[Libguestfs] [PATCH nbdkit v5 FINAL 03/19] server: protocol: Implement Block Status "base:allocation".
Richard W.M. Jones
rjones at redhat.com
Thu Mar 28 16:18:30 UTC 2019
This commit implements the protocol side of supporting
NBD_CMD_BLOCK_STATUS to read "base:allocation" information about
disks. The practical result of this is that clients are able to read
which parts of a disk are allocated, holes or zeroes.
---
docs/nbdkit-protocol.pod | 5 +-
common/protocol/protocol.h | 15 ++
server/internal.h | 8 +
server/protocol-handshake-newstyle.c | 63 ++++++-
server/protocol-handshake.c | 11 ++
server/protocol.c | 240 +++++++++++++++++++++++++--
TODO | 4 +-
7 files changed, 328 insertions(+), 18 deletions(-)
diff --git a/docs/nbdkit-protocol.pod b/docs/nbdkit-protocol.pod
index 4c65e00..a9a3390 100644
--- a/docs/nbdkit-protocol.pod
+++ b/docs/nbdkit-protocol.pod
@@ -134,7 +134,10 @@ Supported in nbdkit E<ge> 1.11.8.
=item Block Status
-I<Not supported>.
+Supported in nbdkit E<ge> 1.11.10.
+
+Only C<base:allocation> (ie. querying which parts of an image are
+sparse) is supported.
=item Resize Extension
diff --git a/common/protocol/protocol.h b/common/protocol/protocol.h
index 06b917e..a7de2f0 100644
--- a/common/protocol/protocol.h
+++ b/common/protocol/protocol.h
@@ -112,6 +112,7 @@ extern const char *name_of_nbd_rep (int);
#define NBD_REP_ACK 1
#define NBD_REP_SERVER 2
#define NBD_REP_INFO 3
+#define NBD_REP_META_CONTEXT 4
#define NBD_REP_ERR_UNSUP 0x80000001
#define NBD_REP_ERR_POLICY 0x80000002
#define NBD_REP_ERR_INVALID 0x80000003
@@ -128,6 +129,18 @@ struct fixed_new_option_reply_info_export {
uint16_t eflags; /* per-export flags */
} __attribute__((packed));
+/* NBD_REP_META_CONTEXT reply (follows fixed_new_option_reply). */
+struct fixed_new_option_reply_meta_context {
+ uint32_t context_id; /* metadata context ID */
+ /* followed by a string */
+} __attribute__((packed));
+
+/* NBD_REPLY_TYPE_BLOCK_STATUS block descriptor. */
+struct block_descriptor {
+ uint32_t length; /* length of block */
+ uint32_t status_flags; /* block type (hole etc) */
+} __attribute__((packed));
+
/* New-style handshake server reply when using NBD_OPT_EXPORT_NAME.
* Modern clients use NBD_OPT_GO instead of this.
*/
@@ -199,10 +212,12 @@ extern const char *name_of_nbd_cmd (int);
#define NBD_CMD_FLUSH 3
#define NBD_CMD_TRIM 4
#define NBD_CMD_WRITE_ZEROES 6
+#define NBD_CMD_BLOCK_STATUS 7
extern const char *name_of_nbd_cmd_flag (int);
#define NBD_CMD_FLAG_FUA (1<<0)
#define NBD_CMD_FLAG_NO_HOLE (1<<1)
+#define NBD_CMD_FLAG_REQ_ONE (1<<3)
/* Error codes (previously errno).
* See http://git.qemu.org/?p=qemu.git;a=commitdiff;h=ca4414804114fd0095b317785bc0b51862e62ebb
diff --git a/server/internal.h b/server/internal.h
index ae51804..d804441 100644
--- a/server/internal.h
+++ b/server/internal.h
@@ -181,8 +181,10 @@ struct connection {
bool can_zero;
bool can_fua;
bool can_multi_conn;
+ bool can_extents;
bool using_tls;
bool structured_replies;
+ bool meta_context_base_allocation;
int sockin, sockout;
connection_recv_function recv;
@@ -219,6 +221,12 @@ extern int protocol_handshake_newstyle (struct connection *conn)
extern int protocol_recv_request_send_reply (struct connection *conn)
__attribute__((__nonnull__ (1)));
+/* The context ID of base:allocation. As far as I can tell it doesn't
+ * matter what this is as long as nbdkit always returns the same
+ * number.
