[Qemu-devel] [PATCH 20/34] qcow2: Support updating driver-specific options in reopen

[Kevin Wolf <kwolf@redhat.com>]

For updating the cache sizes or disabling lazy refcounts there is a bit
more to do than just changing the variables, but otherwise we're all set
for changing options during bdrv_reopen().

Just implement the missing pieces and hook the functions up in
bdrv_reopen().

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow2.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 64 insertions(+), 6 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index fc9375e..940447b 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -596,7 +596,24 @@ static int qcow2_update_options_prepare(BlockDriverState *bs,
         goto fail;
     }
 
-    /* alloc L2 table/refcount block cache */
+    /* alloc new L2 table/refcount block cache, flush old one */
+    if (s->l2_table_cache) {
+        ret = qcow2_cache_flush(bs, s->l2_table_cache);
+        if (ret) {
+            error_setg_errno(errp, -ret, "Failed to flush the L2 table cache");
+            goto fail;
+        }
+    }
+
+    if (s->refcount_block_cache) {
+        ret = qcow2_cache_flush(bs, s->refcount_block_cache);
+        if (ret) {
+            error_setg_errno(errp, -ret,
+                             "Failed to flush the refcount block cache");
+            goto fail;
+        }
+    }
+
     r->l2_table_cache = qcow2_cache_create(bs, l2_cache_size);
     r->refcount_block_cache = qcow2_cache_create(bs, refcount_cache_size);
     if (r->l2_table_cache == NULL || r->refcount_block_cache == NULL) {
@@ -605,7 +622,7 @@ static int qcow2_update_options_prepare(BlockDriverState *bs,
         goto fail;
     }
 
-    /* Enable lazy_refcounts according to image and command line options */
+    /* lazy-refcounts; flush if going from enabled to disabled */
     r->use_lazy_refcounts = qemu_opt_get_bool(opts, QCOW2_OPT_LAZY_REFCOUNTS,
         (s->compatible_features & QCOW2_COMPAT_LAZY_REFCOUNTS));
     if (r->use_lazy_refcounts && s->qcow_version < 3) {
@@ -615,6 +632,14 @@ static int qcow2_update_options_prepare(BlockDriverState *bs,
         goto fail;
     }
 
+    if (s->use_lazy_refcounts && !r->use_lazy_refcounts) {
+        ret = qcow2_mark_clean(bs);
+        if (ret < 0) {
+            error_setg_errno(errp, -ret, "Failed to disable lazy refcounts");
+            goto fail;
+        }
+    }
+
     /* Overlap check options */
     opt_overlap_check = qemu_opt_get(opts, QCOW2_OPT_OVERLAP);
     opt_overlap_check_template = qemu_opt_get(opts, QCOW2_OPT_OVERLAP_TEMPLATE);
@@ -679,6 +704,12 @@ static void qcow2_update_options_commit(BlockDriverState *bs,
     BDRVQcowState *s = bs->opaque;
     int i;
 
+    if (s->l2_table_cache) {
+        qcow2_cache_destroy(bs, s->l2_table_cache);
+    }
+    if (s->refcount_block_cache) {
+        qcow2_cache_destroy(bs, s->refcount_block_cache);
+    }
     s->l2_table_cache = r->l2_table_cache;
     s->refcount_block_cache = r->refcount_block_cache;
 
@@ -1135,26 +1166,51 @@ static int qcow2_set_key(BlockDriverState *bs, const char *key)
     return 0;
 }
 
-/* We have no actual commit/abort logic for qcow2, but we need to write out any
- * unwritten data if we reopen read-only. */
 static int qcow2_reopen_prepare(BDRVReopenState *state,
                                 BlockReopenQueue *queue, Error **errp)
 {
+    Qcow2ReopenState *r;
     int ret;
 
+    r = g_new0(Qcow2ReopenState, 1);
+    state->opaque = r;
+
+    ret = qcow2_update_options_prepare(state->bs, r, state->options,
+                                       state->flags, errp);
+    if (ret < 0) {
+        goto fail;
+    }
+
+    /* We need to write out any unwritten data if we reopen read-only. */
     if ((state->flags & BDRV_O_RDWR) == 0) {
         ret = bdrv_flush(state->bs);
         if (ret < 0) {
-            return ret;
+            goto fail;
         }
 
         ret = qcow2_mark_clean(state->bs);
         if (ret < 0) {
-            return ret;
+            goto fail;
         }
     }
 
     return 0;
+
+fail:
+    qcow2_update_options_abort(state->bs, r);
+    return ret;
+}
+
+static void qcow2_reopen_commit(BDRVReopenState *state)
+{
+    qcow2_update_options_commit(state->bs, state->opaque);
+    g_free(state->opaque);
+}
+
+static void qcow2_reopen_abort(BDRVReopenState *state)
+{
+    qcow2_update_options_abort(state->bs, state->opaque);
+    g_free(state->opaque);
 }
 
 static int64_t coroutine_fn qcow2_co_get_block_status(BlockDriverState *bs,
@@ -3000,6 +3056,8 @@ BlockDriver bdrv_qcow2 = {
     .bdrv_open          = qcow2_open,
     .bdrv_close         = qcow2_close,
     .bdrv_reopen_prepare  = qcow2_reopen_prepare,
+    .bdrv_reopen_commit   = qcow2_reopen_commit,
+    .bdrv_reopen_abort    = qcow2_reopen_abort,
     .bdrv_create        = qcow2_create,
     .bdrv_has_zero_init = bdrv_has_zero_init_1,
     .bdrv_co_get_block_status = qcow2_co_get_block_status,
-- 
1.8.3.1