[PATCH v20210601 13/38] tools/guest: save: move errors array

[Olaf Hering <olaf@xxxxxxxxx>]

Remove allocation from hotpath, move errors array into preallocated space.

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
---
 tools/libs/saverestore/common.h | 2 ++
 tools/libs/saverestore/save.c   | 7 ++-----
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/tools/libs/saverestore/common.h b/tools/libs/saverestore/common.h
index 81d4a79b13..07dfa7d57d 100644
--- a/tools/libs/saverestore/common.h
+++ b/tools/libs/saverestore/common.h
@@ -229,6 +229,8 @@ struct xc_sr_save_arrays {
     xen_pfn_t mfns[MAX_BATCH_SIZE];
     /* write_batch: Types of the batch pfns. */
     xen_pfn_t types[MAX_BATCH_SIZE];
+    /* write_batch: Errors from attempting to map the gfns. */
+    int errors[MAX_BATCH_SIZE];
 };
 
 struct xc_sr_restore_arrays {
diff --git a/tools/libs/saverestore/save.c b/tools/libs/saverestore/save.c
index be65286570..5033f18bef 100644
--- a/tools/libs/saverestore/save.c
+++ b/tools/libs/saverestore/save.c
@@ -92,7 +92,7 @@ static int write_batch(struct xc_sr_context *ctx)
     void *guest_mapping = NULL;
     void **guest_data = NULL;
     void **local_pages = NULL;
-    int *errors = NULL, rc = -1;
+    int *errors = ctx->save.m->errors, rc = -1;
     unsigned int i, p, nr_pages = 0, nr_pages_mapped = 0;
     unsigned int nr_pfns = ctx->save.nr_batch_pfns;
     void *page, *orig_page;
@@ -105,8 +105,6 @@ static int write_batch(struct xc_sr_context *ctx)
 
     assert(nr_pfns != 0);
 
-    /* Errors from attempting to map the gfns. */
-    errors = malloc(nr_pfns * sizeof(*errors));
     /* Pointers to page data to send.  Mapped gfns or local allocations. */
     guest_data = calloc(nr_pfns, sizeof(*guest_data));
     /* Pointers to locally allocated pages.  Need freeing. */
@@ -114,7 +112,7 @@ static int write_batch(struct xc_sr_context *ctx)
     /* iovec[] for writev(). */
     iov = malloc((nr_pfns + 4) * sizeof(*iov));
 
-    if ( !errors || !guest_data || !local_pages || !iov )
+    if ( !guest_data || !local_pages || !iov )
     {
         ERROR("Unable to allocate arrays for a batch of %u pages",
               nr_pfns);
@@ -271,7 +269,6 @@ static int write_batch(struct xc_sr_context *ctx)
     free(iov);
     free(local_pages);
     free(guest_data);
-    free(errors);
 
     return rc;
 }