[PATCH v5 06/12] nbd: Update qapi to support exporting multiple bitmaps

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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 as distinct metadata
contexts that the NBD client may request, but the actual support for
more than one will require a further patch to the server.

Signed-off-by: Eric Blake <eblake@xxxxxxxxxx>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx>
---
 docs/system/deprecated.rst |  4 +++-
 qapi/block-export.json     | 18 ++++++++++++------
 blockdev-nbd.c             | 13 +++++++++++++
 nbd/server.c               | 19 +++++++++++++------
 qemu-nbd.c                 | 10 +++++-----
 5 files changed, 46 insertions(+), 18 deletions(-)

diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
index 905628f3a0cb..d6cd027ac740 100644
--- a/docs/system/deprecated.rst
+++ b/docs/system/deprecated.rst
@@ -268,7 +268,9 @@ the 'wait' field, which is only applicable to sockets in server mode
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 Use the more generic commands ``block-export-add`` and ``block-export-del``
-instead.
+instead.  As part of this deprecation, it is now preferred to export a
+list of dirty bitmaps via ``bitmaps``, rather than a single bitmap via
+``bitmap``.

 Human Monitor Protocol (HMP) commands
 -------------------------------------
diff --git a/qapi/block-export.json b/qapi/block-export.json
index 893d5cde5dfe..c7c749d61097 100644
--- a/qapi/block-export.json
+++ b/qapi/block-export.json
@@ -74,10 +74,10 @@
 # @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 the
-#          metadata context name "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
+#           the metadata context name "qemu:dirty-bitmap:BITMAP" to inspect
+#           each bitmap. (since 5.2)
 #
 # @allocation-depth: Also export the allocation depth map for @device, so
 #                    the NBD client can use NBD_OPT_SET_META_CONTEXT with
@@ -88,7 +88,7 @@
 ##
 { 'struct': 'BlockExportOptionsNbd',
   'data': { '*name': 'str', '*description': 'str',
-            '*bitmap': 'str', '*allocation-depth': 'bool' } }
+            '*bitmaps': ['str'], '*allocation-depth': 'bool' } }

 ##
 # @NbdServerAddOptions:
@@ -100,12 +100,18 @@
 # @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 the metadata
+#          context name "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 cee9134b12eb..cfd46223bf4d 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -192,6 +192,19 @@ 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;
+        QAPI_LIST_ADD(arg->bitmaps, 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.
diff --git a/nbd/server.c b/nbd/server.c
index 30cfe0eee467..884ffa00f1bd 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 847fde435a7f..5473821216f7 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;
     const char *tlscredsid = NULL;
     bool imageOpts = false;
     bool writethrough = true;
@@ -701,7 +701,7 @@ int main(int argc, char **argv)
             alloc_depth = true;
             break;
         case 'B':
-            bitmap = optarg;
+            QAPI_LIST_ADD(bitmaps, g_strdup(optarg));
             break;
         case 'k':
             sockpath = optarg;
@@ -798,7 +798,7 @@ 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 +1082,8 @@ 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_allocation_depth = alloc_depth,
             .allocation_depth     = alloc_depth,
         },
-- 
2.29.0




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