xl: improve return and exit codes of memory related functions

by making them more consistent with other examples in xl.

While there, make freemem() of boolean return type, which
looks more natural, and add comment explaining why
parse_mem_size_kb() needs to diverge from the pattern.

Signed-off-by: Harmandeep Kaur <write.harmandeep@gmail.com>
Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

tools/libxl/xl_cmdimpl.c

@@ -2680,40 +2680,45 @@ static int preserve_domain(uint32_t *r_domid, libxl_event *event,
     return rc == 0 ? 1 : 0;
 }
 
-static int freemem(uint32_t domid, libxl_domain_build_info *b_info)
+/*
+ * Returns false if memory can't be freed, but also if we encounter errors.
+ * Returns true in case there is already, or we manage to free it, enough
+ * memory, but also if autoballoon is false.
+ */
+static bool freemem(uint32_t domid, libxl_domain_build_info *b_info)
 {
     int rc, retries = 3;
     uint32_t need_memkb, free_memkb;
 
     if (!autoballoon)
-        return 0;
+        return true;
 
     rc = libxl_domain_need_memory(ctx, b_info, &need_memkb);
     if (rc < 0)
-        return rc;
+        return false;
 
     do {
         rc = libxl_get_free_memory(ctx, &free_memkb);
         if (rc < 0)
-            return rc;
+            return false;
 
         if (free_memkb >= need_memkb)
-            return 0;
+            return true;
 
         rc = libxl_set_memory_target(ctx, 0, free_memkb - need_memkb, 1, 0);
         if (rc < 0)
-            return rc;
+            return false;
 
         /* wait until dom0 reaches its target, as long as we are making
          * progress */
         rc = libxl_wait_for_memory_target(ctx, 0, 10);
         if (rc < 0)
-            return rc;
+            return false;
 
         retries--;
     } while (retries > 0);
 
-    return ERROR_NOMEM;
+    return false;
 }
 
 static void autoconnect_console(libxl_ctx *ctx_ignored,
@@ -2980,8 +2985,7 @@ start:
         goto error_out;
 
     if (domid_soft_reset == INVALID_DOMID) {
-        ret = freemem(domid, &d_config.b_info);
-        if (ret < 0) {
+        if (!freemem(domid, &d_config.b_info)) {
             fprintf(stderr, "failed to free memory for the domain\n");
             ret = ERROR_FAIL;
             goto error_out;
@@ -3245,6 +3249,7 @@ void help(const char *command)
     }
 }
 
+/* Returns -1 on failure; the amount of memory on success. */
 static int64_t parse_mem_size_kb(const char *mem)
 {
     char *endptr;
@@ -3391,7 +3396,7 @@ static int set_memory_max(uint32_t domid, const char *mem)
     memorykb = parse_mem_size_kb(mem);
     if (memorykb == -1) {
         fprintf(stderr, "invalid memory size: %s\n", mem);
-        exit(3);
+        return EXIT_FAILURE;
     }
 
     if (libxl_domain_setmaxmem(ctx, domid, memorykb)) {
@@ -3425,7 +3430,7 @@ static int set_memory_target(uint32_t domid, const char *mem)
     memorykb = parse_mem_size_kb(mem);
     if (memorykb == -1)  {
         fprintf(stderr, "invalid memory size: %s\n", mem);
-        exit(3);
+        return EXIT_FAILURE;
     }
 
     if (libxl_set_memory_target(ctx, domid, memorykb, 0, /* enforce */ 1)) {
@@ -6132,7 +6137,7 @@ int main_sharing(int argc, char **argv)
         info = libxl_list_domain(ctx, &nb_domain);
         if (!info) {
             fprintf(stderr, "libxl_list_domain failed.\n");
-            return 1;
+            return EXIT_FAILURE;
         }
         info_free = info;
     } else if (optind == argc-1) {
@@ -6141,17 +6146,17 @@ int main_sharing(int argc, char **argv)
         if (rc == ERROR_DOMAIN_NOTFOUND) {
             fprintf(stderr, "Error: Domain \'%s\' does not exist.\n",
                 argv[optind]);
-            return -rc;
+            return EXIT_FAILURE;
         }
         if (rc) {
             fprintf(stderr, "libxl_domain_info failed (code %d).\n", rc);
-            return -rc;
+            return EXIT_FAILURE;
         }
         info = &info_buf;
         nb_domain = 1;
     } else {
         help("sharing");
-        return 2;
+        return EXIT_FAILURE;
     }
 
     sharing(info, nb_domain);
@@ -6161,7 +6166,7 @@ int main_sharing(int argc, char **argv)
     else
         libxl_dominfo_dispose(info);
 
-    return 0;
+    return EXIT_SUCCESS;
 }
 
 static int sched_domain_get(libxl_scheduler sched, int domid,