[Qemu-devel] [PATCH 6/7] qcow2: implement bdrv_invalidate_cache

[Anthony Liguori <aliguori@us.ibm.com>]

We don't reopen the actual file, but instead invoke the close and open routines.
We specifically ignore the backing file since it's contents are read-only and
therefore immutable.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
---
 block/qcow2.c |   19 +++++++++++++++++++
 block/qcow2.h |    2 ++
 2 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index e4126b7..b5171e0 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -241,6 +241,7 @@ static int qcow2_open(BlockDriverState *bs, int flags)
     s->cluster_data = qemu_blockalign(bs, QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size
                                   + 512);
     s->cluster_cache_offset = -1;
+    s->flags = flags;
 
     ret = qcow2_refcount_init(bs);
     if (ret != 0) {
@@ -641,6 +642,22 @@ static void qcow2_close(BlockDriverState *bs)
     qcow2_refcount_close(bs);
 }
 
+static void qcow2_invalidate_cache(BlockDriverState *bs)
+{
+    BDRVQcowState *s = bs->opaque;
+    int flags = s->flags;
+
+    /*
+     * Backing files are read-only which makes all of their metadata immutable,
+     * that means we don't have to worry about reopening them here.
+     */
+
+    qcow2_close(bs);
+
+    memset(s, 0, sizeof(BDRVQcowState));
+    qcow2_open(bs, flags);
+}
+
 /*
  * Updates the variable length parts of the qcow2 header, i.e. the backing file
  * name and all extensions. qcow2 was not designed to allow such changes, so if
@@ -1278,6 +1295,8 @@ static BlockDriver bdrv_qcow2 = {
 
     .bdrv_change_backing_file   = qcow2_change_backing_file,
 
+    .bdrv_invalidate_cache      = qcow2_invalidate_cache,
+
     .create_options = qcow2_create_options,
     .bdrv_check = qcow2_check,
 };
diff --git a/block/qcow2.h b/block/qcow2.h
index 0734b23..6312cd9 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -127,6 +127,8 @@ typedef struct BDRVQcowState {
     QCowSnapshot *snapshots;
 
     Error *migration_blocker;
+
+    int flags;
 } BDRVQcowState;
 
 /* XXX: use std qcow open function ? */
-- 
1.7.4.1