linux-kernel - Re: [Question Resend] About z3fold page migration

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Date:   Tue, 13 Oct 2020 01:46:57 +0000
From:   linmiaohe <linmiaohe@...wei.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        Vitaly Wool <vitaly.wool@...sulko.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Question Resend] About z3fold page migration

Matthew Wilcox <willy@...radead.org> wrote:
> On Mon, Oct 12, 2020 at 02:00:17PM +0000, linmiaohe wrote:
>> Hi all:
>> 
>> 	Many thanks for brilliant z3fold code. I am reading it and have some questions about it. It's very nice of you if you can explain it for me.
>> 	1.page->private is used in z3fold but PagePrivate flag is never set, should we SetPagePrivate for it?
>
>No.  SetPagePrivate and page->private are related in interesting and complicated ways.  I'm working on some documentation for it at the moment, but the short answer is: no.

I can't wait to read your document. PagePrivate confuses me now.

>
>> 	2.Since PagePrivate flag is never set, why we ClearPagePrivate in free_z3fold_page and z3fold_page_migrate?
>
>That's probably a bug.
>
>
>> 	3.Should we add page to the unbuddied list in z3fold_page_putback() 
>> when zhdr->refcount does not reach 0 since we remove it from unbuddied list in z3fold_page_isolate? Or When we will add page to the unbuddied list after z3fold_page_putback?
>
>This one I do not know the answer to.
>

Many thanks for your reply. Enjoy your day! ;)