Merge remote-tracking branch 'mreitz/tags/pull-block-2017-11-17' into queue-block

Block patches for 2.11.0-rc2

# gpg: Signature made Fri Nov 17 18:22:07 2017 CET
# gpg:                using RSA key F407DB0061D5CF40
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>"
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* mreitz/tags/pull-block-2017-11-17:
  iotests: Make 087 pass without AIO enabled
  block: Make bdrv_next() keep strong references
  qcow2: Fix overly broad madvise()
  qcow2: Refuse to get unaligned offsets from cache
  qcow2: Add bounds check to get_refblock_offset()
  block: Guard against NULL bs->drv
  qcow2: Unaligned zero cluster in handle_alloc()
  qcow2: check_errors are fatal
  qcow2: reject unaligned offsets in write compressed
  iotests: Add test for failing qemu-img commit
  tests: Add check-qobject for equality tests
  iotests: Add test for non-string option reopening
  block: qobject_is_equal() in bdrv_reopen_prepare()
  qapi: Add qobject_is_equal()
  qapi/qlist: Add qlist_append_null() macro
  qapi/qnull: Add own header

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -720,6 +720,10 @@ static int refresh_total_sectors(BlockDriverState *bs, int64_t hint)
 {
     BlockDriver *drv = bs->drv;
 
+    if (!drv) {
+        return -ENOMEDIUM;
+    }
+
     /* Do not attempt drv->bdrv_getlength() on scsi-generic devices */
     if (bdrv_is_sg(bs))
         return 0;
@@ -3074,19 +3078,26 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue,
         const QDictEntry *entry = qdict_first(reopen_state->options);
 
         do {
-            QString *new_obj = qobject_to_qstring(entry->value);
-            const char *new = qstring_get_str(new_obj);
-            /*
-             * Caution: while qdict_get_try_str() is fine, getting
-             * non-string types would require more care.  When
-             * bs->options come from -blockdev or blockdev_add, its
-             * members are typed according to the QAPI schema, but
-             * when they come from -drive, they're all QString.
-             */
-            const char *old = qdict_get_try_str(reopen_state->bs->options,
-                                                entry->key);
+            QObject *new = entry->value;
+            QObject *old = qdict_get(reopen_state->bs->options, entry->key);
 
-            if (!old || strcmp(new, old)) {
+            /*
+             * TODO: When using -drive to specify blockdev options, all values
+             * will be strings; however, when using -blockdev, blockdev-add or
+             * filenames using the json:{} pseudo-protocol, they will be
+             * correctly typed.
+             * In contrast, reopening options are (currently) always strings
+             * (because you can only specify them through qemu-io; all other
+             * callers do not specify any options).
+             * Therefore, when using anything other than -drive to create a BDS,
+             * this cannot detect non-string options as unchanged, because
+             * qobject_is_equal() always returns false for objects of different
+             * type.  In the future, this should be remedied by correctly typing
+             * all options.  For now, this is not too big of an issue because
+             * the user can simply omit options which cannot be changed anyway,
+             * so they will stay unchanged.
+             */
+            if (!qobject_is_equal(new, old)) {
                 error_setg(errp, "Cannot change the option '%s'", entry->key);
                 ret = -EINVAL;
                 goto error;
@@ -3424,6 +3435,10 @@ int bdrv_change_backing_file(BlockDriverState *bs,
     BlockDriver *drv = bs->drv;
     int ret;
 
+    if (!drv) {
+        return -ENOMEDIUM;
+    }
+
     /* Backing file format doesn't make sense without a backing file */
     if (backing_fmt && !backing_file) {
         return -EINVAL;
@@ -3909,7 +3924,9 @@ int bdrv_has_zero_init_1(BlockDriverState *bs)
 
 int bdrv_has_zero_init(BlockDriverState *bs)
 {
-    assert(bs->drv);
+    if (!bs->drv) {
+        return 0;
+    }
 
