[PATCH v3 3/6] nbd: Update qapi to support multiple bitmaps

[Eric Blake <eblake@redhat.com>]

Since 'nbd-server-add' is deprecated, and 'block-export-add' is new to
5.2, we can still tweak the interface.  Allowing 'bitmaps':['str'] is
nicer than 'bitmap':'str'.  This wires up the qapi and qemu-nbd
changes to permit passing multiple bitmaps, but the actual support
will require a further patch to the server.

Signed-off-by: Eric Blake <eblake@redhat.com>
---
 qapi/block-export.json | 16 +++++++++++-----
 blockdev-nbd.c         | 18 ++++++++++++++++--
 nbd/server.c           | 19 +++++++++++++------
 qemu-nbd.c             | 13 ++++++++-----
 4 files changed, 48 insertions(+), 18 deletions(-)

diff --git a/qapi/block-export.json b/qapi/block-export.json
index 524cd3a94400..2dc45a54e364 100644
--- a/qapi/block-export.json
+++ b/qapi/block-export.json
@@ -74,9 +74,9 @@
 # @description: Free-form description of the export, up to 4096 bytes.
 #               (Since 5.0)
 #
-# @bitmap: Also export the dirty bitmap reachable from @device, so the
-#          NBD client can use NBD_OPT_SET_META_CONTEXT with
-#          "qemu:dirty-bitmap:NAME" to inspect the bitmap. (since 4.0)
+# @bitmaps: Also export each of the named dirty bitmaps reachable from
+#           @device, so the NBD client can use NBD_OPT_SET_META_CONTEXT with
+#           "qemu:dirty-bitmap:BITMAP" to inspect each bitmap. (since 5.2)
 #
 # @alloc: Also export the allocation map for @device, so the NBD client
 #         can use NBD_OPT_SET_META_CONTEXT with "qemu:allocation-depth"
@@ -86,7 +86,7 @@
 ##
 { 'struct': 'BlockExportOptionsNbd',
   'data': { '*name': 'str', '*description': 'str',
-            '*bitmap': 'str', '*alloc': 'bool' } }
+            '*bitmaps': ['str'], '*alloc': 'bool' } }

 ##
 # @NbdServerAddOptions:
@@ -98,12 +98,18 @@
 # @writable: Whether clients should be able to write to the device via the
 #            NBD connection (default false).
 #
+# @bitmap: Also export a single dirty bitmap reachable from @device, so the
+#          NBD client can use NBD_OPT_SET_META_CONTEXT with
+#          "qemu:dirty-bitmap:BITMAP" to inspect the bitmap (since 4.0);
+#          mutually exclusive with @bitmaps, and newer clients should use
+#          that instead.
+#
 # Since: 5.0
 ##
 { 'struct': 'NbdServerAddOptions',
   'base': 'BlockExportOptionsNbd',
   'data': { 'device': 'str',
-            '*writable': 'bool' } }
+            '*writable': 'bool', '*bitmap': 'str' } }

 ##
 # @nbd-server-add:
diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index f9012f93e2bb..f0a03c830c5f 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -190,6 +190,20 @@ void qmp_nbd_server_add(NbdServerAddOptions *arg, Error **errp)
         return;
     }

+    /*
+     * New code should use the list 'bitmaps'; but until this code is
+     * gone, we must support the older single 'bitmap'.  Use only one.
+     */
+    if (arg->has_bitmap) {
+        if (arg->has_bitmaps) {
+            error_setg(errp, "Can't mix 'bitmap' and 'bitmaps'");
+            return;
+        }
+        arg->has_bitmaps = true;
+        arg->bitmaps = g_new0(strList, 1);
+        arg->bitmaps->value = g_strdup(arg->bitmap);
+    }
+
     /*
      * block-export-add would default to the node-name, but we may have to use
      * the device name as a default here for compatibility.
@@ -210,8 +224,8 @@ void qmp_nbd_server_add(NbdServerAddOptions *arg, Error **errp)
             .name               = g_strdup(arg->name),
             .has_description    = arg->has_description,
             .description        = g_strdup(arg->description),
-            .has_bitmap         = arg->has_bitmap,
-            .bitmap             = g_strdup(arg->bitmap),
+            .has_bitmaps        = arg->has_bitmaps,
+            .bitmaps            = g_steal_pointer(&arg->bitmaps),
             .has_alloc          = arg->alloc,
             .alloc              = arg->alloc,
         },
diff --git a/nbd/server.c b/nbd/server.c
index e24495d93e2e..ea5de0b503cd 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1495,6 +1495,7 @@ static int nbd_export_create(BlockExport *blk_exp, BlockExportOptions *exp_args,
     uint64_t perm, shared_perm;
     bool readonly = !exp_args->writable;
     bool shared = !exp_args->writable;
+    strList *bitmaps;
     int ret;

     assert(exp_args->type == BLOCK_EXPORT_TYPE_NBD);
@@ -1556,12 +1557,18 @@ static int nbd_export_create(BlockExport *blk_exp, BlockExportOptions *exp_args,
     }
     exp->size = QEMU_ALIGN_DOWN(size, BDRV_SECTOR_SIZE);

