From: Chris Mason <chris.mason@oracle.com>
Subject: Re: ftruncate-mmap: pages are lost after writing to mmaped file.
Date: Tue, 24 Mar 2009 10:01:45 -0400
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Cc: Nick Piggin <nickpiggin@yahoo.com.au>,
        "Martin J. Bligh" <mbligh@mbligh.org>, linux-ext4@vger.kernel.org,
        Ying Han <yinghan@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>, guichaz@gmail.com,
        Alex Khesin <alexk@google.com>, Mike Waychison <mikew@google.com>,
        Rohit Seth <rohitseth@google.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Jan Kara <jack@suse.cz>
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On Tue, 2009-03-24 at 14:26 +0100, Jan Kara wrote:
> On Tue 24-03-09 13:55:10, Jan Kara wrote:

> >   And one more interesting thing I don't yet fully understand - I see pages
> > having PageError() set when they are removed from page cache (and they have
> > been faulted in before). It's probably some interaction with pagecache
> > readahead...
>   Argh... So the problem seems to be that get_block() occasionally returns
> ENOSPC and we then discard the dirty data (hmm, we could give at least a
> warning for that). I'm not yet sure why getblock behaves like this because
> the filesystem seems to have enough space but anyway this seems to be some
> strange fs trouble as well.
> 

Ouch.  Perhaps the free space is waiting on a journal commit?

-chris


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