tools/migration: Fix iovec handling in send_checkpoint_dirty_pfn_list()

We shouldn't be using two struct iovec's to write half of 'rec' each, and
there is no need to malloc() for two struct iovec's at all.

Simplify down to just two - one covering the whole of 'rec', and one covering
the pfns array.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Olaf Hering <olaf@aepfle.de>

diff --git a/tools/libs/guest/xg_sr_restore.c b/tools/libs/guest/xg_sr_restore.c
index 074b56d263ef1842c0da845ecce92a5e4d053db7..7314a24cf9d5a89a6925ceb64cc4a0b15262ddce 100644 (file)
--- a/tools/libs/guest/xg_sr_restore.c
+++ b/tools/libs/guest/xg_sr_restore.c
@@ -425,11 +425,13 @@ static int send_checkpoint_dirty_pfn_list(struct xc_sr_context *ctx)
     int rc = -1;
     unsigned int count, written;
     uint64_t i, *pfns = NULL;
-    struct iovec *iov = NULL;
     xc_shadow_op_stats_t stats = { 0, ctx->restore.p2m_size };
     struct xc_sr_record rec = {
         .type = REC_TYPE_CHECKPOINT_DIRTY_PFN_LIST,
     };
+    struct iovec iov[2] = {
+        { &rec, sizeof(rec) },
+    };
     DECLARE_HYPERCALL_BUFFER_SHADOW(unsigned long, dirty_bitmap,
                                     &ctx->restore.dirty_bitmap_hbuf);
 
@@ -471,26 +473,12 @@ static int send_checkpoint_dirty_pfn_list(struct xc_sr_context *ctx)
         pfns[written++] = i;
     }
 
-    /* iovec[] for writev(). */
-    iov = malloc(3 * sizeof(*iov));
-    if ( !iov )
-    {
-        ERROR("Unable to allocate memory for sending dirty bitmap");
-        goto err;
-    }
-
     rec.length = count * sizeof(*pfns);
 
-    iov[0].iov_base = &rec.type;
-    iov[0].iov_len = sizeof(rec.type);
-
-    iov[1].iov_base = &rec.length;
-    iov[1].iov_len = sizeof(rec.length);
-
-    iov[2].iov_base = pfns;
-    iov[2].iov_len = count * sizeof(*pfns);
+    iov[1].iov_base = pfns;
+    iov[1].iov_len = rec.length;
 
-    if ( writev_exact(ctx->restore.send_back_fd, iov, 3) )
+    if ( writev_exact(ctx->restore.send_back_fd, iov, ARRAY_SIZE(iov)) )
     {
         PERROR("Failed to write dirty bitmap to stream");
         goto err;
@@ -499,7 +487,6 @@ static int send_checkpoint_dirty_pfn_list(struct xc_sr_context *ctx)
     rc = 0;
  err:
     free(pfns);
-    free(iov);
     return rc;
 }