[Devel] [PATCH RHEL10 COMMIT] mm/vmstat: build the /proc/vmstat virtualization only with CONFIG_VE

[Konstantin Khorenko <khorenko@virtuozzo.com>]

The commit is pushed to "branch-rh10-6.12.0-211.39.1.16.x.vz10-ovz" and will appear at git at bitbucket.org:openvz/vzkernel.git
after rh10-6.12.0-211.39.1.16.6.vz10
------>
commit 22b53c9453944fb0053512af4128df347b9de26c
Author: Eva Kurchatova <eva.kurchatova@virtuozzo.com>
Date:   Fri Aug 21 18:36:57 2026 +0200

    mm/vmstat: build the /proc/vmstat virtualization only with CONFIG_VE
    
    fill_vmstat_ve() fills the Container view of /proc/vmstat from the
    Container's memory cgroup, looked up by memory_cgrp_id.  It is compiled
    unconditionally, so with CONFIG_MEMCG=n - which CONFIG_VE=n allows, and
    plain "make defconfig" used to produce - the build fails:
    
      mm/vmstat.c: error: 'memory_cgrp_id' undeclared (first use in this
                   function)
    
    CONFIG_VE selects CONFIG_MEMCG, so compile both the helper and its call
    site under CONFIG_VE.  The 've' variable moves into the guarded block:
    left at function scope it would be unused with CONFIG_VE=n, which is a
    build failure of its own once CONFIG_WERROR=y, as x86_64 defconfig has
    it.
    
    Fixes: e15a9e29a433 ("ve/memcg: Virtualize /proc/vmstat view inside CT")
    Feature: procfs: virtualize /proc/vmstat
    https://virtuozzo.atlassian.net/browse/VSTOR-134732
    Signed-off-by: Eva Kurchatova <eva.kurchatova@virtuozzo.com>
    
    Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
---
 mm/vmstat.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 47cb6bf4ecec6..d97eb1d33f8a2 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1855,6 +1855,7 @@ static const struct seq_operations zoneinfo_op = {
 			 (IS_ENABLED(CONFIG_VM_EVENT_COUNTERS) ? \
 			  NR_VM_EVENT_ITEMS : 0))
 
+#ifdef CONFIG_VE
 static void fill_vmstat_ve(unsigned long *stat, struct ve_struct *ve)
 {
 	struct cgroup_subsys_state *css;
@@ -1863,10 +1864,10 @@ static void fill_vmstat_ve(unsigned long *stat, struct ve_struct *ve)
 	mem_cgroup_fill_vmstat(mem_cgroup_from_css(css), stat);
 	css_put(css);
 }
+#endif
 
 static void *vmstat_start(struct seq_file *m, loff_t *pos)
 {
-	struct ve_struct *ve;
 	unsigned long *v;
 	int i;
 
@@ -1880,12 +1881,18 @@ static void *vmstat_start(struct seq_file *m, loff_t *pos)
 	if (!v)
 		return ERR_PTR(-ENOMEM);
 
-	ve = get_exec_env();
-	if (!ve_is_super(ve)) {
-		memset(v, 0, NR_VMSTAT_ITEMS * sizeof(unsigned long));
-		fill_vmstat_ve(v, ve);
-		return (unsigned long *)m->private + *pos;
+#ifdef CONFIG_VE
+	{
+		struct ve_struct *ve = get_exec_env();
+
+		if (!ve_is_super(ve)) {
+			memset(v, 0,
+			       NR_VMSTAT_ITEMS * sizeof(unsigned long));
+			fill_vmstat_ve(v, ve);
+			return (unsigned long *)m->private + *pos;
+		}
 	}
+#endif
 
 	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
 		v[i] = global_zone_page_state(i);