linux-kernel - Re: [PATCH v3 4/4] vfs: Use dlock list for superblock's inode list

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Date:	Tue, 19 Jul 2016 14:35:47 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Waiman Long <Waiman.Long@....com>, Jan Kara <jack@...e.com>,
	Jeff Layton <jlayton@...chiereds.net>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	Dave Chinner <dchinner@...hat.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Scott J Norton <scott.norton@....com>,
	Douglas Hatch <doug.hatch@....com>
Subject: Re: [PATCH v3 4/4] vfs: Use dlock list for superblock's inode list

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