On Fri, Aug 05, 2011 at 10:27:00AM +0100, Stefan Hajnoczi wrote:
> On Fri, Aug 5, 2011 at 10:04 AM, Paolo Bonzini <pbonz...@redhat.com> wrote:
> > On 08/05/2011 10:40 AM, Stefan Hajnoczi wrote:
> >>
> >> 4. Implement bdrv_reopen()
> >>
> >> First call bdrv_extract_fds() to stash the file descriptors, then close
> >> the
> >> block device. Try opening the new image but if that fails, reopen using
> >> the
> >> stashed file descriptors.
> >
> > Why not do the latter unconditionally?
>
> Because you cannot change O_DIRECT on an open fd :(. This is why
> we're going through this pain.
Hmm, I remember hearing that before, but looking at the current fcntl()
manpage, it claims you *can* change O_DIRECT using SET_FL. Perhaps this
is a newish feature, but it'd be nicer to use it if possible ?
[man 2 fcntl]
F_SETFL (long)
Set the file status flags to the value specified by arg. File
access mode (O_RDONLY, O_WRONLY, O_RDWR) and file creation flags
(i.e., O_CREAT, O_EXCL, O_NOCTTY, O_TRUNC) in arg are ignored.
On Linux this command can only change the O_APPEND, O_ASYNC,
O_DIRECT, O_NOATIME, and O_NONBLOCK flags.
[/man]
Regards,
Daniel
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