From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f71.google.com (mail-pa0-f71.google.com [209.85.220.71]) by kanga.kvack.org (Postfix) with ESMTP id 610146B0069 for ; Tue, 18 Oct 2016 14:35:27 -0400 (EDT) Received: by mail-pa0-f71.google.com with SMTP id tz10so831418pab.3 for ; Tue, 18 Oct 2016 11:35:27 -0700 (PDT) Received: from mga04.intel.com (mga04.intel.com. [192.55.52.120]) by mx.google.com with ESMTPS id y20si36846657pfd.167.2016.10.18.11.35.26 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 18 Oct 2016 11:35:26 -0700 (PDT) Date: Tue, 18 Oct 2016 12:35:25 -0600 From: Ross Zwisler Subject: Re: [PATCH 16/20] mm: Provide helper for finishing mkwrite faults Message-ID: <20161018183525.GC7796@linux.intel.com> References: <1474992504-20133-1-git-send-email-jack@suse.cz> <1474992504-20133-17-git-send-email-jack@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1474992504-20133-17-git-send-email-jack@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Jan Kara Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org, Dan Williams , Ross Zwisler , "Kirill A. Shutemov" On Tue, Sep 27, 2016 at 06:08:20PM +0200, Jan Kara wrote: > Provide a helper function for finishing write faults due to PTE being > read-only. The helper will be used by DAX to avoid the need of > complicating generic MM code with DAX locking specifics. > > Signed-off-by: Jan Kara > --- > include/linux/mm.h | 1 + > mm/memory.c | 65 +++++++++++++++++++++++++++++++----------------------- > 2 files changed, 39 insertions(+), 27 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 1055f2ece80d..e5a014be8932 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -617,6 +617,7 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma) > int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg, > struct page *page); > int finish_fault(struct vm_fault *vmf); > +int finish_mkwrite_fault(struct vm_fault *vmf); > #endif > > /* > diff --git a/mm/memory.c b/mm/memory.c > index f49e736d6a36..8c8cb7f2133e 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -2266,6 +2266,36 @@ oom: > return VM_FAULT_OOM; > } > > +/** > + * finish_mkrite_fault - finish page fault making PTE writeable once the page finish_mkwrite_fault > @@ -2315,26 +2335,17 @@ static int wp_page_shared(struct vm_fault *vmf) > put_page(vmf->page); > return tmp; > } > - /* > - * Since we dropped the lock we need to revalidate > - * the PTE as someone else may have changed it. If > - * they did, we just return, as we can count on the > - * MMU to tell us if they didn't also make it writable. > - */ > - vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, > - vmf->address, &vmf->ptl); > - if (!pte_same(*vmf->pte, vmf->orig_pte)) { > + tmp = finish_mkwrite_fault(vmf); > + if (unlikely(!tmp || (tmp & > + (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) { The 'tmp' return from finish_mkwrite_fault() can only be 0 or VM_FAULT_WRITE. I think this test should just be if (unlikely(!tmp)) { With that and the small spelling fix: Reviewed-by: Ross Zwisler -- 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