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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 9:37 PM, Jon Nelson <jnelson@jamponi.net> wrote:
    > On Tue, Dec 7, 2010 at 1:35 PM, Ted Ts'o <tytso@mit.edu> wrote:
    >> On Tue, Dec 07, 2010 at 01:22:43PM -0500, Mike Snitzer wrote:
    >>> > 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.
    >>
    >> So I just tried to reproduce this on an Ubuntu 10.04 system running
    >> 2.6.37-rc5 (completely stock except for a few apparmor patches that I
    >> needed to keep the apparmor userspace from complaining).  I'm using
    >> Postgres 8.4.5-0ubuntu10.04.
    >>
    >> Using the above procedure, I wasn't able to reproduce.  Then I
    >> realized this might have been because I was using an SSD root file
    >> system (which is secured using LUKS/dm-crypt, with LVM on top of
    >> dm-crypt).  So I mounted a file system on a 5400 rpm SSD disk, which
    >> is also protected using LUKS/dm-crypt with LVM on top.  I then
    >> executed the PostgresQL commands:
    >>
    >> CREATE TABLESPACE test LOCATION '/kbuild/postgres';
    >> SET default_tablespace = test;
    >> COMMIT
    >> \quit
    >>
    >> I then re-ran the above proceduing, and verified that all of the I/O
    >> was going to the 5400rpm laptop disk.
    >>
    >> I then ran the above procedure a half-dozen times, and I still haven't
    >> been able to reproduce any Postgresql errors or kernel errors.
    >>
    >> Jon, can you help me identify what might be different with your run
    >> and mine?  What version of Postgres are you using?
    >
    > One difference is the location of the transaction logs (pg_xlog). In
    > my case, /var/lib/pgsql/data *is* mountpoint for the test volume
    > (actually, it's a symlink to the mount point). In your case, that is
    > not so. Perhaps that makes a difference?  pgsql_tmp might also be on
    > two different volumes in your case (I can't be sure).


    I grabbed a Kubuntu iso and installed Kubuntu 10.10, and then upgraded
    to 'natty', and eventually to 2.6.37-8-generic.

    With that install, and postgresql's "data" (/var/lib/postgresql/data)
    being located on a LUKS+ext4 volume, I easily observe the behavior.

    Does this help?

    --
    Jon
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