[Libguestfs] [PATCH nbdkit v5 FINAL 03/19] server: protocol: Implement Block Status "base:allocation".

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=ca4414804114fd0095b317785b... 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