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    SubjectRe: [PATCH 2/2] mm: make do_writepages() use plugging
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    Hi Peter,
    Thanks for pointing out.

    While checking the plug support in Write code flow, I came across this
    main point from which - we invoke
    writepages(mapping->a_ops->writepages(mapping, wbc)) from almost all
    the the filesystems.

    By mistake I checked 2 different kernel versions for this code(and
    missed that the current version already has put plug in
    mpage_writepages) ... so may be this patch is not worth considering.

    Regards,
    Amit Sahrawat


    On Fri, Feb 3, 2012 at 7:02 PM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
    > On Fri, 2012-02-03 at 18:57 +0530, Amit Sahrawat wrote:
    >> This will cover all the invocations for writepages to be called with
    >> plugging support.
    >
    > This changelog fails to explain why this is a good thing... I thought
    > the idea of the new plugging stuff was that we now don't need to
    > sprinkle plugs all over the kernel..
    >
    >> Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com>
    >> ---
    >>  mm/page-writeback.c |    4 ++++
    >>  1 files changed, 4 insertions(+), 0 deletions(-)
    >>
    >> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
    >> index 363ba70..2bea32c 100644
    >> --- a/mm/page-writeback.c
    >> +++ b/mm/page-writeback.c
    >> @@ -1866,14 +1866,18 @@ EXPORT_SYMBOL(generic_writepages);
    >>
    >>  int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
    >>  {
    >> +     struct blk_plug plug;
    >>       int ret;
    >>
    >>       if (wbc->nr_to_write <= 0)
    >>               return 0;
    >> +
    >> +     blk_start_plug(&plug);
    >>       if (mapping->a_ops->writepages)
    >>               ret = mapping->a_ops->writepages(mapping, wbc);
    >>       else
    >>               ret = generic_writepages(mapping, wbc);
    >> +     blk_finish_plug(&plug);
    >>       return ret;
    >>  }
    >>
    >
    >
    >
    --
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