block/export/export.c

   1 /*
   2  * Common block export infrastructure
   3  *
   4  * Copyright (c) 2012, 2020 Red Hat, Inc.
   5  *
   6  * Authors:
   7  * Paolo Bonzini <pbonzini@redhat.com>
   8  * Kevin Wolf <kwolf@redhat.com>
   9  *
  10  * This work is licensed under the terms of the GNU GPL, version 2 or
  11  * later.  See the COPYING file in the top-level directory.
  12  */
  13
  14 #include "qemu/osdep.h"
  15
  16 #include "block/block.h"
  17 #include "sysemu/block-backend.h"
  18 #include "sysemu/iothread.h"
  19 #include "block/export.h"
  20 #include "block/fuse.h"
  21 #include "block/nbd.h"
  22 #include "qapi/error.h"
  23 #include "qapi/qapi-commands-block-export.h"
  24 #include "qapi/qapi-events-block-export.h"
  25 #include "qemu/id.h"
  26 #ifdef CONFIG_VHOST_USER_BLK_SERVER
  27 #include "vhost-user-blk-server.h"
  28 #endif
  29 #ifdef CONFIG_VDUSE_BLK_EXPORT
  30 #include "vduse-blk.h"
  31 #endif
  32
  33 static const BlockExportDriver *blk_exp_drivers[] = {
  34     &blk_exp_nbd,
  35 #ifdef CONFIG_VHOST_USER_BLK_SERVER
  36     &blk_exp_vhost_user_blk,
  37 #endif
  38 #ifdef CONFIG_FUSE
  39     &blk_exp_fuse,
  40 #endif
  41 #ifdef CONFIG_VDUSE_BLK_EXPORT
  42     &blk_exp_vduse_blk,
  43 #endif
  44 };
  45
  46 /* Only accessed from the main thread */
  47 static QLIST_HEAD(, BlockExport) block_exports =
  48     QLIST_HEAD_INITIALIZER(block_exports);
  49
  50 BlockExport *blk_exp_find(const char *id)
  51 {
  52     BlockExport *exp;
  53
  54     QLIST_FOREACH(exp, &block_exports, next) {
  55         if (strcmp(id, exp->id) == 0) {
  56             return exp;
  57         }
  58     }
  59
  60     return NULL;
  61 }
  62
  63 static const BlockExportDriver *blk_exp_find_driver(BlockExportType type)
  64 {
  65     int i;
  66
  67     for (i = 0; i < ARRAY_SIZE(blk_exp_drivers); i++) {
  68         if (blk_exp_drivers[i]->type == type) {
  69             return blk_exp_drivers[i];
  70         }
  71     }
  72     return NULL;
  73 }
  74
  75 BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
  76 {
  77     bool fixed_iothread = export->has_fixed_iothread && export->fixed_iothread;
  78     const BlockExportDriver *drv;
  79     BlockExport *exp = NULL;
  80     BlockDriverState *bs;
  81     BlockBackend *blk = NULL;
  82     AioContext *ctx;
  83     uint64_t perm;
  84     int ret;
  85
  86     GLOBAL_STATE_CODE();
  87
  88     if (!id_wellformed(export->id)) {
  89         error_setg(errp, "Invalid block export id");
  90         return NULL;
  91     }
  92     if (blk_exp_find(export->id)) {
  93         error_setg(errp, "Block export id '%s' is already in use", export->id);
  94         return NULL;
  95     }
  96
  97     drv = blk_exp_find_driver(export->type);
  98     if (!drv) {
  99         error_setg(errp, "No driver found for the requested export type");
 100         return NULL;
 101     }
 102
 103     bs = bdrv_lookup_bs(NULL, export->node_name, errp);
 104     if (!bs) {
 105         return NULL;
 106     }
 107
 108     if (!export->has_writable) {
 109         export->writable = false;
 110     }
 111     if (bdrv_is_read_only(bs) && export->writable) {
 112         error_setg(errp, "Cannot export read-only node as writable");
 113         return NULL;
 114     }
 115
 116     ctx = bdrv_get_aio_context(bs);
 117
 118     if (export->iothread) {
 119         IOThread *iothread;
 120         AioContext *new_ctx;
 121         Error **set_context_errp;
 122
 123         iothread = iothread_by_id(export->iothread);
 124         if (!iothread) {
 125             error_setg(errp, "iothread \"%s\" not found", export->iothread);
 126             goto fail;
 127         }
 128
 129         new_ctx = iothread_get_aio_context(iothread);
 130
 131         /* Ignore errors with fixed-iothread=false */
 132         set_context_errp = fixed_iothread ? errp : NULL;
 133         ret = bdrv_try_change_aio_context(bs, new_ctx, NULL, set_context_errp);
 134         if (ret == 0) {
 135             ctx = new_ctx;
 136         } else if (fixed_iothread) {
 137             goto fail;
 138         }
 139     }
 140
 141     /*
 142      * Block exports are used for non-shared storage migration. Make sure
 143      * that BDRV_O_INACTIVE is cleared and the image is ready for write
 144      * access since the export could be available before migration handover.
