From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753346AbaEUUoU (ORCPT ); Wed, 21 May 2014 16:44:20 -0400 Received: from g2t1383g.austin.hp.com ([15.217.136.92]:16353 "EHLO g2t1383g.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752629AbaEUUoR (ORCPT ); Wed, 21 May 2014 16:44:17 -0400 Message-ID: <1400704507.18128.23.camel@misato.fc.hp.com> Subject: Re: [PATCH v7 07/22] Replace the XIP page fault handler with the DAX page fault handler From: Toshi Kani To: Matthew Wilcox Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, willy@linux.intel.com Date: Wed, 21 May 2014 14:35:07 -0600 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.8.5 (3.8.5-2.fc19) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2014-03-23 at 15:08 -0400, Matthew Wilcox wrote: : > +static int do_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, > + get_block_t get_block) > +{ : > + error = dax_get_pfn(inode, &bh, &pfn); > + if (error > 0) > + error = vm_insert_mixed(vma, vaddr, pfn); > + mutex_unlock(&mapping->i_mmap_mutex); > + > + if (page) { > + delete_from_page_cache(page); > + unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT, > + PAGE_CACHE_SIZE, 0); > + unlock_page(page); > + page_cache_release(page); Hi Matthew, I am seeing a problem in this code path, where it deletes a page cache page mapped to a hole. Sometimes, page->_mapcount is 0, not -1, which leads __delete_from_page_cache(), called from delete_from_page_cache(), to hit the following BUG_ON. BUG_ON(page_mapped(page)) I suppose such page has a shared mapping. Does this code need to take care of replacing shared mappings in such case? Thanks, -Toshi