[PATCH v5 2/7] migration/multifd: put IOV initialization into compression method

[Yuan Liu]

Different compression methods may require different numbers of IOVs.
Based on streaming compression of zlib and zstd, all pages will be
compressed to a data block, so two IOVs are needed for packet header
and compressed data block.

Signed-off-by: Yuan Liu <yuan1....@intel.com>
Reviewed-by: Nanhai Zou <nanhai....@intel.com>
---
 migration/multifd-zlib.c | 4 ++++
 migration/multifd-zstd.c | 6 +++++-
 migration/multifd.c      | 8 +++++---
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/migration/multifd-zlib.c b/migration/multifd-zlib.c
index 99821cd4d5..8095ef8e28 100644
--- a/migration/multifd-zlib.c
+++ b/migration/multifd-zlib.c
@@ -70,6 +70,10 @@ static int zlib_send_setup(MultiFDSendParams *p, Error 
**errp)
         goto err_free_zbuff;
     }
     p->compress_data = z;
+
+    assert(p->iov == NULL);
+    /* For packet header and zlib streaming compression block */
+    p->iov = g_new0(struct iovec, 2);
     return 0;
 
 err_free_zbuff:
diff --git a/migration/multifd-zstd.c b/migration/multifd-zstd.c
index 02112255ad..9c9217794e 100644
--- a/migration/multifd-zstd.c
+++ b/migration/multifd-zstd.c
@@ -52,7 +52,6 @@ static int zstd_send_setup(MultiFDSendParams *p, Error **errp)
     struct zstd_data *z = g_new0(struct zstd_data, 1);
     int res;
 
-    p->compress_data = z;
     z->zcs = ZSTD_createCStream();
     if (!z->zcs) {
         g_free(z);
@@ -77,6 +76,11 @@ static int zstd_send_setup(MultiFDSendParams *p, Error 
**errp)
         error_setg(errp, "multifd %u: out of memory for zbuff", p->id);
         return -1;
     }
+    p->compress_data = z;
+
+    assert(p->iov == NULL);
+    /* For packet header and zstd streaming compression block */
+    p->iov = g_new0(struct iovec, 2);
     return 0;
 }
 
diff --git a/migration/multifd.c b/migration/multifd.c
index 0179422f6d..5155e02ae3 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -1181,9 +1181,11 @@ bool multifd_send_setup(void)
             p->packet = g_malloc0(p->packet_len);
             p->packet->magic = cpu_to_be32(MULTIFD_MAGIC);
             p->packet->version = cpu_to_be32(MULTIFD_VERSION);
-
-            /* We need one extra place for the packet header */
-            p->iov = g_new0(struct iovec, page_count + 1);
+            /* IOVs are initialized in send_setup of compression method */
+            if (!migrate_multifd_compression()) {
+                /* We need one extra place for the packet header */
+                p->iov = g_new0(struct iovec, page_count + 1);
+            }
         } else {
             p->iov = g_new0(struct iovec, page_count);
         }
-- 
2.39.3