disk scan.
*/
if (lvmcache_contains_lock_type_sanlock(cmd)) {
/* FIXME: we could check that all are started, and then check that none have gl enabled. */
log_error("Global lock failed: start existing sanlock VGs to access global lock.");
log_error("(If all sanlock VGs are started, enable global lock with lvmlockctl.)");
return 0;
}
log_print_unless_silent("Enabling sanlock global lock");
return 1;
}