Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757491AbaGWLWK (ORCPT ); Wed, 23 Jul 2014 07:22:10 -0400 Received: from mta-out1.inet.fi ([62.71.2.202]:53853 "EHLO jenni1.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757412AbaGWLWJ (ORCPT ); Wed, 23 Jul 2014 07:22:09 -0400 Date: Wed, 23 Jul 2014 14:21:56 +0300 From: "Kirill A. Shutemov" To: Matthew Wilcox Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, willy@linux.intel.com Subject: Re: [PATCH v8 01/22] Fix XIP fault vs truncate race Message-ID: <20140723112156.GA10317@node.dhcp.inet.fi> References: <78c38d32aa62db1bb86315cf3e287b24be900c5e.1406058387.git.matthew.r.wilcox@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <78c38d32aa62db1bb86315cf3e287b24be900c5e.1406058387.git.matthew.r.wilcox@intel.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 22, 2014 at 03:47:49PM -0400, Matthew Wilcox wrote: > Pagecache faults recheck i_size after taking the page lock to ensure that > the fault didn't race against a truncate. We don't have a page to lock > in the XIP case, so use the i_mmap_mutex instead. It is locked in the > truncate path in unmap_mapping_range() after updating i_size. So while > we hold it in the fault path, we are guaranteed that either i_size has > already been updated in the truncate path, or that the truncate will > subsequently call zap_page_range_single() and so remove the mapping we > have just inserted. > > There is a window of time in which i_size has been reduced and the > thread has a mapping to a page which will be removed from the file, > but this is harmless as the page will not be allocated to a different > purpose before the thread's access to it is revoked. > > Signed-off-by: Matthew Wilcox > Reviewed-by: Jan Kara > --- > mm/filemap_xip.c | 24 ++++++++++++++++++++++-- > 1 file changed, 22 insertions(+), 2 deletions(-) > > diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c > index d8d9fe3..c8d23e9 100644 > --- a/mm/filemap_xip.c > +++ b/mm/filemap_xip.c > @@ -260,8 +260,17 @@ again: > __xip_unmap(mapping, vmf->pgoff); > > found: > + /* We must recheck i_size under i_mmap_mutex */ > + mutex_lock(&mapping->i_mmap_mutex); > + size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> > + PAGE_CACHE_SHIFT; round_up() ? Acked-by: Kirill A. Shutemov -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/