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Date: Tue, 19 Jul 2016 14:35:47 -0400
From: Tejun Heo <tj@kernel.org>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Waiman Long <Waiman.Long@hpe.com>, Jan Kara <jack@suse.com>,
        Jeff Layton <jlayton@poochiereds.net>,
        "J. Bruce Fields" <bfields@fieldses.org>,
        Christoph Lameter <cl@linux-foundation.org>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>,
        Andi Kleen <andi@firstfloor.org>, Dave Chinner <dchinner@redhat.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Scott J Norton <scott.norton@hpe.com>,
        Douglas Hatch <doug.hatch@hpe.com>
Subject: Re: [PATCH v3 4/4] vfs: Use dlock list for superblock's inode list
Message-ID: <20160719183547.GL3078@mtj.duckdns.org>
References: <1468604383-40362-1-git-send-email-Waiman.Long@hpe.com>
 <1468604383-40362-5-git-send-email-Waiman.Long@hpe.com>
 <20160719052342.GF2356@ZenIV.linux.org.uk>
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Hello,

On Tue, Jul 19, 2016 at 06:23:42AM +0100, Al Viro wrote:
> On Fri, Jul 15, 2016 at 01:39:43PM -0400, Waiman Long wrote:
> > +		inode   = list_entry(iter.curr, struct inode, i_sb_list);
> > +		mapping = inode->i_mapping;
> 
> TBH, I would very much prefer something like
> 	DEFINE_DLOCK_LIST_ITER(iter, &blockdev_superblock->s_inodes);
> 
> 	dlist_for_each_entry(inode, &iter, i_sb_list) {
> 		mapping = inode->i_mapping;
> 
> > -		spin_unlock(&blockdev_superblock->s_inode_list_lock);
> > +		spin_unlock(iter.lock);
> 
> ... and this might be worth dlist_{un,re}lock(&iter);

If iterating requires prep / cleanup stages, it might as well do

	DEFINE_DLOCK_LIST_ITER(iter);

	dlock_list_iter_start(&iter, &blockdev_superblock->s_inodes);

	// iterate

	dlock_list_iter_end(&iter);

And probably provide dlist_for_each_entry() macro which handles
everything.

Thanks.

-- 
tejun