From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DD16E2FD1B3; Wed, 1 Apr 2026 14:38:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775054311; cv=none; b=iALtiRL6bzNfAn0Paqs1tMNV7qti73zoaQ8Jnuva0d5InqpD1I8f90EH4pro6wFky1eX6tV93FMPCLU/VY6ipAkHJvnWlSznd70J70MHxoBSRJ4kDRox5uQYD/bPVFRuOIEKoiRHDhKXdLp2rivuk5ztDeAtOC45r6iN7FsM0Eg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775054311; c=relaxed/simple; bh=IYpu66gqA4awdKDYhB4MiwLR+Zk0dYRc4YHZqrv0M9Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=T/LPcm5UfpzO6qJveupPBPHOsMNNbPbwaJmwF3aH4pSAyN8XohXjNaw+b85girH+M0CImyKKAlVkmryjR+zaC9QYyYWDuTUnc4fg6gfwtZHuYqbvHiVWIVKMCo1XenUFC+sXP/3HsvmLgDHaAvleGEOzWK8TJhdWOnRlin59PjU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=I1JeGroo; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="I1JeGroo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 784FBC2BCB0; Wed, 1 Apr 2026 14:38:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775054310; bh=IYpu66gqA4awdKDYhB4MiwLR+Zk0dYRc4YHZqrv0M9Y=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=I1JeGroo5hMIqTqxRa9QFMgft/zZ2PWbwIK+GJHof+NucF9RGKXu06QCYnxZ1izgD VbwCrk+dYOlxJQLJ7HhTThd5XmYRA9pg6KNyqX7+95qIhlwTJJ8M86rc2IxOuqjTMS KzKMutpZYR7A+bH/IliIGo1NS7jSKG/R+lOCJQA/gk64/YG7XBFSmThGeTBsoBBVJ/ 9rg3ENyOIFI7CMS5xIou2ziewdT8gGkHb1w7VE0BSiMN17MSCaOw4q4oskKNy5vw+o 0kAj6gGT8+ghznlOpAUxMyAe2wE7zZmz+lvg99mMqQSGEnsqW9sIhedMARplbaKD1i O8nkVwtBTCcUg== Message-ID: Date: Wed, 1 Apr 2026 16:38:21 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 05/10] mm/huge_memory: remove READ_ONLY_THP_FOR_FS from file_thp_enabled() To: Matthew Wilcox , WANG Rui Cc: ziy@nvidia.com, ljs@kernel.org, Liam.Howlett@oracle.com, akpm@linux-foundation.org, baohua@kernel.org, baolin.wang@linux.alibaba.com, brauner@kernel.org, clm@fb.com, dev.jain@arm.com, dsterba@suse.com, jack@suse.cz, lance.yang@linux.dev, linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, npache@redhat.com, rppt@kernel.org, ryan.roberts@arm.com, shuah@kernel.org, songliubraving@fb.com, surenb@google.com, vbabka@kernel.org, viro@zeniv.linux.org.uk References: <20260330160942.173324-1-r@hev.cc> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/30/26 18:19, Matthew Wilcox wrote: > On Tue, Mar 31, 2026 at 12:09:42AM +0800, WANG Rui wrote: >> Given the diversity of filesystems in use, each one requires dedicated >> engineering effort to implement and validate large folio support, and >> that assumes both sufficient resources and prioritization on the >> filesystem side. Even after support lands, coverage across different >> base page sizes and configurations may take additional time to mature. >> >> What I am really concerned about is the transition period: if filesystem >> support is not yet broadly ready, while we have already removed the >> fallback path, we may end up in a situation where PMD-sized mappings >> become effectively unavailable on many systems for some time. >> >> This is not about the long-term direction, but about the timing and >> practical readiness. > > If we leave this fallback in place, we'll never get filesystems to move > forward. It's time to rip off this bandaid; they've got eight months > before the next stable kernel. I guess if we don't force them to work on it I guess this will never happen. They shouldn't be holding our THP hacks we want to remove hostage. -- Cheers, David