nbd: BLOCK_STATUS for standard get_block_status function: client part

Minimal realization: only one extent in server answer is supported.
Flag NBD_CMD_FLAG_REQ_ONE is used to force this behavior.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180312152126.286890-6-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: grammar tweaks, fix min_block check and 32-bit cap, use -1
instead of errno on failure in nbd_negotiate_simple_meta_context,
ensure that block status makes progress on success]
Signed-off-by: Eric Blake <eblake@redhat.com>

3 files changed, 159 insertions, 0 deletions

diff --git a/block/nbd-client.c b/block/nbd-client.c
index 0d9f73a137..e64e346d69 100644
--- a/block/nbd-client.c
+++ b/block/nbd-client.c
@@ -228,6 +228,48 @@ static int nbd_parse_offset_hole_payload(NBDStructuredReplyChunk *chunk,
     return 0;
 }
 
+/* nbd_parse_blockstatus_payload
+ * support only one extent in reply and only for
+ * base:allocation context
+ */
+static int nbd_parse_blockstatus_payload(NBDClientSession *client,
+                                         NBDStructuredReplyChunk *chunk,
+                                         uint8_t *payload, uint64_t orig_length,
+                                         NBDExtent *extent, Error **errp)
+{
+    uint32_t context_id;
+
+    if (chunk->length != sizeof(context_id) + sizeof(extent)) {
+        error_setg(errp, "Protocol error: invalid payload for "
+                         "NBD_REPLY_TYPE_BLOCK_STATUS");
+        return -EINVAL;
+    }
+
+    context_id = payload_advance32(&payload);
+    if (client->info.meta_base_allocation_id != context_id) {
+        error_setg(errp, "Protocol error: unexpected context id %d for "
+                         "NBD_REPLY_TYPE_BLOCK_STATUS, when negotiated context "
+                         "id is %d", context_id,
+                         client->info.meta_base_allocation_id);
+        return -EINVAL;
+    }
+
+    extent->length = payload_advance32(&payload);
+    extent->flags = payload_advance32(&payload);
+
+    if (extent->length == 0 ||
+        (client->info.min_block && !QEMU_IS_ALIGNED(extent->length,
+                                                    client->info.min_block)) ||
+        extent->length > orig_length)
+    {
+        error_setg(errp, "Protocol error: server sent status chunk with "
+                   "invalid length");
+        return -EINVAL;
+    }
+
+    return 0;
+}
+
 /* nbd_parse_error_payload
  * on success @errp contains message describing nbd error reply
  */
@@ -642,6 +684,68 @@ static int nbd_co_receive_cmdread_reply(NBDClientSession *s, uint64_t handle,
     return iter.ret;
 }
 
+static int nbd_co_receive_blockstatus_reply(NBDClientSession *s,
+                                            uint64_t handle, uint64_t length,
+                                            NBDExtent *extent, Error **errp)
+{
+    NBDReplyChunkIter iter;
+    NBDReply reply;
+    void *payload = NULL;
+    Error *local_err = NULL;
+    bool received = false;
+
+    assert(!extent->length);
+    NBD_FOREACH_REPLY_CHUNK(s, iter, handle, s->info.structured_reply,
+                            NULL, &reply, &payload)
+    {
+        int ret;
+        NBDStructuredReplyChunk *chunk = &reply.structured;
+
+        assert(nbd_reply_is_structured(&reply));
+
+        switch (chunk->type) {
+        case NBD_REPLY_TYPE_BLOCK_STATUS:
+            if (received) {
+                s->quit = true;
+                error_setg(&local_err, "Several BLOCK_STATUS chunks in reply");
+                nbd_iter_error(&iter, true, -EINVAL, &local_err);
+            }
+            received = true;
+
+            ret = nbd_parse_blockstatus_payload(s, &reply.structured,
+                                                payload, length, extent,
+                                                &local_err);
+            if (ret < 0) {
+                s->quit = true;
+                nbd_iter_error(&iter, true, ret, &local_err);
+            }
+            break;
+        default:
+            if (!nbd_reply_type_is_error(chunk->type)) {
+                s->quit = true;
+                error_setg(&local_err,
+                           "Unexpected reply type: %d (%s) "
+                           "for CMD_BLOCK_STATUS",
+                           chunk->type, nbd_reply_type_lookup(chunk->type));
+                nbd_iter_error(&iter, true, -EINVAL, &local_err);
+            }
+        }
+
+        g_free(payload);
+        payload = NULL;
+    }
+
+    if (!extent->length && !iter.err) {
+        error_setg(&iter.err,
+                   "Server did not reply with any status extents");
+        if (!iter.ret) {
+            iter.ret = -EIO;
+        }
+    }
+    error_propagate(errp, iter.err);
+    return iter.ret;
+}
+
 static int nbd_co_request(BlockDriverState *bs, NBDRequest *request,
                           QEMUIOVector *write_qiov)
 {
@@ -784,6 +888,51 @@ int nbd_client_co_pdiscard(BlockDriverState *bs, int64_t offset, int bytes)
     return nbd_co_request(bs, &request, NULL);
 }
 
