linux-kernel - Re: [patch 3/6] vfs: mountinfo stable peer group id

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Message-ID: <20080324093436.GH10722@ZenIV.linux.org.uk>
Date:	Mon, 24 Mar 2008 09:34:36 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Ram Pai <linuxram@...ibm.com>
Cc:	Miklos Szeredi <miklos@...redi.hu>, akpm@...ux-foundation.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 3/6] vfs: mountinfo stable peer group id

On Mon, Mar 24, 2008 at 01:19:41AM -0700, Ram Pai wrote:
> > 	* in do_change_type(), outside of vfsmount_lock, do invent_group_ids()
> > If it fails - bugger off, if not - proceed as now.
> 
> Has it to be done outside vfsmount_lock?  AFAICT, invent_group_ids()
> does not sleep, nor does change_mnt_propagation().

It does allocation.  And no, GFP_ATOMIC is not appropriate for that.
The same goes for mount IDs, BTW, and there we _also_ don't need
vfsmount_lock - see my current tree, there we have clone_mnt()
serialized by namespace_sem in all cases.

> > 	* in attach_recursive_mnt() if IS_MNT_SHARED(dest_mnt) do
> > invent_group_ids() on the dest_mnt immediately and if it fails do
> 
> I think you meant, invent_group_ids() on the source_mnt.
Yes

> But again
> applying invent_group_ids() on the source_mnt has to be done carefully,
> because, source_mnt may have been shared to begin with.

And?  See the original posting - invent_group_ids() skips the vfsmounts
with already set group ID.
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