• Theodore Ts'o's avatar
    ext4: Turn off multiple page-io submission by default · 1449032b
    Theodore Ts'o authored
    Jon Nelson has found a test case which causes postgresql to fail with
    the error:
    
    psql:t.sql:4: ERROR: invalid page header in block 38269 of relation base/16384/16581
    
    Under memory pressure, it looks like part of a file can end up getting
    replaced by zero's.  Until we can figure out the cause, we'll roll
    back the change and use block_write_full_page() instead of
    ext4_bio_write_page().  The new, more efficient writing function can
    be used via the mount option mblk_io_submit, so we can test and fix
    the new page I/O code.
    
    To reproduce the problem, install postgres 8.4 or 9.0, and pin enough
    memory such that the system just at the end of triggering writeback
    before running the following sql script:
    
    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;
    
    If the temporary table is created on a hard drive partition which is
    encrypted using dm_crypt, then under memory pressure, approximately
    30-40% of the time, pgsql will issue the above failure.
    
    This patch should fix this problem, and the problem will come back if
    the file system is mounted with the mblk_io_submit mount option.
    Reported-by: default avatarJon Nelson <jnelson@jamponi.net>
    Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
    1449032b
super.c 134 KB