The patch titled
Subject: mm: separate folio_split_memcg_refs() from split_page_memcg()
has been added to the -mm mm-unstable branch. Its filename is
mm-separate-folio_split_memcg_refs-from-split_page_memcg.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-separate-folio_split_memcg_refs-from-split_page_memcg.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: mm: separate folio_split_memcg_refs() from split_page_memcg()
Date: Fri, 14 Mar 2025 13:36:11 +0000
Patch series "Minor memcg cleanups & prep for memdescs", v2.
Separate the handling of accounted folios and GFP_ACCOUNT pages for easier
to understand code. For more detail, see
https://lore.kernel.org/linux-mm/Z9LwTOudOlCGny3f@xxxxxxxxxxxxxxxxxxxx/
This patch (of 5):
Folios always use memcg_data to refer to the mem_cgroup while pages
allocated with GFP_ACCOUNT have a pointer to the obj_cgroup. Since the
caller already knows what it has, split the function into two and then we
don't need to check.
Move the assignment of split folio memcg_data to the point where we set up
the other parts of the new folio. That leaves folio_split_memcg_refs()
just handling the memcg accounting.
Link: https://lkml.kernel.org/r/20250314133617.138071-1-willy@xxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20250314133617.138071-2-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Acked-by: Zi Yan <ziy@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Matthew Wilcow (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 7 +++++++
mm/huge_memory.c | 16 ++++------------
mm/memcontrol.c | 17 +++++++++++++----
3 files changed, 24 insertions(+), 16 deletions(-)
--- a/include/linux/memcontrol.h~mm-separate-folio_split_memcg_refs-from-split_page_memcg
+++ a/include/linux/memcontrol.h
@@ -1039,6 +1039,8 @@ static inline void memcg_memory_event_mm
}
void split_page_memcg(struct page *head, int old_order, int new_order);
+void folio_split_memcg_refs(struct folio *folio, unsigned old_order,
+ unsigned new_order);
static inline u64 cgroup_id_from_mm(struct mm_struct *mm)
{
@@ -1463,6 +1465,11 @@ static inline void split_page_memcg(stru
{
}
+static inline void folio_split_memcg_refs(struct folio *folio,
+ unsigned old_order, unsigned new_order)
+{
+}
+
static inline u64 cgroup_id_from_mm(struct mm_struct *mm)
{
return 0;
--- a/mm/huge_memory.c~mm-separate-folio_split_memcg_refs-from-split_page_memcg
+++ a/mm/huge_memory.c
@@ -3394,6 +3394,9 @@ static void __split_folio_to_order(struc
folio_set_young(new_folio);
if (folio_test_idle(folio))
folio_set_idle(new_folio);
+#ifdef CONFIG_MEMCG
+ new_folio->memcg_data = folio->memcg_data;
+#endif
folio_xchg_last_cpupid(new_folio, folio_last_cpupid(folio));
}
@@ -3525,18 +3528,7 @@ static int __split_unmapped_folio(struct
}
}
- /*
- * Reset any memcg data overlay in the tail pages.
- * folio_nr_pages() is unreliable until prep_compound_page()
- * was called again.
- */
-#ifdef NR_PAGES_IN_LARGE_FOLIO
- folio->_nr_pages = 0;
-#endif
-
-
- /* complete memcg works before add pages to LRU */
- split_page_memcg(&folio->page, old_order, split_order);
+ folio_split_memcg_refs(folio, old_order, split_order);
split_page_owner(&folio->page, old_order, split_order);
pgalloc_tag_split(folio, old_order, split_order);
--- a/mm/memcontrol.c~mm-separate-folio_split_memcg_refs-from-split_page_memcg
+++ a/mm/memcontrol.c
@@ -3081,10 +3081,19 @@ void split_page_memcg(struct page *head,
for (i = new_nr; i < old_nr; i += new_nr)
folio_page(folio, i)->memcg_data = folio->memcg_data;
- if (folio_memcg_kmem(folio))
- obj_cgroup_get_many(__folio_objcg(folio), old_nr / new_nr - 1);
- else
- css_get_many(&folio_memcg(folio)->css, old_nr / new_nr - 1);
+ obj_cgroup_get_many(__folio_objcg(folio), old_nr / new_nr - 1);
+}
+
+void folio_split_memcg_refs(struct folio *folio, unsigned old_order,
+ unsigned new_order)
+{
+ unsigned new_refs;
+
+ if (mem_cgroup_disabled() || !folio_memcg_charged(folio))
+ return;
+
+ new_refs = (1 << (old_order - new_order)) - 1;
+ css_get_many(&__folio_memcg(folio)->css, new_refs);
}
unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
mm-decline-to-manipulate-the-refcount-on-a-slab-page.patch
dax-remove-access-to-page-index.patch
dax-use-folios-more-widely-within-dax.patch
fs-convert-block_commit_write-to-take-a-folio.patch
fs-remove-page_file_mapping.patch
fs-remove-folio_file_mapping.patch
mm-assert-the-folio-is-locked-in-folio_start_writeback.patch
hugetlb-convert-hugetlb_vma_maps_page-to-hugetlb_vma_maps_pfn.patch
hugetlb-convert-adjust_range_hwpoison-to-take-a-folio.patch
mm-convert-lru_add_page_tail-to-lru_add_split_folio.patch
mm-separate-folio_split_memcg_refs-from-split_page_memcg.patch
mm-simplify-split_page_memcg.patch
mm-remove-references-to-folio-in-split_page_memcg.patch
mm-simplify-folio_memcg_charged.patch
mm-remove-references-to-folio-in-__memcg_kmem_uncharge_page.patch
ocfs2-use-memcpy_to_folio-in-ocfs2_symlink_get_block.patch
ocfs2-remove-reference-to-bh-b_page.patch
