Re: ext2/3/4: punch support?
From: Dave Young
Date: Mon Feb 28 2011 - 20:27:48 EST
On Mon, Feb 28, 2011 at 11:17 PM, Eric Sandeen <sandeen@xxxxxxxxxx> wrote:
> On 2/28/11 8:29 AM, Dave Young wrote:
>> On Mon, Feb 28, 2011 at 9:11 PM, Josef Bacik <josef@xxxxxxxxxx> wrote:
>>> On Mon, Feb 28, 2011 at 03:03:40PM +0800, Dave Young wrote:
>>>> Hi, josef and ext guys
>>>> Do you have any plan with ext4 hole punching support? And the
>>>> fallocate for ext2/3?
>>>> What's the obstacle to work on this? could someone tell the status of
>>>> this issue?
>>> There is no obstacle, just nobody has bothered to do it. ÂIf you want to do it
>>> go for it. ÂThanks,
>> Yes, I want to do some kvm image space discard stuff,
>> I use ext4 as my filesystem, but currently only xfs support something
>> like trim/discard.
> As Lukas said, ext4 & ext3 support various forms of trim/discard already.
> But that's different from punch...
Lukas and Eric, thanks for pointing out, I think I means punch,
although trim/discard is
useful as well in guest side.
> And as for fallocate on ext3, you need somewhere to put the metadata to indicate a block is allocated but not written. ÂThis was a lot more straightforward for ext4, since it describes a large range of blocks with a single extent structure.
As for ext3 fallocate, I found some interesting discuss:
Andrew, do you know what's the status of above issue?
>> I know general knowledge about ext filesystem, but nearly new to ext4 code,
>> could you give some hint where to start?
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