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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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