Merge remote-tracking branch 'bonzini/nbd-next' into staging

* bonzini/nbd-next:
  nbd: add nbd_export_get_blockdev
  nbd: negotiate with named exports
  nbd: register named exports
  qemu-nbd: rewrite termination conditions to use a state machine
  nbd: add notification for closing an NBDExport
  nbd: track clients into NBDExport
  nbd: add reference counting to NBDExport
  nbd: do not leak nbd_trip coroutines when a connection is torn down
  nbd: make refcount interface public
  nbd: do not close BlockDriverState in nbd_export_close
  nbd: pass NBDClient to nbd_send_negotiate
  nbd: add more constants

nbd.c

@@ -57,9 +57,12 @@
 
 /* This is all part of the "official" NBD API */
 
+#define NBD_REQUEST_SIZE        (4 + 4 + 8 + 8 + 4)
 #define NBD_REPLY_SIZE          (4 + 4 + 8)
 #define NBD_REQUEST_MAGIC       0x25609513
 #define NBD_REPLY_MAGIC         0x67446698
+#define NBD_OPTS_MAGIC          0x49484156454F5054LL
+#define NBD_CLIENT_MAGIC        0x0000420281861253LL
 
 #define NBD_SET_SOCK            _IO(0xab, 0)
 #define NBD_SET_BLKSIZE         _IO(0xab, 1)
@@ -75,6 +78,49 @@
 
 #define NBD_OPT_EXPORT_NAME     (1 << 0)
 
+/* Definitions for opaque data types */
+
+typedef struct NBDRequest NBDRequest;
+
+struct NBDRequest {
+    QSIMPLEQ_ENTRY(NBDRequest) entry;
+    NBDClient *client;
+    uint8_t *data;
+};
+
+struct NBDExport {
+    int refcount;
+    void (*close)(NBDExport *exp);
+
+    BlockDriverState *bs;
+    char *name;
+    off_t dev_offset;
+    off_t size;
+    uint32_t nbdflags;
+    QTAILQ_HEAD(, NBDClient) clients;
+    QSIMPLEQ_HEAD(, NBDRequest) requests;
+    QTAILQ_ENTRY(NBDExport) next;
+};
+
+static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
+
+struct NBDClient {
+    int refcount;
+    void (*close)(NBDClient *client);
+
+    NBDExport *exp;
+    int sock;
+
+    Coroutine *recv_coroutine;
+
+    CoMutex send_lock;
+    Coroutine *send_coroutine;
+
+    QTAILQ_ENTRY(NBDClient) next;
+    int nb_requests;
+    bool closing;
+};
+
 /* That's all folks */
 
 ssize_t nbd_wr_sync(int fd, void *buffer, size_t size, bool do_read)
@@ -192,11 +238,23 @@ int unix_socket_outgoing(const char *path)
     return unix_connect(path);
 }
 
-/* Basic flow
+/* Basic flow for negotiation
 
    Server         Client
-
    Negotiate
+
+   or
+
+   Server         Client
+   Negotiate #1
+                  Option
+   Negotiate #2
+
+   ----
+
+   followed by
+
+   Server         Client
                   Request
    Response
                   Request
@@ -204,18 +262,111 @@ int unix_socket_outgoing(const char *path)
                   ...
    ...
                   Request (type == 2)
+
 */
 
