linux-ext4 - Re: [RFC v2 03/10] vfs: add one new mount option '-o hottrack'

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Message-ID: <20120927070508.GS15236@dastard>
Date:	Thu, 27 Sep 2012 17:05:08 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Zhi Yong Wu <zwu.kernel@...il.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org,
	linuxram@...ux.vnet.ibm.com, viro@...iv.linux.org.uk,
	cmm@...ibm.com, tytso@....edu, marco.stornelli@...il.com,
	stroetmann@...olinux.com, diegocg@...il.com, chris@...muel.org,
	Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
Subject: Re: [RFC v2 03/10] vfs: add one new mount option '-o hottrack'

On Thu, Sep 27, 2012 at 01:25:34PM +0800, Zhi Yong Wu wrote:
> On Tue, Sep 25, 2012 at 5:28 PM, Dave Chinner <david@...morbit.com> wrote:
> > On Sun, Sep 23, 2012 at 08:56:28PM +0800, zwu.kernel@...il.com wrote:
> >> From: Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
> >>
> >>   Introduce one new mount option '-o hottrack',
> >> and add its parsing support.
> >>   Its usage looks like:
> >>    mount -o hottrack
> >>    mount -o nouser,hottrack
> >>    mount -o nouser,hottrack,loop
> >>    mount -o hottrack,nouser
> >
> > I think that this option parsing should be done by the filesystem,
> > even though the tracking functionality is in the VFS. That way ony
> > the filesystems that can use the tracking information will turn it
> > on, rather than being able to turn it on for everything regardless
> > of whether it is useful or not.
> >
> > Along those lines, just using a normal superblock flag to indicate
> > it is active (e.g. MS_HOT_INODE_TRACKING in sb->s_flags) means you
> > don't need to allocate the sb->s_hot_info structure just to be able
> If we don't allocate one sb->s_hot_info, where will those hash list
> head and btree roots locate?

I wrote that thinking (mistakenly) that s-hot)info was dynamically
allocated rather than being embedded in the struct super_block.

Indeed, if the mount option is held in s_flags, then it could be
dynamically allocated, but I don't think that's really necessary...

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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