[PATCH v20210701 16/40] tools: save: move mfns array

[Olaf Hering <olaf@xxxxxxxxx>]

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

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
---
 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 968bb8af13..1415a182d2 100644
--- a/tools/libs/saverestore/common.h
+++ b/tools/libs/saverestore/common.h
@@ -225,6 +225,8 @@ static inline int update_blob(struct xc_sr_blob *blob,
 
 struct sr_save_arrays {
     xen_pfn_t batch_pfns[MAX_BATCH_SIZE];
+    /* write_batch: Mfns of the batch pfns. */
+    xen_pfn_t mfns[MAX_BATCH_SIZE];
 };
 
 struct sr_restore_arrays {
diff --git a/tools/libs/saverestore/save.c b/tools/libs/saverestore/save.c
index e29b6e1d66..6b09784be8 100644
--- a/tools/libs/saverestore/save.c
+++ b/tools/libs/saverestore/save.c
@@ -88,7 +88,7 @@ static int write_checkpoint_record(struct xc_sr_context *ctx)
 static int write_batch(struct xc_sr_context *ctx)
 {
     xc_interface *xch = ctx->xch;
-    xen_pfn_t *mfns = NULL, *types = NULL;
+    xen_pfn_t *mfns = ctx->save.m->mfns, *types = NULL;
     void *guest_mapping = NULL;
     void **guest_data = NULL;
     void **local_pages = NULL;
@@ -105,8 +105,6 @@ static int write_batch(struct xc_sr_context *ctx)
 
     assert(nr_pfns != 0);
 
-    /* Mfns of the batch pfns. */
-    mfns = malloc(nr_pfns * sizeof(*mfns));
     /* Types of the batch pfns. */
     types = malloc(nr_pfns * sizeof(*types));
     /* Errors from attempting to map the gfns. */
@@ -118,7 +116,7 @@ static int write_batch(struct xc_sr_context *ctx)
     /* iovec[] for writev(). */
     iov = malloc((nr_pfns + 4) * sizeof(*iov));
 
-    if ( !mfns || !types || !errors || !guest_data || !local_pages || !iov )
+    if ( !types || !errors || !guest_data || !local_pages || !iov )
     {
         ERROR("Unable to allocate arrays for a batch of %u pages",
               nr_pfns);
@@ -277,7 +275,6 @@ static int write_batch(struct xc_sr_context *ctx)
     free(guest_data);
     free(errors);
     free(types);
-    free(mfns);
 
     return rc;
 }