[PATCH v2 4/7] xenguest: Reduce number of I/O vectors in write_batch

[Frediano Ziglio <freddy77@xxxxxxxxx>]

From: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>

Each page was sent using a different iovec item. This potentially exceed
Linux maximum (1024).
Also some implementation (MiniOS) emulate writev with multiple write calls.

Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>
---
 tools/libs/guest/xg_sr_save.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/tools/libs/guest/xg_sr_save.c b/tools/libs/guest/xg_sr_save.c
index 1700d819051a..62a39dfecc7a 100644
--- a/tools/libs/guest/xg_sr_save.c
+++ b/tools/libs/guest/xg_sr_save.c
@@ -240,13 +240,20 @@ static int write_batch(struct xc_sr_context *ctx)
     {
         for ( i = 0; i < nr_pfns; ++i )
         {
-            if ( guest_data[i] )
+            if ( !guest_data[i] )
+                continue;
+
+            if ( iov[iovcnt-1].iov_base + iov[iovcnt-1].iov_len != 
guest_data[i] )
             {
                 iov[iovcnt].iov_base = guest_data[i];
                 iov[iovcnt].iov_len = PAGE_SIZE;
                 iovcnt++;
-                --nr_pages;
             }
+            else
+            {
+                iov[iovcnt-1].iov_len += PAGE_SIZE;
+            }
+            --nr_pages;
         }
     }
 
-- 
2.53.0