linux-ext4 - Re: possible dev branch regression

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <51475043.4010505@redhat.com>
Date:	Mon, 18 Mar 2013 12:34:59 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	"Theodore Ts'o" <tytso@....edu>
CC:	Eric Whitney <enwlinux@...il.com>, linux-ext4@...r.kernel.org,
	xfs-oss <xfs@....sgi.com>
Subject: Re: possible dev branch regression - xfstest 285/1k

On 3/18/13 12:09 PM, Theodore Ts'o wrote:
> On Mon, Mar 18, 2013 at 11:10:51AM -0500, Eric Sandeen wrote:

<previous discussion thread about test 285 SEEK_HOLE test
breaking on ext4 due to change in opportunistic hole-filling
behavior and how to make it work again on ext4, and mention
of sysctl which makes it pass>

>> The test could do this too, right?
>>
>> _need_to_be_root
>>
>> and:
>>
>> if [ "$FSTYP" == "ext4" ]; then
>> 	ORIG_ZEROOUT_KB=`cat /sys/fs/ext4/$TEST_DEV/extent_max_zeroout_kb`
>> 	echo 0 > /sys/fs/ext4/$TEST_DEV/extent_max_zeroout_kb
>> fi
>>
>> and put it back to default in _cleanup:
>>
>> 	echo $ORIG_ZEROOUT_KB > /sys/fs/ext4/$TEST_DEV/extent_max_zeroout_kb
>>
>> That way we'd be testing seek hole correctness w/o being subject to
>> the vagaries in allocator behavior.
> 
> Yeah, the question is whether it would be more acceptable to put
> ext4-specific hacks like this into the test, or to modify
> src/seek_sanity_test.c so that it writes the test block-size block
> using pwrite at offset blocksize*42 instead of offset blocksize*10.

That seems like more of an obtuse hack, since it depends on current
default behavior, right?

Explicitly setting the zeroout to 0, with a comment as to why, should
make it clear to the reader of the test I think.

I'll have to look, xfs speculative preallocation fills in holes in
some cases as well, I'm not certain how it behaves on this test.

But we could put in a specific tuning for xfs as well if needed.

If it becomes clear that every fs requires tuning to not opportunistically
fill in holes, then maybe we should make it non-generic, and only support
filesystems we've tested or tuned to work with the testcase.

> I had assumed putting hacks which tweaked sysfs tunables into the
> xfstest script itself would be frowned upon, but if that's considered
> OK, that would be great.

I don't see any real problem with it, myself.

cc: xfs list to see if there are any objections...

-Eric

> 
> 	      	 		       - Ted
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html