From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752237AbbKKPVz (ORCPT ); Wed, 11 Nov 2015 10:21:55 -0500 Received: from static.68.134.40.188.clients.your-server.de ([188.40.134.68]:43142 "EHLO mail02.iobjects.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750862AbbKKPVy (ORCPT ); Wed, 11 Nov 2015 10:21:54 -0500 To: LKML , Jens Axboe From: =?UTF-8?Q?Holger_Hoffst=c3=a4tte?= Subject: [PATCH] loop: properly observe rotational flag of underlying device X-Enigmail-Draft-Status: N1110 Organization: Applied Asynchrony, Inc. Message-ID: <56435D0F.80006@googlemail.com> Date: Wed, 11 Nov 2015 16:21:51 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The loop driver always declares the rotational flag of its device as rotational, even when the device of the mapped file is nonrotational, as is the case with SSDs or on tmpfs. This can confuse filesystem tools which are SSD-aware; in my case I frequently forget to tell mkfs.btrfs that my loop device on tmpfs is nonrotational, and that I really don't need any automatic metadata redundancy. The attached patch fixes this by introspecting the rotational flag of the mapped file's underlying block device, if it exists. If the mapped file's filesystem has no associated block device - as is the case on e.g. tmpfs - we assume nonrotational storage. If there is a better way to identify such non-devices I'd love to hear them. Signed-off-by: Holger Hoffstätte --- drivers/block/loop.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 423f4ca..2984aca 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -843,6 +843,24 @@ static void loop_config_discard(struct loop_device *lo) queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q); } +static void loop_update_rotational(struct loop_device *lo) +{ + struct file *file = lo->lo_backing_file; + struct inode *file_inode = file->f_mapping->host; + struct block_device *file_bdev = file_inode->i_sb->s_bdev; + struct request_queue *q = lo->lo_queue; + bool nonrot = true; + + /* not all filesystems (e.g. tmpfs) have a sb->s_bdev */ + if (file_bdev) + nonrot = blk_queue_nonrot(bdev_get_queue(file_bdev)); + + if (nonrot) + queue_flag_set_unlocked(QUEUE_FLAG_NONROT, q); + else + queue_flag_clear_unlocked(QUEUE_FLAG_NONROT, q); +} + static void loop_unprepare_queue(struct loop_device *lo) { flush_kthread_worker(&lo->worker); @@ -939,6 +957,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode, if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync) blk_queue_flush(lo->lo_queue, REQ_FLUSH); + loop_update_rotational(lo); loop_update_dio(lo); set_capacity(lo->lo_disk, size); bd_set_size(bdev, size << 9); -- 2.6.3