blockdev-nbd.c

   1 /*
   2  * Serving QEMU block devices via NBD
   3  *
   4  * Copyright (c) 2012 Red Hat, Inc.
   5  *
   6  * Author: Paolo Bonzini <pbonzini@redhat.com>
   7  *
   8  * This work is licensed under the terms of the GNU GPL, version 2 or
   9  * later.  See the COPYING file in the top-level directory.
  10  */
  11
  12 #include "blockdev.h"
  13 #include "hw/block-common.h"
  14 #include "monitor.h"
  15 #include "qerror.h"
  16 #include "sysemu.h"
  17 #include "qmp-commands.h"
  18 #include "trace.h"
  19 #include "nbd.h"
  20 #include "qemu_socket.h"
  21
  22 static int server_fd = -1;
  23
  24 static void nbd_accept(void *opaque)
  25 {
  26     struct sockaddr_in addr;
  27     socklen_t addr_len = sizeof(addr);
  28
  29     int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
  30     if (fd >= 0) {
  31         nbd_client_new(NULL, fd, nbd_client_put);
  32     }
  33 }
  34
  35 void qmp_nbd_server_start(SocketAddress *addr, Error **errp)
  36 {
  37     if (server_fd != -1) {
  38         error_setg(errp, "NBD server already running");
  39         return;
  40     }
  41
  42     server_fd = socket_listen(addr, errp);
  43     if (server_fd != -1) {
  44         qemu_set_fd_handler2(server_fd, NULL, nbd_accept, NULL, NULL);
  45     }
  46 }
  47
  48 /* Hook into the BlockDriverState notifiers to close the export when
  49  * the file is closed.
  50  */
  51 typedef struct NBDCloseNotifier {
  52     Notifier n;
  53     NBDExport *exp;
  54     QTAILQ_ENTRY(NBDCloseNotifier) next;
  55 } NBDCloseNotifier;
  56
  57 static QTAILQ_HEAD(, NBDCloseNotifier) close_notifiers =
  58     QTAILQ_HEAD_INITIALIZER(close_notifiers);
  59
  60 static void nbd_close_notifier(Notifier *n, void *data)
  61 {
  62     NBDCloseNotifier *cn = DO_UPCAST(NBDCloseNotifier, n, n);
  63
  64     notifier_remove(&cn->n);
  65     QTAILQ_REMOVE(&close_notifiers, cn, next);
  66
  67     nbd_export_close(cn->exp);
  68     nbd_export_put(cn->exp);
  69     g_free(cn);
  70 }
  71
  72 static void nbd_server_put_ref(NBDExport *exp)
  73 {
  74     BlockDriverState *bs = nbd_export_get_blockdev(exp);
  75     drive_put_ref(drive_get_by_blockdev(bs));
  76 }
  77
  78 void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
  79                         Error **errp)
  80 {
  81     BlockDriverState *bs;
  82     NBDExport *exp;
  83     NBDCloseNotifier *n;
  84
  85     if (nbd_export_find(device)) {
  86         error_setg(errp, "NBD server already exporting device '%s'", device);
  87         return;
  88     }
  89
  90     bs = bdrv_find(device);
  91     if (!bs) {
  92         error_set(errp, QERR_DEVICE_NOT_FOUND, device);
  93         return;
  94     }
  95
  96     if (!has_writable) {
  97         writable = true;
  98     }
  99     if (bdrv_is_read_only(bs)) {
 100         writable = false;
 101     }
 102
 103     exp = nbd_export_new(bs, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY,
 104                          nbd_server_put_ref);
 105
 106     nbd_export_set_name(exp, device);
 107     drive_get_ref(drive_get_by_blockdev(bs));
 108
 109     n = g_malloc0(sizeof(NBDCloseNotifier));
 110     n->n.notify = nbd_close_notifier;
 111     n->exp = exp;
 112     bdrv_add_close_notifier(bs, &n->n);
 113     QTAILQ_INSERT_TAIL(&close_notifiers, n, next);
 114 }
 115
 116 void qmp_nbd_server_stop(Error **errp)
 117 {
 118     while (!QTAILQ_EMPTY(&close_notifiers)) {
 119         NBDCloseNotifier *cn = QTAILQ_FIRST(&close_notifiers);
 120         nbd_close_notifier(&cn->n, nbd_export_get_blockdev(cn->exp));
 121     }
 122
 123     if (server_fd != -1) {
 124         qemu_set_fd_handler2(server_fd, NULL, NULL, NULL, NULL);
 125         close(server_fd);
 126         server_fd = -1;
 127     }
 128 }