+ */
+#define base_allocation_id 1
+
/* crypto.c */
#define root_tls_certificates_dir sysconfdir "/pki/" PACKAGE_NAME
extern void crypto_init (bool tls_set_on_cli);
diff --git a/server/protocol-handshake-newstyle.c b/server/protocol-handshake-newstyle.c
index db01f7b..6899e6c 100644
--- a/server/protocol-handshake-newstyle.c
+++ b/server/protocol-handshake-newstyle.c
@@ -133,6 +133,34 @@ send_newstyle_option_reply_info_export (struct connection *conn,
return 0;
}
+static int
+send_newstyle_option_reply_meta_context (struct connection *conn,
+ uint32_t option, uint32_t reply,
+ uint32_t context_id,
+ const char *name)
+{
+ struct fixed_new_option_reply fixed_new_option_reply;
+ struct fixed_new_option_reply_meta_context context;
+ const size_t namelen = strlen (name);
+
+ fixed_new_option_reply.magic = htobe64 (NBD_REP_MAGIC);
+ fixed_new_option_reply.option = htobe32 (option);
+ fixed_new_option_reply.reply = htobe32 (reply);
+ fixed_new_option_reply.replylen = htobe32 (sizeof context + namelen);
+ context.context_id = htobe32 (context_id);
+
+ if (conn->send (conn,
+ &fixed_new_option_reply,
+ sizeof fixed_new_option_reply) == -1 ||
+ conn->send (conn, &context, sizeof context) == -1 ||
+ conn->send (conn, name, namelen) == -1) {
+ nbdkit_error ("write: %m");
+ return -1;
+ }
+
+ return 0;
+}
+
/* Sub-function during negotiate_handshake_newstyle, to uniformly handle
* a client hanging up on a message boundary.
*/
@@ -503,7 +531,15 @@ negotiate_handshake_newstyle_options (struct connection *conn)
* for SET: nr_queries == 0 means reset all contexts
*/
if (nr_queries == 0) {
- /* Nothing is supported now. */
+ if (option == NBD_OPT_SET_META_CONTEXT)
+ conn->meta_context_base_allocation = false;
+ else /* LIST */ {
+ if (send_newstyle_option_reply_meta_context
+ (conn, option, NBD_REP_META_CONTEXT,
+ 0, "base:allocation") == -1)
+ return -1;
+ }
+
if (send_newstyle_option_reply (conn, option, NBD_REP_ACK) == -1)
return -1;
}
@@ -525,7 +561,30 @@ negotiate_handshake_newstyle_options (struct connection *conn)
option == NBD_OPT_LIST_META_CONTEXT ? "query" : "set",
(int) querylen, &data[opt_index]);
- /* Ignore query - nothing is supported. */
+ /* For LIST, "base:" returns all supported contexts in the
+ * base namespace. We only support "base:allocation".
+ */
+ if (option == NBD_OPT_LIST_META_CONTEXT &&
+ querylen == 5 &&
+ strncmp (&data[opt_index], "base:", 5) == 0) {
+ if (send_newstyle_option_reply_meta_context
+ (conn, option, NBD_REP_META_CONTEXT,
+ 0, "base:allocation") == -1)
+ return -1;
+ }
+ /* "base:allocation" requested by name. */
+ else if (querylen == 15 &&
+ strncmp (&data[opt_index], "base:allocation", 15) == 0) {
+ if (send_newstyle_option_reply_meta_context
+ (conn, option, NBD_REP_META_CONTEXT,
+ option == NBD_OPT_SET_META_CONTEXT
+ ? base_allocation_id : 0,
+ "base:allocation") == -1)
+ return -1;
+ if (option == NBD_OPT_SET_META_CONTEXT)
+ conn->meta_context_base_allocation = true;
+ }
+ /* Every other query must be ignored. */
opt_index += querylen;
nr_queries--;
diff --git a/server/protocol-handshake.c b/server/protocol-handshake.c
index 79a5999..9653210 100644
--- a/server/protocol-handshake.c
+++ b/server/protocol-handshake.c
@@ -110,6 +110,17 @@ protocol_compute_eflags (struct connection *conn, uint16_t *flags)
conn->can_multi_conn = true;
}
+ /* The result of this is not returned to callers here (or at any
+ * time during the handshake). However it makes sense to do it once
+ * per connection and store the result in the handle anyway. This
+ * protocol_compute_eflags function is a bit misnamed XXX.
