Re: [libvirt] [PATCH v2] vz: handle gracefully races on undefining domain

This patch is not critical but nice to have. The original motivation was error message in logs on undefining domain thru vz driver. Undefine procedure drops domain lock while waiting for detaching disks vz sdk call. Meanwhile vz sdk event domain-config-changed arrives, its handler finds domain and is blocked waiting for job condition. After undefine API call finishes event processing procedes and tries to refreshes domain config thru existing vz sdk domain handle. Domain does not exists anymore and event processing fails. Everything is fine we just don't want to see error message in log for this particular case. Fortunately domain has flag that domain is removed from list. This also imply that vz sdk domain is also undefined. Thus if we check for this flag right after domain is locked again on accuiring job condition we gracefully handle this situation. Actually the race can happen in other situations too. Any time we wait for job condition in mutualy exclusive job in time when we acquire it vz sdk domain can cease to exist. So instead of general internal error we can return domain not found which is easier to handle. We don't need to patch other places in mutually exclusive jobs where domain lock is dropped as if job is started domain can't be undefine by mutually exclusive undefine job. The code of this patch is quite similar to qemu driver checks for is domain is active after acquiring a job. The difference only while qemu domain is operational while process is active vz domain is operational while domain exists. Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy(a)virtuozzo.com&gt; --- Changes from v1: 1. drop changes for API calls that do not accquire job condition. 2. fix prlsdkDomainChangeState to report error properly. src/vz/vz_driver.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ src/vz/vz_sdk.c | 13 +++++++++++++ 2 files changed, 59 insertions(+) diff --git a/src/vz/vz_driver.c b/src/vz/vz_driver.c index 1569278..711a354 100644 --- a/src/vz/vz_driver.c +++ b/src/vz/vz_driver.c @@ -716,6 +716,22 @@ vzDomainGetAutostart(virDomainPtr domain, int *autostart) return 0; } +static bool +vzDomainObjIsExist(virDomainObjPtr dom) +{ + char uuidstr[VIR_UUID_STRING_BUFLEN]; + + if (!dom->removing) + return true; + + virUUIDFormat(dom->def->uuid, uuidstr); + virReportError(VIR_ERR_NO_DOMAIN, + _("no domain with matching uuid '%s' (%s)"), + uuidstr, dom->def->name); + + return false; +} +

static virDomainPtr vzDomainDefineXMLFlags(virConnectPtr conn, const char *xml, unsigned int flags) { @@ -782,6 +798,9 @@ vzDomainDefineXMLFlags(virConnectPtr conn, const char *xml, unsigned int flags) goto cleanup; job = true; + if (!vzDomainObjIsExist(dom)) + goto cleanup; + if (prlsdkApplyConfig(driver, dom, def)) goto cleanup; @@ -1012,6 +1031,9 @@ vzDomainUndefineFlags(virDomainPtr domain, goto cleanup; job = true; + if (!vzDomainObjIsExist(dom)) + goto cleanup; + ret = prlsdkUnregisterDomain(privconn->driver, dom, flags); cleanup: @@ -1070,6 +1092,9 @@ vzDomainManagedSave(virDomainPtr domain, unsigned int flags) goto cleanup; job = true; + if (!vzDomainObjIsExist(dom)) + goto cleanup; + state = virDomainObjGetState(dom, &reason); if (state == VIR_DOMAIN_RUNNING && (flags & VIR_DOMAIN_SAVE_PAUSED)) { @@ -1160,6 +1185,9 @@ static int vzDomainAttachDeviceFlags(virDomainPtr domain, const char *xml, goto cleanup; job = true; + if (!vzDomainObjIsExist(dom)) + goto cleanup; + switch (dev->type) { case VIR_DOMAIN_DEVICE_DISK: ret = prlsdkAttachVolume(privconn->driver, dom, dev->data.disk); @@ -1228,6 +1256,9 @@ static int vzDomainDetachDeviceFlags(virDomainPtr domain, const char *xml, goto cleanup; job = true; + if (!vzDomainObjIsExist(dom)) + goto cleanup; + switch (dev->type) { case VIR_DOMAIN_DEVICE_DISK: ret = prlsdkDetachVolume(dom, dev->data.disk); @@ -1285,6 +1316,9 @@ vzDomainSetUserPassword(virDomainPtr domain, goto cleanup; job = true; + if (!vzDomainObjIsExist(dom)) + goto cleanup; + ret = prlsdkDomainSetUserPassword(dom, user, password); cleanup: @@ -1618,6 +1652,9 @@ static int vzDomainSetMemoryFlagsImpl(virDomainPtr domain, unsigned long memory, goto cleanup; job = true; + if (!vzDomainObjIsExist(dom)) + goto cleanup; + ret = prlsdkSetMemsize(dom, memory >> 10); cleanup: @@ -2102,6 +2139,9 @@ vzDomainSnapshotCreateXML(virDomainPtr domain, goto cleanup; job = true; + if (!vzDomainObjIsExist(dom)) + goto cleanup; + /* snaphot name is ignored, it will be set to auto generated by sdk uuid */ if (prlsdkCreateSnapshot(dom, def->description) < 0) goto cleanup; @@ -2163,6 +2203,9 @@ vzDomainRevertToSnapshot(virDomainSnapshotPtr snapshot, unsigned int flags) goto cleanup; job = true; + if (!vzDomainObjIsExist(dom)) + goto cleanup; + ret = prlsdkSwitchToSnapshot(dom, snapshot->name, flags & VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED); cleanup: @@ -2533,6 +2576,9 @@ vzDomainMigratePerformStep(virDomainPtr domain, goto cleanup; job = true; + if (!vzDomainObjIsExist(dom)) + goto cleanup; + if (!(vzuri = vzParseVzURI(miguri))) goto cleanup; diff --git a/src/vz/vz_sdk.c b/src/vz/vz_sdk.c index 551df10..ba3c28e 100644 --- a/src/vz/vz_sdk.c +++ b/src/vz/vz_sdk.c @@ -1812,6 +1812,9 @@ prlsdkHandleVmConfigEvent(vzDriverPtr driver, goto cleanup; job = true; + if (dom->removing) + goto cleanup; + if (prlsdkUpdateDomain(driver, dom) < 0) goto cleanup; @@ -2078,6 +2081,16 @@ prlsdkDomainChangeState(virDomainPtr domain, goto cleanup; job = true; + if (dom->removing) { + char uuidstr[VIR_UUID_STRING_BUFLEN]; + + virUUIDFormat(dom->def->uuid, uuidstr); + virReportError(VIR_ERR_NO_DOMAIN, + _("no domain with matching uuid '%s' (%s)"), + uuidstr, dom->def->name); + goto cleanup; + } + ret = prlsdkDomainChangeStateLocked(privconn->driver, dom, chstate); cleanup: