From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f200.google.com (mail-pg1-f200.google.com [209.85.215.200]) by kanga.kvack.org (Postfix) with ESMTP id 006846B027E for ; Mon, 16 Jul 2018 13:11:34 -0400 (EDT) Received: by mail-pg1-f200.google.com with SMTP id t20-v6so3861184pgu.9 for ; Mon, 16 Jul 2018 10:11:34 -0700 (PDT) Received: from mga05.intel.com (mga05.intel.com. [192.55.52.43]) by mx.google.com with ESMTPS id j185-v6si986431pgc.419.2018.07.16.10.11.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 16 Jul 2018 10:11:33 -0700 (PDT) Subject: [PATCH v2 09/14] s390, dcssblk: Allow a NULL-pfn to ->direct_access() From: Dan Williams Date: Mon, 16 Jul 2018 10:01:08 -0700 Message-ID: <153176046886.12695.7487453664953251895.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <153176041838.12695.3365448145295112857.stgit@dwillia2-desk3.amr.corp.intel.com> References: <153176041838.12695.3365448145295112857.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org Cc: Huaisheng Ye , Jan Kara , vishal.l.verma@intel.com, hch@lst.de, linux-mm@kvack.orgjack@suse.cz, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org From: Huaisheng Ye dcssblk_direct_access() needs to check the validity of pointer pfn for NULL assignment. If pfn equals to NULL, it doesn't need to calculate the value. This is in support of asynchronous memmap init and avoid page lookups when possible. Signed-off-by: Huaisheng Ye Reviewed-by: Jan Kara Signed-off-by: Dan Williams --- drivers/s390/block/dcssblk.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c index ed607288e696..a645b2c93c34 100644 --- a/drivers/s390/block/dcssblk.c +++ b/drivers/s390/block/dcssblk.c @@ -923,8 +923,9 @@ __dcssblk_direct_access(struct dcssblk_dev_info *dev_info, pgoff_t pgoff, dev_sz = dev_info->end - dev_info->start + 1; *kaddr = (void *) dev_info->start + offset; - *pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset), - PFN_DEV|PFN_SPECIAL); + if (pfn) + *pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset), + PFN_DEV|PFN_SPECIAL); return (dev_sz - offset) / PAGE_SIZE; }