     /* If BS is a copy on write image, it is initialized to
        the contents of the base image, which may not be zeroes.  */
@@ -4238,6 +4255,7 @@ void bdrv_invalidate_cache_all(Error **errp)
         aio_context_release(aio_context);
         if (local_err) {
             error_propagate(errp, local_err);
+            bdrv_next_cleanup(&it);
             return;
         }
     }
@@ -4249,6 +4267,10 @@ static int bdrv_inactivate_recurse(BlockDriverState *bs,
     BdrvChild *child, *parent;
     int ret;
 
+    if (!bs->drv) {
+        return -ENOMEDIUM;
+    }
+
     if (!setting_flag && bs->drv->bdrv_inactivate) {
         ret = bs->drv->bdrv_inactivate(bs);
         if (ret < 0) {
@@ -4309,6 +4331,7 @@ int bdrv_inactivate_all(void)
         for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
             ret = bdrv_inactivate_recurse(bs, pass);
             if (ret < 0) {
+                bdrv_next_cleanup(&it);
                 goto out;
             }
         }
@@ -4783,6 +4806,9 @@ void bdrv_remove_aio_context_notifier(BlockDriverState *bs,
 int bdrv_amend_options(BlockDriverState *bs, QemuOpts *opts,
                        BlockDriverAmendStatusCB *status_cb, void *cb_opaque)
 {
+    if (!bs->drv) {
+        return -ENOMEDIUM;
+    }
     if (!bs->drv->bdrv_amend_options) {
         return -ENOTSUP;
     }
@@ -4840,6 +4866,7 @@ bool bdrv_is_first_non_filter(BlockDriverState *candidate)
 
         /* candidate is the first non filter */
         if (perm) {
+            bdrv_next_cleanup(&it);
             return true;
         }
     }

block/block-backend.c

@@ -442,21 +442,37 @@ BlockBackend *blk_next(BlockBackend *blk)
  * the monitor or attached to a BlockBackend */
 BlockDriverState *bdrv_next(BdrvNextIterator *it)
 {
-    BlockDriverState *bs;
+    BlockDriverState *bs, *old_bs;
+
+    /* Must be called from the main loop */
+    assert(qemu_get_current_aio_context() == qemu_get_aio_context());
 
     /* First, return all root nodes of BlockBackends. In order to avoid
      * returning a BDS twice when multiple BBs refer to it, we only return it
      * if the BB is the first one in the parent list of the BDS. */
     if (it->phase == BDRV_NEXT_BACKEND_ROOTS) {
+        BlockBackend *old_blk = it->blk;
+
+        old_bs = old_blk ? blk_bs(old_blk) : NULL;
+
         do {
             it->blk = blk_all_next(it->blk);
             bs = it->blk ? blk_bs(it->blk) : NULL;
         } while (it->blk && (bs == NULL || bdrv_first_blk(bs) != it->blk));
 
+        if (it->blk) {
+            blk_ref(it->blk);
+        }
+        blk_unref(old_blk);
+
         if (bs) {
+            bdrv_ref(bs);
+            bdrv_unref(old_bs);
             return bs;
         }
         it->phase = BDRV_NEXT_MONITOR_OWNED;
+    } else {
+        old_bs = it->bs;
     }
 
     /* Then return the monitor-owned BDSes without a BB attached. Ignore all
@@ -467,18 +483,46 @@ BlockDriverState *bdrv_next(BdrvNextIterator *it)
         bs = it->bs;
     } while (bs && bdrv_has_blk(bs));
 
+    if (bs) {
+        bdrv_ref(bs);
+    }
+    bdrv_unref(old_bs);
+
     return bs;
 }
 
-BlockDriverState *bdrv_first(BdrvNextIterator *it)
+static void bdrv_next_reset(BdrvNextIterator *it)
 {
     *it = (BdrvNextIterator) {
         .phase = BDRV_NEXT_BACKEND_ROOTS,
     };
+}
 
+BlockDriverState *bdrv_first(BdrvNextIterator *it)
+{
+    bdrv_next_reset(it);
     return bdrv_next(it);
 }
 
