linux-kernel - Re: [BUG] uprobe: failed to work on 9pfs

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Message-ID: <20150306085017.GW21418@twins.programming.kicks-ass.net>
Date:	Fri, 6 Mar 2015 09:50:17 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	He Kuang <hekuang@...wei.com>
Cc:	paulus@...ba.org, mingo@...hat.com, acme@...nel.org,
	ericvh@...il.com, rminnich@...dia.gov, lucho@...kov.net,
	wangnan0@...wei.com, linux-kernel@...r.kernel.org
Subject: Re: [BUG] uprobe: failed to work on 9pfs

On Fri, Mar 06, 2015 at 01:18:47PM +0800, He Kuang wrote:
> Uprobe uses inode address to index all registered uprobes in a
> rb_tree, this works well in most filesystems but failed on 9pfs.
> 
> 9pfs allocate more than one vfs inode to the same file, the inode
> address when we create uprobe is not same as the inode address we
> run later. As a result, neither perf record nor events/uprobe can
> capture the predefined uprobe events.

How does 9pfs work with the vfs/mm in this regard? The file cache very
much assumes the same thing uprobes does.

File caching is per inode, so if you have multiple inodes on the same
file you get multiple copies of your data with all sorts of braindamaged
corruption as a result.

I would very much chalk this up to 9pfs being insane.
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