Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753028Ab0DVG0r (ORCPT ); Thu, 22 Apr 2010 02:26:47 -0400 Received: from lazybastard.de ([212.112.238.170]:46448 "EHLO longford.logfs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751679Ab0DVG0q (ORCPT ); Thu, 22 Apr 2010 02:26:46 -0400 Date: Thu, 22 Apr 2010 08:26:31 +0200 From: =?utf-8?B?SsO2cm4=?= Engel To: Linus Torvalds Cc: Jens Axboe , David Woodhouse , linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, Christoph Hellwig Subject: Re: [PATCH] [MTD] Fix JFFS2 sync silent failure Message-ID: <20100422062631.GC27309@logfs.org> References: <20100417184016.GA17345@logfs.org> <20100419073843.GN27497@kernel.dk> <20100419101559.GA4145@logfs.org> <20100419102056.GS27497@kernel.dk> <20100422055448.GA27309@logfs.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20100422055448.GA27309@logfs.org> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2287 Lines: 70 Linus, I think this is bad enough that you should be involved. 32a88aa1 broke a number of filesystems in a way that sync() would return 0 without doing any work. Even politicians are better at keeping the promises. This is caused by the two-liner in __sync_filesystem: if (!sb->s_bdi) return 0; s_bdi is set implicitly for all filesystems using set_bdev_super(), so most block device based filesystems are safe. There are, however, a number of odd-balls around: On Thu, 22 April 2010 07:54:48 +0200, Jörn Engel wrote: > > 9p no s_bdi > afs no s_bdi > ceph creates its own s_bdi > cifs no s_bdi > coda no s_bdi > ecryptfs no s_bdi > exofs no s_bdi > fuse creates its own s_bdi? > gfs2 creates its own s_bdi? > jffs2 patch exists > logfs fixed now > ncpfs no s_bdi > nfs creates its own s_bdi > ocfs2 no s_bdi > smbfs no s_bdi > ubifs creates its own s_bdi Obviously this list should get checked and all affected filesystems get repaired. Additionally we should add an assertion and BUG() or refuse to mount or something. My original patch to that extend was this: diff --git a/fs/super.c b/fs/super.c index f35ac60..e8af253 100644 --- a/fs/super.c +++ b/fs/super.c @@ -954,6 +954,8 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void if (error < 0) goto out_free_secdata; BUG_ON(!mnt->mnt_sb); + BUG_ON(!mnt->mnt_sb->s_bdi && + (mnt->mnt_sb->s_bdev || mnt->mnt_sb->s_mtd)); error = security_sb_kern_mount(mnt->mnt_sb, flags, secdata); if (error) goto out_sb; The real problem is finding a condition that has neither false positives nor false negatives. The "(mnt->mnt_sb->s_bdev || mnt->mnt_sb->s_mtd)" part takes care of false positives like tmpfs, but it would catch none of the network filesystems. Should we instead annotate tmpfs and friends with something like sb->s_dont_need_bdi? It is the only way I can think of not to miss something. Jörn -- People will accept your ideas much more readily if you tell them that Benjamin Franklin said it first. -- unknown -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/