procfs-util: expose functionality to query total memory

procfs_memory_get_current is renamed to procfs_memory_get_used, because
"current" can mean anything, including total memory, used memory, and free
memory, as long as the value is up to date.

No functional change.

src/basic/procfs-util.c

@@ -201,13 +201,11 @@ int procfs_cpu_get_usage(nsec_t *ret) {
         return 0;
 }
 
-int procfs_memory_get_current(uint64_t *ret) {
+int procfs_memory_get(uint64_t *ret_total, uint64_t *ret_used) {
         uint64_t mem_total = UINT64_MAX, mem_free = UINT64_MAX;
         _cleanup_fclose_ FILE *f = NULL;
         int r;
 
-        assert(ret);
-
         f = fopen("/proc/meminfo", "re");
         if (!f)
                 return -errno;
@@ -262,6 +260,9 @@ int procfs_memory_get_current(uint64_t *ret) {
         if (mem_free > mem_total)
                 return -EINVAL;
 
-        *ret = (mem_total - mem_free) * 1024U;
+        if (ret_total)
+                *ret_total = mem_total * 1024U;
+        if (ret_used)
+                *ret_used = (mem_total - mem_free) * 1024U;
         return 0;
 }

src/basic/procfs-util.h

@@ -11,4 +11,7 @@ int procfs_tasks_get_current(uint64_t *ret);
 
 int procfs_cpu_get_usage(nsec_t *ret);
 
-int procfs_memory_get_current(uint64_t *ret);
+int procfs_memory_get(uint64_t *ret_total, uint64_t *ret_used);
+static inline int procfs_memory_get_used(uint64_t *ret) {
+        return procfs_memory_get(NULL, ret);
+}