Messages in this thread | | | Date | Thu, 21 Mar 2013 17:15:12 -0700 | Subject | Re: VFS deadlock ? | From | Linus Torvalds <> |
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On Thu, Mar 21, 2013 at 5:08 PM, Al Viro <viro@zeniv.linux.org.uk> wrote: > > 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...
Hmm. But again, that can't actually happen here. We're in /proc. You can't move the entries around. Also, we only changed the locking order for the "inode is identical" case where we take only *one* lock, we didn't change it for the cases where we take multiple locks (and order them topologically).
So I agree that we need to avoid aliased directories in the *general* case. I'm just arguing that for the specific case of /proc, we should be ok. No?
Linus
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