-    if (arg->bitmap) {
+    /* XXX Allow more than one bitmap */
+    if (arg->bitmaps && arg->bitmaps->next) {
+        error_setg(errp, "multiple bitmaps per export not supported yet");
+        return -EOPNOTSUPP;
+    }
+    for (bitmaps = arg->bitmaps; bitmaps; bitmaps = bitmaps->next) {
+        const char *bitmap = bitmaps->value;
         BlockDriverState *bs = blk_bs(blk);
         BdrvDirtyBitmap *bm = NULL;

         while (bs) {
-            bm = bdrv_find_dirty_bitmap(bs, arg->bitmap);
+            bm = bdrv_find_dirty_bitmap(bs, bitmap);
             if (bm != NULL) {
                 break;
             }
@@ -1571,7 +1578,7 @@ static int nbd_export_create(BlockExport *blk_exp, BlockExportOptions *exp_args,

         if (bm == NULL) {
             ret = -ENOENT;
-            error_setg(errp, "Bitmap '%s' is not found", arg->bitmap);
+            error_setg(errp, "Bitmap '%s' is not found", bitmap);
             goto fail;
         }

@@ -1585,15 +1592,15 @@ static int nbd_export_create(BlockExport *blk_exp, BlockExportOptions *exp_args,
             ret = -EINVAL;
             error_setg(errp,
                        "Enabled bitmap '%s' incompatible with readonly export",
-                       arg->bitmap);
+                       bitmap);
             goto fail;
         }

         bdrv_dirty_bitmap_set_busy(bm, true);
         exp->export_bitmap = bm;
-        assert(strlen(arg->bitmap) <= BDRV_BITMAP_MAX_NAME_SIZE);
+        assert(strlen(bitmap) <= BDRV_BITMAP_MAX_NAME_SIZE);
         exp->export_bitmap_context = g_strdup_printf("qemu:dirty-bitmap:%s",
-                                                     arg->bitmap);
+                                                     bitmap);
         assert(strlen(exp->export_bitmap_context) < NBD_MAX_STRING_SIZE);
     }

diff --git a/qemu-nbd.c b/qemu-nbd.c
index e3cff17d6760..8648a39d0ab9 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -572,7 +572,7 @@ int main(int argc, char **argv)
     const char *export_name = NULL; /* defaults to "" later for server mode */
     const char *export_description = NULL;
     bool alloc_depth = false;
-    const char *bitmap = NULL;
+    strList *bitmaps = NULL, *tmp;
     const char *tlscredsid = NULL;
     bool imageOpts = false;
     bool writethrough = true;
@@ -701,7 +701,10 @@ int main(int argc, char **argv)
             alloc_depth = true;
             break;
         case 'B':
-            bitmap = optarg;
+            tmp = g_new(strList, 1);
+            tmp->value = g_strdup(optarg);
+            tmp->next = bitmaps;
+            bitmaps = tmp;
             break;
         case 'k':
             sockpath = optarg;
@@ -798,7 +801,7 @@ int main(int argc, char **argv)
         }
         if (export_name || export_description || dev_offset ||
             device || disconnect || fmt || sn_id_or_name || alloc_depth ||
-            bitmap || seen_aio || seen_discard || seen_cache) {
+            bitmaps || seen_aio || seen_discard || seen_cache) {
             error_report("List mode is incompatible with per-device settings");
             exit(EXIT_FAILURE);
         }
@@ -1082,8 +1085,8 @@ int main(int argc, char **argv)
             .name               = g_strdup(export_name),
             .has_description    = !!export_description,
             .description        = g_strdup(export_description),
-            .has_bitmap         = !!bitmap,
-            .bitmap             = g_strdup(bitmap),
+            .has_bitmaps        = !!bitmaps,
+            .bitmaps            = bitmaps,
             .has_alloc          = alloc_depth,
             .alloc              = alloc_depth,
         },
-- 
2.28.0