From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dave Jones <davej@redhat.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
"Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: VFS deadlock ?
Date: Fri, 22 Mar 2013 00:08:03 +0000 [thread overview]
Message-ID: <20130322000803.GG21522@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CA+55aFyLJ9vVm1T994EaE4tnEbV8rHj43m+cWsFFBi_qndao1A@mail.gmail.com>
On Thu, Mar 21, 2013 at 04:58:41PM -0700, Linus Torvalds wrote:
> And the only other reason we don't want to allow it is to make sure
> you can't have directory loops etc, afaik, and again, for this
> particular case of /proc, we happen to be ok.
Not really. Do that and yes, this deadlock goes away. But the locking
order in general goes to hell - we order directory inodes by "which dentry
is an ancestor of another?" So we have no warranty that we won't get
alias1/foo/bar/baz < alias2/foo. Take rename_lock() on those two and
have it race with rmdir alias2/foo/bar/baz (locks alias2/foo/bar, then
alias2/foo/bar/baz) and rmdir alias2/foo/bar (locks alias2/foo and
alias2/foo/bar). Oops - we have a cycle now...
next prev parent reply other threads:[~2013-03-22 0:08 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-21 19:06 VFS deadlock ? Dave Jones
2013-03-21 19:21 ` Al Viro
2013-03-21 20:31 ` Dave Jones
2013-03-21 19:29 ` Al Viro
2013-03-21 20:15 ` Linus Torvalds
2013-03-21 20:26 ` Dave Jones
2013-03-21 20:32 ` Linus Torvalds
2013-03-21 20:36 ` Dave Jones
2013-03-21 20:47 ` Al Viro
2013-03-21 21:02 ` Dave Jones
2013-03-21 21:18 ` Linus Torvalds
2013-03-21 21:26 ` Al Viro
2013-03-21 21:41 ` Dave Jones
2013-03-21 21:47 ` Linus Torvalds
2013-03-21 21:55 ` Al Viro
2013-03-21 21:57 ` Linus Torvalds
2013-03-21 22:03 ` Al Viro
2013-03-21 21:52 ` Al Viro
2013-03-21 22:12 ` Dave Jones
2013-03-21 22:29 ` Dave Jones
2013-03-21 22:53 ` Linus Torvalds
2013-03-21 23:07 ` Dave Jones
2013-03-21 23:36 ` Al Viro
2013-03-21 23:58 ` Linus Torvalds
2013-03-22 0:01 ` Linus Torvalds
2013-03-22 0:12 ` Al Viro
2013-03-22 0:20 ` Al Viro
2013-03-22 0:22 ` Linus Torvalds
2013-03-22 1:22 ` Al Viro
2013-03-22 1:33 ` Linus Torvalds
2013-03-22 1:40 ` Al Viro
2013-03-22 4:37 ` [CFT] " Al Viro
2013-03-22 4:55 ` Linus Torvalds
2013-03-22 5:18 ` Al Viro
2013-03-22 5:33 ` Linus Torvalds
2013-03-22 6:09 ` Al Viro
2013-03-22 6:22 ` Al Viro
2013-03-22 16:23 ` Dave Jones
2013-03-22 19:43 ` Linus Torvalds
2013-03-22 21:28 ` Al Viro
2013-03-22 22:57 ` Eric W. Biederman
2013-03-22 5:19 ` Linus Torvalds
2013-03-22 0:08 ` Al Viro [this message]
2013-03-22 0:15 ` Linus Torvalds
2013-03-22 0:19 ` Linus Torvalds
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