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    SubjectRe: hunt for 2.6.37 dm-crypt+ext4 corruption? (was: Re: dm-crypt barrier support is effective)
    On Tue, Dec 7, 2010 at 12:22 PM, Mike Snitzer <snitzer@redhat.com> wrote:
    > On Tue, Dec 07 2010 at  1:10pm -0500,
    > Jon Nelson <jnelson@jamponi.net> wrote:
    >
    >> I finally found some time to test this out. With 2.6.37-rc4 (openSUSE
    >> KOTD kernel) I easily encounter the issue.
    >>
    >> Using a virtual machine, I created a stock, minimal openSUSE 11.3 x86_64
    >> install, installed all updates, installed postgresql and the 'KOTD'
    >> (Kernel of the Day)
    >> kernel, and ran the following tests (as postgres user because I'm
    >> lazy).
    >>
    >> 1. create a database (from bash):
    >>
    >> createdb test
    >>
    >> 2. place the following contents in a file (I used 't.sql'):
    >>
    >> begin;
    >> create temporary table foo as select x as a, ARRAY[x] as b FROM
    >> generate_series(1, 10000000 ) AS x;
    >> create index foo_a_idx on foo (a);
    >> create index foo_b_idx on foo USING GIN (b);
    >> rollback;
    >>
    >> 3. execute that sql:
    >>
    >> psql -f t.sql --echo-all test
    >>
    >>
    >> With 2.6.34.7 I can re-run [3] all day long, as many times as I want,
    >> without issue.
    >>
    >> With 2.6.37-rc4-13 (the currently-installed KOTD kernel) if tails
    >> pretty frequently.
    >
    > How does it fail?  postgres errors?  kernel errors?

    postgresql errors. Typically, header corruption but from the limited
    visibility I've had into this via strace, what I see is zeroed pages
    where there shouldn't be.

    I just ran a test and got:

    ERROR: invalid page header in block 37483 of relation base/16384/16417

    but that is not the only error one might get.

    >> Then I tested with the 'vanilla' kernel available here:
    >>
    >> http://download.opensuse.org/repositories/Kernel:/vanilla/standard/
    >>
    >> The 'vanilla' kernel exhibited the same problems.
    >> The version I tested:  2.6.37-rc4-219-g771f8bc-vanilla.
    >>
    >> Incidentally, quick tests of jfs, xfs, and ext3 do _not_ show the same
    >> problems, although I will note that I usually saw failure at least 1
    >> in 3, but sometimes had to re-run the sql test 4 or 5 times before I
    >> saw failure.
    >>
    >> I will continue to do some testing, but I will hold off on testing the
    >> commits above until I receive further testing suggestions.
    >
    > OK, so to be clear: your testing is on dm-crypt + ext4?

    Yes. I took a virtual hard disk which shows up as /dev/sdb, used
    cryptsetup to format it as a LUKS volume, mounted the LUKS volume,
    formatted as ext4 (or whatever), mounted that, rsync'd over a blank
    postgresql 'data' directory, started postgresql, became the postgres
    user, and proceeded to create the db and run the sql.

    > And you're testing upstream based kernels (meaning the dm-crypt
    > scalability patch that has been in question is _not_ in the mix)?

    I am testing both the KOTD kernels and the "vanilla" kernels - neither
    of which has the dm-crypt patches (as far as I know).

    --
    Jon
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