linux-kernel - Re: [PATCH 3/5] mm: export zap_page_range_single and list_lru

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Message-ID: <2f908340-a983-42c7-bb59-2d6f3a80c834@kernel.org>
Date: Thu, 5 Feb 2026 12:12:23 +0100
From: "David Hildenbrand (arm)" <david@...nel.org>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Carlos Llamas <cmllamas@...gle.com>, Alexander Viro
 <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>,
 Jan Kara <jack@...e.cz>, Paul Moore <paul@...l-moore.com>,
 James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Dave Chinner
 <david@...morbit.com>, Qi Zheng <zhengqi.arch@...edance.com>,
 Roman Gushchin <roman.gushchin@...ux.dev>,
 Muchun Song <muchun.song@...ux.dev>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka
 <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
 Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
 Miguel Ojeda <ojeda@...nel.org>, Boqun Feng <boqun.feng@...il.com>,
 Gary Guo <gary@...yguo.net>, Björn Roy Baron
 <bjorn3_gh@...tonmail.com>, Benno Lossin <lossin@...nel.org>,
 Andreas Hindborg <a.hindborg@...nel.org>, Trevor Gross <tmgross@...ch.edu>,
 Danilo Krummrich <dakr@...nel.org>, kernel-team@...roid.com,
 linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-security-module@...r.kernel.org, linux-mm@...ck.org,
 rust-for-linux@...r.kernel.org
Subject: Re: [PATCH 3/5] mm: export zap_page_range_single and list_lru_add/del

On 2/5/26 12:04, Alice Ryhl wrote:
> On Thu, Feb 05, 2026 at 11:59:47AM +0100, David Hildenbrand (arm) wrote:
>> On 2/5/26 11:51, Alice Ryhl wrote:
>>> These are the functions needed by Binder's shrinker.
>>>
>>> Binder uses zap_page_range_single in the shrinker path to remove an
>>> unused page from the mmap'd region. Note that pages are only removed
>>> from the mmap'd region lazily when shrinker asks for it.
>>>
>>> Binder uses list_lru_add/del to keep track of the shrinker lru list, and
>>> it can't use _obj because the list head is not stored inline in the page
>>> actually being lru freed, so page_to_nid(virt_to_page(item)) on the list
>>> head computes the nid of the wrong page.
>>>
>>> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
>>> ---
>>>    mm/list_lru.c | 2 ++
>>>    mm/memory.c   | 1 +
>>>    2 files changed, 3 insertions(+)
>>>
>>> diff --git a/mm/list_lru.c b/mm/list_lru.c
>>> index ec48b5dadf519a5296ac14cda035c067f9e448f8..bf95d73c9815548a19db6345f856cee9baad22e3 100644
>>> --- a/mm/list_lru.c
>>> +++ b/mm/list_lru.c
>>> @@ -179,6 +179,7 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item, int nid,
>>>    	unlock_list_lru(l, false);
>>>    	return false;
>>>    }
>>> +EXPORT_SYMBOL_GPL(list_lru_add);
>>>    bool list_lru_add_obj(struct list_lru *lru, struct list_head *item)
>>>    {
>>> @@ -216,6 +217,7 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item, int nid,
>>>    	unlock_list_lru(l, false);
>>>    	return false;
>>>    }
>>> +EXPORT_SYMBOL_GPL(list_lru_del);
>>>    bool list_lru_del_obj(struct list_lru *lru, struct list_head *item)
>>>    {
>>> diff --git a/mm/memory.c b/mm/memory.c
>>> index da360a6eb8a48e29293430d0c577fb4b6ec58099..64083ace239a2caf58e1645dd5d91a41d61492c4 100644
>>> --- a/mm/memory.c
>>> +++ b/mm/memory.c
>>> @@ -2168,6 +2168,7 @@ void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
>>>    	zap_page_range_single_batched(&tlb, vma, address, size, details);
>>>    	tlb_finish_mmu(&tlb);
>>>    }
>>> +EXPORT_SYMBOL(zap_page_range_single);
>>
>> Why not EXPORT_SYMBOL_GPL?
> 
> I just tried to match other symbols in the same file.

We were probably a bit too sloppy with some of these in the past. But:

davhil01@...2025:~/git/linux$ grep -c "EXPORT_SYMBOL(" mm/memory.c
12
davhil01@...2025:~/git/linux$ grep -c "EXPORT_SYMBOL_GPL(" mm/memory.c
10

So just go with EXPORT_SYMBOL_GPL unless there is a good reason why not.

-- 
Cheers,

David