From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:37072 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726563AbgBJUxY (ORCPT ); Mon, 10 Feb 2020 15:53:24 -0500 Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 01AKnMaZ109540 for ; Mon, 10 Feb 2020 15:53:22 -0500 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0b-001b2d01.pphosted.com with ESMTP id 2y38gxed61-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 10 Feb 2020 15:53:22 -0500 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 10 Feb 2020 20:53:20 -0000 Date: Mon, 10 Feb 2020 21:53:15 +0100 From: Gerald Schaefer Subject: Re: [PATCH v3 4/7] s390,dcssblk,dax: Add dax zero_page_range operation to dcssblk driver In-Reply-To: <20200207202652.1439-5-vgoyal@redhat.com> References: <20200207202652.1439-1-vgoyal@redhat.com> <20200207202652.1439-5-vgoyal@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-Id: <20200210215315.27b7e310@thinkpad> Sender: linux-s390-owner@vger.kernel.org List-ID: To: Vivek Goyal Cc: linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org, hch@infradead.org, dan.j.williams@intel.com, dm-devel@redhat.com, vishal.l.verma@intel.com, linux-s390@vger.kernel.org On Fri, 7 Feb 2020 15:26:49 -0500 Vivek Goyal wrote: > Add dax operation zero_page_range for dcssblk driver. > > CC: linux-s390@vger.kernel.org > Suggested-by: Christoph Hellwig > Signed-off-by: Vivek Goyal > --- > drivers/s390/block/dcssblk.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c > index 63502ca537eb..331abab5d066 100644 > --- a/drivers/s390/block/dcssblk.c > +++ b/drivers/s390/block/dcssblk.c > @@ -57,11 +57,28 @@ static size_t dcssblk_dax_copy_to_iter(struct dax_device *dax_dev, > return copy_to_iter(addr, bytes, i); > } > > +static int dcssblk_dax_zero_page_range(struct dax_device *dax_dev, u64 offset, > + size_t len) > +{ > + long rc; > + void *kaddr; > + pgoff_t pgoff = offset >> PAGE_SHIFT; > + unsigned page_offset = offset_in_page(offset); > + > + rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr, NULL); Why do you pass only 1 page as nr_pages argument for dax_direct_access()? In some other patch in this series there is a comment that this will currently only be used for one page, but support for more pages might be added later. Wouldn't it make sense to rather use something like PAGE_ALIGN(page_offset + len) >> PAGE_SHIFT instead of 1 here, so that this won't have to be changed when callers will be ready to use it with more than one page? Of course, I guess then we'd also need some check on the return value from dax_direct_access(), i.e. if the returned available range is large enough for the requested range.