From: Marco Stornelli Subject: Re: [RFC, PATCH, RESEND] fs: push rcu_barrier() from deactivate_locked_super() to filesystems Date: Sat, 09 Jun 2012 09:06:28 +0200 Message-ID: <4FD2F5F4.1000106@gmail.com> References: <1339191663-17693-1-git-send-email-kirill.shutemov@linux.intel.com> <20120608150253.e42464a6.akpm@linux-foundation.org> <20120608221446.GA18250@otc-wbsnb-06> <20120608152550.258d6a30.akpm@linux-foundation.org> <20120608222734.GT30000@ZenIV.linux.org.uk> <20120608153120.b722d7c3.akpm@linux-foundation.org> <20120608233127.GB18981@otc-wbsnb-06> <20120608163751.7a8ec2bc.akpm@linux-foundation.org> <20120608172842.9826b5cd.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Linus Torvalds , "Kirill A. Shutemov" , Al Viro , Boaz Harrosh , Tao Ma , Nick Piggin , "Dmitry V. Levin" , v9fs-developer@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org, linux-btrfs@vger.kernel.org, ceph-devel@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, codalist@telemann.coda.cs.cmu.edu, ecryptfs@vger.kernel.org, osd-dev@open-osd.org, linux-ext4@vger.kernel.org, fuse-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, jfs-discussion@lists.sourceforge.net, logfs@logfs.org, linux-nfs@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, ocfs2-devel@oss.oracle.com, rei To: Andrew Morton Return-path: In-Reply-To: <20120608172842.9826b5cd.akpm@linux-foundation.org> Sender: ceph-devel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Il 09/06/2012 02:28, Andrew Morton ha scritto: > On Fri, 8 Jun 2012 16:46:47 -0700 Linus Torvalds wrote: > >> Of course, if you just mean having a VFS wrapper that does >> >> static void vfs_inode_kmem_cache_destroy(struct kmem_cache *cachep) >> { >> rcu_barrier(); >> kmem_cache_destroy(cachep); >> } >> >> then we could do that. Not much better than what Kirill's patch did, >> but at least we could have that comment in just one single place. > > That's conceptually what I meant. But it has the problem that new and > out-of-tree filesystems might forget to do it. Which is why I suggest > adding a kmem_cache* argument to unregister_filesystem() for this. > > It's a bit awkward, and the fs can pass in NULL if it knows what it's > doing. But it's reliable. > -- The call of rcu_barrier should be mandatory for the "unload fs module" problem, right? If the fs is compiled statically maybe we could avoid it, but (eventually) this kind of decision is per-fs, so this could be a clue that the call of rcu_barrier maybe is inside each fs not in VFS. Marco