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Mon, 10 Jun 2024 04:38:43 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id iLK2BFODZmYoGgAAD6G6ig (envelope-from ); Mon, 10 Jun 2024 04:38:43 +0000 Date: Mon, 10 Jun 2024 06:38:33 +0200 From: Oscar Salvador To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Jonathan Corbet Subject: Re: [PATCH v1 2/6] fs/proc/task_mmu: don't indicate PM_MMAP_EXCLUSIVE without PM_PRESENT Message-ID: References: <20240607122357.115423-1-david@redhat.com> <20240607122357.115423-3-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240607122357.115423-3-david@redhat.com> X-Rspamd-Action: no action X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 1E29AC000C X-Stat-Signature: tino75bt3p6g661i8tnk6m4oa93adz3e X-HE-Tag: 1717994325-121129 X-HE-Meta: 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 gdwSAW5I lWKkIwRsxUkz9o2Is2/kVouxOClX9mXkSq2ZkbkP0XO19bKRNE/o4i8/W+hE0j4lr0nyvzhXoUOe3oMq0EIOlWURDJ11W2MBiXwn3DNMrO0lRQYwFNLas6tK42FRvN57zPOv65giFN0HuXRgYESv78TgbLgG77ws7bhl0eTkp6xt9ktTaUy/feYJaTo5f+lNmYkEvpGt53sSM4PwAzV2CFmdE4lHQ/rh+HEwjAsZty8mddUivZ9UTvDlMZHXk+JZRCzZhjxcrAdgpeG+ofjwibK919A== 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: List-Subscribe: List-Unsubscribe: On Fri, Jun 07, 2024 at 02:23:53PM +0200, David Hildenbrand wrote: > Relying on the mapcount for non-present PTEs that reference pages > doesn't make any sense: they are not accounted in the mapcount, so > page_mapcount() == 1 won't return the result we actually want to know. > > While we don't check the mapcount for migration entries already, we > could end up checking it for swap, hwpoison, device exclusive, ... > entries, which we really shouldn't. > > There is one exception: device private entries, which we consider > fake-present (e.g., incremented the mapcount). But we won't care about > that for now for PM_MMAP_EXCLUSIVE, because indicating PM_SWAP for them > although they are fake-present already sounds suspiciously wrong. > > Let's never indicate PM_MMAP_EXCLUSIVE without PM_PRESENT. Alternatively we could use is_pfn_swap_entry? But the PM_PRESENT approach seems more correct. > Signed-off-by: David Hildenbrand Signed-off-by: Oscar Salvador -- Oscar Salvador SUSE Labs