Messages in this thread | | | Date | Fri, 22 Mar 2013 00:08:03 +0000 | From | Al Viro <> | Subject | Re: VFS deadlock ? |
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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...
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