On Thu, Jan 31, 2019 at 03:31:51PM +0100, Kevin Wolf wrote: > bdrv_co_invalidate_cache() clears the BDRV_O_INACTIVE flag before > actually activating a node so that the correct permissions etc. are > taken. In case of errors, the flag must be restored so that the next > call to bdrv_co_invalidate_cache() retries activation. > > Restoring the flag was missing in the error path for a failed > parent->role->activate() call. The consequence is that this attempt to > activate all images correctly fails because we still set errp, however > on the next attempt BDRV_O_INACTIVE is already clear, so we return > success without actually retrying the failed action. > > An example where this is observable in practice is migration to a QEMU > instance that has a raw format block node attached to a guest device > with share-rw=off (the default) while another process holds > BLK_PERM_WRITE for the same image. In this case, all activation steps > before parent->role->activate() succeed because raw can tolerate other > writers to the image. Only the parent callback (in particular > blk_root_activate()) tries to implement the share-rw=on property and > requests exclusive write permissions. This fails when the migration > completes and correctly displays an error. However, a manual 'cont' will > incorrectly resume the VM without calling blk_root_activate() again. > > This case is described in more detail in the following bug report: > https://bugzilla.redhat.com/show_bug.cgi?id=1531888 > > Fix this by correctly restoring the BDRV_O_INACTIVE flag in the error > path. > > Cc: qemu-sta...@nongnu.org > Signed-off-by: Kevin Wolf <kw...@redhat.com> > --- > block.c | 1 + > 1 file changed, 1 insertion(+)
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
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