Re: [libvirt] [RFC PATCH] qcow2: Fix race in cache invalidation

On 09/25/2014 08:20 PM, Kevin Wolf wrote: > Am 25.09.2014 um 11:55 hat Alexey Kardashevskiy geschrieben: >> Right. Cool. So is below what was suggested? I am doublechecking as it does >> not solve the original issue - the bottomhalf is called first and then >> nbd_trip() crashes in qcow2_co_flush_to_os(). >> >> diff --git a/block.c b/block.c >> index d06dd51..1e6dfd1 100644 >> --- a/block.c >> +++ b/block.c >> @@ -5037,20 +5037,22 @@ void bdrv_invalidate_cache(BlockDriverState *bs, >> Error **errp) >> if (local_err) { >> error_propagate(errp, local_err); >> return; >> } >> >> ret = refresh_total_sectors(bs, bs->total_sectors); >> if (ret < 0) { >> error_setg_errno(errp, -ret, "Could not refresh total sector count"); >> return; >> } >> + >> + bdrv_drain_all(); >> } > > Try moving the bdrv_drain_all() call to the top of the function (at > least it must be called before bs->drv->bdrv_invalidate_cache). Ok, I did. Did not help. > >> +static QEMUBH *migration_complete_bh; >> +static void process_incoming_migration_complete(void *opaque); >> + >> static void process_incoming_migration_co(void *opaque) >> { >> QEMUFile *f = opaque; >> - Error *local_err = NULL; >> int ret; >> >> ret = qemu_loadvm_state(f); >> qemu_fclose(f); > > Paolo suggested to move eveything starting from here, but as far as I > can tell, leaving the next few lines here shouldn't hurt. Ouch. I was looking at wrong qcow2_fclose() all this time :) Aaaany what you suggested did not help - bdrv_co_flush() calls qemu_coroutine_yield() while this BH is being executed and the situation is still the same.