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blockdev-backup: don't check aio_context too early 

in blockdev_backup_prepare, we check to make sure that the target is
associated with a compatible aio context. However, do_blockdev_backup is
called later and has some logic to move the target to a compatible
aio_context. The transaction version will fail certain commands
needlessly early as a result.

Allow blockdev_backup_prepare to simply call do_blockdev_backup, which
will ultimately decide if the contexts are compatible or not.

Note: the transaction version has always disallowed this operation since
its initial commit bd8baecd (2014), whereas the version of
qmp_blockdev_backup at the time, from commit c29c1dd312, tried to
enforce the aio_context switch instead. It's not clear, and I can't see
from the mailing list archives at the time, why the two functions take a
different approach. It wasn't until later in efd7556708 (2016) that the
standalone version tried to determine if it could set the context or
not.

Reported-by: aihua liang <aliang@redhat.com>
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1683498
Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 20190523170643.20794-2-jsnow@redhat.com
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
stable-4.1
John Snow 2019-05-23 13:06:39 -04:00 committed by Max Reitz
parent 5ec2eca83d
commit d81e1efbea
1 changed files with 0 additions and 4 deletions
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4
blockdev.c
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@ -1876,10 +1876,6 @@ static void blockdev_backup_prepare(BlkActionState *common, Error **errp)
}
aio_context = bdrv_get_aio_context(bs);
if (aio_context != bdrv_get_aio_context(target)) {
error_setg(errp, "Backup between two IO threads is not implemented");
return;
}
aio_context_acquire(aio_context);
state->bs = bs;