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Date: Fri, 31 Aug 2012 10:42:49 -0400
From: Jeff Cody <jcody@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 3/7] block: raw-posix image file reopen
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To: Eric Blake <eblake@redhat.com>
Cc: kwolf@redhat.com, pbonzini@redhat.com, stefanha@gmail.com, qemu-devel@nongnu.org, supriyak@linux.vnet.ibm.com

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.

> 
>> +        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.