linux-kernel - Re: [PATCH] xfs: getattr ignore blocks beyond eof

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Message-ID: <20220331054811.GF1544202@dread.disaster.area>
Date:   Thu, 31 Mar 2022 16:48:11 +1100
From:   Dave Chinner <david@...morbit.com>
To:     wang.yi59@....com.cn
Cc:     djwong@...nel.org, linux-xfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, xue.zhihong@....com.cn,
        wang.liang82@....com.cn, cheng.lin130@....com.cn
Subject: Re: [PATCH] xfs: getattr ignore blocks beyond eof

On Thu, Mar 31, 2022 at 04:33:40PM +1100, Dave Chinner wrote:
> On Thu, Mar 31, 2022 at 11:28:59AM +0800, wang.yi59@....com.cn wrote:
> > The above problems can be explained by fs preallocation.
> > If the impact of preallocation are closed in fs, not visible to
> > the outside, the result is stable and real for the application.
....

> If your application is dependent on block counts exactly matching
> the file data space for waht ever reason, then what speculative
> preallocation does is the least of your problems.

That said, if you have written an application that cannot handle
this behaviour, then you can *turn it off* by using the allocsize
mount option. But then subsequent file fragmentation issues are your
own problem to solve, not ours.

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com