+/* Must be called when aborting a bdrv_next() iteration before
+ * bdrv_next() returns NULL */
+void bdrv_next_cleanup(BdrvNextIterator *it)
+{
+    /* Must be called from the main loop */
+    assert(qemu_get_current_aio_context() == qemu_get_aio_context());
+
+    if (it->phase == BDRV_NEXT_BACKEND_ROOTS) {
+        if (it->blk) {
+            bdrv_unref(blk_bs(it->blk));
+            blk_unref(it->blk);
+        }
+    } else {
+        bdrv_unref(it->bs);
+    }
+
+    bdrv_next_reset(it);
+}
+
 /*
  * Add a BlockBackend into the list of backends referenced by the monitor, with
  * the given @name acting as the handle for the monitor.

block/io.c

@@ -853,6 +853,10 @@ static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs,
 
     assert(!(flags & ~BDRV_REQ_MASK));
 
+    if (!drv) {
+        return -ENOMEDIUM;
+    }
+
     if (drv->bdrv_co_preadv) {
         return drv->bdrv_co_preadv(bs, offset, bytes, qiov, flags);
     }
@@ -894,6 +898,10 @@ static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
 
     assert(!(flags & ~BDRV_REQ_MASK));
 
+    if (!drv) {
+        return -ENOMEDIUM;
+    }
+
     if (drv->bdrv_co_pwritev) {
         ret = drv->bdrv_co_pwritev(bs, offset, bytes, qiov,
                                    flags & bs->supported_write_flags);
@@ -945,6 +953,10 @@ bdrv_driver_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
 {
     BlockDriver *drv = bs->drv;
 
+    if (!drv) {
+        return -ENOMEDIUM;
+    }
+
     if (!drv->bdrv_co_pwritev_compressed) {
         return -ENOTSUP;
     }
@@ -975,6 +987,10 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
                                     BDRV_REQUEST_MAX_BYTES);
     unsigned int progress = 0;
 
+    if (!drv) {
+        return -ENOMEDIUM;
+    }
+
     /* FIXME We cannot require callers to have write permissions when all they
      * are doing is a read request. If we did things right, write permissions
      * would be obtained anyway, but internally by the copy-on-read code. As
@@ -1291,6 +1307,10 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
                         bs->bl.request_alignment);
     int max_transfer = MIN_NON_ZERO(bs->bl.max_transfer, MAX_BOUNCE_BUFFER);
 
+    if (!drv) {
+        return -ENOMEDIUM;
+    }
+
     assert(alignment % bs->bl.request_alignment == 0);
     head = offset % alignment;
     tail = (offset + bytes) % alignment;
@@ -1397,6 +1417,10 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
     uint64_t bytes_remaining = bytes;
     int max_transfer;
 
+    if (!drv) {
+        return -ENOMEDIUM;
+    }
+
     if (bdrv_has_readonly_bitmaps(bs)) {
         return -EPERM;
     }
@@ -1863,6 +1887,8 @@ static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs,
         bytes = n;
     }
 
+    /* Must be non-NULL or bdrv_getlength() would have failed */
+    assert(bs->drv);
     if (!bs->drv->bdrv_co_get_block_status) {
         *pnum = bytes;
         ret = BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED;
@@ -2373,6 +2399,12 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
     }
 
     BLKDBG_EVENT(bs->file, BLKDBG_FLUSH_TO_DISK);
+    if (!bs->drv) {
+        /* bs->drv->bdrv_co_flush() might have ejected the BDS
+         * (even in case of apparent success) */
+        ret = -ENOMEDIUM;
+        goto out;
+    }
     if (bs->drv->bdrv_co_flush_to_disk) {
         ret = bs->drv->bdrv_co_flush_to_disk(bs);
     } else if (bs->drv->bdrv_aio_flush) {
@@ -2542,6 +2574,10 @@ int coroutine_fn bdrv_co_pdiscard(BlockDriverState *bs, int64_t offset,
             num = max_pdiscard;
         }
 
