Messages in this thread | | | Date | Tue, 7 Apr 2009 12:36:11 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 0/8][RFC] IO latency/throughput fixes |
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* Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> 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,
allmod/allyes will enable all sorts of legacy options.
Since besides myself i'm not aware of any other person on this planet actually _booting_ allyes/allmod Linux kernels, i guess this is not a big issue anyway :-)
One small detail only: i'd suggest to name it CONFIG_COMPAT_EXT3_DEFAULTS_TO_ORDERED, to move it more in line with all the CONFIG_COMPAT_* legacy options.
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