+ */
+ fl = backend->can_extents (backend, conn);
+ if (fl == -1)
+ return -1;
+ if (fl)
+ conn->can_extents = true;
+
*flags = eflags;
return 0;
}
diff --git a/server/protocol.c b/server/protocol.c
index f117d42..383938f 100644
--- a/server/protocol.c
+++ b/server/protocol.c
@@ -36,6 +36,7 @@
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
+#include <stdbool.h>
#include <inttypes.h>
#include <string.h>
#include <unistd.h>
@@ -44,6 +45,7 @@
#include "internal.h"
#include "byte-swapping.h"
+#include "minmax.h"
#include "protocol.h"
/* Maximum read or write request that we will handle. */
@@ -78,6 +80,7 @@ validate_request (struct connection *conn,
case NBD_CMD_WRITE:
case NBD_CMD_TRIM:
case NBD_CMD_WRITE_ZEROES:
+ case NBD_CMD_BLOCK_STATUS:
if (!valid_range (conn, offset, count)) {
/* XXX Allow writes to extend the disk? */
nbdkit_error ("invalid request: %s: offset and count are out of range: "
@@ -106,7 +109,8 @@ validate_request (struct connection *conn,
}
/* Validate flags */
- if (flags & ~(NBD_CMD_FLAG_FUA | NBD_CMD_FLAG_NO_HOLE)) {
+ if (flags & ~(NBD_CMD_FLAG_FUA | NBD_CMD_FLAG_NO_HOLE |
+ NBD_CMD_FLAG_REQ_ONE)) {
nbdkit_error ("invalid request: unknown flag (0x%x)", flags);
*error = EINVAL;
return false;
@@ -117,6 +121,12 @@ validate_request (struct connection *conn,
*error = EINVAL;
return false;
}
+ if ((flags & NBD_CMD_FLAG_REQ_ONE) &&
+ cmd != NBD_CMD_BLOCK_STATUS) {
+ nbdkit_error ("invalid request: REQ_ONE flag needs BLOCK_STATUS request");
+ *error = EINVAL;
+ return false;
+ }
if (!conn->can_fua && (flags & NBD_CMD_FLAG_FUA)) {
nbdkit_error ("invalid request: FUA flag not supported");
*error = EINVAL;
@@ -157,14 +167,37 @@ validate_request (struct connection *conn,
return false;
}
+ /* Block status allowed? */
+ if (cmd == NBD_CMD_BLOCK_STATUS) {
+ if (!conn->structured_replies) {
+ nbdkit_error ("invalid request: "
+ "%s: structured replies was not negotiated",
+ name_of_nbd_cmd (cmd));
+ *error = EINVAL;
+ return false;
+ }
+ if (!conn->meta_context_base_allocation) {
+ nbdkit_error ("invalid request: "
+ "%s: base:allocation was not negotiated",
+ name_of_nbd_cmd (cmd));
+ *error = EINVAL;
+ return false;
+ }
+ }
+
return true; /* Command validates. */
}
/* This is called with the request lock held to actually execute the
* request (by calling the plugin). Note that the request fields have
* been validated already in 'validate_request' so we don't have to
- * check them again. 'buf' is either the data to be written or the
- * data to be returned, and points to a buffer of size 'count' bytes.
+ * check them again.
+ *
+ * 'buf' is either the data to be written or the data to be returned,
+ * and points to a buffer of size 'count' bytes.
+ *
+ * 'extents' is an empty extents list used for block status requests
+ * only.
*
* In all cases, the return value is the system errno value that will
* later be converted to the nbd error to send back to the client (0
@@ -173,7 +206,7 @@ validate_request (struct connection *conn,
static uint32_t
handle_request (struct connection *conn,
uint16_t cmd, uint16_t flags, uint64_t offset, uint32_t count,
- void *buf)
+ void *buf, struct nbdkit_extents *extents)
{
uint32_t f = 0;
bool fua = conn->can_fua && (flags & NBD_CMD_FLAG_FUA);
@@ -217,6 +250,33 @@ handle_request (struct connection *conn,
return err;
break;
+ case NBD_CMD_BLOCK_STATUS:
+ /* The other backend methods don't check can_*. That is because
+ * those methods are implicitly suppressed by returning eflags to
+ * the client. However there is no eflag for extents so we must
+ * check it here.
+ */
+ if (conn->can_extents) {
+ if (flags & NBD_CMD_FLAG_REQ_ONE)
+ f |= NBDKIT_FLAG_REQ_ONE;
+ if (backend->extents (backend, conn, count, offset, f,
+ extents, &err) == -1)
+ return err;
+ }
+ else {
+ int r;
+
+ /* By default it is safe assume that everything in the range is
+ * allocated.
+ */
+ errno = 0;
+ r = nbdkit_add_extent (extents, offset, count, 0 /* allocated data */);
+ if (r == -1)
+ return errno ? errno : EINVAL;
+ return 0;
+ }
+ break;
+
default:
abort ();
}
@@ -359,6 +419,143 @@ send_structured_reply_read (struct connection *conn,
return 1; /* command processed ok */
}
+/* Convert a list of extents into NBD_REPLY_TYPE_BLOCK_STATUS blocks.
+ * The rules here are very complicated. Read the spec carefully!
+ */
+static struct block_descriptor *
+extents_to_block_descriptors (struct nbdkit_extents *extents,
+ uint16_t flags,
+ uint32_t count, uint64_t offset,
+ size_t *nr_blocks)
+{
+ const bool req_one = flags & NBD_CMD_FLAG_REQ_ONE;
+ const size_t nr_extents = nbdkit_extents_count (extents);
+ size_t i;
+ struct block_descriptor *blocks;
+
+ /* This is checked in server/plugins.c. */
+ assert (nr_extents >= 1);
+
+ /* We may send fewer than nr_extents blocks, but never more. */
+ blocks = calloc (req_one ? 1 : nr_extents, sizeof (struct block_descriptor));
+ if (blocks == NULL) {
+ nbdkit_error ("malloc");
+ return NULL;
+ }
+
+ if (req_one) {
+ const struct nbdkit_extent e = nbdkit_get_extent (extents, 0);
+
+ /* Checked as a side effect of how the extent list is created. */
+ assert (e.length > 0);
+
+ *nr_blocks = 1;
+
+ /* Must not exceed count of the original request. */
+ blocks[0].length = MIN (e.length, (uint64_t) count);
+ blocks[0].status_flags = e.type & 3;
+ }
+ else {
+ uint64_t pos = offset;
+
+ for (i = 0; i < nr_extents; ++i) {
+ const struct nbdkit_extent e = nbdkit_get_extent (extents, i);
+ uint64_t length;
+
+ if (i == 0)
+ assert (e.offset == offset);
+
+ /* Must not exceed UINT32_MAX. */
+ length = MIN (e.length, UINT32_MAX);
+ blocks[i].status_flags = e.type & 3;
+
+ pos += length;
+ if (pos > offset + count) /* this must be the last block */
+ break;
+
+ /* If we reach here then we must have consumed this whole
+ * extent. This is currently true because the server only sends
+ * 32 bit requests, but if we move to 64 bit requests we will
+ * need to revisit this code so it can split extents into
+ * multiple blocks. XXX
+ */
+ assert (e.length <= length);
+ }
+
+ *nr_blocks = i;
+ }
+
+#if 0
+ for (i = 0; i < *nr_blocks; ++i)
+ nbdkit_debug ("block status: sending block %" PRIu32 " type %" PRIu32,
+ blocks[i].length, blocks[i].status_flags);
+#endif
+
+ /* Convert to big endian for the protocol. */
+ for (i = 0; i < *nr_blocks; ++i) {
+ blocks[i].length = htobe32 (blocks[i].length);
+ blocks[i].status_flags = htobe32 (blocks[i].status_flags);
+ }
+
+ return blocks;
+}
+
+static int
+send_structured_reply_block_status (struct connection *conn,
+ uint64_t handle,
+ uint16_t cmd, uint16_t flags,
+ uint32_t count, uint64_t offset,
+ struct nbdkit_extents *extents)
+{
+ ACQUIRE_LOCK_FOR_CURRENT_SCOPE (&conn->write_lock);
+ struct structured_reply reply;
+ CLEANUP_FREE struct block_descriptor *blocks = NULL;
+ size_t nr_blocks;
+ uint32_t context_id;
+ size_t i;
+ int r;
+
+ assert (conn->meta_context_base_allocation);
+ assert (cmd == NBD_CMD_BLOCK_STATUS);
+
+ blocks = extents_to_block_descriptors (extents, flags, count, offset,
+ &nr_blocks);
+ if (blocks == NULL)
+ return connection_set_status (conn, -1);
+
+ reply.magic = htobe32 (NBD_STRUCTURED_REPLY_MAGIC);
+ reply.handle = handle;
+ reply.flags = htobe16 (NBD_REPLY_FLAG_DONE);
+ reply.type = htobe16 (NBD_REPLY_TYPE_BLOCK_STATUS);
+ reply.length = htobe32 (sizeof context_id +
+ nr_blocks * sizeof (struct block_descriptor));
+
+ r = conn->send (conn, &reply, sizeof reply);
+ if (r == -1) {
+ nbdkit_error ("write reply: %s: %m", name_of_nbd_cmd (cmd));
+ return connection_set_status (conn, -1);
+ }
+
+ /* Send the base:allocation context ID. */
