[Xen-devel] [PATCH 10/11] libxl: Fix libxl_set_memory_target return value

[Paulina Szubarczyk <paulinaszubarczyk@xxxxxxxxx>]

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@xxxxxxxxxx>

CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
CC: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
CC: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 tools/libxl/libxl.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 4291b57..6bdf3b1 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -4672,7 +4672,7 @@ 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, r, abort_transaction = 0;
     uint64_t memorykb;
     uint32_t videoram = 0;
     uint32_t current_target_memkb = 0, new_target_memkb = 0;
@@ -4700,15 +4700,15 @@ 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);
@@ -4716,6 +4716,7 @@ retry_transaction:
             LOGE(ERROR, "invalid memory target %s from %s/memory/target\n",
                  target, dompath);
             abort_transaction = 1;
+            rc = ERROR_FAIL;
             goto out;
         }
     }
@@ -4724,6 +4725,7 @@ 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);
@@ -4731,6 +4733,7 @@ retry_transaction:
         LOGE(ERROR, "invalid max memory %s from %s/memory/static-max\n",
              memmax, dompath);
         abort_transaction = 1;
+        rc = ERROR_FAIL;
         goto out;
     }

@@ -4750,6 +4753,7 @@ retry_transaction:
             "memory_dynamic_max must be less than or equal to"
             " memory_static_max\n");
         abort_transaction = 1;
+        rc = ERROR_INVAL;
         goto out;
     }

@@ -4757,33 +4761,36 @@ 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;
     }

@@ -4797,6 +4804,7 @@ 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)
--
1.9.1

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