Re: [Qemu-devel] [PATCH 3/7] block: raw-posix image file reopen

[Jeff Cody <jcody@redhat.com>]

On 08/31/2012 10:49 AM, Kevin Wolf wrote:
> Am 31.08.2012 16:42, schrieb Jeff Cody:
>> On 08/30/2012 06:15 PM, Eric Blake wrote:
>>> On 08/30/2012 11:47 AM, Jeff Cody wrote:
>>>> This is derived from the Supriya Kannery's reopen patches.
>>>>
>>>> This contains the raw-posix driver changes for the bdrv_reopen_*
>>>> functions.  All changes are staged into a temporary scratch buffer
>>>> during the prepare() stage, and copied over to the live structure
>>>> during commit().  Upon abort(), all changes are abandoned, and the
>>>> live structures are unmodified.
>>>>
>>>> The _prepare() will create an extra fd - either by means of a dup,
>>>> if possible, or opening a new fd if not (for instance, access
>>>> control changes).  Upon _commit(), the original fd is closed and
>>>> the new fd is used.  Upon _abort(), the duplicate/new fd is closed.
>>>>
>>>
>>>> +    if ((raw_s->open_flags & ~fcntl_flags) == (s->open_flags & ~fcntl_flags)) {
>>>> +        /* dup the original fd */
>>>> +        /* TODO: use qemu fcntl wrapper */
>>>> +        raw_s->fd = fcntl(s->fd, F_DUPFD_CLOEXEC, 0);
>>>
>>> I assume this TODO has to be fixed to allow compilation on systems that
>>> lack F_DUPFD_CLOEXEC.
>>
>> Yes, either that or add the logic here.
> 
> Would qemu_dup_flags() from osdep.c be the right thing here? It was
> introduces with Corey's fd passing series.

I think so - that is the one I was thinking about.  It would just need
to be made non-static.

> 
>>>> +        if (raw_s->fd == -1) {
>>>> +            ret = -1;
>>>> +            goto error;
>>>> +        }
>>>> +        ret = fcntl_setfl(raw_s->fd, raw_s->open_flags);
>>>> +    } else {
>>>> +        raw_s->fd = qemu_open(state->bs->filename, raw_s->open_flags, 0644);
>>>
>>> Is raw_s->open_flags every going to contain O_CREAT, or is the 0644 mode
>>> argument spurious?
>>
>> Thanks, you are right, it is spurious.  The raw_s->open_flags are
>> explicitly set via raw_parse_flags(), so we know it will never contain
>> O_CREAT.
> 
> We can probably assert it.
>

OK