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libxl: Add lock process indicator to libxlDomainObjPrivate object

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The libvirt libxl driver has no access to FDs associated with VM disks.
The disks are opened by libxl.so and any related FDs are not exposed to
applications. The prevents using virtlockd's auto-release feature to
release locks when the FD is closed. Acquiring and releasing locks is
explicitly handled by the libxl driver.

The current logic is structured such that locks are acquired in
libxlDomainStart and released in libxlDomainCleanup. This works well
except for migration, where the locks must be released on the source
host before the domain can be started on the destination host, but the
domain cannot be cleaned up until the migration confirmation stage.
When libxlDomainCleanup if finally called in the confirm stage, locks
are again released resulting in confusing errors from virtlockd and
libvirtd

virtlockd[8095]: resource busy: Lockspace resource 'xxxxxx' is not locked
libvirtd[8050]: resource busy: Lockspace resource 'xxxxxx' is not locked
libvirtd[8050]: Unable to release lease on testvm

The error is also encountered in some error cases, e.g. when
libxlDomainStart fails before acquiring locks and libxlDomainCleanup
is still used for cleanup.

In lieu of a mechanism to check if a lock has been acquired, this patch
takes an easy approach to fixing the unnecessary lock releases by adding
an indicator to the libxlDomainPrivate object that can be set when the
lock is acquired and cleared when the lock is released. libxlDomainCleanup
can then skip releasing the lock in cases where it was previously released
or never acquired in the first place.

Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
This commit is contained in:
Jim Fehlig 2021-02-19 14:58:19 -07:00
parent 146beb48ce
commit fa58f571ee
3 changed files with 16 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
src/libxl/libxl_domain.c
View File

@ -861,10 +861,14 @@ libxlDomainCleanup(libxlDriverPrivatePtr driver,
virHostdevReAttachDomainDevices(hostdev_mgr, LIBXL_DRIVER_INTERNAL_NAME,
vm->def, hostdev_flags);
VIR_FREE(priv->lockState);
if (virDomainLockProcessPause(driver->lockManager, vm, &priv->lockState) < 0)
VIR_WARN("Unable to release lease on %s", vm->def->name);
VIR_DEBUG("Preserving lock state '%s'", NULLSTR(priv->lockState));
if (priv->lockProcessRunning) {
VIR_FREE(priv->lockState);
if (virDomainLockProcessPause(driver->lockManager, vm, &priv->lockState) < 0)
VIR_WARN("Unable to release lease on %s", vm->def->name);
else
priv->lockProcessRunning = false;
VIR_DEBUG("Preserving lock state '%s'", NULLSTR(priv->lockState));
}
libxlLoggerCloseFile(cfg->logger, vm->def->id);
vm->def->id = -1;
@ -1426,6 +1430,7 @@ libxlDomainStart(libxlDriverPrivatePtr driver,
priv->lockState) < 0)
goto destroy_dom;
VIR_FREE(priv->lockState);
priv->lockProcessRunning = true;
/* Always enable domain death events */
if (libxl_evenable_domain_death(cfg->ctx, vm->def->id, 0, &priv->deathW))

1
src/libxl/libxl_domain.h
View File

@ -68,6 +68,7 @@ struct _libxlDomainObjPrivate {
virThreadPtr migrationDstReceiveThr;
unsigned short migrationPort;
char *lockState;
bool lockProcessRunning;
struct libxlDomainJobObj job;

8
src/libxl/libxl_migration.c
View File

@ -1242,9 +1242,12 @@ libxlDomainMigrationSrcPerform(libxlDriverPrivatePtr driver,
virObjectLock(vm);
if (ret == 0) {
if (virDomainLockProcessPause(driver->lockManager, vm, &priv->lockState) < 0)
if (virDomainLockProcessPause(driver->lockManager, vm, &priv->lockState) == 0) {
priv->lockProcessRunning = false;
VIR_DEBUG("Preserving lock state '%s'", NULLSTR(priv->lockState));
} else {
VIR_WARN("Unable to release lease on %s", vm->def->name);
VIR_DEBUG("Preserving lock state '%s'", NULLSTR(priv->lockState));
}
} else {
/*
* Confirm phase will not be executed if perform fails. End the
@ -1377,6 +1380,7 @@ libxlDomainMigrationSrcConfirm(libxlDriverPrivatePtr driver,
"xen:///system",
vm,
priv->lockState);
priv->lockProcessRunning = true;
if (libxl_domain_resume(cfg->ctx, vm->def->id, 1, 0) == 0) {
ret = 0;
} else {