linux-kernel - Re: [RFC, PATCH, RESEND] fs: push rcu_barrier() from deactivate_locked

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Message-ID: <20120608233127.GB18981@otc-wbsnb-06>
Date:	Sat, 9 Jun 2012 02:31:27 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Boaz Harrosh <bharrosh@...asas.com>,
	Tao Ma <boyu.mt@...bao.com>, Nick Piggin <npiggin@...nel.dk>,
	"Dmitry V. Levin" <ldv@...linux.org>,
	v9fs-developer@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-afs@...ts.infradead.org,
	linux-btrfs@...r.kernel.org, ceph-devel@...r.kernel.org,
	linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
	codalist@...EMANN.coda.cs.cmu.edu, ecryptfs@...r.kernel.org,
	osd-dev@...n-osd.org, linux-ext4@...r.kernel.org,
	fuse-devel@...ts.sourceforge.net, linux-mtd@...ts.infradead.org,
	jfs-discussion@...ts.sourceforge.net, logfs@...fs.org,
	linux-nfs@...r.kernel.org, linux-nilfs@...r.kernel.org,
	linux-ntfs-dev@...ts.sourceforge.net, ocfs2-devel@....oracle.com,
	reiserfs-devel@...r.kernel.org
Subject: Re: [RFC, PATCH, RESEND] fs: push rcu_barrier() from
 deactivate_locked_super() to filesystems

On Fri, Jun 08, 2012 at 03:31:20PM -0700, Andrew Morton wrote:
> On Fri, 8 Jun 2012 23:27:34 +0100
> Al Viro <viro@...IV.linux.org.uk> wrote:
> 
> > On Fri, Jun 08, 2012 at 03:25:50PM -0700, Andrew Morton wrote:
> > 
> > > A neater implementation might be to add a kmem_cache* argument to
> > > unregister_filesystem().  If that is non-NULL, unregister_filesystem()
> > > does the rcu_barrier() and destroys the cache.  That way we get to
> > > delete (rather than add) a bunch of code from all filesystems and new
> > > and out-of-tree filesystems cannot forget to perform the rcu_barrier().
> > 
> > There's often enough more than one cache, so that one is no-go.
> 
> kmem_cache** ;)
> 
> Which filesystems have multiple inode caches?

Multiple inode caches? No.
Multiple caches with call_rcu() free? See btrfs or gfs2.

-- 
 Kirill A. Shutemov

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