Re: [Libguestfs] [PATCH v3 09/14] nbd/server: Initial support for extended headers

On 15.05.23 22:53, Eric Blake wrote: > Time to support clients that request extended headers. Now we can > finally reach the code added across several previous patches. > > Even though the NBD spec has been altered to allow us to accept > NBD_CMD_READ larger than the max payload size (provided our response > is a hole or broken up over more than one data chunk), we are not > planning to take advantage of that, and continue to cap NBD_CMD_READ > to 32M regardless of header size. > > For NBD_CMD_WRITE_ZEROES and NBD_CMD_TRIM, the block layer already > supports 64-bit operations without any effort on our part. For > NBD_CMD_BLOCK_STATUS, the client's length is a hint, and the previous > patch took care of implementing the required > NBD_REPLY_TYPE_BLOCK_STATUS_EXT. > > Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; > --- > nbd/nbd-internal.h | 5 +- [..] > > static inline void set_be_simple_reply(NBDClient *client, struct iovec *iov, > - uint64_t error, NBDRequest *request) > + uint32_t error, NBDStructuredError *err, > + NBDRequest *request) > { > - NBDSimpleReply *reply = iov->iov_base; > + if (client->header_style >= NBD_HEADER_EXTENDED) { > + NBDExtendedReplyChunk *chunk = iov->iov_base; > > - iov->iov_len = sizeof(*reply); > - stl_be_p(&reply->magic, NBD_SIMPLE_REPLY_MAGIC); > - stl_be_p(&reply->error, error); > - stq_be_p(&reply->handle, request->handle); > + iov->iov_len = sizeof(*chunk); > + stl_be_p(&chunk->magic, NBD_EXTENDED_REPLY_MAGIC); > + stw_be_p(&chunk->flags, NBD_REPLY_FLAG_DONE); > + stq_be_p(&chunk->handle, request->handle); > + stq_be_p(&chunk->offset, request->from); > + if (error) { > + assert(!iov[1].iov_base); > + iov[1].iov_base = err; > + iov[1].iov_len = sizeof(*err); > + stw_be_p(&chunk->type, NBD_REPLY_TYPE_ERROR); > + stq_be_p(&chunk->length, sizeof(*err)); > + stl_be_p(&err->error, error); > + stw_be_p(&err->message_length, 0); > + } else { > + stw_be_p(&chunk->type, NBD_REPLY_TYPE_NONE); > + stq_be_p(&chunk->length, 0); > + } > + } else { > + NBDSimpleReply *reply = iov->iov_base; > + > + iov->iov_len = sizeof(*reply); > + stl_be_p(&reply->magic, NBD_SIMPLE_REPLY_MAGIC); > + stl_be_p(&reply->error, error); > + stq_be_p(&reply->handle, request->handle); > + } > } > > static int coroutine_fn nbd_co_send_simple_reply(NBDClient *client, > @@ -1906,30 +1966,44 @@ static int coroutine_fn nbd_co_send_simple_reply(NBDClient *client, So, that's not _simple_ now.. The function should be renamed. As well as set_be_simple_reply(). _simple_or_extended_ ? a bit too long. But continuing to use "simple" is in bad relation with use of "simple" word in specification.

Probably better to update callers? The only caller isi nbd_send_generic_reply(). So, could we just add nbd_co_send_single_extended_reply() to call from nbd_send_generic_reply() in case of EXTENDED? Also, transformation of set_be_simple_reply() do look like it should be two separate functions. > { > NBDReply hdr; > int nbd_err = system_errno_to_nbd_errno(error); > + NBDStructuredError err; > struct iovec iov[] = { > {.iov_base = &hdr}, > {.iov_base = data, .iov_len = len} > }; > > + assert(!len || !nbd_err); > trace_nbd_co_send_simple_reply(request->handle, nbd_err, > nbd_err_lookup(nbd_err), len); > - set_be_simple_reply(client, &iov[0], nbd_err, request); > + set_be_simple_reply(client, &iov[0], nbd_err, &err, request); > > - return nbd_co_send_iov(client, iov, len ? 2 : 1, errp); > + return nbd_co_send_iov(client, iov, iov[1].iov_len ? 2 : 1, errp);