From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 13 Oct 2015 18:10:53 +0900 From: Minchan Kim To: Vlastimil Babka Cc: Andrew Morton , "Kirill A. Shutemov" , Mel Gorman , Andrea Arcangeli , Hugh Dickins , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Greg Kroah-Hartman , stable@vger.kernel.org, "Kirill A. Shutemov" Subject: Re: [PATCH v2] thp: use is_zero_pfn only after pte_present check Message-ID: <20151013091053.GA6630@bbox> References: <1444703918-16597-1-git-send-email-minchan@kernel.org> <561CB297.9080600@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <561CB297.9080600@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: On Tue, Oct 13, 2015 at 09:28:23AM +0200, Vlastimil Babka wrote: > On 10/13/2015 04:38 AM, Minchan Kim wrote: > >Use is_zero_pfn on pteval only after pte_present check on pteval > >(It might be better idea to introduce is_zero_pte where checks > >pte_present first). Otherwise, it could work with swap or > >migration entry and if pte_pfn's result is equal to zero_pfn > >by chance, we lose user's data in __collapse_huge_page_copy. > >So if you're luck, the application is segfaulted and finally you > >could see below message when the application is exit. > > > >BUG: Bad rss-counter state mm:ffff88007f099300 idx:2 val:3 > > > >Cc: > > More specific: > Cc: # 4.1+ > Fixes: ca0984caa823 ("mm: incorporate zero pages into transparent > huge pages") > > >Acked-by: Kirill A. Shutemov > > Acked-by: Vlastimil Babka Thanks for the detail and review, Vlastimil. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org