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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1719400015; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=BlsfLjsbtDjHybYcEtqAN8YR7uEs/0cedz6exUIwNfY=; b=XJ5Fw1uOqDSOW1NCILNrd7jUWdxaFs7FNGqjIynBY6GwN5N5cuVXvs63m/xAelh5Xjwrcm jN+ZquQE/lxZl/nNIm/wA/mA0SIxi1AL4ziO6EgrymGr3gwzbRig2PeObld59omsIeu+S0 jvIVi2+tHsrSGlehlckIjNrnIMgy/Ns= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5F8A3339; Wed, 26 Jun 2024 04:07:32 -0700 (PDT) Received: from [10.57.73.149] (unknown [10.57.73.149]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D93B53F766; Wed, 26 Jun 2024 04:07:05 -0700 (PDT) Message-ID: <1907a8c0-9860-4ca0-be59-bec0e772332b@arm.com> Date: Wed, 26 Jun 2024 12:07:04 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] kpageflags: fix wrong KPF_THP on non-pmd-mappable compound pages Content-Language: en-GB To: Zi Yan , ran xiaokai , akpm@linux-foundation.org, willy@infradead.org Cc: vbabka@suse.cz, svetly.todorov@memverge.com, ran.xiaokai@zte.com.cn, baohua@kernel.org, peterx@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org References: <20240626024924.1155558-1-ranxiaokai627@163.com> <20240626024924.1155558-3-ranxiaokai627@163.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 64D74100019 X-Stat-Signature: yyh99waycknbi569ifdjykb1qj73om6b X-Rspam-User: X-HE-Tag: 1719400028-698382 X-HE-Meta: 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 dG6ONK4C puq7pjBzkmTTPKeeXA5fGfwJutJyXik00p+bgKj+nKwausmRTbTXZ0Vvw7dtN2nAQ/rmtyJJot0YSkoHrweKoZhcfNzYTe/Tv+pkGnflbfi629L2LC7n1xbCRXiDSmWo8k7UH8solhVQY36ssE7jkpPn7hxUpBFEId38s3zw2YQKAoq636EgejfFXwg2lDagVvLYaGU/vYyQdWediVubpw4mye6TaXIZhEbLBQYsx2eladNnuOSlzDdv3tw== 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 26/06/2024 04:06, Zi Yan wrote: > On Tue Jun 25, 2024 at 10:49 PM EDT, ran xiaokai wrote: >> From: Ran Xiaokai >> >> KPF_COMPOUND_HEAD and KPF_COMPOUND_TAIL are set on "common" compound >> pages, which means of any order, but KPF_THP should only be set >> when the folio is a 2M pmd mappable THP. Why should KPF_THP only be set on 2M THP? What problem does it cause as it is currently configured? I would argue that mTHP is still THP so should still have the flag. And since these smaller mTHP sizes are disabled by default, only mTHP-aware user space will be enabling them, so I'll naively state that it should not cause compat issues as is. Also, the script at tools/mm/thpmaps relies on KPF_THP being set for all mTHP sizes to function correctly. So that would need to be reworked if making this change. Thanks, Ryan