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    SubjectRe: [PATCH 0/8][RFC] IO latency/throughput fixes
    From
    On Tue, Apr 7, 2009 at 01:10, Linus Torvalds
    <torvalds@linux-foundation.org> wrote:
    > On Mon, 6 Apr 2009, Linus Torvalds wrote:
    >> thing that we think people would be happiest with.
    >>
    >> I think "ordered" was a reasonable default, but that was at least partly
    >> because _both_ ordered and writeback sucked (partly in different ways).
    >>
    >> I do think we could make it a config option.
    >
    > A patch _something_ like this.
    >
    > A few notes:
    >
    >  - This is UNTESTED (of course)
    >
    >  - If I did this right, this _only_ overrides the data mode if it's not
    >   explicitly specified on disk in the superblock mount options.
    >
    > IOW, if you have done a
    >
    >        tune2fs -o journal_data_ordered
    >
    > then this will _not_ override that. Only in the absense of any explicit
    > flags should this trigger and then make the choice be 'writeback'.
    >
    > And just to be _extra_ backwards compatible, if you really want the old
    > behavior, and don't want to set the ordering flag explicitly, just answer
    > 'y' to the EXT3_DEFAULTS_TO_ORDERED Kconfig question.
    >
    > What do people think? Anybody want to test?
    >
    >                Linus
    >
    > ---
    >  fs/ext3/Kconfig |   19 +++++++++++++++++++
    >  fs/ext3/super.c |    8 +++++++-
    >  2 files changed, 26 insertions(+), 1 deletions(-)
    >
    > diff --git a/fs/ext3/Kconfig b/fs/ext3/Kconfig
    > index 8e0cfe4..fb3c1a2 100644
    > --- a/fs/ext3/Kconfig
    > +++ b/fs/ext3/Kconfig
    > @@ -28,6 +28,25 @@ config EXT3_FS
    >          To compile this file system support as a module, choose M here: the
    >          module will be called ext3.
    >
    > +config EXT3_DEFAULTS_TO_ORDERED
    > +       bool "Default to 'data=ordered' in ext3 (legacy option)"
    > +       depends on EXT3_FS
    > +       help
    > +         If a filesystem does not explicitly specify a data ordering
    > +         mode, and the journal capability allowed it, ext3 used to
    > +         historically default to 'data=ordered'.
    > +
    > +         That was a rather unfortunate choice, because it leads to all
    > +         kinds of latency problems, and the 'data=writeback' mode is more
    > +         appropriate these days.
    > +
    > +         You should probably always answer 'n' here, and if you really
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    > +         want to use 'data=ordered' mode, set it in the filesystem itself
    > +         with 'tune2fs -o journal_data_ordered'.
    > +
    > +         But if you really want to enable the legacy default, you can do
    > +         so by answering 'y' to this question.
    > +

    So `allmodconfig' will enable it? Is that the right thing to do, or
    should it be inverted?

    Gr{oetje,eeting}s,

    Geert

    --
    Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

    In personal conversations with technical people, I call myself a hacker. But
    when I'm talking to journalists I just say "programmer" or something like that.
    -- Linus Torvalds
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