From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1751937AbcEISVr (ORCPT <rfc822;w@1wt.eu>);
	Mon, 9 May 2016 14:21:47 -0400
Received: from g4t3427.houston.hp.com ([15.201.208.55]:41685 "EHLO
	g4t3427.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751207AbcEISVq (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 9 May 2016 14:21:46 -0400
Message-ID: <1462817565.27137.102.camel@hpe.com>
Subject: Re: [PATCH v3 2/5] block: Add bdev_supports_dax() for dax mount
 checks
From: Toshi Kani <toshi.kani@hpe.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Jan Kara <jack@suse.cz>, david <david@fromorbit.com>,
        Al Viro <viro@zeniv.linux.org.uk>, Jens Axboe <axboe@fb.com>,
        Christoph Hellwig <hch@infradead.org>,
        Boaz Harrosh <boaz@plexistor.com>, "Theodore Ts'o" <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Ross Zwisler <ross.zwisler@linux.intel.com>, micah.parrish@hpe.com,
        "linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Date: Mon, 09 May 2016 12:12:45 -0600
In-Reply-To: <CAPcyv4hKpvF6uqBzV+1seUzFfxDZM-ApordAL_NecRLNcdNgwg@mail.gmail.com>
References: <1462494596-20938-1-git-send-email-toshi.kani@hpe.com>
	 <1462494596-20938-3-git-send-email-toshi.kani@hpe.com>
	 <CAPcyv4hKpvF6uqBzV+1seUzFfxDZM-ApordAL_NecRLNcdNgwg@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
X-Mailer: Evolution 3.18.5.2 (3.18.5.2-1.fc23) 
Mime-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Sun, 2016-05-08 at 12:14 -0700, Dan Williams wrote:
> On Thu, May 5, 2016 at 5:29 PM, Toshi Kani <toshi.kani@hpe.com> wrote:
 :
> > +int bdev_supports_dax(struct super_block *sb, int blocksize)
> > +{
> > +       struct blk_dax_ctl dax = {
> > +               .sector = 0,
> > +               .size = PAGE_SIZE,
> > +       };
> > +       int err;
> > +
> > +       if (blocksize != PAGE_SIZE) {
> > +               vfs_msg(sb, KERN_ERR, "error: unsupported blocksize for
> > dax");
> > +               return -EINVAL;
> > +       }
> > +
> > +       err = bdev_direct_access(sb->s_bdev, &dax);
> > +       if (err < 0) {
> > +               switch (err) {
> > +               case -EOPNOTSUPP:
> > +                       vfs_msg(sb, KERN_ERR,
> > +                               "error: device does not support dax");
> > +                       break;
> > +               case -EINVAL:
> > +                       vfs_msg(sb, KERN_ERR,
> > +                               "error: unaligned partition for dax");
> > +                       break;
> > +               default:
> > +                       vfs_msg(sb, KERN_ERR,
> > +                               "error: dax access failed (%d)", err);
> > +               }
> > +               return err;
> > +       }
> > +
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(bdev_supports_dax);
>
> This patch should replace blkdev_dax_capable(), or just reuse that
> existing routine, or am I missing something?

Good question.  bdev_supports_dax() is a helper function tailored for the
filesystem's mount -o dax case.  While blkdev_dax_capable() is similar, it
does not need error messages like "device does not support dax" since it
implicitly enables dax when capable.  So, I think we can keep
blkdev_dax_capable(), but change it to call bdev_direct_access() so that
actual check is performed in a single place.

Thanks,
-Toshi