Re: [libvirt] [PATCH 1/2] storage: Resolve storage driver crash

On Mon, 2017-11-06 at 15:53 -0500, John Ferlan wrote: > Resolve a storage driver crash as a result of a long running > storageVolCreateXML when the virStorageVolPoolRefreshThread is > run as a result of a storageVolUpload complete and ran the > virStoragePoolObjClearVols without checking if the creation > code was currently processing a buildVol after incrementing > the driver->asyncjob count. > > The refreshThread needs to wait until all creation threads > are completed so as to not alter the volume list while the > volume is being built. > > Crash from valgrind is as follows (with a bit of editing): > > ==21309== Invalid read of size 8 > ==21309== at 0x153E47AF: storageBackendUpdateVolTargetInfo > ==21309== by 0x153E4C30: virStorageBackendUpdateVolInfo > ==21309== by 0x153E52DE: virStorageBackendVolRefreshLocal > ==21309== by 0x153DE29E: storageVolCreateXML > ==21309== by 0x562035B: virStorageVolCreateXML > ==21309== by 0x147366: remoteDispatchStorageVolCreateXML > ... > ==21309== Address 0x2590a720 is 64 bytes inside a block of size 336 free'd > ==21309== at 0x4C2F2BB: free > ==21309== by 0x54CB9FA: virFree > ==21309== by 0x55BC800: virStorageVolDefFree > ==21309== by 0x55BF1D8: virStoragePoolObjClearVols > ==21309== by 0x153D967E: virStorageVolPoolRefreshThread > ... > ==21309== Block was alloc'd at > ==21309== at 0x4C300A5: calloc > ==21309== by 0x54CB483: virAlloc > ==21309== by 0x55BDC1F: virStorageVolDefParseXML > ==21309== by 0x55BDC1F: virStorageVolDefParseNode > ==21309== by 0x55BE5A4: virStorageVolDefParse > ==21309== by 0x153DDFF1: storageVolCreateXML > ==21309== by 0x562035B: virStorageVolCreateXML > ==21309== by 0x147366: remoteDispatchStorageVolCreateXML > ... > > Signed-off-by: John Ferlan <jferlan(a)redhat.com&gt; > --- > src/storage/storage_driver.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/src/storage/storage_driver.c b/src/storage/storage_driver.c > index b0edf9f885..5e920fc14c 100644 > --- a/src/storage/storage_driver.c > +++ b/src/storage/storage_driver.c > @@ -2257,6 +2257,7 @@ virStorageVolPoolRefreshThread(void *opaque) > virStorageBackendPtr backend; > virObjectEventPtr event = NULL; > > + retry: > storageDriverLock(); > if (cbdata->vol_path) { > if (virStorageBackendPloopRestoreDesc(cbdata->vol_path) < 0) > @@ -2270,6 +2271,14 @@ virStorageVolPoolRefreshThread(void *opaque) > if (!(backend = virStorageBackendForType(def->type))) > goto cleanup; > > + /* Some thread is creating a new volume in the pool, we need to retry */ > + if (virStoragePoolObjGetAsyncjobs(obj) > 0) { > + virStoragePoolObjUnlock(obj); > + storageDriverUnlock(); > + usleep(100 * 1000); > + goto retry; > + } > + > virStoragePoolObjClearVols(obj); > if (backend->refreshPool(NULL, obj) < 0) > VIR_DEBUG("Failed to refresh storage pool"); ACK, does the job here. I'm rather surprised to see you implementing it with sleep, while you pointed me towards virCondWait yesterday. But using sleep is a way less intrusive change.

-- Cedric