• Zach Brown's avatar
    dio: zero struct dio with kzalloc instead of manually · 848c4dd5
    Zach Brown authored
    This patch uses kzalloc to zero all of struct dio rather than manually
    trying to track which fields we rely on being zero.  It passed aio+dio
    stress testing and some bug regression testing on ext3.
    This patch was introduced by Linus in the conversation that lead up to
    Badari's minimal fix to manually zero .map_bh.b_state in commit:
    It makes the code a bit smaller.  Maybe a couple fewer cachelines to
    load, if we're lucky:
       text    data     bss     dec     hex filename
    3285925  568506 1304616 5159047  4eb887 vmlinux
    3285797  568506 1304616 5158919  4eb807 vmlinux.patched
    I was unable to measure a stable difference in the number of cpu cycles
    spent in blockdev_direct_IO() when pushing aio+dio 256K reads at
    So the resulting intent of the patch isn't a performance gain but to
    avoid exposing ourselves to the risk of finding another field like
    .map_bh.b_state where we rely on zeroing but don't enforce it in the
    Signed-off-by: default avatarZach Brown <zach.brown@oracle.com>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
direct-io.c 34.4 KB