Re: [GIT PULL] Fsnotify cleanups

From: Jan Kara <jack@suse.cz>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Jan Kara <jack@suse.cz>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [GIT PULL] Fsnotify cleanups
Date: Mon, 11 Jun 2018 18:03:11 +0200	[thread overview]
Message-ID: <20180611160311.dsehobeuvwiq2j6c@quack2.suse.cz> (raw)
In-Reply-To: <CAOQ4uxj1SbiMkwOT2-LxGP4ZM=aJDPrNSkLhe-wP5si-oAtO1g@mail.gmail.com>

On Mon 11-06-18 16:58:14, Amir Goldstein wrote:
> On Mon, Jun 11, 2018 at 4:36 PM, Jan Kara <jack@suse.cz> wrote:
> > > I reworked the cleanup patches to get rid of fsnotify_obj and pushed to:
> > > https://github.com/amir73il/linux.git fsnotify-cleanup
> >
> > Thanks!
> >
> > > Only last 5 patches from fsnotify_for_v4.18-rc1 have been modified
> > > and I removed your S-O-B from the modified patches.
> > >
> > > This leaves struct inode unchanged, in fact no changes to code outside
> > > fsnotify/audit at all.
> > >
> > > mask is now a member of connector for the purpose of generalizing
> > > add/remove mark, but struct inode/mount still have a copy of the mask
> > > for the purpose of the VFS optimizations.
> >
> > Looking through those patches, is it really beneficial to add mask to
> > connector when you keep it in inode / vfsmount? A helper function to get
> > mask from connector would make the same refactoring possible as well, won't
> > it?
> >
> > And adding a helper function to set mask given connector would get rid of
> > the remaining checks for connector type due to mask manipulations...
> >
> 
> By moving the checks for object type into the helper?

Yes, that's what I meant.

> Anyway, my thinking was:
> 
> What do we have to loose from keeping the mask also inside the connector?
> 
> Not much. We didn't change the size of connector struct
> and it hardly adds any complexity / performance cost.

You've actually grown the connector by 1 long on x86_64 - spinlock_t is
just 4 bytes there. Also it seems a bit stupid to me to have the mask in
two places (connector & object) just to save ifs in two helper functions.

> What do we have to gain from keeping the mask also inside the connector?
> 
> We can later get rid of the copy of mask in inode struct as I wrote.
> I will follow up on that.

If we can get rid of the mask in inode, I'm definitely fine with moving the
mask to the connector.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR