linux-kernel - Re: [PATCHv2, RFC 18/30] thp, mm: truncate support for transparent huge page cache

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: <20130328153152.54DDAE0085@blue.fi.intel.com>
Date:	Thu, 28 Mar 2013 17:31:52 +0200 (EET)
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Dave <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 18/30] thp, mm: truncate support for transparent
 huge page cache

Dave wrote:
> On 03/14/2013 10:50 AM, Kirill A. Shutemov wrote:
> > @@ -280,6 +291,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
> >  			if (index > end)
> >  				break;
> >  
> > +			VM_BUG_ON(PageTransHuge(page));
> >  			lock_page(page);
> >  			WARN_ON(page->index != index);
> >  			wait_on_page_writeback(page);
> 
> This looks to be during the second truncate pass where things are
> allowed to block.  What's the logic behind it not being possible to
> encounter TransHugePage()s here?

Good question.

The only way how the page can be created from under us is collapsing, but
it's not implemented for file pages and I'm not sure yet how to implement
it...

Probably, I'll replace the BUG with

if (PageTransHuge(page))
	split_huge_page(page);

It should be good enough.

-- 
 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/