-static int nbd_send_negotiate(int csock, off_t size, uint32_t flags)
+static int nbd_receive_options(NBDClient *client)
 {
+    int csock = client->sock;
+    char name[256];
+    uint32_t tmp, length;
+    uint64_t magic;
+    int rc;
+
+    /* Client sends:
+        [ 0 ..   3]   reserved (0)
+        [ 4 ..  11]   NBD_OPTS_MAGIC
+        [12 ..  15]   NBD_OPT_EXPORT_NAME
+        [16 ..  19]   length
+        [20 ..  xx]   export name (length bytes)
+     */
+
+    rc = -EINVAL;
+    if (read_sync(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
+        LOG("read failed");
+        goto fail;
+    }
+    TRACE("Checking reserved");
+    if (tmp != 0) {
+        LOG("Bad reserved received");
+        goto fail;
+    }
+
+    if (read_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
+        LOG("read failed");
+        goto fail;
+    }
+    TRACE("Checking reserved");
+    if (magic != be64_to_cpu(NBD_OPTS_MAGIC)) {
+        LOG("Bad magic received");
+        goto fail;
+    }
+
+    if (read_sync(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
+        LOG("read failed");
+        goto fail;
+    }
+    TRACE("Checking option");
+    if (tmp != be32_to_cpu(NBD_OPT_EXPORT_NAME)) {
+        LOG("Bad option received");
+        goto fail;
+    }
+
+    if (read_sync(csock, &length, sizeof(length)) != sizeof(length)) {
+        LOG("read failed");
+        goto fail;
+    }
+    TRACE("Checking length");
+    length = be32_to_cpu(length);
+    if (length > 255) {
+        LOG("Bad length received");
+        goto fail;
+    }
+    if (read_sync(csock, name, length) != length) {
+        LOG("read failed");
+        goto fail;
+    }
+    name[length] = '\0';
+
+    client->exp = nbd_export_find(name);
+    if (!client->exp) {
+        LOG("export not found");
+        goto fail;
+    }
+
+    QTAILQ_INSERT_TAIL(&client->exp->clients, client, next);
+    nbd_export_get(client->exp);
+
+    TRACE("Option negotiation succeeded.");
+    rc = 0;
+fail:
+    return rc;
+}
+
+static int nbd_send_negotiate(NBDClient *client)
+{
+    int csock = client->sock;
     char buf[8 + 8 + 8 + 128];
     int rc;
+    const int myflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM |
+                         NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA);
 
-    /* Negotiate
+    /* Negotiation header without options:
         [ 0 ..   7]   passwd       ("NBDMAGIC")
-        [ 8 ..  15]   magic    (0x00420281861253)
+        [ 8 ..  15]   magic        (NBD_CLIENT_MAGIC)
         [16 ..  23]   size
-        [24 ..  27]   flags
+        [24 ..  25]   server flags (0)
+        [24 ..  27]   export flags
+        [28 .. 151]   reserved     (0)
+
+       Negotiation header with options, part 1:
+        [ 0 ..   7]   passwd       ("NBDMAGIC")
+        [ 8 ..  15]   magic        (NBD_OPTS_MAGIC)
+        [16 ..  17]   server flags (0)
+
+       part 2 (after options are sent):
+        [18 ..  25]   size
+        [26 ..  27]   export flags
         [28 .. 151]   reserved     (0)
      */
 
@@ -224,17 +375,40 @@ static int nbd_send_negotiate(int csock, off_t size, uint32_t flags)
 
     TRACE("Beginning negotiation.");
     memcpy(buf, "NBDMAGIC", 8);
-    cpu_to_be64w((uint64_t*)(buf + 8), 0x00420281861253LL);
-    cpu_to_be64w((uint64_t*)(buf + 16), size);
-    cpu_to_be32w((uint32_t*)(buf + 24),
-                 flags | NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM |
-                 NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA);
+    if (client->exp) {
+        assert ((client->exp->nbdflags & ~65535) == 0);
+        cpu_to_be64w((uint64_t*)(buf + 8), NBD_CLIENT_MAGIC);
+        cpu_to_be64w((uint64_t*)(buf + 16), client->exp->size);
+        cpu_to_be16w((uint16_t*)(buf + 26), client->exp->nbdflags | myflags);
+    } else {
+        cpu_to_be64w((uint64_t*)(buf + 8), NBD_OPTS_MAGIC);
+    }
     memset(buf + 28, 0, 124);
 
+    if (client->exp) {
         if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
             LOG("write failed");
             goto fail;
         }
+    } else {
+        if (write_sync(csock, buf, 18) != 18) {
+            LOG("write failed");
+            goto fail;
+        }
+        rc = nbd_receive_options(client);
+        if (rc < 0) {
+            LOG("option negotiation failed");
+            goto fail;
+        }
+
+        assert ((client->exp->nbdflags & ~65535) == 0);
+        cpu_to_be64w((uint64_t*)(buf + 18), client->exp->size);
+        cpu_to_be16w((uint16_t*)(buf + 26), client->exp->nbdflags | myflags);
+        if (write_sync(csock, buf + 18, sizeof(buf) - 18) != sizeof(buf) - 18) {
+            LOG("write failed");
+            goto fail;
+        }
+    }
 
