From: bugme-daemon@bugzilla.kernel.org
Subject: [Bug 12829] kernel complains on ENOSPC
Date: Sun, 8 Mar 2009 22:17:01 -0700 (PDT)
Message-ID: <20090309051701.C6465108040@picon.linux-foundation.org>
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------- Comment #3 from aneesh.kumar@linux.vnet.ibm.com 2009-03-08 22:17 -------
On Fri, Mar 06, 2009 at 03:02:21PM -0800, bugme-daemon@bugzilla.kernel.org
wrote:
>
>
> ------- Comment #1 from tytso@mit.edu 2009-03-06 15:02 -------
> What are the precise reproduction details? We're supposed to keep track of
> how many delayed allocation blocks are outstanding, so that we return ENOSPC
> *before* we get to this stage.
Yes. We should not get the ENOSPC during writeback. That would imply the
block reservation is going wrong.
>
> I'm not sure we do the right thing if we mmap into an unallocated region of
> file; when do we actually track delayed allocation blocks? The right answer
> would be at mmap() time, but OTOH that means if we mmap a 2GB region, do we
> immediately take a 2GB charge because the process might write into this region?
> And does free space returned by 'df' immediately drop by 2GB?
For mmap block reservation is doing during page_mkwrite.
>
> Do you know if there was any allocation by mmap going on in your reproduction
> case? That seems the most likely cause to me, if I had to guess....
>
-aneesh
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