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Date: Mon, 6 Apr 2015 09:51:34 -0400
From: Jarod Wilson <jarod@redhat.com>
To: Ming Lei <ming.lei@canonical.com>
Cc: Jens Axboe <axboe@kernel.dk>, linux-kernel@vger.kernel.org,
        Christoph Hellwig <hch@infradead.org>, Tejun Heo <tj@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        David Herrmann <dh.herrmann@gmail.com>,
        Markus Pargmann <mpa@pengutronix.de>,
        nbd-general@lists.sourceforge.net,
        Stefan Haberland <stefan.haberland@de.ibm.com>,
        Sebastian Ott <sebott@linux.vnet.ibm.com>,
        Fabian Frederick <fabf@skynet.be>, linux-s390@vger.kernel.org
Subject: Re: [PATCH 5/6] block: dasd_genhd: convert to blkdev_reread_part
Message-ID: <20150406135134.GG14217@redhat.com>
References: <1428218688-4092-1-git-send-email-ming.lei@canonical.com>
 <1428218688-4092-6-git-send-email-ming.lei@canonical.com>
 <20150406134655.GE14217@redhat.com>
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On Mon, Apr 06, 2015 at 09:46:55AM -0400, Jarod Wilson wrote:
> On Sun, Apr 05, 2015 at 03:24:47PM +0800, Ming Lei wrote:
> > Also remove the obsolete comment.
> > 
> > Signed-off-by: Ming Lei <ming.lei@canonical.com>
> > ---
> >  drivers/s390/block/dasd_genhd.c |    9 +++------
> >  1 file changed, 3 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/s390/block/dasd_genhd.c b/drivers/s390/block/dasd_genhd.c
> > index 90f39f7..2af4619 100644
> > --- a/drivers/s390/block/dasd_genhd.c
> > +++ b/drivers/s390/block/dasd_genhd.c
> > @@ -116,14 +116,11 @@ int dasd_scan_partitions(struct dasd_block *block)
> >  			      rc);
> >  		return -ENODEV;
> >  	}
> > -	/*
> > -	 * See fs/partition/check.c:register_disk,rescan_partitions
> > -	 * Can't call rescan_partitions directly. Use ioctl.
> > -	 */
> > -	rc = ioctl_by_bdev(bdev, BLKRRPART, 0);
> > +
> > +	rc = blkdev_reread_part(bdev);
> >  	while (rc == -EBUSY && retry > 0) {
> >  		schedule();
> > -		rc = ioctl_by_bdev(bdev, BLKRRPART, 0);
> > +		rc = blkdev_reread_part(bdev);
> >  		retry--;
> >  		DBF_DEV_EVENT(DBF_ERR, block->base,
> >  			      "scan partitions error, retry %d rc %d",
> 
> Note: patch 6/6 in the series makes this whole while() loops pointless,
> since the possibility of the -EBUSY return goes away.

Minor clarification: the -EBUSY due to the trylock, which is why that
retry loop exists, goes away. You *could* still get an -EBUSY through
blkdev_reread_part()->rescan_partitions()->drop_partitions() if
bdev->bd_part_count is non-zero.

-- 
Jarod Wilson
jarod@redhat.com