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Subject: Re: [PATCH] anobjrmap 2/6 mapping
From: "Stephen C. Tweedie" <sct@redhat.com>
To: Andrew Morton <akpm@digeo.com>
Cc: Hugh Dickins <hugh@veritas.com>,
       linux-kernel <linux-kernel@vger.kernel.org>, linux-mm@kvack.org,
       Stephen Tweedie <sct@redhat.com>
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Hi,

On Fri, 2003-03-21 at 06:48, Andrew Morton wrote:

> It goes BUG in try_to_free_buffers().
> 
> We really should fix this up for other reasons, probably by making ext3's
> per-page truncate operations wait on commit, and be more aggressive about
> pulling the page's buffers off the transaction at truncate time.

Ouch.

> The same thing _could_ happen with other filesystems; not too sure about
> that.

XFS used to have synchronous truncates, for similar sorts of reasons. 
It was dog slow for unlinks.  They worked pretty hard to fix that; I'd
really like to avoid adding extra synchronicity to ext3 in this case.

Pulling buffers off the transaction more aggressively would certainly be
worth looking at.  Trouble is, if a truncate transaction on disk gets
interrupted by a crash, you really do have to be able to undo it, so you
simply don't have the luxury of throwing the buffers away until a commit
has occurred (unless you're in writeback mode.)

--Stephen

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