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     if (!id_wellformed(export->id)) {
  87         error_setg(errp, "Invalid block export id");
  88         return NULL;
  89     }
  90     if (blk_exp_find(export->id)) {
  91         error_setg(errp, "Block export id '%s' is already in use", export->id);
  92         return NULL;
  93     }
  94
  95     drv = blk_exp_find_driver(export->type);
  96     if (!drv) {
  97         error_setg(errp, "No driver found for the requested export type");
  98         return NULL;
  99     }
 100
 101     bs = bdrv_lookup_bs(NULL, export->node_name, errp);
 102     if (!bs) {
 103         return NULL;
 104     }
 105
 106     if (!export->has_writable) {
 107         export->writable = false;
 108     }
 109     if (bdrv_is_read_only(bs) && export->writable) {
 110         error_setg(errp, "Cannot export read-only node as writable");
 111         return NULL;
 112     }
 113
 114     ctx = bdrv_get_aio_context(bs);
 115     aio_context_acquire(ctx);
 116
 117     if (export->iothread) {
 118         IOThread *iothread;
 119         AioContext *new_ctx;
 120         Error **set_context_errp;
 121
 122         iothread = iothread_by_id(export->iothread);
 123         if (!iothread) {
 124             error_setg(errp, "iothread \"%s\" not found", export->iothread);
 125             goto fail;
 126         }
 127
 128         new_ctx = iothread_get_aio_context(iothread);
 129
 130         /* Ignore errors with fixed-iothread=false */
 131         set_context_errp = fixed_iothread ? errp : NULL;
 132         ret = bdrv_try_change_aio_context(bs, new_ctx, NULL, set_context_errp);
 133         if (ret == 0) {
 134             aio_context_release(ctx);
 135             aio_context_acquire(new_ctx);
 136             ctx = new_ctx;
 137         } else if (fixed_iothread) {
 138             goto fail;
 139         }
 140     }
 141
 142     /*
 143      * Block exports are used for non-shared storage migration. Make sure
 144      * that BDRV_O_INACTIVE is cleared and the image is ready for write
 145      * access since the export could be available before migration handover.
 146      * ctx was acquired in the caller.
 147      */
 148     bdrv_activate(bs, NULL);
 149
 150     perm = BLK_PERM_CONSISTENT_READ;
 151     if (export->writable) {
 152         perm |= BLK_PERM_WRITE;
 153     }
 154
 155     blk = blk_new(ctx, perm, BLK_PERM_ALL);
 156
 157     if (!fixed_iothread) {
 158         blk_set_allow_aio_context_change(blk, true);
 159     }
 160
 161     ret = blk_insert_bs(blk, bs, errp);
 162     if (ret < 0) {
 163         goto fail;
 164     }
 165
 166     if (!export->has_writethrough) {
 167         export->writethrough = false;
 168     }
 169     blk_set_enable_write_cache(blk, !export->writethrough);
 170
 171     assert(drv->instance_size >= sizeof(BlockExport));
 172     exp = g_malloc0(drv->instance_size);
 173     *exp = (BlockExport) {
 174         .drv        = drv,
 175         .refcount   = 1,
 176         .user_owned = true,
 177         .id         = g_strdup(export->id),
 178         .ctx        = ctx,
 179         .blk        = blk,
 180     };
 181
 182     ret = drv->create(exp, export, errp);
 183     if (ret < 0) {
 184         goto fail;
 185     }
 186
 187     assert(exp->blk != NULL);
 188
 189     QLIST_INSERT_HEAD(&block_exports, exp, next);
 190
 191     aio_context_release(ctx);
 192     return exp;
 193
 194 fail:
 195     if (blk) {
 196         blk_set_dev_ops(blk, NULL, NULL);
 197         blk_unref(blk);
 198     }
 199     aio_context_release(ctx);
 200     if (exp) {
 201         g_free(exp->id);
 202         g_free(exp);
 203     }
 204     return NULL;
 205 }
 206
 207 void blk_exp_ref(BlockExport *exp)
 208 {
 209     assert(qatomic_read(&exp->refcount) > 0);
 210     qatomic_inc(&exp->refcount);
 211 }
 212
 213 /* Runs in the main thread */
 214 static void blk_exp_delete_bh(void *opaque)
 215 {
 216     BlockExport *exp = opaque;
 217     AioContext *aio_context = exp->ctx;
 218
 219     aio_context_acquire(aio_context);
 220
 221     assert(exp->refcount == 0);
 222     QLIST_REMOVE(exp, next);
 223     exp->drv->delete(exp);
 224     blk_set_dev_ops(exp->blk, NULL, NULL);
 225     blk_unref(exp->blk);
 226     qapi_event_send_block_export_deleted(exp->id);
 227     g_free(exp->id);
 228     g_free(exp);
 229
 230     aio_context_release(aio_context);
 231 }
 232
 233 void blk_exp_unref(BlockExport *exp)
 234 {
 235     assert(qatomic_read(&exp->refcount) > 0);
 236     if (qatomic_fetch_dec(&exp->refcount) == 1) {
 237         /* Touch the block_exports list only in the main thread */
 238         aio_bh_schedule_oneshot(qemu_get_aio_context(), blk_exp_delete_bh,
 239                                 exp);
 240     }
 241 }
 242
 243 /*
 244  * Drops the user reference to the export and requests that all client
 245  * connections and other internally held references start to shut down. When
 246  * the function returns, there may still be active references while the export
 247  * is in the process of shutting down.
