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authorJeff Cody <jcody@redhat.com>2016-02-01 20:33:10 -0500
committerMax Reitz <mreitz@redhat.com>2016-02-02 18:04:47 +0100
commitf8aa905a4fec89863c82de4186352447d851871e (patch)
tree7dc6068e4654df55b38fd0bdac467bc1279c1362 /block.c
parentc7fc50d37620550c52854ca15c2a18da1b8155e0 (diff)
downloadqemu-arm-f8aa905a4fec89863c82de4186352447d851871e.tar.gz
block: set device_list.tqe_prev to NULL on BDS removal
This fixes a regression introduced with commit 3f09bfbc7. Multiple bugs arise in conjunction with live snapshots and mirroring operations (which include active layer commit). After a live snapshot occurs, the active layer and the base layer both have a non-NULL tqe_prev field in the device_list, although the base node's tqe_prev field points to a NULL entry. This non-NULL tqe_prev field occurs after the bdrv_append() in the external snapshot calls change_parent_backing_link(). In change_parent_backing_link(), when the previous active layer is removed from device_list, the device_list.tqe_prev pointer is not set to NULL. The operating scheme in the block layer is to indicate that a BDS belongs in the bdrv_states device_list iff the device_list.tqe_prev pointer is non-NULL. This patch does two things: 1.) Introduces a new block layer helper bdrv_device_remove() to remove a BDS from the device_list, and 2.) uses that new API, which also fixes the regression once used in change_parent_backing_link(). Signed-off-by: Jeff Cody <jcody@redhat.com> Message-id: 0cd51e11c0666c04ddb7c05293fe94afeb551e89.1454376655.git.jcody@redhat.com Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
Diffstat (limited to 'block.c')
-rw-r--r--block.c24
1 files changed, 14 insertions, 10 deletions
diff --git a/block.c b/block.c
index ff1aafc85f..dff3a3a3f9 100644
--- a/block.c
+++ b/block.c
@@ -2242,21 +2242,25 @@ void bdrv_close_all(void)
}
}
+/* Note that bs->device_list.tqe_prev is initially null,
+ * and gets set to non-null by QTAILQ_INSERT_TAIL(). Establish
+ * the useful invariant "bs in bdrv_states iff bs->tqe_prev" by
+ * resetting it to null on remove. */
+void bdrv_device_remove(BlockDriverState *bs)
+{
+ QTAILQ_REMOVE(&bdrv_states, bs, device_list);
+ bs->device_list.tqe_prev = NULL;
+}
+
/* make a BlockDriverState anonymous by removing from bdrv_state and
* graph_bdrv_state list.
Also, NULL terminate the device_name to prevent double remove */
void bdrv_make_anon(BlockDriverState *bs)
{
- /*
- * Take care to remove bs from bdrv_states only when it's actually
- * in it. Note that bs->device_list.tqe_prev is initially null,
- * and gets set to non-null by QTAILQ_INSERT_TAIL(). Establish
- * the useful invariant "bs in bdrv_states iff bs->tqe_prev" by
- * resetting it to null on remove.
- */
+ /* Take care to remove bs from bdrv_states only when it's actually
+ * in it. */
if (bs->device_list.tqe_prev) {
- QTAILQ_REMOVE(&bdrv_states, bs, device_list);
- bs->device_list.tqe_prev = NULL;
+ bdrv_device_remove(bs);
}
if (bs->node_name[0] != '\0') {
QTAILQ_REMOVE(&graph_bdrv_states, bs, node_list);
@@ -2297,7 +2301,7 @@ static void change_parent_backing_link(BlockDriverState *from,
if (!to->device_list.tqe_prev) {
QTAILQ_INSERT_BEFORE(from, to, device_list);
}
- QTAILQ_REMOVE(&bdrv_states, from, device_list);
+ bdrv_device_remove(from);
}
}