linux-ext4 - Re: Bug in delayed allocation: really bad block layouts!

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Message-ID: <489F397A.1040709@redhat.com>
Date:	Sun, 10 Aug 2008 13:54:50 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Theodore Tso <tytso@....edu>
CC:	linux-ext4@...r.kernel.org
Subject: Re: Bug in delayed allocation: really bad block layouts!

Theodore Tso wrote:
> On Sun, Aug 10, 2008 at 12:54:00PM -0500, Eric Sandeen wrote:
>> Hm, and I tried writing out 10 files in order as a simple test but
>> umount/remount brought me back many 0-byte files, I need to update my
>> patchset I guess.  :)
>>
> 
> One of the questions in my mind is whether this is a regression
> triggered by the some of our most recent patches....  since I only
> have 2.2% files reported a fragmented by e2fsck, and if this problem
> had always been there, I would have expected a much higher
> fragmentation number.  So if you have some older kernels, you might
> want to see if you can replicate the problem.  I've since found that
> just doing a copy via "(tar -cf - -C / usr/include ) | tar -C /mnt -xf -)"
> is sufficient to see the problem.  Just add a "sync; sleep 5" before 
> the umount.  :-)

It may be; I tried this and then a quick filefrag run:

# filefrag  usr/include/*.h | grep -v extents | awk -F : '{print $2}' |
sort | uniq -c
    146  1 extent found

so everything came out contiguous.

This was with 2.6.27-0.186.rc0.git15.fc10.x86_64

-Eric
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