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 BCA13246788 for ; Wed, 13 May 2026 13:32:47 +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=1778679167; cv=none; b=WQVZi+nqGuF2LS/JJxr9Oh57yWNn+uTh6z3D8RFNQBBkorKt/d2ljwpOF7wtSGjq+1kyZtaT9H9yZmd1udnY2xXzLjoNgG9x+R9P+zmac+W1GA3jbLjcTivwP/U1iBtUp3cMb2JrKBg5tNeRL/V9ltmbBxLE63PKb2guubuLDs0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778679167; c=relaxed/simple; bh=1LPOlNdTHQ29EdBrQwlh6+e8buQWy/XaIzEsZF4XOHA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Xg9sn+UswRL+9kNpyIblZTR2QBDkscCThU+BGDe5lh8x+QN/dDmsd5ejI+wwDj8UdlYujVi08dl+f6pXRGpx2b78pZO1W39p+SOH9+7MKaXqX3IB4ocG9byJDflOsqYLA+Yqd8PEjRGGhgpImeBE8HrKvUzmWImdbCbRV2qb53w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=epglIZV0; 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="epglIZV0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5D70CC2BCB7; Wed, 13 May 2026 13:32:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778679167; bh=1LPOlNdTHQ29EdBrQwlh6+e8buQWy/XaIzEsZF4XOHA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=epglIZV0uoZaT80vFVWdtHmZqXPnsjY6/muJ+HR0W/VouAvP503PuJ4yZv277w9IC rHBJBu3qRE0fF+qOCIqRouqZtRSKo3ZI+slljQj0Nn63tFjesROdSmZo69e9Hc9rqx tLv3o3e0kOq+PAMYU9c+QbBqyNSBTg10rmEl1mxtbEJGskPeM8Mx81oZxI5Xc5WiXY I9fyurSd7Wke8lEK4Kae6VQsUyfAbVbR9obHw9P4wFxNLncaJeK6/VPk0U5BoJDYM1 Nix4l1AGOiB+afN2oOImTA/4/hqGbYU/2nDnWhes2UaEeo5ZGLcHS0GmFLtKL5ZRKd iHEzdmXBcFGpg== Message-ID: <993c88a1-1644-44e1-94c6-09bac9f02978@kernel.org> Date: Wed, 13 May 2026 15:32:39 +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 02/13] mm: extract ensure_on_mmlist() helper To: Usama Arif , Andrew Morton , chrisl@kernel.org, kasong@tencent.com, ljs@kernel.org, ziy@nvidia.com Cc: bhe@redhat.com, willy@infradead.org, youngjun.park@lge.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr, kas@kernel.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, npache@redhat.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, kernel-team@meta.com References: <20260427100553.2754667-1-usama.arif@linux.dev> <20260427100553.2754667-3-usama.arif@linux.dev> 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 4/27/26 12:01, Usama Arif wrote: > When a swap entry is installed in a page table, the mm must be added > to init_mm.mmlist so that swapoff can find and unuse its swap entries. > This double-checked locking pattern is currently open-coded in > try_to_unmap_one() and copy_nonpresent_pte(). > > Move it into ensure_on_mmlist() in mm/internal.h and convert both > callers so it can be reused by upcoming PMD-level swap entry code > paths that also need to register the mm with swapoff. > > copy_nonpresent_pte() previously inserted into &src_mm->mmlist rather > than &init_mm.mmlist, but the insertion point is irrelevant, mmlist > is a circular list and swapoff walks it entirely from init_mm.mmlist, > so only membership matters, not position. > > Signed-off-by: Usama Arif > --- > mm/internal.h | 13 +++++++++++++ > mm/memory.c | 9 +-------- > mm/rmap.c | 7 +------ > 3 files changed, 15 insertions(+), 14 deletions(-) > > diff --git a/mm/internal.h b/mm/internal.h > index 5a2ddcf68e0b..7de489689f54 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -1952,4 +1952,17 @@ static inline int get_sysctl_max_map_count(void) > bool may_expand_vm(struct mm_struct *mm, const vma_flags_t *vma_flags, > unsigned long npages); > > +/* > + * Ensure @mm is on the init_mm.mmlist so swapoff can find it. > + */ > +static inline void ensure_on_mmlist(struct mm_struct *mm) > +{ > + if (list_empty(&mm->mmlist)) { > + spin_lock(&mmlist_lock); > + if (list_empty(&mm->mmlist)) > + list_add(&mm->mmlist, &init_mm.mmlist); > + spin_unlock(&mmlist_lock); > + } > +} Instead of talking about the low level detail ("add to mmlist"), maybe we could just talk about the high-level goal: make sure that the MM can hold swap entries. mm_prepare_for_swap() or sth like that? -- Cheers, David