Re: [Libguestfs] [libnbd PATCH v3 01/22] block_status: Refactor array storage

For 32-bit block status, we were able to cheat and use an array with an odd number of elements, with array[0] holding the context id, and passing &array[1] to the user's callback. But once we have 64-bit extents, we can no longer abuse array element 0 like that, for two reasons: 64-bit extents contain uint64_t which might not be alignment-compatible with an array of uint32_t on all architectures, and the new NBD_REPLY_TYPE_BLOCK_STATUS_EXT adds an additional count field before the array. Split out a new state STRUCTURED_REPLY.BS_HEADER to receive the context id (and eventually the new count field for 64-bit replies) separately from the extents array, and add another structured_reply type in the payload section for tracking it. No behavioral change, other than the rare possibility of landing in the new state. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- lib/internal.h | 1 + lib/nbd-protocol.h | 17 +++++---- generator/state_machine.ml | 9 ++++- generator/states-reply-structured.c | 56 ++++++++++++++++++++--------- 4 files changed, 60 insertions(+), 23 deletions(-) diff --git a/lib/internal.h b/lib/internal.h index b155681d..25eeea34 100644 --- a/lib/internal.h +++ b/lib/internal.h @@ -242,6 +242,7 @@ struct nbd_handle { union { struct nbd_structured_reply_offset_data offset_data; struct nbd_structured_reply_offset_hole offset_hole; + struct nbd_structured_reply_block_status_hdr bs_hdr; struct { struct nbd_structured_reply_error error; char msg[NBD_MAX_STRING]; /* Common to all error types */ diff --git a/lib/nbd-protocol.h b/lib/nbd-protocol.h index 0217891e..f4640a98 100644 --- a/lib/nbd-protocol.h +++ b/lib/nbd-protocol.h @@ -182,12 +182,6 @@ struct nbd_fixed_new_option_reply_meta_context { /* followed by a string */ } NBD_ATTRIBUTE_PACKED; -/* NBD_REPLY_TYPE_BLOCK_STATUS block descriptor. */ -struct nbd_block_descriptor { - uint32_t length; /* length of block */ - uint32_t status_flags; /* block type (hole etc) */ -} NBD_ATTRIBUTE_PACKED; - /* Request (client -> server). */ struct nbd_request { uint32_t magic; /* NBD_REQUEST_MAGIC. */ @@ -224,6 +218,17 @@ struct nbd_structured_reply_offset_hole { uint32_t length; /* Length of hole. */ } NBD_ATTRIBUTE_PACKED; +/* NBD_REPLY_TYPE_BLOCK_STATUS block descriptor. */ +struct nbd_block_descriptor { + uint32_t length; /* length of block */ + uint32_t status_flags; /* block type (hole etc) */ +} NBD_ATTRIBUTE_PACKED; + +struct nbd_structured_reply_block_status_hdr { + uint32_t context_id; /* metadata context ID */ + /* followed by array of nbd_block_descriptor extents */ +} NBD_ATTRIBUTE_PACKED; + struct nbd_structured_reply_error { uint32_t error; /* NBD_E* error number */ uint16_t len; /* Length of human readable error. */ diff --git a/generator/state_machine.ml b/generator/state_machine.ml index 126159b9..1f0d00b0 100644 --- a/generator/state_machine.ml +++ b/generator/state_machine.ml @@ -871,10 +871,17 @@ and external_events = []; }; + State { + default_state with + name = "RECV_BS_HEADER"; + comment = "Receive header of structured reply block-status payload"; + external_events = []; + }; + State { default_state with name = "RECV_BS_ENTRIES"; - comment = "Receive a structured reply block-status payload"; + comment = "Receive entries array of structured reply block-status payload"; external_events = []; }; diff --git a/generator/states-reply-structured.c b/generator/states-reply-structured.c index 5aca7262..96182222 100644 --- a/generator/states-reply-structured.c +++ b/generator/states-reply-structured.c @@ -126,19 +126,10 @@ REPLY.STRUCTURED_REPLY.CHECK: length < 12 || ((length-4) & 7) != 0)

goto resync; assert (CALLBACK_IS_NOT_NULL (cmd->cb.fn.extent)); - /* We read the context ID followed by all the entries into a - * single array and deal with it at the end. - */ - free (h->bs_entries); - h->bs_entries = malloc (length); - if (h->bs_entries == NULL) { - SET_NEXT_STATE (%.DEAD); - set_error (errno, "malloc"); - break; - } - h->rbuf = h->bs_entries; - h->rlen = length; - SET_NEXT_STATE (%RECV_BS_ENTRIES); + /* Start by reading the context ID. */ + h->rbuf = &h->sbuf.sr.payload.bs_hdr; + h->rlen = sizeof h->sbuf.sr.payload.bs_hdr; + SET_NEXT_STATE (%RECV_BS_HEADER); break; default:

@@ -424,9 +415,41 @@ REPLY.STRUCTURED_REPLY.RECV_OFFSET_HOLE: } return 0; + REPLY.STRUCTURED_REPLY.RECV_BS_HEADER: + struct command *cmd = h->reply_cmd; + uint32_t length; + + switch (recv_into_rbuf (h)) { + case -1: SET_NEXT_STATE (%.DEAD); return 0; + case 1: + save_reply_state (h); + SET_NEXT_STATE (%.READY); + return 0; + case 0: + length = be32toh (h->sbuf.sr.structured_reply.length); + + assert (cmd); /* guaranteed by CHECK */ + assert (cmd->type == NBD_CMD_BLOCK_STATUS); + assert (length >= 12);

+ length -= sizeof h->sbuf.sr.payload.bs_hdr;

+ + free (h->bs_entries); + h->bs_entries = malloc (length); + if (h->bs_entries == NULL) { + SET_NEXT_STATE (%.DEAD); + set_error (errno, "malloc"); + return 0; + } + h->rbuf = h->bs_entries; + h->rlen = length; + SET_NEXT_STATE (%RECV_BS_ENTRIES); + } + return 0; +

REPLY.STRUCTURED_REPLY.RECV_BS_ENTRIES: struct command *cmd = h->reply_cmd; uint32_t length; + uint32_t count; size_t i; uint32_t context_id; @@ -445,15 +468,16 @@ REPLY.STRUCTURED_REPLY.RECV_BS_ENTRIES: assert (h->bs_entries); assert (length >= 12); assert (h->meta_valid); + count = (length - sizeof h->sbuf.sr.payload.bs_hdr) / sizeof *h->bs_entries;

/* Need to byte-swap the entries returned, but apart from that we * don't validate them. */ - for (i = 0; i < length/4; ++i) + for (i = 0; i < count; ++i) h->bs_entries[i] = be32toh (h->bs_entries[i]); /* Look up the context ID. */ - context_id = h->bs_entries[0]; + context_id = be32toh (h->sbuf.sr.payload.bs_hdr.context_id); for (i = 0; i < h->meta_contexts.len; ++i) if (context_id == h->meta_contexts.ptr[i].context_id) break; @@ -464,7 +488,7 @@ REPLY.STRUCTURED_REPLY.RECV_BS_ENTRIES: if (CALL_CALLBACK (cmd->cb.fn.extent, h->meta_contexts.ptr[i].name, cmd->offset, - &h->bs_entries[1], (length-4) / 4, + h->bs_entries, count, &error) == -1) if (cmd->error == 0) cmd->error = error ? error : EPROTO;