[Ocfs2-tools-devel] [PATCH 1/1] Ocfs2-tools: Let o2image.c also correctly deal with LARGEFILE.

[Coly Li]

tristan.ye Wrote:
> On Fri, 2009-02-27 at 16:15 +0800, Coly Li wrote:
>> Joel Becker Wrote:
>>> On Fri, Feb 27, 2009 at 03:43:01PM +0800, tristan.ye wrote:
>>>> On Fri, 2009-02-27 at 15:29 +0800, Coly Li wrote:
>>>>> Joel Becker Wrote:
>>>>>> On Tue, Feb 24, 2009 at 10:36:12AM +0800, Tristan Ye wrote:
>>>>>>> We may not need to switch the open64() on by marco HAVE_OPEN64 here,
>>>>>>> since actually the HAVE_OPEN64 seems never was defined in the scope of
>>>>>>> o2image.c. To be more explicit, we simply could use open64() directly since
>>>>>>> such 64bits utility will never affect on 32bits Linux.
>>>>>>>
>>>>>>> Signed-off-by: Tristan Ye <tristan.ye at oracle.com>
>>>>>> This change is correct anyway, because _LARGEFILE64_SOURCE explicitly
>>>>>> means we have open64().  If a system is broken enough not to have it, we
>>>>>> just want to fail.
>>>>>>
>>>>> Since include/ocfs2/ocfs2.h declares _LARGEFILES64_SOURCE explicitly, can we say if:
>>>>> 1) a source file includes "ocfs2/ocfs2.h"
>>>>> 2) a device file (e.g. /dev/sda or /dev/sda1) to be opened
>>>>> an open64() should be used other than open() ?
>>>> Coly,
>>>>
>>>> We only need to use 64bits io system call alternatives where large io is
>>>> going to happen, such as opening a LARGE file, growing a file up to 2G,
>>>> etc.
>>>>
>>>> I personally think there is no need to use open64 to open a device
>>>> special file, anyway, it may not hurt us if we use 64 bits io system
>>>> calls everywhere since it only takes effect on a 32bits linux. Joel, how
>>>> dou you think about it?
>>> 	I personally use open64() everywhere.  You never know what might
>>> happen, and it's easier to have open64() and never need it than to be
>>> stuck with binaries using open() and failing at a 2G boundary.
>>>
>> Oh, a more question: I only know lseek will fail at 2G limitation, will open() also fail on a >2GB
>> file ?
>> I just write a test code to open a 2.6G iso file, only open it with open(2) seems OK.
> 
> For a large file(more than 2G) on 32bits linux, a simple open() will not
> fail, but with such a 32bits open(), following io operations such as
> read, write,lseek etc will definitely failed at 2G boundary.
> 
> Could try to read the whole 2.6G until its end or just append some bits
> to its end, i bet it will fail.
> 
Nice answer !

Thanks you for the patient text :)))

-- 
Coly Li
SuSE Labs