Re: [Qemu-devel] Safely reopening image files by stashing fds

[Stefan Hajnoczi]

On Fri, Aug 5, 2011 at 10:04 AM, Paolo Bonzini <address@hidden> 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.

The only method I've found that works is to open("/proc/self/fd/X",
new_flags) but that's non-portable.

Stefan