qapi: add nbd-server-remove

Add command for removing an export. It is needed for cases when we
don't want to keep the export after the operation on it was completed.
The other example is a temporary node, created with blockdev-add.
If we want to delete it we should firstly remove any corresponding
NBD export.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180119135719.24745-3-vsementsov@virtuozzo.com>
[eblake: drop dead nb_clients code]
Signed-off-by: Eric Blake <eblake@redhat.com>

diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index 104789e521c167ad3ce49e308dadec121ecd6fe6..a9f79c6778e8bc737514fcb951ccbf6a6c1d199e 100644 (file)
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -189,6 +189,30 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
     nbd_export_put(exp);
 }
 
+void qmp_nbd_server_remove(const char *name,
+                           bool has_mode, NbdServerRemoveMode mode,
+                           Error **errp)
+{
+    NBDExport *exp;
+
+    if (!nbd_server) {
+        error_setg(errp, "NBD server not running");
+        return;
+    }
+
+    exp = nbd_export_find(name);
+    if (exp == NULL) {
+        error_setg(errp, "Export '%s' is not found", name);
+        return;
+    }
+
+    if (!has_mode) {
+        mode = NBD_SERVER_REMOVE_MODE_SAFE;
+    }
+
+    nbd_export_remove(exp, mode, errp);
+}
+
 void qmp_nbd_server_stop(Error **errp)
 {
     nbd_export_close_all();

diff --git a/include/block/nbd.h b/include/block/nbd.h
index 978e44336642beaca09d88e7790fe13568c5b25e..ee74ec391a8a2cc0b87bc737c61634dd0982d63b 100644 (file)
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -261,6 +261,7 @@ NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size,
                           bool writethrough, BlockBackend *on_eject_blk,
                           Error **errp);
 void nbd_export_close(NBDExport *exp);
+void nbd_export_remove(NBDExport *exp, NbdServerRemoveMode mode, Error **errp);
 void nbd_export_get(NBDExport *exp);
 void nbd_export_put(NBDExport *exp);
 

diff --git a/nbd/server.c b/nbd/server.c
index 6caa8d17be7370e493a6d2aa152511f3fade8536..112e3f69dff7b336f05a5db1638dbd1ecf7bbc53 100644 (file)
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1177,6 +1177,19 @@ void nbd_export_close(NBDExport *exp)
     nbd_export_put(exp);
 }
 
+void nbd_export_remove(NBDExport *exp, NbdServerRemoveMode mode, Error **errp)
+{
+    if (mode == NBD_SERVER_REMOVE_MODE_HARD || QTAILQ_EMPTY(&exp->clients)) {
+        nbd_export_close(exp);
+        return;
+    }
+
+    assert(mode == NBD_SERVER_REMOVE_MODE_SAFE);
+
+    error_setg(errp, "export '%s' still in use", exp->name);
+    error_append_hint(errp, "Use mode='hard' to force client disconnect\n");
+}
+
 void nbd_export_get(NBDExport *exp)
 {
     assert(exp->refcount > 0);

diff --git a/qapi/block.json b/qapi/block.json
index 353e3a45bdf8e340a2983d8e7a3fad4331718321..c69452400291c4a8412091b378fee1379d5945f5 100644 (file)
--- a/qapi/block.json
+++ b/qapi/block.json
@@ -227,6 +227,47 @@
 { 'command': 'nbd-server-add',
   'data': {'device': 'str', '*name': 'str', '*writable': 'bool'} }
 
+##
+# @NbdServerRemoveMode:
+#
+# Mode for removing an NBD export.
+#
+# @safe: Remove export if there are no existing connections, fail otherwise.
+#
+# @hard: Drop all connections immediately and remove export.
+#
+# Potential additional modes to be added in the future:
+#
+# hide: Just hide export from new clients, leave existing connections as is.
+#       Remove export after all clients are disconnected.
+#
+# soft: Hide export from new clients, answer with ESHUTDOWN for all further
+#       requests from existing clients.
+#
+# Since: 2.12
+##
+{'enum': 'NbdServerRemoveMode', 'data': ['safe', 'hard']}
+
+##
+# @nbd-server-remove:
+#
+# Remove NBD export by name.
+#
+# @name: Export name.
+#
+# @mode: Mode of command operation. See @NbdServerRemoveMode description.
+#        Default is 'safe'.
+#
+# Returns: error if
+#            - the server is not running
+#            - export is not found
+#            - mode is 'safe' and there are existing connections
+#
+# Since: 2.12
+##
+{ 'command': 'nbd-server-remove',
+  'data': {'name': 'str', '*mode': 'NbdServerRemoveMode'} }
+
 ##
 # @nbd-server-stop:
 #