[PATCH v4 2/5] libxl: Fix libxl_set_memory_target return value

[George Dunlap <george.dunlap@eu.citrix.com>]

libxl_set_memory_target seems to have the following return values:

* 1 on failure, if the failure happens because of a xenstore error *or* invalid target

* -1 if the setmaxmem hypercall

* -errno if the set_pod_target hypercall target fails

* 0 on success

Make it consistently return ERROR_FAIL on failure, unless the
parameters were invalid, in which case return ERROR_INVAL.

In accordance with CODING_SYTLE:

1. Leave rc uninitialized, and set when an error is detected

2. Use 'r' for return values to functions whose return values are a
different error space (like xc_domain_setmaxmem and
xc_domain_set_pod_target), or where a failure means retry, rather than
fail the whole function (libxl__fill_dom0_memory_info), to reduce the
risk that

Signed-off-by: George Dunlap <george.dunlap@citrix.com>
---
v4:
 - Use 'r' instead of 'lrc'
 - Set 'rc' before jumping to error path, rather than initializing at the beginning
 - Move removal of xc_domain_getinfolist to another patch

CC: Ian Campbell <ian.campbell@citrix.com>
CC: Ian Jackson <ian.jackson@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
---
 tools/libxl/libxl.c | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index a36101d..d05e58e 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -4742,7 +4742,7 @@ int libxl_set_memory_target(libxl_ctx *ctx, uint32_t domid,
         int32_t target_memkb, int relative, int enforce)
 {
     GC_INIT(ctx);
-    int rc = 1, abort_transaction = 0;
+    int rc, abort_transaction = 0, r;
     uint64_t memorykb;
     uint32_t videoram = 0;
     uint32_t current_target_memkb = 0, new_target_memkb = 0;
@@ -4770,15 +4770,15 @@ retry_transaction:
     if (!target && !domid) {
         if (!xs_transaction_end(ctx->xsh, t, 1))
             goto out_no_transaction;
-        rc = libxl__fill_dom0_memory_info(gc, &current_target_memkb,
+        r = libxl__fill_dom0_memory_info(gc, &current_target_memkb,
                                           &current_max_memkb);
-        if (rc < 0)
-            goto out_no_transaction;
+        if (r < 0) { rc = ERROR_FAIL; goto out_no_transaction; }
         goto retry_transaction;
     } else if (!target) {
         LOGE(ERROR, "cannot get target memory info from %s/memory/target",
              dompath);
         abort_transaction = 1;
+        rc = ERROR_FAIL;
         goto out;
     } else {
         current_target_memkb = strtoul(target, &endptr, 10);
@@ -4786,6 +4786,7 @@ retry_transaction:
             LOGE(ERROR, "invalid memory target %s from %s/memory/target\n",
                  target, dompath);
             abort_transaction = 1;
+            rc = ERROR_FAIL;
             goto out;
         }
     }
@@ -4794,6 +4795,7 @@ retry_transaction:
         LOGE(ERROR, "cannot get memory info from %s/memory/static-max",
              dompath);
         abort_transaction = 1;
+        rc = ERROR_FAIL;
         goto out;
     }
     memorykb = strtoul(memmax, &endptr, 10);
@@ -4801,6 +4803,7 @@ retry_transaction:
         LOGE(ERROR, "invalid max memory %s from %s/memory/static-max\n",
              memmax, dompath);
         abort_transaction = 1;
+        rc = ERROR_FAIL;
         goto out;
     }
 
@@ -4820,6 +4823,7 @@ retry_transaction:
             "memory_dynamic_max must be less than or equal to"
             " memory_static_max\n");
         abort_transaction = 1;
+        rc = ERROR_INVAL;
         goto out;
     }
 
@@ -4827,33 +4831,36 @@ retry_transaction:
         LOG(ERROR, "new target %d for dom0 is below the minimum threshold",
             new_target_memkb);
         abort_transaction = 1;
+        rc = ERROR_INVAL;
         goto out;
     }
 
     if (enforce) {
         memorykb = new_target_memkb + videoram;
-        rc = xc_domain_setmaxmem(ctx->xch, domid, memorykb +
+        r = xc_domain_setmaxmem(ctx->xch, domid, memorykb +
                 LIBXL_MAXMEM_CONSTANT);
-        if (rc != 0) {
+        if (r != 0) {
             LOGE(ERROR,
                  "xc_domain_setmaxmem domid=%u memkb=%"PRIu64" failed ""rc=%d\n",
                  domid,
                  memorykb + LIBXL_MAXMEM_CONSTANT,
-                 rc);
+                 r);
             abort_transaction = 1;
+            rc = ERROR_FAIL;
             goto out;
         }
     }
 
-    rc = xc_domain_set_pod_target(ctx->xch, domid,
+    r = xc_domain_set_pod_target(ctx->xch, domid,
             (new_target_memkb + LIBXL_MAXMEM_CONSTANT) / 4, NULL, NULL, NULL);
-    if (rc != 0) {
+    if (r != 0) {
         LOGE(ERROR,
              "xc_domain_set_pod_target domid=%d, memkb=%d ""failed rc=%d\n",
              domid,
              new_target_memkb / 4,
-             rc);
+             r);
         abort_transaction = 1;
+        rc = ERROR_FAIL;
         goto out;
     }
 
@@ -4867,6 +4874,8 @@ retry_transaction:
                      "%"PRIu32, new_target_memkb / 1024);
     libxl_dominfo_dispose(&ptr);
 
+    rc = 0;
+
 out:
     if (!xs_transaction_end(ctx->xsh, t, abort_transaction)
         && !abort_transaction)
-- 
2.1.4