Re: [libvirt] [Qemu-devel] [PATCH v3] Add support for fd: protocol

Am 26.07.2011 18:57, schrieb Corey Bryant: >>>> diff --git a/block/cow.c b/block/cow.c >>>> index 4cf543c..e17f8e7 100644 >>>> --- a/block/cow.c >>>> +++ b/block/cow.c >>>> @@ -82,6 +82,11 @@ static int cow_open(BlockDriverState *bs, int flags) >>>> pstrcpy(bs->backing_file, sizeof(bs->backing_file), >>>> cow_header.backing_file); >>>> >>>> + if (bs->backing_file[0] != '\0'&& bdrv_is_fd_protocol(bs)) { >>>> + /* backing file currently not supported by fd: protocol */ >>>> + goto fail; >>>> + } >> I don't think these checks are strictly needed. Without the check you >> can open the image itself using an fd, and the backing file using good >> old raw-posix. We shouldn't decide for our users that this isn't useful. >> >> In any case, it would have to move into block.c, you can't modify >> independent drivers for this. >> > > I understand the point on not modifying independent drivers. > > But if the backing file resides on NFS, wouldn't the the proposed > SELinux changes prevent the open? Probably. But what about cases where the backing file is local? Or even a non-libvirt, non-SELinux use case? > Or are you talking about support where libvirt opens the backing file > and passes the fd to Qemu? If so there was some discussion about future > support for this here: > http://lists.gnu.org/archive/html/qemu-devel/2011-06/msg01496.html Not really, but implementing this will be a bit easier if you don't forbid using backing files with fd.