[qemu-xen master] migration/block-dirty-bitmap: keep bitmap state for all bitmaps

[patchbot@xxxxxxx]

commit 0a47190a009614598dc5ae3d9d25138575184520
Author:     Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx>
AuthorDate: Mon Jul 27 22:42:29 2020 +0300
Commit:     Eric Blake <eblake@xxxxxxxxxx>
CommitDate: Mon Jul 27 15:39:59 2020 -0500

    migration/block-dirty-bitmap: keep bitmap state for all bitmaps
    
    Keep bitmap state for disabled bitmaps too. Keep the state until the
    end of the process. It's needed for the following commit to implement
    bitmap postcopy canceling.
    
    To clean-up the new list the following logic is used:
    We need two events to consider bitmap migration finished:
    1. chunk with DIRTY_BITMAP_MIG_FLAG_COMPLETE flag should be received
    2. dirty_bitmap_mig_before_vm_start should be called
    These two events may come in any order, so we understand which one is
    last, and on the last of them we remove bitmap migration state from the
    list.
    
    Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx>
    Reviewed-by: Andrey Shinkevich <andrey.shinkevich@xxxxxxxxxxxxx>
    Message-Id: <20200727194236.19551-15-vsementsov@xxxxxxxxxxxxx>
    Signed-off-by: Eric Blake <eblake@xxxxxxxxxx>
---
 migration/block-dirty-bitmap.c | 64 ++++++++++++++++++++++++++++--------------
 1 file changed, 43 insertions(+), 21 deletions(-)

diff --git a/migration/block-dirty-bitmap.c b/migration/block-dirty-bitmap.c
index 405a259296..eb4ffeac4d 100644
--- a/migration/block-dirty-bitmap.c
+++ b/migration/block-dirty-bitmap.c
@@ -132,6 +132,7 @@ typedef struct LoadBitmapState {
     BlockDriverState *bs;
     BdrvDirtyBitmap *bitmap;
     bool migrated;
+    bool enabled;
 } LoadBitmapState;
 
 /* State of the dirty bitmap migration (DBM) during load process */
@@ -142,8 +143,10 @@ typedef struct DBMLoadState {
     BlockDriverState *bs;
     BdrvDirtyBitmap *bitmap;
 
-    GSList *enabled_bitmaps;
-    QemuMutex lock; /* protect enabled_bitmaps */
+    bool before_vm_start_handled; /* set in dirty_bitmap_mig_before_vm_start */
+
+    GSList *bitmaps;
+    QemuMutex lock; /* protect bitmaps */
 } DBMLoadState;
 
 typedef struct DBMState {
@@ -526,6 +529,7 @@ static int dirty_bitmap_load_start(QEMUFile *f, 
DBMLoadState *s)
     Error *local_err = NULL;
     uint32_t granularity = qemu_get_be32(f);
     uint8_t flags = qemu_get_byte(f);
+    LoadBitmapState *b;
 
     if (s->bitmap) {
         error_report("Bitmap with the same name ('%s') already exists on "
@@ -552,45 +556,59 @@ static int dirty_bitmap_load_start(QEMUFile *f, 
DBMLoadState *s)
 
     bdrv_disable_dirty_bitmap(s->bitmap);
     if (flags & DIRTY_BITMAP_MIG_START_FLAG_ENABLED) {
-        LoadBitmapState *b;
-
         bdrv_dirty_bitmap_create_successor(s->bitmap, &local_err);
         if (local_err) {
             error_report_err(local_err);
             return -EINVAL;
         }
-
-        b = g_new(LoadBitmapState, 1);
-        b->bs = s->bs;
-        b->bitmap = s->bitmap;
-        b->migrated = false;
-        s->enabled_bitmaps = g_slist_prepend(s->enabled_bitmaps, b);
     }
 
+    b = g_new(LoadBitmapState, 1);
+    b->bs = s->bs;
+    b->bitmap = s->bitmap;
+    b->migrated = false;
+    b->enabled = flags & DIRTY_BITMAP_MIG_START_FLAG_ENABLED;
+
+    s->bitmaps = g_slist_prepend(s->bitmaps, b);
+
     return 0;
 }
 
-void dirty_bitmap_mig_before_vm_start(void)
+/*
+ * before_vm_start_handle_item
+ *
+ * g_slist_foreach helper
+ *
+ * item is LoadBitmapState*
+ * opaque is DBMLoadState*
+ */
+static void before_vm_start_handle_item(void *item, void *opaque)
 {
-    DBMLoadState *s = &dbm_state.load;
-    GSList *item;
-
-    qemu_mutex_lock(&s->lock);
-
-    for (item = s->enabled_bitmaps; item; item = g_slist_next(item)) {
-        LoadBitmapState *b = item->data;
+    DBMLoadState *s = opaque;
+    LoadBitmapState *b = item;
 
+    if (b->enabled) {
         if (b->migrated) {
             bdrv_enable_dirty_bitmap(b->bitmap);
         } else {
             bdrv_dirty_bitmap_enable_successor(b->bitmap);
         }
+    }
 
+    if (b->migrated) {
+        s->bitmaps = g_slist_remove(s->bitmaps, b);
         g_free(b);
     }
+}
 
-    g_slist_free(s->enabled_bitmaps);
-    s->enabled_bitmaps = NULL;
+void dirty_bitmap_mig_before_vm_start(void)
+{
+    DBMLoadState *s = &dbm_state.load;
+    qemu_mutex_lock(&s->lock);
+
+    assert(!s->before_vm_start_handled);
+    g_slist_foreach(s->bitmaps, before_vm_start_handle_item, s);
+    s->before_vm_start_handled = true;
 
     qemu_mutex_unlock(&s->lock);
 }
@@ -607,11 +625,15 @@ static void dirty_bitmap_load_complete(QEMUFile *f, 
DBMLoadState *s)
         bdrv_reclaim_dirty_bitmap(s->bitmap, &error_abort);
     }
 
-    for (item = s->enabled_bitmaps; item; item = g_slist_next(item)) {
+    for (item = s->bitmaps; item; item = g_slist_next(item)) {
         LoadBitmapState *b = item->data;
 
         if (b->bitmap == s->bitmap) {
             b->migrated = true;
+            if (s->before_vm_start_handled) {
+                s->bitmaps = g_slist_remove(s->bitmaps, b);
+                g_free(b);
+            }
             break;
         }
     }
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#master