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 0C65935E958 for ; Wed, 13 May 2026 19:22:32 +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=1778700152; cv=none; b=pokXEMScxZ7j7RFl/Qkz8iQ08bT2Q+I60E4AIm0RuwewLIZ9Vtdu/d3REY467AZkVhS/1Se4B0auHwLHeGXI7QEEOJsnL8jU956lT3koTDzGHnusdvcqn2B2XTPfBOmzfI6fW5rsbnJUM+aqA4pVKDnat/vHig43S/So6Mt+xks= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778700152; c=relaxed/simple; bh=cXHW8eqSlL7DHvFso++pQlmhplPS/WCiJJt0tunDVaI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=iMM7qpndOhEiivgZ2BcOCUEavXUuiQEFBeUQHgA9HqgToarh8UmkVZLuSsOSa5kCjaamq3SBKpLGTDWxozUazry+xfB9niNPGPoESB4N54FDjjW0OJQIVBUlh5UVAVE7kU7C7sPvUCoybsSrWrtB22uBzArxd7UPAa3+P9aSo1Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XFCNx0MF; 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="XFCNx0MF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 59916C19425; Wed, 13 May 2026 19:22:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778700151; bh=cXHW8eqSlL7DHvFso++pQlmhplPS/WCiJJt0tunDVaI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=XFCNx0MFR5T1kDNQNCTASzlAFjObYoTL3/FggOUxkPM+DjizN74/fuWYF0Lk9XiNO tbJnCbPOaPy2XVO+HFKHBsjY6cJDjMhgDAxxajaDp0EztqtFYJyEnJICtCrgXSDk1E 676jSA13+QUUAPQvtYkAEly7AOiEWKl7QVVqi/+tfochkHsRqSKsQrc4VMD/GWAbSZ lE5mUWRL2fFq040hM4VNyPNGeuzQVLfpky7oTBSA/3CH0zeM8th6uFM6Ws2fBMtEjx 37zW9akVL16PRBXlhx/OtDCINeqY4RtJVQ+rqO0w2i6rfUQZfmWjUbxYuAjan2WXQg SpOdaqSdWTMYw== Message-ID: <0c95ad89-bd18-45d5-a65b-b15fe5d12242@kernel.org> Date: Wed, 13 May 2026 21:22:20 +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> <993c88a1-1644-44e1-94c6-09bac9f02978@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 5/13/26 19:21, Usama Arif wrote: > > > On 13/05/2026 14:32, David Hildenbrand (Arm) wrote: >> 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? >> > > Thanks for the review! Planning on doing more ... > > Ah so basically rename the function to mm_prepare_for_swap(). I felt like it > makes the function sound more important than it is? But it is a better > name than ensure_on_mmlist(). Maybe mm_prepare_for_swapoff()? As the mmlist > is only used for swapoff. Maybe the clearest thing is mm_prepare_for_swap_entries(), because that's what we're about to establish in these code paths: swap entries. I wouldn't mention swapoff, but both are better than ensure_on_mmlist ;) -- Cheers, David