+        if (!bs->drv) {
+            ret = -ENOMEDIUM;
+            goto out;
+        }
         if (bs->drv->bdrv_co_pdiscard) {
             ret = bs->drv->bdrv_co_pdiscard(bs, offset, num);
         } else {

block/qapi.c

@@ -39,8 +39,14 @@ BlockDeviceInfo *bdrv_block_device_info(BlockBackend *blk,
 {
     ImageInfo **p_image_info;
     BlockDriverState *bs0;
-    BlockDeviceInfo *info = g_malloc0(sizeof(*info));
+    BlockDeviceInfo *info;
 
+    if (!bs->drv) {
+        error_setg(errp, "Block device %s is ejected", bs->node_name);
+        return NULL;
+    }
+
+    info = g_malloc0(sizeof(*info));
     info->file                   = g_strdup(bs->filename);
     info->ro                     = bs->read_only;
     info->drv                    = g_strdup(bs->drv->format_name);

block/qcow2-cache.c

@@ -62,6 +62,18 @@ static inline int qcow2_cache_get_table_idx(BlockDriverState *bs,
     return idx;
 }
 
+static inline const char *qcow2_cache_get_name(BDRVQcow2State *s, Qcow2Cache *c)
+{
+    if (c == s->refcount_block_cache) {
+        return "refcount block";
+    } else if (c == s->l2_table_cache) {
+        return "L2 table";
+    } else {
+        /* Do not abort, because this is not critical */
+        return "unknown";
+    }
+}
+
 static void qcow2_cache_table_release(BlockDriverState *bs, Qcow2Cache *c,
                                       int i, int num_tables)
 {
@@ -73,7 +85,7 @@ static void qcow2_cache_table_release(BlockDriverState *bs, Qcow2Cache *c,
     size_t mem_size = (size_t) s->cluster_size * num_tables;
     size_t offset = QEMU_ALIGN_UP((uintptr_t) t, align) - (uintptr_t) t;
     size_t length = QEMU_ALIGN_DOWN(mem_size - offset, align);
-    if (length > 0) {
+    if (mem_size > offset && length > 0) {
         madvise((uint8_t *) t + offset, length, MADV_DONTNEED);
     }
 #endif
@@ -314,9 +326,18 @@ static int qcow2_cache_do_get(BlockDriverState *bs, Qcow2Cache *c,
     uint64_t min_lru_counter = UINT64_MAX;
     int min_lru_index = -1;
 
+    assert(offset != 0);
+
     trace_qcow2_cache_get(qemu_coroutine_self(), c == s->l2_table_cache,
                           offset, read_from_disk);
 
+    if (offset_into_cluster(s, offset)) {
+        qcow2_signal_corruption(bs, true, -1, -1, "Cannot get entry from %s "
+                                "cache: Offset %#" PRIx64 " is unaligned",
+                                qcow2_cache_get_name(s, c), offset);
+        return -EIO;
+    }
+
     /* Check if the table is already cached */
     i = lookup_index = (offset / s->cluster_size * 4) % c->size;
     do {

block/qcow2-cluster.c

@@ -1308,10 +1308,21 @@ static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
         (!*host_offset ||
          start_of_cluster(s, *host_offset) == (entry & L2E_OFFSET_MASK)))
     {
+        int preallocated_nb_clusters;
+
+        if (offset_into_cluster(s, entry & L2E_OFFSET_MASK)) {
+            qcow2_signal_corruption(bs, true, -1, -1, "Preallocated zero "
+                                    "cluster offset %#llx unaligned (guest "
+                                    "offset: %#" PRIx64 ")",
+                                    entry & L2E_OFFSET_MASK, guest_offset);
+            ret = -EIO;
+            goto fail;
+        }
+
         /* Try to reuse preallocated zero clusters; contiguous normal clusters
          * would be fine, too, but count_cow_clusters() above has limited
          * nb_clusters already to a range of COW clusters */
-        int preallocated_nb_clusters =
+        preallocated_nb_clusters =
             count_contiguous_clusters(nb_clusters, s->cluster_size,
                                       &l2_table[l2_index], QCOW_OFLAG_COPIED);
         assert(preallocated_nb_clusters > 0);

