linux-kernel - Re: [PATCH v2 10/10] mm: remove SWAP

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Message-ID: <20170316055754.GB464@jagdpanzerIV.localdomain>
Date:   Thu, 16 Mar 2017 14:57:54 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kernel-team@....com, Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 10/10] mm: remove SWAP_[SUCCESS|AGAIN|FAIL]

On (03/16/17 14:51), Minchan Kim wrote:
[..]
> > > @@ -1414,7 +1414,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
> > >  			 */
> > >  			if (unlikely(PageSwapBacked(page) != PageSwapCache(page))) {
> > >  				WARN_ON_ONCE(1);
> > > -				ret = SWAP_FAIL;
> > > +				ret = false;
> > >  				page_vma_mapped_walk_done(&pvmw);
> > >  				break;
> > >  			}
> > 
> > 
> > one thing to notice here is that 'ret = false' and 'ret = SWAP_FAIL'
> > are not the same and must produce different results. `ret' is bool
> > and SWAP_FAIL was 2. it's return 1 vs return 0, isn't it? so was
> > there a bug before?
> 
> No, it was not a bug. Just my patchset changed return value meaning.
> Look at this.
> https://marc.info/?l=linux-mm&m=148955552314806&w=2
> 
> So, false means SWAP_FAIL(ie., stop rmap scanning and bail out) now.

ah, indeed. sorry, didn't notice that.

thanks.

	-ss