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Date:   Sun, 17 Sep 2023 08:06:51 -0700
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Subject: Re: /proc/*/maps broken on nommu
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To:     Max Filippov <jcmvbkbc@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux Memory Management List <linux-mm@kvack.org>
Cc:     Matthew Wilcox <willy@infradead.org>, Yu Zhao <yuzhao@google.com>,
        "Liam R. Howlett" <Liam.Howlett@oracle.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Andrew Morton <akpm@linux-foundation.org>
References: <CAMo8BfLb6U9xtMtt1t9vQX_nKek7kEt+Rvv5NwpvTHu0kdiXcg@mail.gmail.com>
From:   Randy Dunlap <rdunlap@infradead.org>
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On 9/17/23 04:38, Max Filippov wrote:
> Hello,
> 
> As of v6.5 cat /proc/*/maps produces empty output on nommu xtensa systems.
> Bisection points to the commit 0c563f148043 ("proc: remove VMA rbtree
> use from nommu").
> It looks like the issue may be not in the m_start (where find_vma(mm,
> addr) returns
> NULL), but in the nommu version of find_vma itself. I've tried replacing nommu
> find_vma implementation with an implementation of the MMU version and it
> fixes the /proc/*/maps output. Kind of (it works as expected on one of
> my systems,
> but consistently locks up on the other).
> 
> Any suggestions of what might be wrong/how to fix it properly?
> 

Hi Max,

There is already a proposed patch and some discussion:

https://lore.kernel.org/lkml/20230915160055.971059-2-ben.wolsieffer@hefring.com/

-- 
~Randy