linux-ext4 - Re: [PATCH 4/4] ext4: fix end of region partial cluster handling

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Message-ID: <20141123170508.GA2813@wallace>
Date:	Sun, 23 Nov 2014 12:05:08 -0500
From:	Eric Whitney <enwlinux@...il.com>
To:	Theodore Ts'o <tytso@....edu>
Cc:	Eric Whitney <enwlinux@...il.com>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 4/4] ext4: fix end of region partial cluster handling

The retry occurs at the end of ext4_ext_remove_space where the code loops
back to the top of the function if err == -EAGAIN, leading to another call
to ext4_ext_rm_leaf.  Nothing new needs to be added - we simply want to
avoid using invalid state to decide whether to free a partial cluster (on
occurrence of -EAGAIN), and the existing retry loop will eventually get us
valid state.

(I actually saw this in testing, but it takes a lot of runs to get there.)

Sorry if I edited down my comment a little too far - I'd be happy to beef
that up if desired.

Thanks,
Eric

* Theodore Ts'o <tytso@....edu>:
> On Fri, Nov 21, 2014 at 09:59:04AM -0500, Eric Whitney wrote:
> > ext4_ext_remove_space() can incorrectly free a partial_cluster if
> > EAGAIN is encountered while truncating or punching.  Extent removal
> > should be retried in this case.
> 
> I don't see anything in the patch below which retries the extent
> removal; am I missing something?
> 
> Thanks,
> 
> 						- Ted
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