linux-kernel - Re: [RFC][PATCH] kmap_atomic

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Message-Id: <1255019362.26976.311.camel@twins>
Date:	Thu, 08 Oct 2009 18:29:22 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Avi Kivity <avi@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"hugh.dickins" <hugh.dickins@...cali.co.uk>,
	David Howells <dhowells@...hat.com>,
	lkml <linux-kernel@...r.kernel.org>,
	linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [RFC][PATCH] kmap_atomic_push

On Thu, 2009-10-08 at 17:53 +0200, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > The below patchlet changes the kmap_atomic interface to a stack based 
> > one that doesn't require the KM_types anymore.
> > 
> > This significantly simplifies some code (more still than are present 
> > in this patch -- ie. pte_map_nested can go now)
> > 
> > This obviously requires that push and pop are matched, I fixed a few 
> > cases that were not properly nested, the (x86) code checks for this 
> > and will go BUG when trying to pop a vaddr that isn't the top one so 
> > abusers should be rather visible.
> 
> Looks great IMO! Last i proposed this i think either Andrew or Avi had 
> second thoughts about the hard-to-calculate worst-case mapping limit - 
> but i dont think that's a big issue.

That would've been me ;-)

> Lets not change the API names though - the rule is that map/unmap must 
> be properly nested.

Right, so I did that full rename just so that people wouldn't get
confused or something, but if both you and Linus think it should remain:
kmap_atomic() and kunmap_atomic(), I can certainly undo that part.


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