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    SubjectRe: [PATCH v4] mm: add replace_page_cache_page() function
    > On Wed, 19 Jan 2011 09:27:33 +0900
    > Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
    >
    >> On Tue, 18 Jan 2011 15:28:44 -0800
    >> Andrew Morton <akpm@linux-foundation.org> wrote:
    >>
    >> > On Tue, 18 Jan 2011 12:18:11 +0100
    >> > Miklos Szeredi <miklos@szeredi.hu> wrote:
    >> >
    >> > > +int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
    >> > > +{
    >> > > + int error;
    >> > > + struct mem_cgroup *memcg = NULL;
    >> >
    >> > I'm suspecting that the unneeded initialisation was added to suppress a
    >> > warning?
    >> >
    >> No.
    >> It's necessary for mem_cgroup_{prepare|end}_migration().
    >> mem_cgroup_prepare_migration() will return without doing anything in
    >> "if (mem_cgroup_disabled()" case(iow, "memcg" is not overwritten),
    >> but mem_cgroup_end_migration() depends on the value of "memcg" to decide
    >> whether prepare_migration has succeeded or not.
    >> This may not be a good implementation, but IMHO I'd like to to initialize
    >> valuable before using it in general.
    >>
    >
    > I think it can be initlized in mem_cgroup_prepare_migration().
    > I'll send patch later.
    >
    I see, thanks.

    I think you know it, but just a note:
    mem_cgroup_{try_charge|commit_charge}_swapin()
    use the same logic, so try_charge_swapin() should also be changed
    for consistency.

    Thanks,
    Daisuke Nishimura.


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