linux-kernel - Re: [GIT PULL] uprobes: tmpfs support

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Message-ID: <20140602192344.GA30792@redhat.com>
Date:	Mon, 2 Jun 2014 21:23:44 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Denys Vlasenko <dvlasenk@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] uprobes: tmpfs support

On 06/02, Christoph Hellwig wrote:
>
> On Mon, Jun 02, 2014 at 04:14:06PM +0200, Oleg Nesterov wrote:
> > Ingo, please pull from
> >
> >   git://git.kernel.org/pub/scm/linux/kernel/git/oleg/misc uprobes/core
> >
> > Based on tip:perf/uprobes
>
> Eww, adding tmpfs-specific code to uprobes screams layering violation.
>
> Hugh, what is the problem with implementing ->readpage for tmpfs again?

I leave this to you and Hugh.

But I hope you are not arguing with this patch, it is very simple and we
do want to support tmpfs. If tmpfs has ->readpage again we can revert this
patch.

BTW. Is it safe to pass file == NULL to read_mapping_page() and ->readpage()?
Last time I tried to check this looked safe but this is not documented. We
need to call read_mapping_page() from uprobe_register() but it doesn't have
"struct file *" and thus we need to delay arch_uprobe_analyze_insn() until
we find the first mapping, too bad.

And why read_mapping_page() has "void *data" but not "struct file *file"...

Oleg.

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