 145      * ctx was acquired in the caller.
 146      */
 147     bdrv_graph_rdlock_main_loop();
 148     bdrv_activate(bs, NULL);
 149     bdrv_graph_rdunlock_main_loop();
 150
 151     perm = BLK_PERM_CONSISTENT_READ;
 152     if (export->writable) {
 153         perm |= BLK_PERM_WRITE;
 154     }
 155
 156     blk = blk_new(ctx, perm, BLK_PERM_ALL);
 157
 158     if (!fixed_iothread) {
 159         blk_set_allow_aio_context_change(blk, true);
 160     }
 161
 162     ret = blk_insert_bs(blk, bs, errp);
 163     if (ret < 0) {
 164         goto fail;
 165     }
 166
 167     if (!export->has_writethrough) {
 168         export->writethrough = false;
 169     }
 170     blk_set_enable_write_cache(blk, !export->writethrough);
 171
 172     assert(drv->instance_size >= sizeof(BlockExport));
 173     exp = g_malloc0(drv->instance_size);
 174     *exp = (BlockExport) {
 175         .drv        = drv,
 176         .refcount   = 1,
 177         .user_owned = true,
 178         .id         = g_strdup(export->id),
 179         .ctx        = ctx,
 180         .blk        = blk,
 181     };
 182
 183     ret = drv->create(exp, export, errp);
 184     if (ret < 0) {
 185         goto fail;
 186     }
 187
 188     assert(exp->blk != NULL);
 189
 190     QLIST_INSERT_HEAD(&block_exports, exp, next);
 191     return exp;
 192
 193 fail:
 194     if (blk) {
 195         blk_set_dev_ops(blk, NULL, NULL);
 196         blk_unref(blk);
 197     }
 198     if (exp) {
 199         g_free(exp->id);
 200         g_free(exp);
 201     }
 202     return NULL;
 203 }
 204
 205 void blk_exp_ref(BlockExport *exp)
 206 {
 207     assert(qatomic_read(&exp->refcount) > 0);
 208     qatomic_inc(&exp->refcount);
 209 }
 210
 211 /* Runs in the main thread */
 212 static void blk_exp_delete_bh(void *opaque)
 213 {
 214     BlockExport *exp = opaque;
 215
 216     assert(exp->refcount == 0);
 217     QLIST_REMOVE(exp, next);
 218     exp->drv->delete(exp);
 219     blk_set_dev_ops(exp->blk, NULL, NULL);
 220     blk_unref(exp->blk);
 221     qapi_event_send_block_export_deleted(exp->id);
 222     g_free(exp->id);
 223     g_free(exp);
 224 }
 225
 226 void blk_exp_unref(BlockExport *exp)
 227 {
 228     assert(qatomic_read(&exp->refcount) > 0);
 229     if (qatomic_fetch_dec(&exp->refcount) == 1) {
 230         /* Touch the block_exports list only in the main thread */
 231         aio_bh_schedule_oneshot(qemu_get_aio_context(), blk_exp_delete_bh,
 232                                 exp);
 233     }
 234 }
 235
 236 /*
 237  * Drops the user reference to the export and requests that all client
 238  * connections and other internally held references start to shut down. When
 239  * the function returns, there may still be active references while the export
 240  * is in the process of shutting down.