+int coroutine_fn nbd_client_co_block_status(BlockDriverState *bs,
+                                            bool want_zero,
+                                            int64_t offset, int64_t bytes,
+                                            int64_t *pnum, int64_t *map,
+                                            BlockDriverState **file)
+{
+    int64_t ret;
+    NBDExtent extent = { 0 };
+    NBDClientSession *client = nbd_get_client_session(bs);
+    Error *local_err = NULL;
+
+    NBDRequest request = {
+        .type = NBD_CMD_BLOCK_STATUS,
+        .from = offset,
+        .len = MIN(MIN_NON_ZERO(QEMU_ALIGN_DOWN(INT_MAX,
+                                                bs->bl.request_alignment),
+                                client->info.max_block), bytes),
+        .flags = NBD_CMD_FLAG_REQ_ONE,
+    };
+
+    if (!client->info.base_allocation) {
+        *pnum = bytes;
+        return BDRV_BLOCK_DATA;
+    }
+
+    ret = nbd_co_send_request(bs, &request, NULL);
+    if (ret < 0) {
+        return ret;
+    }
+
+    ret = nbd_co_receive_blockstatus_reply(client, request.handle, bytes,
+                                           &extent, &local_err);
+    if (local_err) {
+        error_report_err(local_err);
+    }
+    if (ret < 0) {
+        return ret;
+    }
+
+    assert(extent.length);
+    *pnum = extent.length;
+    return (extent.flags & NBD_STATE_HOLE ? 0 : BDRV_BLOCK_DATA) |
+           (extent.flags & NBD_STATE_ZERO ? BDRV_BLOCK_ZERO : 0);
+}
+
 void nbd_client_detach_aio_context(BlockDriverState *bs)
 {
     NBDClientSession *client = nbd_get_client_session(bs);
@@ -828,6 +977,7 @@ int nbd_client_init(BlockDriverState *bs,
 
     client->info.request_sizes = true;
     client->info.structured_reply = true;
+    client->info.base_allocation = true;
     ret = nbd_receive_negotiate(QIO_CHANNEL(sioc), export,
                                 tlscreds, hostname,
                                 &client->ioc, &client->info, errp);
diff --git a/block/nbd-client.h b/block/nbd-client.h
index 612c4c21a0..0ece76e5af 100644
--- a/block/nbd-client.h
+++ b/block/nbd-client.h
@@ -61,4 +61,10 @@ void nbd_client_detach_aio_context(BlockDriverState *bs);
 void nbd_client_attach_aio_context(BlockDriverState *bs,
                                    AioContext *new_context);
 
+int coroutine_fn nbd_client_co_block_status(BlockDriverState *bs,
+                                            bool want_zero,
+                                            int64_t offset, int64_t bytes,
+                                            int64_t *pnum, int64_t *map,
+                                            BlockDriverState **file);
+
 #endif /* NBD_CLIENT_H */
diff --git a/block/nbd.c b/block/nbd.c
index d4e4172c08..1e2b3ba2d3 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -585,6 +585,7 @@ static BlockDriver bdrv_nbd = {
     .bdrv_detach_aio_context    = nbd_detach_aio_context,
     .bdrv_attach_aio_context    = nbd_attach_aio_context,
     .bdrv_refresh_filename      = nbd_refresh_filename,
+    .bdrv_co_block_status       = nbd_client_co_block_status,
 };
 
 static BlockDriver bdrv_nbd_tcp = {
@@ -604,6 +605,7 @@ static BlockDriver bdrv_nbd_tcp = {
     .bdrv_detach_aio_context    = nbd_detach_aio_context,
     .bdrv_attach_aio_context    = nbd_attach_aio_context,
     .bdrv_refresh_filename      = nbd_refresh_filename,
+    .bdrv_co_block_status       = nbd_client_co_block_status,
 };
 
 static BlockDriver bdrv_nbd_unix = {
@@ -623,6 +625,7 @@ static BlockDriver bdrv_nbd_unix = {
     .bdrv_detach_aio_context    = nbd_detach_aio_context,
     .bdrv_attach_aio_context    = nbd_attach_aio_context,
     .bdrv_refresh_filename      = nbd_refresh_filename,
+    .bdrv_co_block_status       = nbd_client_co_block_status,
 };
 
 static void bdrv_nbd_init(void)