linux-kernel - Re: [PATCHv2, RFC 14/30] thp, mm: naive support of thp in generic read/write routines

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: <20130328122557.2D6A7E0085@blue.fi.intel.com>
Date:	Thu, 28 Mar 2013 14:25:57 +0200 (EET)
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Dave Hansen <dave@...1.net>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Hugh Dickins <hughd@...gle.com>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>,
	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Hillf Danton <dhillf@...il.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2, RFC 14/30] thp, mm: naive support of thp in generic
 read/write routines

Dave Hansen wrote:
> On 03/14/2013 10:50 AM, Kirill A. Shutemov wrote:
> > From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> > 
> > For now we still write/read at most PAGE_CACHE_SIZE bytes a time.
> > 
> > This implementation doesn't cover address spaces with backing store.
> ...
> > --- a/mm/filemap.c
> > +++ b/mm/filemap.c
> > @@ -1165,12 +1165,23 @@ find_page:
> >  			if (unlikely(page == NULL))
> >  				goto no_cached_page;
> >  		}
> > +		if (PageTransTail(page)) {
> > +			page_cache_release(page);
> > +			page = find_get_page(mapping,
> > +					index & ~HPAGE_CACHE_INDEX_MASK);
> > +			if (!PageTransHuge(page)) {
> > +				page_cache_release(page);
> > +				goto find_page;
> > +			}
> > +		}
> 
> So, we're going to do a read of a file, and we pulled a tail page out of
> the page cache.  Why can't we just deal with the tail page directly?

Good point. I'll redo it once again.

First I thought to make it possible to read/write more PAGE_SIZE at once.
If not take this option in account for now, it's possible to make code much
cleaner.

-- 
 Kirill A. Shutemov
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/