[Qemu-devel] [PATCH 31/35] ram: refactor ram_save_block() return value

[Juan Quintela <quintela@redhat.com>]

It could only return 0 if we only found dirty xbzrle pages that hadn't
changed (i.e. they were written with the same content).  We don't care
about that case, it is the same than nothing dirty.

So now the return of the function is how much have it written, nothing
else. Adjust callers.

And we also made ram_save_iterate() return the number of transferred
bytes, not the number of transferred pages.

Signed-off-by: Juan Quintela <quintela@redhat.com>
---
 arch_init.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 3e82588..723529a 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -422,9 +422,8 @@ static void migration_bitmap_sync(void)
 /*
  * ram_save_block: Writes a page of memory to the stream f
  *
- * Returns:  0: if the page hasn't changed
- *          -1: if there are no more dirty pages
- *           n: the amount of bytes written in other case
+ * Returns:  The number of bytes written.
+ *           0 means no dirty pages
  */

 static int ram_save_block(QEMUFile *f, bool last_stage)
@@ -432,7 +431,7 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
     RAMBlock *block = last_seen_block;
     ram_addr_t offset = last_offset;
     bool complete_round = false;
-    int bytes_sent = -1;
+    int bytes_sent = 0;
     MemoryRegion *mr;
     ram_addr_t current_addr;

@@ -460,6 +459,8 @@ static int ram_save_block(QEMUFile *f, bool last_stage)

             p = memory_region_get_ram_ptr(mr) + offset;

+            /* In doubt sent page as normal */
+            bytes_sent = -1;
             if (is_dup_page(p)) {
                 acct_info.dup_pages++;
                 bytes_sent = save_block_hdr(f, block, offset, cont,
@@ -475,7 +476,7 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
                 }
             }

-            /* either we didn't send yet (we may have had XBZRLE overflow) */
+            /* XBZRLE overflow or normal page */
             if (bytes_sent == -1) {
                 bytes_sent = save_block_hdr(f, block, offset, cont, RAM_SAVE_FLAG_PAGE);
                 qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
@@ -484,7 +485,7 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
             }

             /* if page is unmodified, continue to the next */
-            if (bytes_sent != 0) {
+            if (bytes_sent > 0) {
                 last_sent_block = block;
                 break;
             }
@@ -631,6 +632,7 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
     int ret;
     int i;
     int64_t t0;
+    int total_sent = 0;

     qemu_mutex_lock_ramlist();

@@ -645,10 +647,10 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)

         bytes_sent = ram_save_block(f, false);
         /* no more blocks to sent */
-        if (bytes_sent < 0) {
+        if (bytes_sent == 0) {
             break;
         }
-        bytes_transferred += bytes_sent;
+        total_sent += bytes_sent;
         acct_info.iterations++;
         /* we want to check in the 1st loop, just in case it was the 1st time
            and we had to sync the dirty bitmap.
@@ -667,13 +669,16 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
     }

     if (ret < 0) {
+        bytes_transferred += total_sent;
         return ret;
     }

     qemu_mutex_unlock_ramlist();
     qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
+    total_sent += 8;
+    bytes_transferred += total_sent;

-    return i;
+    return total_sent;
 }

 static int ram_save_complete(QEMUFile *f, void *opaque)
@@ -690,7 +695,7 @@ static int ram_save_complete(QEMUFile *f, void *opaque)

         bytes_sent = ram_save_block(f, true);
         /* no more blocks to sent */
-        if (bytes_sent < 0) {
+        if (bytes_sent == 0) {
             break;
         }
         bytes_transferred += bytes_sent;
-- 
1.7.11.7