From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f171.google.com (mail-wi0-f171.google.com [209.85.212.171]) by kanga.kvack.org (Postfix) with ESMTP id F346F6B006C for ; Tue, 7 Apr 2015 09:26:42 -0400 (EDT) Received: by wiun10 with SMTP id n10so18625675wiu.1 for ; Tue, 07 Apr 2015 06:26:41 -0700 (PDT) Received: from kirsi1.inet.fi (mta-out1.inet.fi. [62.71.2.227]) by mx.google.com with ESMTP id bb7si12729144wjb.154.2015.04.07.06.26.39 for ; Tue, 07 Apr 2015 06:26:40 -0700 (PDT) Date: Tue, 7 Apr 2015 16:26:01 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCH 1/3 v6] mm(v4.1): New pfn_mkwrite same as page_mkwrite for VM_PFNMAP Message-ID: <20150407132601.GA14252@node.dhcp.inet.fi> References: <55239645.9000507@plexistor.com> <552397E6.5030506@plexistor.com> <5523D43C.1060708@plexistor.com> <20150407131700.GA13946@node.dhcp.inet.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150407131700.GA13946@node.dhcp.inet.fi> Sender: owner-linux-mm@kvack.org List-ID: To: Boaz Harrosh Cc: Dave Chinner , Matthew Wilcox , Andrew Morton , "Kirill A. Shutemov" , Jan Kara , Hugh Dickins , Mel Gorman , linux-mm@kvack.org, linux-nvdimm , linux-fsdevel , Eryu Guan , Christoph Hellwig , Stable Tree On Tue, Apr 07, 2015 at 04:17:00PM +0300, Kirill A. Shutemov wrote: > On Tue, Apr 07, 2015 at 03:57:32PM +0300, Boaz Harrosh wrote: > > +/* > > + * Handle write page faults for VM_MIXEDMAP or VM_PFNMAP for a VM_SHARED > > + * mapping > > + */ > > +static int wp_pfn_shared(struct mm_struct *mm, > > + struct vm_area_struct *vma, unsigned long address, > > + pte_t *page_table, spinlock_t *ptl, pte_t orig_pte, > > + pmd_t *pmd) > > +{ > > + if (vma->vm_ops && vma->vm_ops->pfn_mkwrite) { > > + struct vm_fault vmf = { > > + .page = NULL, > > + .pgoff = linear_page_index(vma, address), > > + .virtual_address = (void __user *)(address & PAGE_MASK), > > + .flags = FAULT_FLAG_WRITE | FAULT_FLAG_MKWRITE, > > + }; > > + int ret; > > + > > + pte_unmap_unlock(page_table, ptl); > > + ret = vma->vm_ops->pfn_mkwrite(vma, &vmf); > > + if (ret & VM_FAULT_ERROR) > > + return ret; > > + page_table = pte_offset_map_lock(mm, pmd, address, &ptl); > > + /* Did pfn_mkwrite already fixed up the pte */ Oh. I guess you've missunderstood why we need pte_same() check below. It's not about ->pfn_mkwrite() changing the pte (generatlly, it should not). It's requited to address race with parallel page fault to the pte. > > + if (!pte_same(*page_table, orig_pte)) { > > + pte_unmap_unlock(page_table, ptl); > > + return ret; > > This should be "return 0;", shouldn't it? > > VM_FAULT_NOPAGE would imply you've installed new pte, but you did not. -- Kirill A. Shutemov -- 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