linux-kernel - Re: [PATCH -mm -v2] mm, swap, frontswap: Fix THP swap if frontswap enabled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180208102521.GB74192@eng-minchan1.roam.corp.google.com>
Date:   Thu, 8 Feb 2018 02:25:21 -0800
From:   Minchan Kim <minchan@...nel.org>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "Huang, Ying" <ying.huang@...el.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Huang Ying <huang.ying.caritas@...il.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Dan Streetman <ddstreet@...e.org>,
        Seth Jennings <sjenning@...hat.com>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Shaohua Li <shli@...nel.org>, Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Shakeel Butt <shakeelb@...gle.com>, stable@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [PATCH -mm -v2] mm, swap, frontswap: Fix THP swap if frontswap
 enabled

On Thu, Feb 08, 2018 at 10:36:35AM +0900, Sergey Senozhatsky wrote:
> On (02/07/18 13:05), Andrew Morton wrote:
> [..]
> > hm.  This is assuming that "cluster==true" means "this is thp swap". 
> > That's presently true, but is it appropriate that get_swap_pages() is
> > peeking at "cluster" to work out why it is being called?
> > 
> > Or would it be cleaner to do this in get_swap_page()?  Something like
> > 
> > --- a/mm/swap_slots.c~a
> > +++ a/mm/swap_slots.c
> > @@ -317,8 +317,11 @@ swp_entry_t get_swap_page(struct page *p
> >  	entry.val = 0;
> >  
> >  	if (PageTransHuge(page)) {
> > -		if (IS_ENABLED(CONFIG_THP_SWAP))
> > -			get_swap_pages(1, true, &entry);
> > +		/* Frontswap doesn't support THP */
> > +		if (!frontswap_enabled()) {
> > +			if (IS_ENABLED(CONFIG_THP_SWAP))
> > +				get_swap_pages(1, true, &entry);
> > +		}
> >  		return entry;
> >  	}
> 
> I have proposed exactly the same thing [1], Minchan commented that
> it would introduce frontswap dependency to swap_slots.c [2]. Which
> is true, but I'd still probably prefer to handle it all in
> get_swap_page. Minchan, any objections?

I didn't want to spread out frontswap stuff unless it has good value
because most of frontswap functions are located in mm/swapfile.c
at this moment. It gives me good feeling frontswap's abstraction
is wonderful.
However, if frontswap matainer has no problem, I am not against, either.

Thanks.