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Message-ID: <6bbf6ca2-0c46-43b7-82d8-b990f01ae5dd@gmail.com>
Date: Wed, 13 Aug 2025 12:18:56 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: Byungchul Park <byungchul@...com>, akpm@...ux-foundation.org,
kuba@...nel.org
Cc: linux-kernel@...r.kernel.org, kernel_team@...ynix.com,
harry.yoo@...cle.com, ast@...nel.org, daniel@...earbox.net,
davem@...emloft.net, hawk@...nel.org, john.fastabend@...il.com,
sdf@...ichev.me, saeedm@...dia.com, leon@...nel.org, tariqt@...dia.com,
mbloch@...dia.com, andrew+netdev@...n.ch, edumazet@...gle.com,
pabeni@...hat.com, david@...hat.com, lorenzo.stoakes@...cle.com,
Liam.Howlett@...cle.com, vbabka@...e.cz, rppt@...nel.org, surenb@...gle.com,
mhocko@...e.com, horms@...nel.org, jackmanb@...gle.com, hannes@...xchg.org,
ziy@...dia.com, ilias.apalodimas@...aro.org, willy@...radead.org,
brauner@...nel.org, kas@...nel.org, yuzhao@...gle.com,
usamaarif642@...il.com, baolin.wang@...ux.alibaba.com,
almasrymina@...gle.com, toke@...hat.com, bpf@...r.kernel.org,
linux-rdma@...r.kernel.org, sfr@...b.auug.org.au, linux-mm@...ck.org,
netdev@...r.kernel.org
Subject: Re: [PATCH linux-next v3] mm, page_pool: introduce a new page type
for page pool in page type
On 8/13/25 07:09, Byungchul Park wrote:
> On Tue, Jul 29, 2025 at 08:02:10PM +0900, Byungchul Park wrote:
...>> For net_iov, use ->pp to identify if it's pp, with making sure that ->pp
>> is NULL for non-pp net_iov.
>>
>> This work was inspired by the following link:
>>
>> [1] https://lore.kernel.org/all/582f41c0-2742-4400-9c81-0d46bf4e8314@gmail.com/
>>
>> While at it, move the sanity check for page pool to on free.
>
> Hi, Andrew and Jakub
>
> I will spin the next one with some modified, once the following patch,
> [1], gets merged.
>
> [1] https://lore.kernel.org/all/a8643abedd208138d3d550db71631d5a2e4168d1.1754929026.git.asml.silence@gmail.com/
>
> This is about both mm and network. I have no idea which tree should I
> aim at between mm tree and network tree? I prefer the network tree tho.
>
> However, it's totally fine regardless of what it would be. Suggestion?
It should go to net, there will be enough of conflicts otherwise.
mm maintainers, do you like it as a shared branch or can it just
go through the net tree?
It'd also be better to split mm and net changes into a separate
patches. A patch I had before, it might need a rebase though.
From: Pavel Begunkov <asml.silence@...il.com>
Date: Thu, 17 Jul 2025 11:46:21 +0100
Subject: [PATCH] mm: introduce a page type for page pool
Page pool currently uses ->pp_magic aliased with lru.next to check
whether a page belongs to it. Add a new page type, a later patch will
convert page pool to use it.
Suggested-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
include/linux/mm.h | 20 --------------------
include/linux/page-flags.h | 6 ++++++
mm/page_alloc.c | 7 +++----
3 files changed, 9 insertions(+), 24 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0d4ee569aa6b..21db02e92b33 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4205,26 +4205,6 @@ int arch_lock_shadow_stack_status(struct task_struct *t, unsigned long status);
#define PP_DMA_INDEX_MASK GENMASK(PP_DMA_INDEX_BITS + PP_DMA_INDEX_SHIFT - 1, \
PP_DMA_INDEX_SHIFT)
-/* Mask used for checking in page_pool_page_is_pp() below. page->pp_magic is
- * OR'ed with PP_SIGNATURE after the allocation in order to preserve bit 0 for
- * the head page of compound page and bit 1 for pfmemalloc page, as well as the
- * bits used for the DMA index. page_is_pfmemalloc() is checked in
- * __page_pool_put_page() to avoid recycling the pfmemalloc page.
- */
-#define PP_MAGIC_MASK ~(PP_DMA_INDEX_MASK | 0x3UL)
-
-#ifdef CONFIG_PAGE_POOL
-static inline bool page_pool_page_is_pp(const struct page *page)
-{
- return (page->pp_magic & PP_MAGIC_MASK) == PP_SIGNATURE;
-}
-#else
-static inline bool page_pool_page_is_pp(const struct page *page)
-{
- return false;
-}
-#endif
-
#define PAGE_SNAPSHOT_FAITHFUL (1 << 0)
#define PAGE_SNAPSHOT_PG_BUDDY (1 << 1)
#define PAGE_SNAPSHOT_PG_IDLE (1 << 2)
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 8d3fa3a91ce4..0afdf2ee3fbd 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -933,6 +933,7 @@ enum pagetype {
PGTY_zsmalloc = 0xf6,
PGTY_unaccepted = 0xf7,
PGTY_large_kmalloc = 0xf8,
+ PGTY_net_pp = 0xf9,
PGTY_mapcount_underflow = 0xff
};
@@ -1077,6 +1078,11 @@ PAGE_TYPE_OPS(Zsmalloc, zsmalloc, zsmalloc)
PAGE_TYPE_OPS(Unaccepted, unaccepted, unaccepted)
FOLIO_TYPE_OPS(large_kmalloc, large_kmalloc)
+/*
+ * Marks pages allocated by page_pool. See (see net/core/page_pool.c)
+ */
+PAGE_TYPE_OPS(Net_pp, net_pp, net_pp)
+
/**
* PageHuge - Determine if the page belongs to hugetlbfs
* @page: The page to test.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d1d037f97c5f..67dfd6d8a124 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1042,7 +1042,6 @@ static inline bool page_expected_state(struct page *page,
#ifdef CONFIG_MEMCG
page->memcg_data |
#endif
- page_pool_page_is_pp(page) |
(page->flags & check_flags)))
return false;
@@ -1069,8 +1068,6 @@ static const char *page_bad_reason(struct page *page, unsigned long flags)
if (unlikely(page->memcg_data))
bad_reason = "page still charged to cgroup";
#endif
- if (unlikely(page_pool_page_is_pp(page)))
- bad_reason = "page_pool leak";
return bad_reason;
}
@@ -1379,9 +1376,11 @@ __always_inline bool free_pages_prepare(struct page *page,
mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1);
folio->mapping = NULL;
}
- if (unlikely(page_has_type(page)))
+ if (unlikely(page_has_type(page))) {
+ WARN_ON_ONCE(PageNet_pp(page));
/* Reset the page_type (which overlays _mapcount) */
page->page_type = UINT_MAX;
+ }
if (is_check_pages_enabled()) {
if (free_page_is_bad(page))
--
Pavel Begunkov
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