netdev - Re: [PATCH][RESEND][RFC] Fix 32-bit boot failure due inaccurate page_pool_page_is

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Message-ID: <1757869448@msgid.manchmal.in-ulm.de>
Date: Sun, 14 Sep 2025 19:06:12 +0200
From: Christoph Biedl <linux-kernel.bfrz@...chmal.in-ulm.de>
To: Helge Deller <deller@...nel.org>
Cc: David Hildenbrand <david@...hat.com>,
	Toke Høiland-Jørgensen <toke@...hat.com>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	Ilias Apalodimas <ilias.apalodimas@...aro.org>,
	"David S. Miller" <davem@...emloft.net>,
	Linux Memory Management List <linux-mm@...ck.org>,
	netdev@...r.kernel.org,
	Linux parisc List <linux-parisc@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH][RESEND][RFC] Fix 32-bit boot failure due inaccurate
 page_pool_page_is_pp()

Helge Deller wrote...

> Commit ee62ce7a1d90 ("page_pool: Track DMA-mapped pages and unmap them when
> destroying the pool") changed PP_MAGIC_MASK from 0xFFFFFFFC to 0xc000007c on
> 32-bit platforms.
> 
> The function page_pool_page_is_pp() uses PP_MAGIC_MASK to identify page pool
> pages, but the remaining bits are not sufficient to unambiguously identify
> such pages any longer.
> 
> So page_pool_page_is_pp() now sometimes wrongly reports pages as page pool
> pages and as such triggers a kernel BUG as it believes it found a page pool
> leak.
> 
> There are patches upcoming where page_pool_page_is_pp() will not depend on
> PP_MAGIC_MASK and instead use page flags to identify page pool pages. Until
> those patches are merged, the easiest temporary fix is to disable the check
> on 32-bit platforms.
> 
> Cc: Jesper Dangaard Brouer <hawk@...nel.org>
> Cc: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> Cc: David Hildenbrand <david@...hat.com>
> Acked-by: David Hildenbrand <david@...hat.com>
> Cc: Toke Høiland-Jørgensen <toke@...hat.com>
> Cc: Linux Memory Management List <linux-mm@...ck.org>
> Cc: netdev@...r.kernel.org
> Cc: Linux parisc List <linux-parisc@...r.kernel.org>
> Cc: <stable@...r.kernel.org> # v6.15+
> Signed-off-by: Helge Deller <deller@....de>
> Link: https://www.spinics.net/lists/kernel/msg5849623.html
> Fixes: ee62ce7a1d90 ("page_pool: Track DMA-mapped pages and unmap them when destroying the pool")

Tested-by: Christoph Biedl <linux-kernel.bfrz@...chmal.in-ulm.de>

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