[Libguestfs] [libnbd PATCH v3 01/22] block_status: Refactor array storage
Eric Blake
eblake at redhat.com
Thu May 25 13:00:47 UTC 2023
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 at redhat.com>
---
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;
--
2.40.1
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