Re: [Qemu-devel] [PATCH 2/5] migration: Close file on failed migration load

[Peter Xu <peterx@redhat.com>]

On Tue, Jul 04, 2017 at 07:49:12PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Closing the file before exit on a failure allows
> the source to cleanup better, especially with RDMA.
> 
> Partial fix for https://bugs.launchpad.net/qemu/+bug/1545052

In above bug reported, the issue is that both dst and src VMs hanged
when migration failed (which is a by-design failure). On destination,
it hangs at (copied from the link):

#0 0x00007ffff39141cd in write () at ../sysdeps/unix/syscall-template.S:81
#1 0x00007ffff27fe795 in rdma_get_cm_event.part.15 () from /lib64/librdmacm.so.1
#2 0x000055555593e445 in qemu_rdma_cleanup (rdma=0x7fff9647e010) at migration/rdma.c:2210
#3 0x000055555593ea45 in qemu_rdma_close (opaque=0x555557796770) at migration/rdma.c:2652
#4 0x00005555559397cc in qemu_fclose (f=f@entry=0x5555564b1450) at migration/qemu-file.c:270
#5 0x0000555555936b88 in process_incoming_migration_co (opaque=0x5555564b1450) at migration/migration.c:361
#6 0x0000555555a25a1a in coroutine_trampoline (i0=<optimized out>, i1=<optimized out>) at util/coroutine-ucontext.c:79
#7 0x00007fffef5b3110 in ?? () from /lib64/libc.so.6

So looks like at that time we have qemu_fclose() for the incoming fd,
and that's the thing that caused trouble.

(just to mention that the version caused failure is commit fc1ec1acf,
 which is mentioned in the first comment in the bz)

Now the situation is: we don't have qemu_flose() now in current QEMU
master on the failure path (see below, we just exit() directly). Then
would the bz still valid now? And, if we apply this fix (then we do
qemu_fclose() again), would it hang again instead of fixing anything?

> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>  migration/migration.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index 51ccd1a4c5..21d6902a29 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -355,6 +355,7 @@ static void process_incoming_migration_co(void *opaque)
>                            MIGRATION_STATUS_FAILED);
>          error_report("load of migration failed: %s", strerror(-ret));
>          migrate_decompress_threads_join();
> +        qemu_fclose(mis->from_src_file);
>          exit(EXIT_FAILURE);
>      }
>  
> -- 
> 2.13.0
> 

-- 
Peter Xu