nbd/client: Add x-dirty-bitmap to query bitmap from server

In order to test that the NBD server is properly advertising
dirty bitmaps, we need a bare minimum client that can request
and read the context.  Since feature freeze for 3.0 is imminent,
this is the smallest workable patch, which replaces the qemu
block status report with the results of the NBD server's dirty
bitmap (making it very easy to use 'qemu-img map --output=json'
to learn where the dirty portions are).  Note that the NBD
protocol defines a dirty section with the same bit but opposite
sense that normal "base:allocation" uses to report an allocated
section; so in qemu-img map output, "data":true corresponds to
clean, "data":false corresponds to dirty.

A more complete solution that allows dirty bitmaps to be queried
at the same time as normal block status will be required before
this addition can lose the x- prefix.  Until then, the fact that
this replaces normal status with dirty status means actions
like 'qemu-img convert' will likely misbehave due to treating
dirty regions of the file as if they are unallocated.

The next patch adds an iotest to exercise this new code.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180702191458.28741-2-eblake@redhat.com>

diff --git a/block/nbd-client.c b/block/nbd-client.c
index 8d69eaaa32f84ef1d4a18c4ce5309e054cfc20fb..9686ecbd5eec5704687f7b2317c6cefd4fd011b0 100644 (file)
--- a/block/nbd-client.c
+++ b/block/nbd-client.c
@@ -970,6 +970,7 @@ int nbd_client_init(BlockDriverState *bs,
                     const char *export,
                     QCryptoTLSCreds *tlscreds,
                     const char *hostname,
+                    const char *x_dirty_bitmap,
                     Error **errp)
 {
     NBDClientSession *client = nbd_get_client_session(bs);
@@ -982,9 +983,11 @@ int nbd_client_init(BlockDriverState *bs,
     client->info.request_sizes = true;
     client->info.structured_reply = true;
     client->info.base_allocation = true;
+    client->info.x_dirty_bitmap = g_strdup(x_dirty_bitmap);
     ret = nbd_receive_negotiate(QIO_CHANNEL(sioc), export,
                                 tlscreds, hostname,
                                 &client->ioc, &client->info, errp);
+    g_free(client->info.x_dirty_bitmap);
     if (ret < 0) {
         logout("Failed to negotiate with the NBD server\n");
         return ret;

diff --git a/block/nbd-client.h b/block/nbd-client.h
index 0ece76e5aff85020b63a1e51fa4874ea9f842898..cfc90550b9962c757b441b78db18fadb40ae3c9b 100644 (file)
--- a/block/nbd-client.h
+++ b/block/nbd-client.h
@@ -45,6 +45,7 @@ int nbd_client_init(BlockDriverState *bs,
                     const char *export_name,
                     QCryptoTLSCreds *tlscreds,
                     const char *hostname,
+                    const char *x_dirty_bitmap,
                     Error **errp);
 void nbd_client_close(BlockDriverState *bs);
 

diff --git a/block/nbd.c b/block/nbd.c
index 13db4030e67292a4f4ae4e76c02a8a5081ce3321..b198ad775fb903868e60a24a8535b3f610a4dbb0 100644 (file)
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -378,6 +378,12 @@ static QemuOptsList nbd_runtime_opts = {
             .type = QEMU_OPT_STRING,
             .help = "ID of the TLS credentials to use",
         },
+        {
+            .name = "x-dirty-bitmap",
+            .type = QEMU_OPT_STRING,
+            .help = "experimental: expose named dirty bitmap in place of "
+                    "block status",
+        },
         { /* end of list */ }
     },
 };
@@ -438,8 +444,8 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
     }
 
     /* NBD handshake */
-    ret = nbd_client_init(bs, sioc, s->export,
-                          tlscreds, hostname, errp);
+    ret = nbd_client_init(bs, sioc, s->export, tlscreds, hostname,
+                          qemu_opt_get(opts, "x-dirty-bitmap"), errp);
  error:
     if (sioc) {
         object_unref(OBJECT(sioc));

diff --git a/include/block/nbd.h b/include/block/nbd.h
index daaeae61bf9268cf63d637f8032d077115fa9ca6..4638c839f519928b3d6774df51b7762ebb03fd46 100644 (file)
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -259,6 +259,7 @@ static inline bool nbd_reply_type_is_error(int type)
 struct NBDExportInfo {
     /* Set by client before nbd_receive_negotiate() */
     bool request_sizes;
+    char *x_dirty_bitmap;
 
     /* In-out fields, set by client before nbd_receive_negotiate() and
      * updated by server results during nbd_receive_negotiate() */

diff --git a/nbd/client.c b/nbd/client.c
index 232ff4f46da80e1100c9fd5cb943b9e5614f894c..40b74d9761f804238bacfa7155185fa71e7137f8 100644 (file)
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -1,5 +1,5 @@
 /*
- *  Copyright (C) 2016-2017 Red Hat, Inc.
+ *  Copyright (C) 2016-2018 Red Hat, Inc.
  *  Copyright (C) 2005  Anthony Liguori <anthony@codemonkey.ws>
  *
  *  Network Block Device Client Side
@@ -831,7 +831,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name,
 
             if (info->structured_reply && base_allocation) {
                 result = nbd_negotiate_simple_meta_context(
-                        ioc, name, "base:allocation",
+                        ioc, name, info->x_dirty_bitmap ?: "base:allocation",
                         &info->meta_base_allocation_id, errp);
                 if (result < 0) {
                     goto fail;

diff --git a/qapi/block-core.json b/qapi/block-core.json
index 577ce5e9991d8349554e06bb86b28fcdb81b7276..90e554ed0ff6d57697bd52c92a8552528cfbe050 100644 (file)
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -3471,12 +3471,17 @@
 #
 # @tls-creds:   TLS credentials ID
 #
+# @x-dirty-bitmap: A "qemu:dirty-bitmap:NAME" string to query in place of
+#                  traditional "base:allocation" block status (see
+#                  NBD_OPT_LIST_META_CONTEXT in the NBD protocol) (since 3.0)
+#
 # Since: 2.9
 ##
 { 'struct': 'BlockdevOptionsNbd',
   'data': { 'server': 'SocketAddress',
             '*export': 'str',
-            '*tls-creds': 'str' } }
+            '*tls-creds': 'str',
+            '*x-dirty-bitmap': 'str' } }
 
 ##
 # @BlockdevOptionsRaw: