[PATCH v9 2/4] libs/guest: move batch_pfns into a separate structure

[Frediano Ziglio <freddy77@xxxxxxxxx>]

Preparation for a followup patch "libs/guest: allocate various migration
arrays just once".

Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>
Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
Changes since v6:
- split from "libs/guest: allocate various migration arrays just once".

Changes since v7:
- initialize "batch_pfns" on declaration.

Changes since v8:
- remove useless check;
- added Reviewed-by.
---
 tools/libs/guest/xg_sr_common.h |  5 ++++-
 tools/libs/guest/xg_sr_save.c   | 28 ++++++++++++++--------------
 2 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/tools/libs/guest/xg_sr_common.h b/tools/libs/guest/xg_sr_common.h
index f1573aefcb..7574c9f5b6 100644
--- a/tools/libs/guest/xg_sr_common.h
+++ b/tools/libs/guest/xg_sr_common.h
@@ -239,11 +239,14 @@ struct xc_sr_context
 
             struct precopy_stats stats;
 
-            xen_pfn_t *batch_pfns;
             unsigned int nr_batch_pfns;
             unsigned long *deferred_pages;
             unsigned long nr_deferred_pages;
             xc_hypercall_buffer_t dirty_bitmap_hbuf;
+            struct xc_sr_context_save_buffers
+            {
+                xen_pfn_t batch_pfns[MAX_BATCH_SIZE];
+            } *buffers;
         } save;
 
         struct /* Restore data. */
diff --git a/tools/libs/guest/xg_sr_save.c b/tools/libs/guest/xg_sr_save.c
index 84fdbe4140..22348db445 100644
--- a/tools/libs/guest/xg_sr_save.c
+++ b/tools/libs/guest/xg_sr_save.c
@@ -75,7 +75,7 @@ static int write_checkpoint_record(struct xc_sr_context *ctx)
 
 /*
  * Writes a batch of memory as a PAGE_DATA record into the stream.  The batch
- * is constructed in ctx->save.batch_pfns.
+ * is constructed in ctx->save.buffers->batch_pfns.
  *
  * This function:
  * - gets the types for each pfn in the batch.
@@ -95,6 +95,7 @@ static int write_batch(struct xc_sr_context *ctx)
     void *page, *orig_page;
     uint64_t *rec_pfns = NULL;
     struct iovec *iov = NULL; int iovcnt = 0;
+    xen_pfn_t *const batch_pfns = ctx->save.buffers->batch_pfns;
     struct {
         struct xc_sr_rhdr rec;
         struct xc_sr_rec_page_data_header page_data;
@@ -110,6 +111,7 @@ static int write_batch(struct xc_sr_context *ctx)
     };
 
     assert(nr_pfns != 0);
+    assert(nr_pfns <= MAX_BATCH_SIZE);
 
     /* Mfns of the batch pfns. */
     mfns = malloc(nr_pfns * sizeof(*mfns));
@@ -141,13 +143,12 @@ static int write_batch(struct xc_sr_context *ctx)
 
     for ( i = 0; i < nr_pfns; ++i )
     {
-        types[i] = mfns[i] = ctx->save.ops.pfn_to_gfn(ctx,
-                                                      ctx->save.batch_pfns[i]);
+        types[i] = mfns[i] = ctx->save.ops.pfn_to_gfn(ctx, batch_pfns[i]);
 
         /* Likely a ballooned page. */
         if ( mfns[i] == INVALID_MFN )
         {
-            set_bit(ctx->save.batch_pfns[i], ctx->save.deferred_pages);
+            set_bit(batch_pfns[i], ctx->save.deferred_pages);
             ++ctx->save.nr_deferred_pages;
         }
     }
@@ -193,7 +194,7 @@ static int write_batch(struct xc_sr_context *ctx)
             if ( errors[p] )
             {
                 ERROR("Mapping of pfn %#"PRIpfn" (mfn %#"PRIpfn") failed %d",
-                      ctx->save.batch_pfns[i], mfns[p], errors[p]);
+                      batch_pfns[i], mfns[p], errors[p]);
                 goto err;
             }
 
@@ -207,7 +208,7 @@ static int write_batch(struct xc_sr_context *ctx)
             {
                 if ( rc == -1 && errno == EAGAIN )
                 {
-                    set_bit(ctx->save.batch_pfns[i], ctx->save.deferred_pages);
+                    set_bit(batch_pfns[i], ctx->save.deferred_pages);
                     ++ctx->save.nr_deferred_pages;
                     types[i] = XEN_DOMCTL_PFINFO_XTAB;
                     --nr_pages;
@@ -235,7 +236,7 @@ static int write_batch(struct xc_sr_context *ctx)
     hdrs.rec.length += nr_pages * PAGE_SIZE;
 
     for ( i = 0; i < nr_pfns; ++i )
-        rec_pfns[i] = ((uint64_t)(types[i]) << 32) | ctx->save.batch_pfns[i];
+        rec_pfns[i] = ((uint64_t)(types[i]) << 32) | batch_pfns[i];
 
     if ( writev_exact(ctx->fd, iov, iovcnt) )
     {
@@ -274,9 +275,9 @@ static int flush_batch(struct xc_sr_context *ctx)
 
     if ( !rc )
     {
-        VALGRIND_MAKE_MEM_UNDEFINED(ctx->save.batch_pfns,
+        VALGRIND_MAKE_MEM_UNDEFINED(ctx->save.buffers->batch_pfns,
                                     MAX_BATCH_SIZE *
-                                    sizeof(*ctx->save.batch_pfns));
+                                    sizeof(*ctx->save.buffers->batch_pfns));
     }
 
     return rc;
@@ -293,7 +294,7 @@ static int add_to_batch(struct xc_sr_context *ctx, 
xen_pfn_t pfn)
         rc = flush_batch(ctx);
 
     if ( rc == 0 )
-        ctx->save.batch_pfns[ctx->save.nr_batch_pfns++] = pfn;
+        ctx->save.buffers->batch_pfns[ctx->save.nr_batch_pfns++] = pfn;
 
     return rc;
 }
@@ -784,11 +785,10 @@ static int setup(struct xc_sr_context *ctx)
 
     dirty_bitmap = xc_hypercall_buffer_alloc_pages(
         xch, dirty_bitmap, NRPAGES(bitmap_size(ctx->save.p2m_size)));
-    ctx->save.batch_pfns = malloc(MAX_BATCH_SIZE *
-                                  sizeof(*ctx->save.batch_pfns));
     ctx->save.deferred_pages = bitmap_alloc(ctx->save.p2m_size);
+    ctx->save.buffers = calloc(1, sizeof(*ctx->save.buffers));
 
-    if ( !ctx->save.batch_pfns || !dirty_bitmap || !ctx->save.deferred_pages )
+    if ( !ctx->save.buffers || !dirty_bitmap || !ctx->save.deferred_pages )
     {
         ERROR("Unable to allocate memory for dirty bitmaps, batch pfns and"
               " deferred pages");
@@ -819,7 +819,7 @@ static void cleanup(struct xc_sr_context *ctx)
     xc_hypercall_buffer_free_pages(xch, dirty_bitmap,
                                    NRPAGES(bitmap_size(ctx->save.p2m_size)));
     free(ctx->save.deferred_pages);
-    free(ctx->save.batch_pfns);
+    free(ctx->save.buffers);
 }
 
 /*
-- 
2.43.0