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Date: Fri, 3 Jun 2016 11:07:57 +0800
From: Changlong Xie <xiecl.fnst@cn.fujitsu.com>
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Subject: Re: [Qemu-devel] [PATCH v5 1/1] Introduce "xen-load-devices-state"
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To: Eric Blake <eblake@redhat.com>, Anthony PERARD <anthony.perard@citrix.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>, zhanghailiang <zhang.zhanghailiang@huawei.com>, Juan Quintela <quintela@redhat.com>, Markus Armbruster <armbru@redhat.com>, qemu devel <qemu-devel@nongnu.org>, Amit Shah <amit.shah@redhat.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>

On 06/03/2016 10:13 AM, Changlong Xie wrote:
> On 06/03/2016 09:45 AM, Eric Blake wrote:
>> On 06/02/2016 07:26 PM, Changlong Xie wrote:
>>
>>>>> +
>>>>> +    ioc = qio_channel_file_new_path(filename, O_WRONLY | O_CREAT,
>>>>> 0660, errp);
>>>>
>>>> This does not look right, it looks like it's going to open the file
>>>> to write to it. You probably want O_RDONLY, also I don't think the
>>>> O_CREAT flag is needed. (and without O_WRONLY, mode can be 0 instead of
>>>> 0660.)
>>>>
>>>
>>> Yes, as you said. We should use 0_RDONLY for open(2), so mode should
>>> be 0.
>>
>> Huh?  mode doesn't affect the current fd, but DOES affect the next
>> person to open the file.  If you are truly creating the file, then a
>> mode of 0 means you won't be able to reopen it without chmod.  And if
>> you are doing O_RDONLY | O_CREAT, all you will be able to create is an
>> empty file, which is a pretty boring read.  So drop the O_CREAT, and
>> then you don't need a mode argument at all.
>>
>
> Yes, i just mean qio_channel_file_new_path(filename, O_RDONLY, 0, errp)

I just notice that, qemu specifies flag 'O_BINARY' to allow system to 
differentiate between a text file and a binary file( I guess so?). For 
backward compatibility, refer to function test_io_channel_file(), i will 
use

qio_channel_file_new_path(filename, O_RDONLY | O_BINARY, 0, errp)

here.

> here. Maybe my poor english make you confused :(
>
> Thanks
>      -Xie
>
>
>
>