block/qcow2-refcount.c

@@ -3077,16 +3077,40 @@ done:
     return ret;
 }
 
+static int64_t get_refblock_offset(BlockDriverState *bs, uint64_t offset)
+{
+    BDRVQcow2State *s = bs->opaque;
+    uint32_t index = offset_to_reftable_index(s, offset);
+    int64_t covering_refblock_offset = 0;
+
+    if (index < s->refcount_table_size) {
+        covering_refblock_offset = s->refcount_table[index] & REFT_OFFSET_MASK;
+    }
+    if (!covering_refblock_offset) {
+        qcow2_signal_corruption(bs, true, -1, -1, "Refblock at %#" PRIx64 " is "
+                                "not covered by the refcount structures",
+                                offset);
+        return -EIO;
+    }
+
+    return covering_refblock_offset;
+}
+
 static int qcow2_discard_refcount_block(BlockDriverState *bs,
                                         uint64_t discard_block_offs)
 {
     BDRVQcow2State *s = bs->opaque;
-    uint64_t refblock_offs = get_refblock_offset(s, discard_block_offs);
+    int64_t refblock_offs;
     uint64_t cluster_index = discard_block_offs >> s->cluster_bits;
     uint32_t block_index = cluster_index & (s->refcount_block_size - 1);
     void *refblock;
     int ret;
 
+    refblock_offs = get_refblock_offset(bs, discard_block_offs);
+    if (refblock_offs < 0) {
+        return refblock_offs;
+    }
+
     assert(discard_block_offs != 0);
 
     ret = qcow2_cache_get(bs, s->refcount_block_cache, refblock_offs,

block/qcow2.c

@@ -1477,7 +1477,10 @@ static int qcow2_do_open(BlockDriverState *bs, QDict *options, int flags,
         BdrvCheckResult result = {0};
 
         ret = qcow2_check(bs, &result, BDRV_FIX_ERRORS | BDRV_FIX_LEAKS);
-        if (ret < 0) {
+        if (ret < 0 || result.check_errors) {
+            if (ret >= 0) {
+                ret = -EIO;
+            }
             error_setg_errno(errp, -ret, "Could not repair dirty image");
             goto fail;
         }
@@ -3358,6 +3361,10 @@ qcow2_co_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
         return bdrv_truncate(bs->file, cluster_offset, PREALLOC_MODE_OFF, NULL);
     }
 
+    if (offset_into_cluster(s, offset)) {
+        return -EINVAL;
+    }
+
     buf = qemu_blockalign(bs, s->cluster_size);
     if (bytes != s->cluster_size) {
         if (bytes > s->cluster_size ||

block/qcow2.h

@@ -527,12 +527,6 @@ uint32_t offset_to_reftable_index(BDRVQcow2State *s, uint64_t offset)
     return offset >> (s->refcount_block_bits + s->cluster_bits);
 }
 
-static inline uint64_t get_refblock_offset(BDRVQcow2State *s, uint64_t offset)
-{
-    uint32_t index = offset_to_reftable_index(s, offset);
-    return s->refcount_table[index] & REFT_OFFSET_MASK;
-}
-
 /* qcow2.c functions */
 int qcow2_backing_read1(BlockDriverState *bs, QEMUIOVector *qiov,
                   int64_t sector_num, int nb_sectors);

block/replication.c

@@ -342,12 +342,24 @@ static void secondary_do_checkpoint(BDRVReplicationState *s, Error **errp)
         return;
     }
 
+    if (!s->active_disk->bs->drv) {
+        error_setg(errp, "Active disk %s is ejected",
+                   s->active_disk->bs->node_name);
+        return;
+    }
+
     ret = s->active_disk->bs->drv->bdrv_make_empty(s->active_disk->bs);
     if (ret < 0) {
         error_setg(errp, "Cannot make active disk empty");
         return;
     }
 
