linux-kernel - Re: [PATCH v1.2 0/5] IMA: making i_readcount a first class inode citizen

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Message-ID: <20101105163504.GB3270@fieldses.org>
Date:	Fri, 5 Nov 2010 12:35:04 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Eric Paris <eparis@...hat.com>
Cc:	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, jmorris@...ei.org,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	viro@...iv.linux.org.uk, Dave Chinner <david@...morbit.com>
Subject: Re: [PATCH v1.2 0/5] IMA: making i_readcount a first class inode
 citizen

On Tue, Nov 02, 2010 at 02:03:29PM -0400, Eric Paris wrote:
> On Tue, 2010-11-02 at 13:08 -0400, Mimi Zohar wrote:
> > Changelog:
> > - renamed iget/iput_readcount to i_readcount_inc/dec (Dave Chinner's suggestion)
> > - finished cleaning up the locking, so that: (based on Eric's comment.)
> > 	- i_lock is not required
> > 	- i_mutex is taken when making measurement decisions to prevent
> > 	  file metadata(eg. permissions, xattr) changing from under it.
> > 	- iint->mutex is taken when accessing/modifying the iint structure.
> > - Based on the previous posting discussion, i_readcount is now defined as
> > atomic. 
> > 
> > This patchset separates the incrementing/decrementing of the i_readcount,
> > in the VFS layer, from other IMA functionality, by replacing the current
> > ima_counts_get() call with i_readcount_inc(). Its unclear whether this
> > call to increment i_readcount should be made earlier, like i_writecount.
> > 
> > The patch ordering is a bit redundant in order to leave removing the ifdef
> > around i_readcount until the last patch. The first four patches: redefines 
> > i_readcount as atomic, defines i_readcount_inc/dec(), moves the IMA
> > functionality in ima_counts_get() to ima_file_check(), and removes the
> > IMA imbalance code, simplifying IMA. The last patch removes the ifdef
> > around i_readcount, making i_readcount into a "first class inode citizen".
> > 
> > The generic_setlease code could then take advantage of i_readcount.
> >  
> > Mimi
> > Mimi Zohar (5):
> >   IMA: convert i_readcount to atomic
> >   IMA: define readcount functions
> >   IMA: maintain i_readcount in the VFS layer
> >   IMA: remove IMA imbalance checking
> >   IMA: making i_readcount a first class inode citizen
> 
> 
> Ack on patches 1-4.  Patch 5 I'm not so sure about.  As long as IMA is
> the only user I don't think we really want to unconditionally compile
> i_readcount in.  I say we either leave it wrapped in CONFIG_IMA until
> there is a second user.  Then we either unconditionally compile it in,
> or we wrap it in something that either user can select in the Kconfig.
> 
> I'll let others voice their opinion.

I think it solves a real problem for the lease code.

--b.
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