linux-kernel - Re: [PATCH 1/2] fs: Do not dispatch FITRIM through separate super

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Message-ID: <4CE539E8.2040107@oracle.com>
Date:	Thu, 18 Nov 2010 22:36:24 +0800
From:	Tao Ma <tao.ma@...cle.com>
To:	Josef Bacik <josef@...hat.com>
CC:	Matthew Wilcox <matthew@....cx>,
	Lukas Czerner <lczerner@...hat.com>, tytso@....edu,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, hch@...radead.org,
	sandeen@...hat.com
Subject: Re: [PATCH 1/2] fs: Do not dispatch FITRIM through separate super_operation



On 11/18/2010 10:31 PM, Josef Bacik wrote:
> On Thu, Nov 18, 2010 at 07:19:58AM -0700, Matthew Wilcox wrote:
>> On Thu, Nov 18, 2010 at 08:48:04AM -0500, Josef Bacik wrote:
>>> On Thu, Nov 18, 2010 at 06:06:30AM -0700, Matthew Wilcox wrote:
>>>> On Thu, Nov 18, 2010 at 08:36:48AM +0100, Lukas Czerner wrote:
>>>>> There was concern that FITRIM ioctl is not common enough to be included
>>>>> in core vfs ioctl, as Christoph Hellwig pointed out there's no real point
>>>>> in dispatching this out to a separate vector instead of just through
>>>>> ->ioctl.
>>>>
>>>> Um, are you and Josef working independently of each other?  You don't
>>>> seem to be cc'ing each other on your patches, and you're basically doing
>>>> the same thing.
>>>>
>>>
>>> I guess they are the same thing in that we're both dealing with free'ing up
>>> space, but thats about where the similarities end.  Lukas' work is in TRIM'ing
>>> already free'd space, mine is in creating free'd space.  Plus I don't know
>>> anything nor wish to ever know anything about TRIM ;).  Thanks,
>>
>> I guess I was assuming that, on receiving a FALLOC_FL_PUNCH_HOLE, a
>> filesystem that was TRIM-aware would pass that information down to the
>> block device that it's mounted on.  I strongly feel that we shouldn't
>> have two interfaces to do essentially the same thing.
>
> But they aren't doing the same thing, his is discarding already free'd space,
> I'm enabling people to de-allocate space in the middle of files, they are two
> seperate things.  Of course if the filesystem is TRIM aware the de-allocation
> would lead to a TRIM, but not if the filesystem isn't mounted with -o discard.
> Hole punching is useful independantly of the ability to do TRIM.  Thanks,
yeah, actually, ocfs2 has implemented punching holes while we don't have 
TRIM support enabled yet.

Regards,
Tao
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