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To: xfs@xxxxxxxxxxx
Subject: Re: about XFS_IOC_RESVSP
From: Joe Hsu <nagual.hsu@xxxxxxxxx>
Date: Sun, 24 May 2009 15:08:37 +0800
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      After days of testing(I only ftruncate to 0 and re-preallocate
files if needed),
fragmentation become much more serious, sigh

2009/5/22 Joe Hsu <nagual.hsu@xxxxxxxxx>:
>        I pre-allocate blocks for a file. Then I use "open" and "write" system
> calls to generate the content for that file. After the file is really
> written to the disk,
> I want to set all the extent(s) of that file unwritten. Then I will
> write new content to
> the same file. Is that possible? That means:
> I want to dis-care the content just written and use the same allocated blocks.
> In another words, I want to restore the state of the file to the state
> when it was
> first pre-allocated.
>        Why am I doing this? Why not just over-write it? When doing
> partial over-writing,
> some blocks may be read for partial update before they are written
> out. This hurts
> some IO performance and If I can, I would prefer to dis-care old
> content of the file and
> use same (pre)allocated blocks. (In my case, I am doing intensive IO.)
>        Any one can give me some hints? Thanks.
> --
> The sun is shinny but the ice is slippery.

The sun is shinny but the ice is slippery.

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