linux-kernel - Re: [PATCH v2 1/3] mm: Trigger bug on if a section is not found in __section

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Date:   Mon, 1 Jul 2019 12:46:58 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Alastair D'Silva <alastair@...ilva.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Oscar Salvador <osalvador@...e.de>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Baoquan He <bhe@...hat.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 1/3] mm: Trigger bug on if a section is not found in
 __section_nr

On Fri 28-06-19 10:46:28, Alastair D'Silva wrote:
[...]
> Given that there is already a VM_BUG_ON in the code, how do you feel
> about broadening the scope from 'VM_BUG_ON(!root)' to 'VM_BUG_ON(!root
> || (root_nr == NR_SECTION_ROOTS))'?

As far as I understand the existing VM_BUG_ON will hit when the
mem_section tree gets corrupted. This is a different situation to an
incorrect section given so I wouldn't really mix those two. And I still
do not see much point to protect from unexpected input parameter as this
is internal function as already pointed out.

-- 
Michal Hocko
SUSE Labs