qcow2: Add .bdrv_join_options callback

qcow2 accepts a few driver-specific options that overlap semantically
(e.g. "overlap-check" is an alias of "overlap-check.template", and any
missing cache size option is derived from the given ones).

When bdrv_reopen() merges the set of updated options with left out
options that should be kept at their old value, we need to consider this
and filter out any duplicates (which would generally cause errors
because new and old value would contradict each other).

This patch adds a .bdrv_join_options callback to BlockDriver and
implements it for qcow2.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>

diff --git a/block/qcow2.c b/block/qcow2.c
index 5b59fa3d7f06a19b8cbb0db23900218bea7d312e..fda1562ed39c30957a2ae29a8f94e43567fea6dc 100644 (file)
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1282,6 +1282,52 @@ static void qcow2_reopen_abort(BDRVReopenState *state)
     g_free(state->opaque);
 }
 
+static void qcow2_join_options(QDict *options, QDict *old_options)
+{
+    bool has_new_overlap_template =
+        qdict_haskey(options, QCOW2_OPT_OVERLAP) ||
+        qdict_haskey(options, QCOW2_OPT_OVERLAP_TEMPLATE);
+    bool has_new_total_cache_size =
+        qdict_haskey(options, QCOW2_OPT_CACHE_SIZE);
+    bool has_all_cache_options;
+
+    /* New overlap template overrides all old overlap options */
+    if (has_new_overlap_template) {
+        qdict_del(old_options, QCOW2_OPT_OVERLAP);
+        qdict_del(old_options, QCOW2_OPT_OVERLAP_TEMPLATE);
+        qdict_del(old_options, QCOW2_OPT_OVERLAP_MAIN_HEADER);
+        qdict_del(old_options, QCOW2_OPT_OVERLAP_ACTIVE_L1);
+        qdict_del(old_options, QCOW2_OPT_OVERLAP_ACTIVE_L2);
+        qdict_del(old_options, QCOW2_OPT_OVERLAP_REFCOUNT_TABLE);
+        qdict_del(old_options, QCOW2_OPT_OVERLAP_REFCOUNT_BLOCK);
+        qdict_del(old_options, QCOW2_OPT_OVERLAP_SNAPSHOT_TABLE);
+        qdict_del(old_options, QCOW2_OPT_OVERLAP_INACTIVE_L1);
+        qdict_del(old_options, QCOW2_OPT_OVERLAP_INACTIVE_L2);
+    }
+
+    /* New total cache size overrides all old options */
+    if (qdict_haskey(options, QCOW2_OPT_CACHE_SIZE)) {
+        qdict_del(old_options, QCOW2_OPT_L2_CACHE_SIZE);
+        qdict_del(old_options, QCOW2_OPT_REFCOUNT_CACHE_SIZE);
+    }
+
+    qdict_join(options, old_options, false);
+
+    /*
+     * If after merging all cache size options are set, an old total size is
+     * overwritten. Do keep all options, however, if all three are new. The
+     * resulting error message is what we want to happen.
+     */
+    has_all_cache_options =
+        qdict_haskey(options, QCOW2_OPT_CACHE_SIZE) ||
+        qdict_haskey(options, QCOW2_OPT_L2_CACHE_SIZE) ||
+        qdict_haskey(options, QCOW2_OPT_REFCOUNT_CACHE_SIZE);
+
+    if (has_all_cache_options && !has_new_total_cache_size) {
+        qdict_del(options, QCOW2_OPT_CACHE_SIZE);
+    }
+}
+
 static int64_t coroutine_fn qcow2_co_get_block_status(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors, int *pnum)
 {
@@ -3145,6 +3191,7 @@ BlockDriver bdrv_qcow2 = {
     .bdrv_reopen_prepare  = qcow2_reopen_prepare,
     .bdrv_reopen_commit   = qcow2_reopen_commit,
     .bdrv_reopen_abort    = qcow2_reopen_abort,
+    .bdrv_join_options    = qcow2_join_options,
     .bdrv_create        = qcow2_create,
     .bdrv_has_zero_init = bdrv_has_zero_init_1,
     .bdrv_co_get_block_status = qcow2_co_get_block_status,

diff --git a/include/block/block_int.h b/include/block/block_int.h
index 66e208d62019c65a2a782b023f812a4bed02c70f..c2ce9655560b6aee5ed3a842b504cbfc8e932ca5 100644 (file)
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -121,6 +121,7 @@ struct BlockDriver {
                                BlockReopenQueue *queue, Error **errp);
     void (*bdrv_reopen_commit)(BDRVReopenState *reopen_state);
     void (*bdrv_reopen_abort)(BDRVReopenState *reopen_state);
+    void (*bdrv_join_options)(QDict *options, QDict *old_options);
 
     int (*bdrv_open)(BlockDriverState *bs, QDict *options, int flags,
                      Error **errp);