On Tue, Nov 16, 2010 at 8:05 AM, Josef Bacik <josef@xxxxxxxxxx> wrote:
> On Tue, Nov 16, 2010 at 03:07:29PM +0200, Avi Kivity wrote:
>> On 11/16/2010 02:50 PM, Josef Bacik wrote:
>>> On Tue, Nov 16, 2010 at 02:25:35PM +0200, Avi Kivity wrote:
>>> > On 11/15/2010 07:05 PM, Josef Bacik wrote:
>>> >> Ext4 doesn't have the ability to punch holes yet, so make sure we return
>>> >> EOPNOTSUPP if we try to use hole punching through fallocate. This support can
>>> >> be added later. Thanks,
>>> >>
>>> >
>>> > Instead of teaching filesystems to fail if they don't support the
>>> > capability, why don't supporting filesystems say so, allowing the fail
>>> > code to be in common code?
>>> >
>>>
>>> There is no simple way to test if a filesystem supports hole punching or not so
>>> the check has to be done per fs. Thanks,
>>
>> Could put a flag word in superblock_operations. Filesystems which
>> support punching (or other features) can enable it there.
>>
>> Or even have its own callback.
>>
>
> Sure but then you have to do the same thing for every other flag you add to
> fallocate and then you have this huge mess of random flags just so you don't
> call into the filesystem. This way is a lesser of two evils I think. Thanks,
>
> Josef
I'm not a true kernel hacker, so my opinion is not critical but I find
it hard to read / expand as
> + /* We only support the FALLOC_FL_KEEP_SIZE mode */
> + if (mode && (mode != FALLOC_FL_KEEP_SIZE))
> + return -EOPNOTSUPP;
How about:
#define EXT4_FALLOC_MODES_SUPPORTED (FALLOC_FL_KEEP_SIZE)
if (modes & ~EXT4_FALLOC_MODES_SUPPORTED)
return -EOPNOTSUPP;
Greg
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