[PATCH v20210713 17/31] tools: restore: preallocate map_errs array

[Olaf Hering <olaf@aepfle.de>]

Remove repeated allocation from migration loop. There will never be
more than MAX_BATCH_SIZE pages to process in an incoming batch.
Allocate the space once.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
---
 tools/libs/guest/xg_sr_common.h  |  1 +
 tools/libs/guest/xg_sr_restore.c | 22 +++++++---------------
 2 files changed, 8 insertions(+), 15 deletions(-)

diff --git a/tools/libs/guest/xg_sr_common.h b/tools/libs/guest/xg_sr_common.h
index 11e45dbdc5..336be98c93 100644
--- a/tools/libs/guest/xg_sr_common.h
+++ b/tools/libs/guest/xg_sr_common.h
@@ -259,6 +259,7 @@ struct xc_sr_context
             xen_pfn_t *pfns;
             uint32_t *types;
             xen_pfn_t *mfns;
+            int *map_errs;
 
             int send_back_fd;
             unsigned long p2m_size;
diff --git a/tools/libs/guest/xg_sr_restore.c b/tools/libs/guest/xg_sr_restore.c
index 24cd8c6a07..866a7c86cd 100644
--- a/tools/libs/guest/xg_sr_restore.c
+++ b/tools/libs/guest/xg_sr_restore.c
@@ -204,21 +204,12 @@ static int process_page_data(struct xc_sr_context *ctx, unsigned int count,
                              xen_pfn_t *pfns, uint32_t *types, void *page_data)
 {
     xc_interface *xch = ctx->xch;
-    int *map_errs = malloc(count * sizeof(*map_errs));
     int rc;
     void *mapping = NULL, *guest_page = NULL;
     unsigned int i, /* i indexes the pfns from the record. */
         j,          /* j indexes the subset of pfns we decide to map. */
         nr_pages = 0;
 
-    if ( !map_errs )
-    {
-        rc = -1;
-        ERROR("Failed to allocate %zu bytes to process page data",
-              count * sizeof(*map_errs));
-        goto err;
-    }
-
     rc = populate_pfns(ctx, count, pfns, types);
     if ( rc )
     {
@@ -240,7 +231,7 @@ static int process_page_data(struct xc_sr_context *ctx, unsigned int count,
 
     mapping = guest_page = xenforeignmemory_map(
         xch->fmem, ctx->domid, PROT_READ | PROT_WRITE,
-        nr_pages, ctx->restore.mfns, map_errs);
+        nr_pages, ctx->restore.mfns, ctx->restore.map_errs);
     if ( !mapping )
     {
         rc = -1;
@@ -254,11 +245,11 @@ static int process_page_data(struct xc_sr_context *ctx, unsigned int count,
         if ( !page_type_has_stream_data(types[i]) )
             continue;
 
-        if ( map_errs[j] )
+        if ( ctx->restore.map_errs[j] )
         {
             rc = -1;
             ERROR("Mapping pfn %#"PRIpfn" (mfn %#"PRIpfn", type %#"PRIx32") failed with %d",
-                  pfns[i], ctx->restore.mfns[j], types[i], map_errs[j]);
+                  pfns[i], ctx->restore.mfns[j], types[i], ctx->restore.map_errs[j]);
             goto err;
         }
 
@@ -296,8 +287,6 @@ static int process_page_data(struct xc_sr_context *ctx, unsigned int count,
     if ( mapping )
         xenforeignmemory_unmap(xch->fmem, mapping, nr_pages);
 
-    free(map_errs);
-
     return rc;
 }
 
@@ -717,7 +706,9 @@ static int setup(struct xc_sr_context *ctx)
     ctx->restore.pfns = malloc(MAX_BATCH_SIZE * sizeof(*ctx->restore.pfns));
     ctx->restore.types = malloc(MAX_BATCH_SIZE * sizeof(*ctx->restore.types));
     ctx->restore.mfns = malloc(MAX_BATCH_SIZE * sizeof(*ctx->restore.mfns));
-    if ( !ctx->restore.pfns || !ctx->restore.types || !ctx->restore.mfns )
+    ctx->restore.map_errs = malloc(MAX_BATCH_SIZE * sizeof(*ctx->restore.map_errs));
+    if ( !ctx->restore.pfns || !ctx->restore.types || !ctx->restore.mfns ||
+         !ctx->restore.map_errs )
     {
         ERROR("Unable to allocate memory");
         rc = -1;
@@ -754,6 +745,7 @@ static void cleanup(struct xc_sr_context *ctx)
 
     free(ctx->restore.buffered_records);
     free(ctx->restore.populated_pfns);
+    free(ctx->restore.map_errs);
     free(ctx->restore.mfns);
     free(ctx->restore.types);
     free(ctx->restore.pfns);