 241  */
 242 void blk_exp_request_shutdown(BlockExport *exp)
 243 {
 244     /*
 245      * If the user doesn't own the export any more, it is already shutting
 246      * down. We must not call .request_shutdown and decrease the refcount a
 247      * second time.
 248      */
 249     if (!exp->user_owned) {
 250         return;
 251     }
 252
 253     exp->drv->request_shutdown(exp);
 254
 255     assert(exp->user_owned);
 256     exp->user_owned = false;
 257     blk_exp_unref(exp);
 258 }
 259
 260 /*
 261  * Returns whether a block export of the given type exists.
 262  * type == BLOCK_EXPORT_TYPE__MAX checks for an export of any type.
 263  */
 264 static bool blk_exp_has_type(BlockExportType type)
 265 {
 266     BlockExport *exp;
 267
 268     if (type == BLOCK_EXPORT_TYPE__MAX) {
 269         return !QLIST_EMPTY(&block_exports);
 270     }
 271
 272     QLIST_FOREACH(exp, &block_exports, next) {
 273         if (exp->drv->type == type) {
 274             return true;
 275         }
 276     }
 277
 278     return false;
 279 }
 280
 281 /* type == BLOCK_EXPORT_TYPE__MAX for all types */
 282 void blk_exp_close_all_type(BlockExportType type)
 283 {
 284     BlockExport *exp, *next;
 285
 286     assert(in_aio_context_home_thread(qemu_get_aio_context()));
 287
 288     QLIST_FOREACH_SAFE(exp, &block_exports, next, next) {
 289         if (type != BLOCK_EXPORT_TYPE__MAX && exp->drv->type != type) {
 290             continue;
 291         }
 292         blk_exp_request_shutdown(exp);
 293     }
 294
 295     AIO_WAIT_WHILE_UNLOCKED(NULL, blk_exp_has_type(type));
 296 }
 297
 298 void blk_exp_close_all(void)
 299 {
 300     blk_exp_close_all_type(BLOCK_EXPORT_TYPE__MAX);
 301 }
 302
 303 void qmp_block_export_add(BlockExportOptions *export, Error **errp)
 304 {
 305     blk_exp_add(export, errp);
 306 }
 307
 308 void qmp_block_export_del(const char *id,
 309                           bool has_mode, BlockExportRemoveMode mode,
 310                           Error **errp)
 311 {
 312     ERRP_GUARD();
 313     BlockExport *exp;
 314
 315     exp = blk_exp_find(id);
 316     if (exp == NULL) {
 317         error_setg(errp, "Export '%s' is not found", id);
 318         return;
 319     }
 320     if (!exp->user_owned) {
 321         error_setg(errp, "Export '%s' is already shutting down", id);
 322         return;
 323     }
 324
 325     if (!has_mode) {
 326         mode = BLOCK_EXPORT_REMOVE_MODE_SAFE;
 327     }
 328     if (mode == BLOCK_EXPORT_REMOVE_MODE_SAFE &&
 329         qatomic_read(&exp->refcount) > 1) {
 330         error_setg(errp, "export '%s' still in use", exp->id);
 331         error_append_hint(errp, "Use mode='hard' to force client "
 332                           "disconnect\n");
 333         return;
 334     }
 335
 336     blk_exp_request_shutdown(exp);
 337 }
 338
 339 BlockExportInfoList *qmp_query_block_exports(Error **errp)
 340 {
 341     BlockExportInfoList *head = NULL, **tail = &head;
 342     BlockExport *exp;
 343
 344     QLIST_FOREACH(exp, &block_exports, next) {
 345         BlockExportInfo *info = g_new(BlockExportInfo, 1);
 346         *info = (BlockExportInfo) {
 347             .id             = g_strdup(exp->id),
 348             .type           = exp->drv->type,
 349             .node_name      = g_strdup(bdrv_get_node_name(blk_bs(exp->blk))),
 350             .shutting_down  = !exp->user_owned,
 351         };
 352
 353         QAPI_LIST_APPEND(tail, info);
 354     }
 355
 356     return head;
 357 }