+ mm-vmstat-fix-build-with-memcg=y-and-vm_event_counters=n.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/vmstat: fix build with MEMCG=y and VM_EVENT_COUNTERS=n
has been added to the -mm mm-new branch.  Its filename is
     mm-vmstat-fix-build-with-memcg=y-and-vm_event_counters=n.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmstat-fix-build-with-memcg=y-and-vm_event_counters=n.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
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------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: mm/vmstat: fix build with MEMCG=y and VM_EVENT_COUNTERS=n
Date: Wed, 4 Jun 2025 12:51:11 +0300

When compiling with MEMCG enabled but VM_EVENT_COUNTERS disabled,
BUILD_BUG_ON() is triggered in vmstat_start because the vmstat_text array
is larger than NR_VMSTAT_ITEMS.

This issue arises because some elements of the vmstat_text array are
present when either MEMCG or VM_EVENT_COUNTERS is enabled, but
NR_VMSTAT_ITEMS only accounts for these elements if VM_EVENT_COUNTERS is
enabled.

And upcoming change in the BUILD_BUG_ON() check made it more strict,
disallowing extra elements in the array, which revealed the issue.

Instead of adjusting the NR_VMSTAT_ITEMS definition to account for MEMCG,
make MEMCG select VM_EVENT_COUNTERS.  VM_EVENT_COUNTERS is enabled in most
configurations anyway.

There is no need to backport this fix to stable trees.  Without the strict
BUILD_BUG_ON(), the issue is not harmful.  The elements in question would
only be read by the memcg code, not by /proc/vmstat.

Link: https://lkml.kernel.org/r/20250604095111.533783-1-kirill.shutemov@linux.intel.com
Fixes: ebc5d83d0443 ("mm/memcontrol: use vmstat names for printing statistics")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/vmstat.h |    4 ++--
 init/Kconfig           |    1 +
 mm/vmstat.c            |    4 ++--
 3 files changed, 5 insertions(+), 4 deletions(-)

--- a/include/linux/vmstat.h~mm-vmstat-fix-build-with-memcg=y-and-vm_event_counters=n
+++ a/include/linux/vmstat.h
@@ -507,7 +507,7 @@ static inline const char *lru_list_name(
 	return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
 }
 
-#if defined(CONFIG_VM_EVENT_COUNTERS) || defined(CONFIG_MEMCG)
+#if defined(CONFIG_VM_EVENT_COUNTERS)
 static inline const char *vm_event_name(enum vm_event_item item)
 {
 	return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
@@ -516,7 +516,7 @@ static inline const char *vm_event_name(
 			   NR_VM_STAT_ITEMS +
 			   item];
 }
-#endif /* CONFIG_VM_EVENT_COUNTERS || CONFIG_MEMCG */
+#endif /* CONFIG_VM_EVENT_COUNTERS */
 
 #ifdef CONFIG_MEMCG
 
--- a/init/Kconfig~mm-vmstat-fix-build-with-memcg=y-and-vm_event_counters=n
+++ a/init/Kconfig
@@ -989,6 +989,7 @@ config MEMCG
 	select PAGE_COUNTER
 	select EVENTFD
 	select SLAB_OBJ_EXT
+	select VM_EVENT_COUNTERS
 	help
 	  Provides control over the memory footprint of tasks in a cgroup.
 
--- a/mm/vmstat.c~mm-vmstat-fix-build-with-memcg=y-and-vm_event_counters=n
+++ a/mm/vmstat.c
@@ -1287,7 +1287,7 @@ const char * const vmstat_text[] = {
 	"nr_memmap_pages",
 	"nr_memmap_boot_pages",
 
-#if defined(CONFIG_VM_EVENT_COUNTERS) || defined(CONFIG_MEMCG)
+#if defined(CONFIG_VM_EVENT_COUNTERS)
 	/* enum vm_event_item counters */
 	"pgpgin",
 	"pgpgout",
@@ -1477,7 +1477,7 @@ const char * const vmstat_text[] = {
 	"kstack_rest",
 #endif
 #endif
-#endif /* CONFIG_VM_EVENT_COUNTERS || CONFIG_MEMCG */
+#endif /* CONFIG_VM_EVENT_COUNTERS */
 };
 #endif /* CONFIG_PROC_FS || CONFIG_SYSFS || CONFIG_NUMA || CONFIG_MEMCG */
 
_

Patches currently in -mm which might be from kirill.shutemov@linux.intel.com are

mm-fix-vmstat-after-removing-nr_bounce.patch
mm-vmstat-fix-build-with-memcg=y-and-vm_event_counters=n.patch
mm-strictly-check-vmstat_text-array-size.patch
mm-vmstat-utilize-designated-initializers-for-the-vmstat_text-array.patch