Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752673AbaG1N04 (ORCPT ); Mon, 28 Jul 2014 09:26:56 -0400 Received: from mta-out1.inet.fi ([62.71.2.232]:34260 "EHLO jenni1.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751686AbaG1N0w (ORCPT ); Mon, 28 Jul 2014 09:26:52 -0400 Date: Mon, 28 Jul 2014 16:25:58 +0300 From: "Kirill A. Shutemov" To: Matthew Wilcox Cc: Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v8 05/22] Add vm_replace_mixed() Message-ID: <20140728132558.GA967@node.dhcp.inet.fi> References: <20140723114540.GD10317@node.dhcp.inet.fi> <20140723135221.GA6754@linux.intel.com> <20140723142048.GA11963@node.dhcp.inet.fi> <20140723142745.GD6754@linux.intel.com> <20140723155500.GA12790@node.dhcp.inet.fi> <20140725194450.GJ6754@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140725194450.GJ6754@linux.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 Fri, Jul 25, 2014 at 03:44:50PM -0400, Matthew Wilcox wrote: > On Wed, Jul 23, 2014 at 06:55:00PM +0300, Kirill A. Shutemov wrote: > > > update_hiwater_rss(mm); > > > > No: you cannot end up with lower rss after replace, iiuc. > > Actually, you can ... when we replace a real page with a PFN, our rss > decreases. Okay. > > Do you mean you pointed to new file all the time? O_CREAT doesn't truncate > > file if it exists, iirc. > > It was pointing to a new file. Still not sure why that one failed to trigger > the problem. The slightly modified version attached triggered the problem > *just fine* :-) > > I've attached all the patches in my tree so far. For the v9 patch kit, > I'll keep patch 3 as a separate patch, but roll patches 1, 2 and 4 into > other patches. > > I am seeing something odd though. When I run double-map with debugging > printks inserted in strategic spots in the kernel, I see four calls to > do_dax_fault(). The first two, as expected, are the loads from the two > mapped addresses. The third is via mkwrite, but then the fourth time > I get a regular page fault for write, and I don't understand why I get it. > > Any ideas? unmap_mapping_range() clears pte you've just set by vm_replace_mixed() on third fault. And locking looks wrong: it seems you need to hold i_mmap_mutex while replacing hole page with pfn. Your VM_BUG_ON() in zap_pte_single() triggers on my setup. > +static void zap_pte_single(struct vm_area_struct *vma, pte_t *pte, > + unsigned long addr) > +{ > + struct mm_struct *mm = vma->vm_mm; > + int force_flush = 0; > + int rss[NR_MM_COUNTERS]; > + > + VM_BUG_ON(!mutex_is_locked(&vma->vm_file->f_mapping->i_mmap_mutex)); It's wrong place for VM_BUG_ON(): zap_pte_single() on anon mapping should work fine) > + > + init_rss_vec(rss); Vector to commit single update to mm counters? What about inline counters update for rss == NULL case? > + update_hiwater_rss(mm); > + flush_cache_page(vma, addr, pte_pfn(*pte)); > + zap_pte(NULL, vma, pte, addr, NULL, rss, &force_flush); > + flush_tlb_page(vma, addr); > + add_mm_rss_vec(mm, rss); > +} > + -- 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/