From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 6461C44236B for ; Mon, 14 Sep 2026 13:20:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789392040; cv=none; b=oi5pEQHE95JmQQN+ChHrA6YLzL/h2MEEnBJPH+xaqnwHUbs3SsEfzaxrXCZ9LdHK8PT4MoSpdrkG0qBHvNrztrxUbZLRfo6r+0qVFVyy6BVU64DzfBqNlJD8Dy6OkJ4fVBz8GDGKGPr7M5tT8HPaz9mSTtI+xDNNTmEesRPIf3k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789392040; c=relaxed/simple; bh=3yaLPciVpIAZ+xMa44FL+/yZ2JI2YsunC2HNCYWVP2w=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=S9FprRUlBk3vqDha49dwxlrnRrgAOReOmg9iMz5YRglhC3r+yaV0tViCh9CQTjtz1wGM/XIN+311cx7y6Oy6VBKWRuafZa5uFsOBMOZKPQYNP9jxHXTPdNSDrxFmPqydhX3TW3IzH+2jZxi6qj6UdYUZAyhfNBZk2t9pB6ublkk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=LBKIsaKR; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="LBKIsaKR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 064621F000FF; Mon, 14 Sep 2026 13:20:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789392039; bh=orxAc0wt0M8waCKEvwFhCIWDtrkkET2gxeAVkxTu4Mg=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=LBKIsaKRTY4xRWlzST/Dz3nKFY7/pWk1362hguSNZVpr34d74xi8W8V2QfMY13Unn iXkAIfAewo6fKchK/hcEGyugaOTQ1HeKpWaNlvsAy0FhQCRkh9blWWBf/TTwonGdYG Sv28VrMD8LcYWGuwtScOEnxptMEx7DHd37JRHsLVZBxtl60SWn4saOHXm45/AzjABX pPjzhlixZEeWGbpW8suidfcDBmomzvVgeDlBGS9sNYooAl+LFWGRRlPMHnDiW+6yAO rPaUlgBn5Uo+UaRV8B5ouV0mCdJC7oLxgLwdxovGP4P0tDdyqvNZVKL6p5rQoGUHmM /yXu5yV1eGEfQ== Message-ID: <37784fda-a91d-4b70-864a-67b62aed1828@kernel.org> Date: Mon, 14 Sep 2026 15:20:34 +0200 Precedence: bulk X-Mailing-List: linux-raid@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/3] md: Use folio_alloc_buffers() To: Matthew Wilcox Cc: Zi Yan , linux-raid@vger.kernel.org, linux-mm@kvack.org References: <20260913-remove-pg_private-v4-0-848550f7574e@nvidia.com> <20260914041830.2072626-1-willy@infradead.org> <7efaff54-3f19-4c0c-a8c9-fcbacb1aa4e2@kernel.org> 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 9/14/26 15:17, Matthew Wilcox wrote: > On Mon, Sep 14, 2026 at 03:12:31PM +0200, David Hildenbrand (Arm) wrote: >> On 9/14/26 06:18, Matthew Wilcox (Oracle) wrote: >>> Remove the last user of alloc_page_buffers(). This isn't _great_, >> >> You should tell us "why" this isn't great. >> >> Because we're allocating folios although these things are not actually folios? I >> can only speculate :) > > Well, we actually aren't allocating folios in md-bitmap: > > for ( ; pnum < num_pages; pnum++) { > store->filemap[pnum] = alloc_page(GFP_KERNEL|__GFP_ZERO); > > and it's not clear to me that we should be allocating folios; they're > internal memory to the md-bitmap code that are never mapped to userspace, > nor enter the page cache. But they do have buffer heads attached to them. Confusing indeed. > > The md-bitmap code probably needs to be rewritten to not use buffer heads > at all, but then I hear from some people that it's scheduled for deletion, > so don't spend any time on it. But I can't find anything official about > that anywhere. > >> Code itself looks good. > > Thanks! I'd assume Zi will pick up your patches and can massage the patch description to summarize why folios are awkward here, but that cleaning this up is future work. -- Cheers, David