 248  *
 249  * Acquires exp->ctx internally. Callers must *not* hold the lock.
 250  */
 251 void blk_exp_request_shutdown(BlockExport *exp)
 252 {
 253     AioContext *aio_context = exp->ctx;
 254
 255     aio_context_acquire(aio_context);
 256
 257     /*
 258      * If the user doesn't own the export any more, it is already shutting
 259      * down. We must not call .request_shutdown and decrease the refcount a
 260      * second time.
 261      */
 262     if (!exp->user_owned) {
 263         goto out;
 264     }
 265
 266     exp->drv->request_shutdown(exp);
 267
 268     assert(exp->user_owned);
 269     exp->user_owned = false;
 270     blk_exp_unref(exp);
 271
 272 out:
 273     aio_context_release(aio_context);
 274 }
 275
 276 /*
 277  * Returns whether a block export of the given type exists.
 278  * type == BLOCK_EXPORT_TYPE__MAX checks for an export of any type.
 279  */
 280 static bool blk_exp_has_type(BlockExportType type)
 281 {
 282     BlockExport *exp;
 283
 284     if (type == BLOCK_EXPORT_TYPE__MAX) {
 285         return !QLIST_EMPTY(&block_exports);
 286     }
 287
 288     QLIST_FOREACH(exp, &block_exports, next) {
 289         if (exp->drv->type == type) {
 290             return true;
 291         }
 292     }
 293
 294     return false;
 295 }
 296
 297 /* type == BLOCK_EXPORT_TYPE__MAX for all types */
 298 void blk_exp_close_all_type(BlockExportType type)
 299 {
 300     BlockExport *exp, *next;
 301
 302     assert(in_aio_context_home_thread(qemu_get_aio_context()));
 303
 304     QLIST_FOREACH_SAFE(exp, &block_exports, next, next) {
 305         if (type != BLOCK_EXPORT_TYPE__MAX && exp->drv->type != type) {
 306             continue;
 307         }
 308         blk_exp_request_shutdown(exp);
 309     }
 310
 311     AIO_WAIT_WHILE_UNLOCKED(NULL, blk_exp_has_type(type));
 312 }
 313
 314 void blk_exp_close_all(void)
 315 {
 316     blk_exp_close_all_type(BLOCK_EXPORT_TYPE__MAX);
 317 }
 318
 319 void qmp_block_export_add(BlockExportOptions *export, Error **errp)
 320 {
 321     blk_exp_add(export, errp);
 322 }
 323
 324 void qmp_block_export_del(const char *id,
 325                           bool has_mode, BlockExportRemoveMode mode,
 326                           Error **errp)
 327 {
 328     ERRP_GUARD();
 329     BlockExport *exp;
 330
 331     exp = blk_exp_find(id);
 332     if (exp == NULL) {
 333         error_setg(errp, "Export '%s' is not found", id);
 334         return;
 335     }
 336     if (!exp->user_owned) {
 337         error_setg(errp, "Export '%s' is already shutting down", id);
 338         return;
 339     }
 340
 341     if (!has_mode) {
 342         mode = BLOCK_EXPORT_REMOVE_MODE_SAFE;
 343     }
 344     if (mode == BLOCK_EXPORT_REMOVE_MODE_SAFE &&
 345         qatomic_read(&exp->refcount) > 1) {
 346         error_setg(errp, "export '%s' still in use", exp->id);
 347         error_append_hint(errp, "Use mode='hard' to force client "
 348                           "disconnect\n");
 349         return;
 350     }
 351
 352     blk_exp_request_shutdown(exp);
 353 }
 354
 355 BlockExportInfoList *qmp_query_block_exports(Error **errp)
 356 {
 357     BlockExportInfoList *head = NULL, **tail = &head;
 358     BlockExport *exp;
 359
 360     QLIST_FOREACH(exp, &block_exports, next) {
 361         BlockExportInfo *info = g_new(BlockExportInfo, 1);
 362         *info = (BlockExportInfo) {
 363             .id             = g_strdup(exp->id),
 364             .type           = exp->drv->type,
 365             .node_name      = g_strdup(bdrv_get_node_name(blk_bs(exp->blk))),
 366             .shutting_down  = !exp->user_owned,
 367         };
 368
 369         QAPI_LIST_APPEND(tail, info);
 370     }
 371
 372     return head;
 373 }