From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:37086 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752079AbdBIPyD (ORCPT ); Thu, 9 Feb 2017 10:54:03 -0500 Date: Thu, 9 Feb 2017 16:52:00 +0100 From: Jan Kara To: Boaz Harrosh Cc: Jan Kara , linux-fsdevel@vger.kernel.org, Christoph Hellwig , linux-block@vger.kernel.org Subject: Re: [PATCH 05/24] fs: Get proper reference for s_bdi Message-ID: <20170209155200.GD3009@quack2.suse.cz> References: <20170202173422.3240-1-jack@suse.cz> <20170202173422.3240-6-jack@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Thu 09-02-17 16:36:13, Boaz Harrosh wrote: > On 02/02/2017 07:34 PM, Jan Kara wrote: > > So far we just relied on block device to hold a bdi reference for us > > while the filesystem is mounted. While that works perfectly fine, it is > > a bit awkward that we have a pointer to a refcounted structure in the > > superblock without proper reference. So make s_bdi hold a proper > > reference to block device's BDI. No filesystem using mount_bdev() > > actually changes s_bdi so this is safe and will make bdev filesystems > > work the same way as filesystems needing to set up their private bdi. > > > > Signed-off-by: Jan Kara > > --- > > fs/super.c | 7 ++----- > > 1 file changed, 2 insertions(+), 5 deletions(-) > > > > diff --git a/fs/super.c b/fs/super.c > > index 31dc4c6450ef..dfb95ccd4351 100644 > > --- a/fs/super.c > > +++ b/fs/super.c > > @@ -1047,12 +1047,9 @@ static int set_bdev_super(struct super_block *s, void *data) > > { > > s->s_bdev = data; > > s->s_dev = s->s_bdev->bd_dev; > > + s->s_bdi = bdi_get(s->s_bdev->bd_bdi); > > + s->s_iflags |= SB_I_DYNBDI; > > > > - /* > > - * We set the bdi here to the queue backing, file systems can > > - * overwrite this in ->fill_super() > > - */ > > Question: So I have an FS that uses mount_bdev but than goes and > overrides sb->s_bdev in ->fill_super() anyway. This is because of two > reasons. One because I have many more devices. (like btrfs I'm > moulti-dev) but I like to use mount_bdev because of the somewhat delicate > handling of automatic bind-mounts. > > For me it is a bigger hack to get the ref-counting and bind-mounts > locking correctly then to bdi_put and say the new super_setup_bdi(sb) in > fill_super. Would you expect problems? No, that should work just fine. Honza -- Jan Kara SUSE Labs, CR