+    if (!s->hidden_disk->bs->drv) {
+        error_setg(errp, "Hidden disk %s is ejected",
+                   s->hidden_disk->bs->node_name);
+        return;
+    }
+
     ret = s->hidden_disk->bs->drv->bdrv_make_empty(s->hidden_disk->bs);
     if (ret < 0) {
         error_setg(errp, "Cannot make hidden disk empty");
@@ -511,6 +523,9 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
             return;
         }
 
+        /* Must be true, or the bdrv_getlength() calls would have failed */
+        assert(s->active_disk->bs->drv && s->hidden_disk->bs->drv);
+
         if (!s->active_disk->bs->drv->bdrv_make_empty ||
             !s->hidden_disk->bs->drv->bdrv_make_empty) {
             error_setg(errp,

block/snapshot.c

@@ -417,6 +417,7 @@ bool bdrv_all_can_snapshot(BlockDriverState **first_bad_bs)
         }
         aio_context_release(ctx);
         if (!ok) {
+            bdrv_next_cleanup(&it);
             goto fail;
         }
     }
@@ -444,6 +445,7 @@ int bdrv_all_delete_snapshot(const char *name, BlockDriverState **first_bad_bs,
         }
         aio_context_release(ctx);
         if (ret < 0) {
+            bdrv_next_cleanup(&it);
             goto fail;
         }
     }
@@ -469,6 +471,7 @@ int bdrv_all_goto_snapshot(const char *name, BlockDriverState **first_bad_bs)
         }
         aio_context_release(ctx);
         if (err < 0) {
+            bdrv_next_cleanup(&it);
             goto fail;
         }
     }
@@ -494,6 +497,7 @@ int bdrv_all_find_snapshot(const char *name, BlockDriverState **first_bad_bs)
         }
         aio_context_release(ctx);
         if (err < 0) {
+            bdrv_next_cleanup(&it);
             goto fail;
         }
     }
@@ -525,6 +529,7 @@ int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
         }
         aio_context_release(ctx);
         if (err < 0) {
+            bdrv_next_cleanup(&it);
             goto fail;
         }
     }
@@ -548,6 +553,7 @@ BlockDriverState *bdrv_all_find_vmstate_bs(void)
         aio_context_release(ctx);
 
         if (found) {
+            bdrv_next_cleanup(&it);
             break;
         }
     }

block/vvfat.c

@@ -2947,7 +2947,7 @@ static int do_commit(BDRVVVFATState* s)
         return ret;
     }
 
-    if (s->qcow->bs->drv->bdrv_make_empty) {
+    if (s->qcow->bs->drv && s->qcow->bs->drv->bdrv_make_empty) {
         s->qcow->bs->drv->bdrv_make_empty(s->qcow->bs);
     }
 

include/block/block.h

@@ -461,6 +461,7 @@ typedef struct BdrvNextIterator {
 
 BlockDriverState *bdrv_first(BdrvNextIterator *it);
 BlockDriverState *bdrv_next(BdrvNextIterator *it);
+void bdrv_next_cleanup(BdrvNextIterator *it);
 
 BlockDriverState *bdrv_next_monitor_owned(BlockDriverState *bs);
 bool bdrv_is_encrypted(BlockDriverState *bs);

include/qapi/qmp/qbool.h

@@ -24,6 +24,7 @@ typedef struct QBool {
 QBool *qbool_from_bool(bool value);
 bool qbool_get_bool(const QBool *qb);
 QBool *qobject_to_qbool(const QObject *obj);
+bool qbool_is_equal(const QObject *x, const QObject *y);
 void qbool_destroy_obj(QObject *obj);
 
 #endif /* QBOOL_H */

include/qapi/qmp/qdict.h

@@ -15,6 +15,7 @@
 
 #include "qapi/qmp/qobject.h"
 #include "qapi/qmp/qlist.h"
+#include "qapi/qmp/qnull.h"
 #include "qapi/qmp/qnum.h"
 #include "qemu/queue.h"
 
