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authorKevin Wolf <kwolf@redhat.com>2015-12-22 14:07:08 +0100
committerKevin Wolf <kwolf@redhat.com>2016-01-20 13:36:23 +0100
commit76b1c7fe1cbc45f46b2cccd471369ccd4b49b6fd (patch)
tree6794eac6c397e14cf194d4beb80c548358098119 /block.c
parent04c01a5c8f006b6e45fa5be8ea857efe7d9c41f9 (diff)
downloadqemu-arm-76b1c7fe1cbc45f46b2cccd471369ccd4b49b6fd.tar.gz
block: Inactivate BDS when migration completes
So far, live migration with shared storage meant that the image is in a not-really-ready don't-touch-me state on the destination while the source is still actively using it, but after completing the migration, the image was fully opened on both sides. This is bad. This patch adds a block driver callback to inactivate images on the source before completing the migration. Inactivation means that it goes to a state as if it was just live migrated to the qemu instance on the source (i.e. BDRV_O_INACTIVE is set). You're then supposed to continue either on the source or on the destination, which takes ownership of the image. A typical migration looks like this now with respect to disk images: 1. Destination qemu is started, the image is opened with BDRV_O_INACTIVE. The image is fully opened on the source. 2. Migration is about to complete. The source flushes the image and inactivates it. Now both sides have the image opened with BDRV_O_INACTIVE and are expecting the other side to still modify it. 3. One side (the destination on success) continues and calls bdrv_invalidate_all() in order to take ownership of the image again. This removes BDRV_O_INACTIVE on the resuming side; the flag remains set on the other side. This ensures that the same image isn't written to by both instances (unless both are resumed, but then you get what you deserve). This is important because .bdrv_close for non-BDRV_O_INACTIVE images could write to the image file, which is definitely forbidden while another host is using the image. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: John Snow <jsnow@redhat.com>
Diffstat (limited to 'block.c')
-rw-r--r--block.c34
1 files changed, 34 insertions, 0 deletions
diff --git a/block.c b/block.c
index 95b2967192..5709d3ddb4 100644
--- a/block.c
+++ b/block.c
@@ -3303,6 +3303,40 @@ void bdrv_invalidate_cache_all(Error **errp)
}
}
+static int bdrv_inactivate(BlockDriverState *bs)
+{
+ int ret;
+
+ if (bs->drv->bdrv_inactivate) {
+ ret = bs->drv->bdrv_inactivate(bs);
+ if (ret < 0) {
+ return ret;
+ }
+ }
+
+ bs->open_flags |= BDRV_O_INACTIVE;
+ return 0;
+}
+
+int bdrv_inactivate_all(void)
+{
+ BlockDriverState *bs;
+ int ret;
+
+ QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
+ AioContext *aio_context = bdrv_get_aio_context(bs);
+
+ aio_context_acquire(aio_context);
+ ret = bdrv_inactivate(bs);
+ aio_context_release(aio_context);
+ if (ret < 0) {
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
/**************************************************************/
/* removable device support */