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Mon, 10 Aug 2020 14:46:18 -0700 (PDT) Date: Mon, 10 Aug 2020 15:46:14 -0600 From: Yu Zhao To: Sonny Rao Cc: linux-mm@kvack.org, bhe@redhat.com, David Rientjes , Andrew Morton Subject: Re: ABI compatibility for /proc/zoneinfo Message-ID: <20200810214614.GA1679980@google.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: EBD541A4A0 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Aug 10, 2020 at 02:24:03PM -0700, Sonny Rao wrote: > We (Chrome OS) noticed recently one of our tests started failing on > upstream kernels while parsing /proc/zoneinfo > I think this patch is the cause: > > 26e7deadaae17 mm/vmstat.c: do not show lowmem reserve protection > information of empty zone > > Maybe our parser was being overly strict by looking for the protection > line, and it's not hard to fix but raised the question of whether there's > any ABI compatibility guarantees about these files? According to Documentation/admin-guide/sysctl/vm.rst, "Each zone has an array of protection pages". I'm not sure if this is the guarantee, but the doc should reflect the actual format.