@@ -42,6 +43,7 @@ void qdict_del(QDict *qdict, const char *key);
 int qdict_haskey(const QDict *qdict, const char *key);
 QObject *qdict_get(const QDict *qdict, const char *key);
 QDict *qobject_to_qdict(const QObject *obj);
+bool qdict_is_equal(const QObject *x, const QObject *y);
 void qdict_iter(const QDict *qdict,
                 void (*iter)(const char *key, QObject *obj, void *opaque),
                 void *opaque);

include/qapi/qmp/qlist.h

@@ -15,6 +15,7 @@
 
 #include "qapi/qmp/qobject.h"
 #include "qapi/qmp/qnum.h"
+#include "qapi/qmp/qnull.h"
 #include "qemu/queue.h"
 
 typedef struct QListEntry {
@@ -37,6 +38,8 @@ typedef struct QList {
         qlist_append(qlist, qbool_from_bool(value))
 #define qlist_append_str(qlist, value) \
         qlist_append(qlist, qstring_from_str(value))
+#define qlist_append_null(qlist) \
+        qlist_append(qlist, qnull())
 
 #define QLIST_FOREACH_ENTRY(qlist, var)             \
         for ((var) = ((qlist)->head.tqh_first);     \
@@ -58,6 +61,7 @@ QObject *qlist_peek(QList *qlist);
 int qlist_empty(const QList *qlist);
 size_t qlist_size(const QList *qlist);
 QList *qobject_to_qlist(const QObject *obj);
+bool qlist_is_equal(const QObject *x, const QObject *y);
 void qlist_destroy_obj(QObject *obj);
 
 static inline const QListEntry *qlist_first(const QList *qlist)

include/qapi/qmp/qnull.h

@@ -0,0 +1,32 @@
+/*
+ * QNull
+ *
+ * Copyright (C) 2015 Red Hat, Inc.
+ *
+ * Authors:
+ *  Markus Armbruster <armbru@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.1
+ * or later.  See the COPYING.LIB file in the top-level directory.
+ */
+
+#ifndef QNULL_H
+#define QNULL_H
+
+#include "qapi/qmp/qobject.h"
+
+struct QNull {
+    QObject base;
+};
+
+extern QNull qnull_;
+
+static inline QNull *qnull(void)
+{
+    QINCREF(&qnull_);
+    return &qnull_;
+}
+
+bool qnull_is_equal(const QObject *x, const QObject *y);
+
+#endif /* QNULL_H */

include/qapi/qmp/qnum.h

@@ -69,6 +69,7 @@ double qnum_get_double(QNum *qn);
 char *qnum_to_string(QNum *qn);
 
 QNum *qobject_to_qnum(const QObject *obj);
+bool qnum_is_equal(const QObject *x, const QObject *y);
 void qnum_destroy_obj(QObject *obj);
 
 #endif /* QNUM_H */

include/qapi/qmp/qobject.h

@@ -67,6 +67,15 @@ static inline void qobject_incref(QObject *obj)
         obj->refcnt++;
 }
 
+/**
+ * qobject_is_equal(): Return whether the two objects are equal.
+ *
+ * Any of the pointers may be NULL; return true if both are.  Always
+ * return false if only one is (therefore a QNull object is not
+ * considered equal to a NULL pointer).
+ */
+bool qobject_is_equal(const QObject *x, const QObject *y);
+
 /**
  * qobject_destroy(): Free resources used by the object
  */
@@ -93,16 +102,4 @@ static inline QType qobject_type(const QObject *obj)
     return obj->type;
 }
 
-struct QNull {
-    QObject base;
-};
-
-extern QNull qnull_;
-
-static inline QNull *qnull(void)
-{
-    QINCREF(&qnull_);
-    return &qnull_;
-}
-
 #endif /* QOBJECT_H */

include/qapi/qmp/qstring.h

@@ -31,6 +31,7 @@ void qstring_append_int(QString *qstring, int64_t value);
 void qstring_append(QString *qstring, const char *str);
 void qstring_append_chr(QString *qstring, int c);
 QString *qobject_to_qstring(const QObject *obj);
+bool qstring_is_equal(const QObject *x, const QObject *y);
 void qstring_destroy_obj(QObject *obj);
 
 #endif /* QSTRING_H */