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Date: Mon, 7 Jan 2002 04:16:36 +0100
From: Andrea Arcangeli <andrea@suse.de>
To: Andrew Morton <akpm@zip.com.au>
Cc: Alexander Viro <viro@math.psu.edu>, lkml <linux-kernel@vger.kernel.org>
Subject: Re: [patch] truncate fixes
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In-Reply-To: <3C390DAA.3339768C@zip.com.au>; from akpm@zip.com.au on Sun, Jan 06, 2002 at 06:53:30PM -0800
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On Sun, Jan 06, 2002 at 06:53:30PM -0800, Andrew Morton wrote:
> Andrea Arcangeli wrote:
> > 
> > I prefer my fix that simply recalls the ->truncate callback if -ENOSPC
> > is returned by prepare_write. vmtruncate seems way overkill,
> 
> No opinion on that here.  This is what was in -ac.  Perhaps Al can
> comment?
> 
> > and after
> > calling ->truncate the __block_prepare_changes above won't be necessary
> > because the leftover will be correctly deallocated (no need to clear
> > them out and to mark them dirty, they will just go away before any
> > readpage can see them).
> 
> No, this code is needed if the write is _inside_ i_size, to an
> uninstantiated block.  truncate won't remove those blocks, and we've
> gone and added them to the file.

I see, I got mistaken because here we're not in a i_sem-less writepage, so
in those cases I wanted to always deallocate the blocks rather than
lefting zeroed leftovers. if the leftover blocks are over i_size (common
case I was thinking about incidentally :) that's automatica with
->truncate, but if they aren't over i_size that's not enough and we miss
a lowlevel API to decallocate a range of blocks, so your patch is the
only way indeed.

> 
> -


Andrea
-
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