From: Linus Torvalds <torvalds@transmeta.com>
To: Steve Lord <lord@sgi.com>
Cc: Marcelo Tosatti <marcelo@conectiva.com.br>,
lkml <linux-kernel@vger.kernel.org>
Subject: Re: Bounce buffer deadlock
Date: Sat, 30 Jun 2001 10:39:59 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.33.0106301032170.1470-100000@penguin.transmeta.com> (raw)
In-Reply-To: <200106301734.f5UHYML03030@jen.americas.sgi.com>
On Sat, 30 Jun 2001, Steve Lord wrote:
>
> It looks to me as if all memory allocations of type GFP_BUFFER which happen
> in generic_make_request downwards can hit the same type of deadlock, so
> bounce buffers, the request functions of the raid and lvm paths can all
> end up in try_to_free_buffers on a buffer they themselves hold the lock on.
.. which is why GFP_BUFFER doesn't exist any more in the most recent
pre-kernels (oops, this is pre8 only, not pre7 like I said in the previous
email)
The problem is that GFP_BUFFER used to mean two things: "don't call
low-level filesystem" and "don't do IO". Some of the pre-kernels starting
to make it mean "don't call low-level FS" only. The later ones split up
the semantics, so that the cases which care about FS deadlocks use
"GFP_NOFS", and the cases that care about IO recursion use "GFP_NOIO", so
that we don't overload the meaning of GFP_BUFFER.
That allows us to do the best we can - still flushing out dirty buffers
when that's ok (like when a filesystem wants more memory), and giving the
allocator better control over exactly _what_ he objects to.
Linus
next prev parent reply other threads:[~2001-06-30 17:42 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-06-29 20:33 Bounce buffer deadlock Steve Lord
2001-06-29 20:42 ` Alan Cox
2001-06-30 15:30 ` Marcelo Tosatti
2001-06-30 15:46 ` Marcelo Tosatti
2001-06-30 17:32 ` Linus Torvalds
2001-06-30 17:34 ` Steve Lord
2001-06-30 16:07 ` Marcelo Tosatti
2001-06-30 18:07 ` Steve Lord
2001-06-30 18:29 ` Marcelo Tosatti
2001-06-30 17:39 ` Linus Torvalds [this message]
2001-06-30 17:48 ` Steve Lord
2001-06-30 17:50 ` Linus Torvalds
2001-06-30 18:23 ` Steve Lord
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