Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760032AbZIPUh7 (ORCPT ); Wed, 16 Sep 2009 16:37:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760019AbZIPUh5 (ORCPT ); Wed, 16 Sep 2009 16:37:57 -0400 Received: from mail-ew0-f206.google.com ([209.85.219.206]:53223 "EHLO mail-ew0-f206.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759989AbZIPUhv (ORCPT ); Wed, 16 Sep 2009 16:37:51 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=WxlUzxQLFXefX1hlaYqDDSlMhKxmqhJdbEBHhTu/qPHtKGakeUl4xQcIYmD6ZJm2IG koXT0/qw37lKQLiyTMJGLAe+/mgWQpTtQsijnVoBbUoyRI7WHxVi5pKT5mOrlKbVDgVY 4XJq0i5TK9XsOpmZ9E+ZU+gnsxeHFvyDglDNI= Date: Wed, 16 Sep 2009 22:37:50 +0200 From: Frederic Weisbecker To: Alexander Beregalov Cc: LKML , Reiserfs Subject: Re: [PATCH 0/4] kill-the-bkl/reiserfs: fix some lock dependency inversions Message-ID: <20090916203747.GB5068@nowhere> References: <1251167570-5233-1-git-send-email-fweisbec@gmail.com> <20090826201330.GA18761@orion> <20090914203749.GF6045@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2371 Lines: 81 On Tue, Sep 15, 2009 at 01:33:42AM +0400, Alexander Beregalov wrote: > > Hi Alexander, > > > > It should be fixed now, still in the following tree: > > Hi! > Another one, similar: > It is v2.6.31-3123-g99bc470 plus your 805031859(kill-the-bkl/reiserfs: > panic in case of lock imbalance), UP. Although I can't reproduce it, I think I see how that can happen. On mount time, we have the following dependency: reiserfs_lock -> bdev_mutex -> sysfs_mutex which happens while calling journal_init_dev() because we open the device there. But also in case of mmap on a reiserfs filesystem we may call reiserfs_readpages(), holding the reiserfs lock while already holding mm->mmap_sem The above dependency is then updated: mmap_sem | | ------- reiserfs_lock -> bdev_mutex -> sysfs_mutex And later, while doing a readdir() on a sysfs directory, sysfs calls filldir, which might_fault, and then might grab mmap_sem. filldir is called there while holding sys_mutex, creating the new following dependency sysfs_mutex -> mmap_sem Hence the inversion. It seems the deadlock can't ever happen, I even don't see corner cases where it could happen. But still, this dependency should disappear. Could you please tell me if the following patch makes it shut down? Otherwise, I may need your config. I don't know why, but I suspect the lock_acquire(mmap_sem) in might_fault doesn't trigger needed the lockdep check, although I have the appropriate debug config, at least it seems. But anyway, it should also happen in my box but it doesn't... Thanks! The patch: diff --git a/fs/reiserfs/journal.c b/fs/reiserfs/journal.c index d23d6d7..59f7a4c 100644 --- a/fs/reiserfs/journal.c +++ b/fs/reiserfs/journal.c @@ -2801,11 +2801,14 @@ int journal_init(struct super_block *sb, const char *j_dev_name, goto free_and_return; } + reiserfs_write_unlock(sb); if (journal_init_dev(sb, journal, j_dev_name) != 0) { reiserfs_warning(sb, "sh-462", "unable to initialize jornal device"); + reiserfs_write_lock(sb); goto free_and_return; } + reiserfs_write_lock(sb); rs = SB_DISK_SUPER_BLOCK(sb); -- 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/