+ context_id = htobe32 (base_allocation_id);
+ r = conn->send (conn, &context_id, sizeof context_id);
+ if (r == -1) {
+ nbdkit_error ("write reply: %s: %m", name_of_nbd_cmd (cmd));
+ return connection_set_status (conn, -1);
+ }
+
+ /* Send each block descriptor. */
+ for (i = 0; i < nr_blocks; ++i) {
+ r = conn->send (conn, &blocks[i], sizeof blocks[i]);
+ if (r == -1) {
+ nbdkit_error ("write reply: %s: %m", name_of_nbd_cmd (cmd));
+ return connection_set_status (conn, -1);
+ }
+ }
+
+ return 1; /* command processed ok */
+}
+
static int
send_structured_reply_error (struct connection *conn,
uint64_t handle, uint16_t cmd, uint32_t error)
@@ -402,6 +599,7 @@ protocol_recv_request_send_reply (struct connection *conn)
uint32_t magic, count, error = 0;
uint64_t offset;
CLEANUP_FREE char *buf = NULL;
+ CLEANUP_EXTENTS_FREE struct nbdkit_extents *extents = NULL;
/* Read the request packet. */
{
@@ -449,6 +647,7 @@ protocol_recv_request_send_reply (struct connection *conn)
if (cmd == NBD_CMD_READ || cmd == NBD_CMD_WRITE) {
buf = malloc (count);
if (buf == NULL) {
+ out_of_memory:
perror ("malloc");
error = ENOMEM;
if (cmd == NBD_CMD_WRITE &&
@@ -458,6 +657,13 @@ protocol_recv_request_send_reply (struct connection *conn)
}
}
+ /* Allocate the extents list for block status only. */
+ if (cmd == NBD_CMD_BLOCK_STATUS) {
+ extents = nbdkit_extents_new (offset, conn->exportsize);
+ if (extents == NULL)
+ goto out_of_memory;
+ }
+
/* Receive the write data buffer. */
if (cmd == NBD_CMD_WRITE) {
r = conn->recv (conn, buf, count);
@@ -478,7 +684,7 @@ protocol_recv_request_send_reply (struct connection *conn)
}
else {
lock_request (conn);
- error = handle_request (conn, cmd, flags, offset, count, buf);
+ error = handle_request (conn, cmd, flags, offset, count, buf, extents);
assert ((int) error >= 0);
unlock_request (conn);
}
@@ -498,15 +704,23 @@ protocol_recv_request_send_reply (struct connection *conn)
}
/* Currently we prefer to send simple replies for everything except
- * where we have to (ie. NBD_CMD_READ when structured_replies have
- * been negotiated). However this prevents us from sending
- * human-readable error messages to the client, so we should
- * reconsider this in future.
+ * where we have to (ie. NBD_CMD_READ and NBD_CMD_BLOCK_STATUS when
+ * structured_replies have been negotiated). However this prevents
+ * us from sending human-readable error messages to the client, so
+ * we should reconsider this in future.
*/
- if (conn->structured_replies && cmd == NBD_CMD_READ) {
- if (!error)
- return send_structured_reply_read (conn, request.handle, cmd,
- buf, count, offset);
+ if (conn->structured_replies &&
+ (cmd == NBD_CMD_READ || cmd == NBD_CMD_BLOCK_STATUS)) {
+ if (!error) {
+ if (cmd == NBD_CMD_READ)
+ return send_structured_reply_read (conn, request.handle, cmd,
+ buf, count, offset);
+ else /* NBD_CMD_BLOCK_STATUS */
+ return send_structured_reply_block_status (conn, request.handle,
+ cmd, flags,
+ count, offset,
+ extents);
+ }
else
return send_structured_reply_error (conn, request.handle, cmd, error);
}
diff --git a/TODO b/TODO
index 7cbc238..c968c2d 100644
--- a/TODO
+++ b/TODO
@@ -24,8 +24,8 @@ General ideas for improvements
to inform nbdkit when the response is ready:
https://www.redhat.com/archives/libguestfs/2018-January/msg00149.html
-* More NBD protocol features. In the upstream pipeline: proposals for
- block status and online resize.
+* More NBD protocol features. The only currently missing feature is
+ online resize.
* Add a callback to let plugins request minimum alignment for the
buffer to pread/pwrite; useful for a plugin utilizing O_DIRECT or
--
2.20.1
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