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 F33493016F5 for ; Wed, 23 Sep 2026 06:32:39 +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=1790145162; cv=none; b=Gqj5Pa307WJNugw31GnsgrMSTtiW+HxMbmh1zPn7sGeJB8sKwLeQ0NPCrK8tPTH4V3484JUEmnl9mmFHat14r6ePP5goykwB5Ya9/9f0K6HXgonMpBJo+6jYoh6qMII+nRwy3oqR5WIcdVOScwmyKt3/NveW2vbeKonPLLLxxRU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790145162; c=relaxed/simple; bh=/5KdU9oqMfs3G4BpcnqGGCo77e13y0O9Cnm4hDnbnHs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=HkR8ZZyEbzs44/HPllpOAa+83jnSwZF7IqvwQrr+zynPiCvB3SWLoReCpm2J3VtnTbN8LZFv3TOoAS8/TRYLu6h03gQt6fR+uj+pNqHqrSOJGcc1zZTUwtvOyjDRNTfsW2Nv1KdqgtNXAGAF/DKWcvaIOnAu05GC6byafc96PMk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hXRHhmrB; 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="hXRHhmrB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 90E4A1F000FF; Wed, 23 Sep 2026 06:32:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790145157; bh=hUUD5AsSXzkphFJZvhrBYYbjoBXgpQvRiJn9WGnnTwc=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=hXRHhmrB9NhcEkiy7kvByZxgQdF2vfg2sXL63KJyiVDOAbH4giWC3rrE1BYeZx3P8 GlMqexvqR1BEnxX+bIlseBFGTRMIe8avCCI/W/HCZEHmRS403M3NHZup7vuVRAhUgx yxoCQJLQTVrxDmhTe5J9/i5t41chXhheoL4AJO/45XmGvDvFOOPQYIguBWMOgbYttC 2ZKj2ODVAjDOEoM3VdCfDZ6XfoXNCkjd+NalL3o1/A5G10ZWYUqS4JVQddQlZkKM6W TLZIQ7Tlh7ff/pR8nFPrWCKUQ69LPN2/R7Ai7w2iOuavHVf8r0TKz6k9uKpIQ6ZX4u BjFAQ7dvmSCVg== Message-ID: <80206444-d0c3-4dab-a5e3-a2909e58ea33@kernel.org> Date: Wed, 23 Sep 2026 08:32:29 +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] mm/page_alloc: let the bulk and folio allocators carry alloc_flags To: Gregory Price , Lance Yang Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, surenb@google.com, mhocko@suse.com, brendan.jackman@linux.dev, hannes@cmpxchg.org, ziy@nvidia.com, david@kernel.org, ljs@kernel.org, liam@infradead.org, rppt@kernel.org, baolin.wang@linux.alibaba.com, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, usama.arif@linux.dev, kas@kernel.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com References: <20260914155115.439742-1-gourry@gourry.net> <20260922130558.48402-1-lance.yang@linux.dev> From: "Vlastimil Babka (SUSE)" Content-Language: en-US Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/23/26 03:59, Gregory Price wrote: > On Tue, Sep 22, 2026 at 09:05:58PM +0800, Lance Yang wrote: >> >> On Mon, Sep 14, 2026 at 11:51:14AM -0400, Gregory Price wrote: >> >__alloc_pages_noprof() takes an explicit alloc_flags, but the bulk and >> >folio entry points do not, so callers cannot select allocator behaviour >> >(e.g. an alternate zonelist) through them. >> > >> >Thread alloc_flags through both, matching __alloc_pages_noprof(), and >> >keep the flag-carrying primitives mm-internal (page_alloc.h) so the >> >public gfp.h wrappers stay flag-free: >> > >> > - add __alloc_pages_bulk_noprof(gfp, ..., alloc_flags) in page_alloc.h >> > alloc_pages_bulk_noprof() becomes a wrapper passing ALLOC_DEFAULT >> > >> > - give __folio_alloc_noprof() an alloc_flags parameter and moves >> > __folio_alloc_node_noprof() moves into page_alloc.h >> > __folio_alloc_noprof() is no longer exported >> > >> >No functional change: every caller passes ALLOC_DEFAULT. >> >> Yeah, but what if a caller passes ALLOC_NOLOCK in the future? >> >> __alloc_pages_noprof() checks alloc_nolock_allowed() first, but >> __alloc_pages_bulk_noprof() can enter its fast path without that check. >> >> That fast path can reach _deferred_grow_zone() or pcp_spin_trylock(). >> Shouldn't we do the same check first? >> >> Or am I missing something? >> >> Cheers, Lance > > There is some concern around NOLOCK here yes, in fact sashiko picked > this issue up and I've been poking at it. It's possible to document it as unsupported, add a VM_WARN_ON_ONCE etc. It's not necessary for bulk alloc to support ALLOC_NOLOCK just because it takes flags. e.g. kmalloc_nolock() supports a subset of gfp flags as well. > I've actually been reworking this patch and pulled in changes from the > ALLOC_UNMAPPED series to address this all at once. I've been developing > a page allocator unit-testing harness to help validate some assumptions > before I post it. > > ~Gregory