[Devel] [PATCH vz10 11/32] mm/vmstat: build the /proc/vmstat virtualization only with CONFIG_VE

[Konstantin Khorenko]

From: Eva Kurchatova <eva.kurchatova at virtuozzo.com>

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 at virtuozzo.com>
Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
 mm/vmstat.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 47cb6bf4ecec..d97eb1d33f8a 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);
-- 
2.47.1