From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>,
Andi Kleen <andi@firstfloor.org>,
linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org
Subject: Re: [RFC PATCH 0/2] Fix up the NFS mmap code
Date: Sat, 9 Jan 2010 02:30:35 +0000 [thread overview]
Message-ID: <20100109023035.GH30528@ZenIV.linux.org.uk> (raw)
In-Reply-To: <alpine.LFD.2.00.1001081814240.7821-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
On Fri, Jan 08, 2010 at 06:22:01PM -0800, Linus Torvalds wrote:
>
>
> On Sat, 9 Jan 2010, Al Viro wrote:
> >
> > Well, sure - it steps on i_mutex-before-mmmap_sem first from ls somewhere and
> > records the ordering for posterity. Then NFS steps into mmap() (on a
> > different inode) and gets conflicting ordering.
>
> Look closer: the inodes for directories and for non-directories have
> i_mutex in different lockdep classes.
>
> So that "on a different inode" thing should have made it a non-issue,
> since there is no actual chain back. There is "mmap_sem ->
> i_mutex_regular_file" (for mmap) and there is "i_mutex_directory ->
> mmap_sem" (for filldir), but that isn't an ABBA.
>
> The problem _seems_ to be (if I read Andi's chain correctly) that a
> directory hasn't gone through the i_mutex_dir_key change, so filldir ends
> up being counted against the default i_mutex_key.
Interesting... There's nfs_update_inode(), but it ought to scream bloody
murder on the type change (and its return value is ignore by nfs_fhget(),
BTW).
next prev parent reply other threads:[~2010-01-09 2:30 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1262913974.2659.101.camel@localhost>
2010-01-09 0:56 ` [RFC PATCH 0/2] Fix up the NFS mmap code Trond Myklebust
2010-01-09 0:56 ` [RFC PATCH 2/2] NFS: Fix a potential deadlock in nfs_file_mmap() Trond Myklebust
[not found] ` <20100109005624.7473.15560.stgit-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2010-01-09 1:54 ` Al Viro
[not found] ` <20100109005624.7473.33215.stgit-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2010-01-09 0:56 ` [RFC PATCH 1/2] VFS: Add a mmap_file() callback to struct file_operations Trond Myklebust
2010-01-09 1:17 ` [RFC PATCH 0/2] Fix up the NFS mmap code Linus Torvalds
[not found] ` <alpine.LFD.2.00.1001081709470.7821-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2010-01-09 1:38 ` Al Viro
2010-01-09 1:46 ` Al Viro
2010-01-09 1:57 ` Linus Torvalds
[not found] ` <alpine.LFD.2.00.1001081750080.7821-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2010-01-09 2:11 ` Al Viro
2010-01-09 2:22 ` Linus Torvalds
[not found] ` <alpine.LFD.2.00.1001081814240.7821-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2010-01-09 2:30 ` Al Viro [this message]
2010-01-09 2:40 ` Al Viro
2010-01-09 2:43 ` Al Viro
2010-01-10 2:00 ` Andi Kleen
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