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X-CSE-ConnectionGUID: s2096rSVRc+QY9jMXt4Qvw== X-CSE-MsgGUID: ArfXyWC/S5SQcUMbK9a75g== X-IronPort-AV: E=McAfee;i="6800,10657,11886"; a="105528265" X-IronPort-AV: E=Sophos;i="6.25,243,1779174000"; d="scan'208";a="105528265" Received: from fmviesa007.fm.intel.com ([10.60.135.147]) by orvoesa102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2026 09:29:05 -0700 X-CSE-ConnectionGUID: mgNl+wbvT/KI+p85qn1Kbw== X-CSE-MsgGUID: DSYkTyNNRuScATp1o+CtlQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,243,1779174000"; d="scan'208";a="264069086" Received: from aschende-mobl.amr.corp.intel.com (HELO [10.125.109.12]) ([10.125.109.12]) by fmviesa007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2026 09:29:04 -0700 Message-ID: <3663d64f-7376-4bd1-b8ab-401825579d42@intel.com> Date: Tue, 25 Aug 2026 09:29:04 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 1/3] mm: make persistent huge zero folio read-only To: Xueyuan Chen , akpm@linux-foundation.org Cc: david@kernel.org, ljs@kernel.org, usama.arif@linux.dev, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, rppt@kernel.org, ryan.roberts@arm.com, ziy@nvidia.com, baohua@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Lance Yang References: <20260730090647.2401252-1-xueyuan.chen21@gmail.com> <20260730090647.2401252-2-xueyuan.chen21@gmail.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 8FD34140009 X-Stat-Signature: 8w3fcs1ipeann1xugqeddjad51i1bdpp X-HE-Tag: 1787675346-814653 X-HE-Meta: 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 hG4tNXPX 3+DqsL8QRqSCuG/T7j+jj/I0tnir8jgUVBjLnFAHDJW1PGVGHLOhnLWL9Jfy06rd4zCgtQQSToTmM0Q1SEzVBHNBiKX2uS10Zv5LXKmetT6B7Mh4DazBuucZP2qLL+Xyg/EQypAyBJ/2SZk619IAiafR8NF0qYnH1m6c501YhpzHEV5WH10UVUfxAwkKn5tFUaWN9ZSjZkbGQXSusn+Sz5oLJcPbxW52xPtseM6pezTO/AUCXWnKPR0+4lBppi0xHS334DFtV/ATzzKcMfYdPP3nkGg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/30/26 02:06, Xueyuan Chen wrote: > + * Return: 0 on success or when direct-map permission changes are unsupported, > + * or a negative errno on failure. > + */ > +static inline int set_direct_map_ro_noflush(const void *addr, > + unsigned long nr_pages) > +{ > + return 0; > +} I think this is probably not the best API. First, it isn't consistent with the other set_direct_map*() functions. Second, it's unusable for things that matter. This would be a buggy function: int this_must_succeed_for_security(unsigned long addr) { return set_direct_map_ro_noflush(addr, 1); } ... despite looking just fine. The best thing, IMNHO, is to return an actual error when the stub gets used and have the callers deal with it (or not deal with it if they don't care).