From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2CF201090255 for ; Thu, 19 Mar 2026 16:56:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1C27B6B055D; Thu, 19 Mar 2026 12:56:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 19A1F6B055E; Thu, 19 Mar 2026 12:56:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0D7916B055F; Thu, 19 Mar 2026 12:56:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id EF8C36B055D for ; Thu, 19 Mar 2026 12:56:22 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 74A24BA8F6 for ; Thu, 19 Mar 2026 16:56:22 +0000 (UTC) X-FDA: 84563415804.05.A03C0ED Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf20.hostedemail.com (Postfix) with ESMTP id CC89B1C0002 for ; Thu, 19 Mar 2026 16:56:20 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=vQdBaC0Q; spf=none (imf20.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=pass (policy=none) header.from=infradead.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1773939380; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=rCeA8gaapekYBXGTYyy6inc745Q+Z1LM+wKjknp8DGE=; b=Atim+lhBRFAR8yE0zfXupEoXlg7sdJwf5Ep5Ig6JFBNkaJQqXR/X3fMLCGOfM2Jz3VfBqb koKfYk7Xhc3Rm4tqSzuPvRCLnMW8xHvFfb8OKhZz0Mm5oo6Jl4U0ejMQ/ACAhK7safAx4T g7sAONudUSoGSGLvJK5n1KbmVidqHyg= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=vQdBaC0Q; spf=none (imf20.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=pass (policy=none) header.from=infradead.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1773939380; a=rsa-sha256; cv=none; b=2yqxLXBer24PGnJfw0MA+UUPfyS9Y9cYYmwf/FOkFpS2KHYxXhDmD0W68oMpyPRQEeavEC DRN56ooGrZ54gHZN+qDuNsICtzWiWNXBhU2IJ7l8puaQ734sMy5bQAhIunvyrcSm6mB6t+ QRHCP4bQBXCwEnp8dHevHfJBvL92MR8= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=rCeA8gaapekYBXGTYyy6inc745Q+Z1LM+wKjknp8DGE=; b=vQdBaC0QVupOLntmdIDaZrn0Xg 121fyQDxZ+Dio6hLHiv7v9o+AE8SMLj30MEUKRC6o3LdExnLhUrL8RKRW2YRllz5pXo86pKjobU5q rjKmS51loCTwT24MKISGl1Ng/eisEvfF5XTDBCMozkrHN91kAO2dvlfOi07rsG8tCeimlHIN7aTWY jjEq4HW+DuyOs7HXJTeEexZq44JURy3AXG2knfOdokqjmSBETN5nA8AMNnaI3NZcwFGIB6o32rngC IoFGb6NwQ1M/G2ZnMXPPSEiXHPnE/4ZWguUPBcWk59L3J/E+h9lBWCIoh9qrdJ4rGnrpFbfB7XtGs 53mzPz8g==; Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1w3GfL-00000006Osb-1cvh; Thu, 19 Mar 2026 16:56:11 +0000 Date: Thu, 19 Mar 2026 16:56:11 +0000 From: Matthew Wilcox To: Brendan Jackman Cc: Andrew Morton , Michal Hocko , David Rientjes , Shakeel Butt , Vlastimil Babka , Suren Baghdasaryan , Johannes Weiner , Zi Yan , Harry Yoo , Hao Li , Christoph Lameter , Roman Gushchin , Uladzislau Rezki , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 0/5] mm: Switch gfp_t to unsigned long Message-ID: References: <20260319-gfp64-v1-0-2c73b8d42b7f@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260319-gfp64-v1-0-2c73b8d42b7f@google.com> X-Rspamd-Queue-Id: CC89B1C0002 X-Rspamd-Server: rspam07 X-Stat-Signature: wkz58ns8subsfihj1gkpz3jcry7tp8y1 X-Rspam-User: X-HE-Tag: 1773939380-941184 X-HE-Meta: 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 QrKkmUKp E5utfQLb8tlVNiJD66zyoQr565ojMX2KFt4516h2joBO5DCjaB3Cas6lNWmbjcTjfKsR4ZOcLXODUCOnPS3Egq46/z7sPvPs6MgI6qmZiUWJH3DkfrqYAGbGF/Fgdv2nq2+6HXUhB5KodIVO1Et9Ysp1kyg9df3ofveVEpflAejzdeKdQtqE6oBaCURh+slQas7uarYcbk8TFqm6vXzEicL7EbPbZVAEKFJfIl9T+I0rDsNajV5brcj7DU+bppegtqsqnacawmnOl2BUiT4suhBqjxKIYagcm0Dw4FrBsgQNlx4o= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Mar 19, 2026 at 04:03:23PM +0000, Brendan Jackman wrote: > As pointed out by Vlastimil in [0], my proposal for __GFP_UNMAPPED is > probably not needed for 32-bit. This offers a way out of the GFP flag > scarcity so in preparation for this, flip gfp_t to be 64-bit on 64-bit > machines, while leaving it 32-bit on 32-bit machines. Ugh. This grows struct xarray: struct xarray { spinlock_t xa_lock; /* private: The rest of the data structure is not to be used directly. */ gfp_t xa_flags; void __rcu * xa_head; }; which grows a lot of key data structures. It would probably have been good for you to have run pahole before/after this change and diff the results. Now, you're probably saying "But this makes no damn sense, why on earth is xa_flags of type gfp_t?" And the short answer is "because the radix tree has a ridiculous API". But you'll learn all about it with your new patch in this series which converts xa_flags from being gfp_t to a plain unsigned int ;-)