     TRACE("Negotiation succeeded.");
     rc = 0;
@@ -295,7 +469,7 @@ int nbd_receive_negotiate(int csock, const char *name, uint32_t *flags,
         uint32_t namesize;
 
         TRACE("Checking magic (opts_magic)");
-        if (magic != 0x49484156454F5054LL) {
+        if (magic != NBD_OPTS_MAGIC) {
             LOG("Bad magic received");
             goto fail;
         }
@@ -334,7 +508,7 @@ int nbd_receive_negotiate(int csock, const char *name, uint32_t *flags,
     } else {
         TRACE("Checking magic (cli_magic)");
 
-        if (magic != 0x00420281861253LL) {
+        if (magic != NBD_CLIENT_MAGIC) {
             LOG("Bad magic received");
             goto fail;
         }
@@ -477,7 +651,7 @@ int nbd_client(int fd)
 
 ssize_t nbd_send_request(int csock, struct nbd_request *request)
 {
-    uint8_t buf[4 + 4 + 8 + 8 + 4];
+    uint8_t buf[NBD_REQUEST_SIZE];
     ssize_t ret;
 
     cpu_to_be32w((uint32_t*)buf, NBD_REQUEST_MAGIC);
@@ -504,7 +678,7 @@ ssize_t nbd_send_request(int csock, struct nbd_request *request)
 
 static ssize_t nbd_receive_request(int csock, struct nbd_request *request)
 {
-    uint8_t buf[4 + 4 + 8 + 8 + 4];
+    uint8_t buf[NBD_REQUEST_SIZE];
     uint32_t magic;
     ssize_t ret;
 
@@ -582,7 +756,7 @@ ssize_t nbd_receive_reply(int csock, struct nbd_reply *reply)
 
 static ssize_t nbd_send_reply(int csock, struct nbd_reply *reply)
 {
-    uint8_t buf[4 + 4 + 8];
+    uint8_t buf[NBD_REPLY_SIZE];
     ssize_t ret;
 
     /* Reply
@@ -610,58 +784,47 @@ static ssize_t nbd_send_reply(int csock, struct nbd_reply *reply)
 
 #define MAX_NBD_REQUESTS 16
 
-typedef struct NBDRequest NBDRequest;
-
-struct NBDRequest {
-    QSIMPLEQ_ENTRY(NBDRequest) entry;
-    NBDClient *client;
-    uint8_t *data;
-};
-
-struct NBDExport {
-    BlockDriverState *bs;
-    off_t dev_offset;
-    off_t size;
-    uint32_t nbdflags;
-    QSIMPLEQ_HEAD(, NBDRequest) requests;
-};
-
-struct NBDClient {
-    int refcount;
-    void (*close)(NBDClient *client);
-
-    NBDExport *exp;
-    int sock;
-
-    Coroutine *recv_coroutine;
-
-    CoMutex send_lock;
-    Coroutine *send_coroutine;
-
-    int nb_requests;
-};
-
-static void nbd_client_get(NBDClient *client)
+void nbd_client_get(NBDClient *client)
 {
     client->refcount++;
 }
 
-static void nbd_client_put(NBDClient *client)
+void nbd_client_put(NBDClient *client)
 {
     if (--client->refcount == 0) {
+        /* The last reference should be dropped by client->close,
+         * which is called by nbd_client_close.
+         */
+        assert(client->closing);
+
+        qemu_set_fd_handler2(client->sock, NULL, NULL, NULL, NULL);
+        close(client->sock);
+        client->sock = -1;
+        if (client->exp) {
+            QTAILQ_REMOVE(&client->exp->clients, client, next);
+            nbd_export_put(client->exp);
+        }
         g_free(client);
     }
 }
 
-static void nbd_client_close(NBDClient *client)
+void nbd_client_close(NBDClient *client)
 {
-    qemu_set_fd_handler2(client->sock, NULL, NULL, NULL, NULL);
-    close(client->sock);
-    client->sock = -1;
+    if (client->closing) {
+        return;
+    }
+
+    client->closing = true;
+
+    /* Force requests to finish.  They will drop their own references,
+     * then we'll close the socket and free the NBDClient.
+     */
+    shutdown(client->sock, 2);
+
+    /* Also tell the client, so that they release their reference.  */
     if (client->close) {
         client->close(client);
     }
-    nbd_client_put(client);
 }
 
 static NBDRequest *nbd_request_get(NBDClient *client)
@@ -695,19 +858,86 @@ static void nbd_request_put(NBDRequest *req)
 }
 
 NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset,
-                          off_t size, uint32_t nbdflags)
+                          off_t size, uint32_t nbdflags,
+                          void (*close)(NBDExport *))
 {
     NBDExport *exp = g_malloc0(sizeof(NBDExport));
     QSIMPLEQ_INIT(&exp->requests);
+    exp->refcount = 1;
+    QTAILQ_INIT(&exp->clients);
     exp->bs = bs;
     exp->dev_offset = dev_offset;
     exp->nbdflags = nbdflags;
     exp->size = size == -1 ? bdrv_getlength(bs) : size;
+    exp->close = close;
+    return exp;
+}
+
+NBDExport *nbd_export_find(const char *name)
+{
+    NBDExport *exp;
+    QTAILQ_FOREACH(exp, &exports, next) {
+        if (strcmp(name, exp->name) == 0) {
             return exp;
+        }
+    }
+
+    return NULL;
+}
+
+void nbd_export_set_name(NBDExport *exp, const char *name)
+{
+    if (exp->name == name) {
+        return;
+    }
+
+    nbd_export_get(exp);
+    if (exp->name != NULL) {
+        g_free(exp->name);
+        exp->name = NULL;
+        QTAILQ_REMOVE(&exports, exp, next);
+        nbd_export_put(exp);
+    }
+    if (name != NULL) {
+        nbd_export_get(exp);
+        exp->name = g_strdup(name);
+        QTAILQ_INSERT_TAIL(&exports, exp, next);
+    }
+    nbd_export_put(exp);
 }
 
 void nbd_export_close(NBDExport *exp)
 {
+    NBDClient *client, *next;
+
+    nbd_export_get(exp);
+    QTAILQ_FOREACH_SAFE(client, &exp->clients, next, next) {
+        nbd_client_close(client);
+    }
+    nbd_export_set_name(exp, NULL);
+    nbd_export_put(exp);
+}
+
+void nbd_export_get(NBDExport *exp)
+{
+    assert(exp->refcount > 0);
+    exp->refcount++;
+}
+
+void nbd_export_put(NBDExport *exp)
+{
+    assert(exp->refcount > 0);
+    if (exp->refcount == 1) {
+        nbd_export_close(exp);
+    }
+
+    if (--exp->refcount == 0) {
+        assert(exp->name == NULL);
+
+        if (exp->close) {
+            exp->close(exp);
+        }
+
         while (!QSIMPLEQ_EMPTY(&exp->requests)) {
             NBDRequest *first = QSIMPLEQ_FIRST(&exp->requests);
             QSIMPLEQ_REMOVE_HEAD(&exp->requests, entry);
@@ -715,8 +945,22 @@ void nbd_export_close(NBDExport *exp)
             g_free(first);
         }
 
-    bdrv_close(exp->bs);
         g_free(exp);
+    }
+}
+
+BlockDriverState *nbd_export_get_blockdev(NBDExport *exp)
+{
+    return exp->bs;
+}
+
+void nbd_export_close_all(void)
+{
+    NBDExport *exp, *next;
+
+    QTAILQ_FOREACH_SAFE(exp, &exports, next, next) {
+        nbd_export_close(exp);
+    }
 }
 
 static int nbd_can_read(void *opaque);
@@ -805,14 +1049,18 @@ out:
 static void nbd_trip(void *opaque)
 {
     NBDClient *client = opaque;
-    NBDRequest *req = nbd_request_get(client);
     NBDExport *exp = client->exp;
+    NBDRequest *req;
     struct nbd_request request;
     struct nbd_reply reply;
     ssize_t ret;
 
     TRACE("Reading request.");
+    if (client->closing) {
+        return;
+    }
 
+    req = nbd_request_get(client);
     ret = nbd_co_receive_request(req, &request);
     if (ret == -EAGAIN) {
         goto done;
@@ -974,15 +1222,21 @@ NBDClient *nbd_client_new(NBDExport *exp, int csock,
                           void (*close)(NBDClient *))
 {
     NBDClient *client;
-    if (nbd_send_negotiate(csock, exp->size, exp->nbdflags) < 0) {
-        return NULL;
-    }
     client = g_malloc0(sizeof(NBDClient));
     client->refcount = 1;
     client->exp = exp;
     client->sock = csock;
+    if (nbd_send_negotiate(client) < 0) {
+        g_free(client);
+        return NULL;
+    }
     client->close = close;
     qemu_co_mutex_init(&client->send_lock);
     qemu_set_fd_handler2(csock, nbd_can_read, nbd_read, NULL, client);
+
+    if (exp) {
+        QTAILQ_INSERT_TAIL(&exp->clients, client, next);
+        nbd_export_get(exp);
+    }
     return client;
 }

nbd.h

@@ -79,9 +79,22 @@ typedef struct NBDExport NBDExport;
 typedef struct NBDClient NBDClient;
 
 NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset,
-                          off_t size, uint32_t nbdflags);
+                          off_t size, uint32_t nbdflags,
+                          void (*close)(NBDExport *));
 void nbd_export_close(NBDExport *exp);
+void nbd_export_get(NBDExport *exp);
+void nbd_export_put(NBDExport *exp);
+
+BlockDriverState *nbd_export_get_blockdev(NBDExport *exp);
+
+NBDExport *nbd_export_find(const char *name);
+void nbd_export_set_name(NBDExport *exp, const char *name);
+void nbd_export_close_all(void);
+
 NBDClient *nbd_client_new(NBDExport *exp, int csock,
                           void (*close)(NBDClient *));
+void nbd_client_close(NBDClient *client);
+void nbd_client_get(NBDClient *client);
+void nbd_client_put(NBDClient *client);
 
 #endif

qemu-nbd.c

@@ -41,8 +41,8 @@ static NBDExport *exp;
 static int verbose;
 static char *srcpath;
 static char *sockpath;
-static bool sigterm_reported;
-static bool nbd_started;
+static int persistent = 0;
+static enum { RUNNING, TERMINATE, TERMINATING, TERMINATED } state;
 static int shared = 1;
 static int nb_fds;
 
@@ -186,7 +186,7 @@ static int find_partition(BlockDriverState *bs, int partition,
 
 static void termsig_handler(int signum)
 {
-    sigterm_reported = true;
+    state = TERMINATE;
     qemu_notify_event();
 }
 
@@ -269,10 +269,20 @@ static int nbd_can_accept(void *opaque)
     return nb_fds < shared;
 }
 
+static void nbd_export_closed(NBDExport *exp)
+{
+    assert(state == TERMINATING);
+    state = TERMINATED;
+}
+
 static void nbd_client_closed(NBDClient *client)
 {
     nb_fds--;
+    if (nb_fds == 0 && !persistent && state == RUNNING) {
+        state = TERMINATE;
+    }
     qemu_notify_event();
+    nbd_client_put(client);
 }
 
 static void nbd_accept(void *opaque)
@@ -282,7 +292,11 @@ static void nbd_accept(void *opaque)
     socklen_t addr_len = sizeof(addr);
 
     int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
-    nbd_started = true;
+    if (state >= TERMINATE) {
+        close(fd);
+        return;
+    }
+
     if (fd >= 0 && nbd_client_new(exp, fd, nbd_client_closed)) {
         nb_fds++;
     }
@@ -329,7 +343,6 @@ int main(int argc, char **argv)
     int partition = -1;
     int ret;
     int fd;
-    int persistent = 0;
     bool seen_cache = false;
 #ifdef CONFIG_LINUX_AIO
     bool seen_aio = false;
@@ -546,7 +559,7 @@ int main(int argc, char **argv)
         }
     }
 
-    exp = nbd_export_new(bs, dev_offset, fd_size, nbdflags);
+    exp = nbd_export_new(bs, dev_offset, fd_size, nbdflags, nbd_export_closed);
 
     if (sockpath) {
         fd = unix_socket_incoming(sockpath);
@@ -581,11 +594,18 @@ int main(int argc, char **argv)
         err(EXIT_FAILURE, "Could not chdir to root directory");
     }
 
+    state = RUNNING;
     do {
         main_loop_wait(false);
-    } while (!sigterm_reported && (persistent || !nbd_started || nb_fds > 0));
-
+        if (state == TERMINATE) {
+            state = TERMINATING;
             nbd_export_close(exp);
+            nbd_export_put(exp);
+            exp = NULL;
+        }
+    } while (state != TERMINATED);
+
+    bdrv_close(bs);
     if (sockpath) {
         unlink(sockpath);
     }