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->has_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     blk_unref(blk);
 196     aio_context_release(ctx);
 197     if (exp) {
 198         g_free(exp->id);
 199         g_free(exp);
 200     }
 201     return NULL;
 202 }
 203
 204 /* Callers must hold exp->ctx lock */
 205 void blk_exp_ref(BlockExport *exp)
 206 {
 207     assert(exp->refcount > 0);
 208     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     AioContext *aio_context = exp->ctx;
 216
 217     aio_context_acquire(aio_context);
 218
 219     assert(exp->refcount == 0);
 220     QLIST_REMOVE(exp, next);
 221     exp->drv->delete(exp);
 222     blk_unref(exp->blk);
 223     qapi_event_send_block_export_deleted(exp->id);
 224     g_free(exp->id);
 225     g_free(exp);
 226
 227     aio_context_release(aio_context);
 228 }
 229
 230 /* Callers must hold exp->ctx lock */
 231 void blk_exp_unref(BlockExport *exp)
 232 {
 233     assert(exp->refcount > 0);
 234     if (--exp->refcount == 0) {
 235         /* Touch the block_exports list only in the main thread */
 236         aio_bh_schedule_oneshot(qemu_get_aio_context(), blk_exp_delete_bh,
 237                                 exp);
 238     }
 239 }
 240
 241 /*
 242  * Drops the user reference to the export and requests that all client
 243  * connections and other internally held references start to shut down. When
 244  * the function returns, there may still be active references while the export
 245  * is in the process of shutting down.
 246  *
 247  * Acquires exp->ctx internally. Callers must *not* hold the lock.
 248  */
 249 void blk_exp_request_shutdown(BlockExport *exp)
 250 {
 251     AioContext *aio_context = exp->ctx;
 252
 253     aio_context_acquire(aio_context);
 254
 255     /*
 256      * If the user doesn't own the export any more, it is already shutting
 257      * down. We must not call .request_shutdown and decrease the refcount a
 258      * second time.
 259      */
 260     if (!exp->user_owned) {
 261         goto out;
 262     }
 263
 264     exp->drv->request_shutdown(exp);
 265
 266     assert(exp->user_owned);
 267     exp->user_owned = false;
 268     blk_exp_unref(exp);
 269
 270 out:
 271     aio_context_release(aio_context);
 272 }
 273
 274 /*
 275  * Returns whether a block export of the given type exists.
 276  * type == BLOCK_EXPORT_TYPE__MAX checks for an export of any type.
 277  */
 278 static bool blk_exp_has_type(BlockExportType type)
 279 {
 280     BlockExport *exp;
 281
 282     if (type == BLOCK_EXPORT_TYPE__MAX) {
 283         return !QLIST_EMPTY(&block_exports);
 284     }
 285
 286     QLIST_FOREACH(exp, &block_exports, next) {
 287         if (exp->drv->type == type) {
 288             return true;
 289         }
 290     }
 291
 292     return false;
 293 }
 294
 295 /* type == BLOCK_EXPORT_TYPE__MAX for all types */
 296 void blk_exp_close_all_type(BlockExportType type)
 297 {
 298     BlockExport *exp, *next;
 299
 300     assert(in_aio_context_home_thread(qemu_get_aio_context()));
 301
 302     QLIST_FOREACH_SAFE(exp, &block_exports, next, next) {
 303         if (type != BLOCK_EXPORT_TYPE__MAX && exp->drv->type != type) {
 304             continue;
 305         }
 306         blk_exp_request_shutdown(exp);
 307     }
 308
 309     AIO_WAIT_WHILE(NULL, blk_exp_has_type(type));
 310 }
 311
 312 void blk_exp_close_all(void)
 313 {
 314     blk_exp_close_all_type(BLOCK_EXPORT_TYPE__MAX);
 315 }
 316
 317 void qmp_block_export_add(BlockExportOptions *export, Error **errp)
 318 {
 319     blk_exp_add(export, errp);
 320 }
 321
 322 void qmp_block_export_del(const char *id,
 323                           bool has_mode, BlockExportRemoveMode mode,
 324                           Error **errp)
 325 {
 326     ERRP_GUARD();
 327     BlockExport *exp;
 328
 329     exp = blk_exp_find(id);
 330     if (exp == NULL) {
 331         error_setg(errp, "Export '%s' is not found", id);
 332         return;
 333     }
 334     if (!exp->user_owned) {
 335         error_setg(errp, "Export '%s' is already shutting down", id);
 336         return;
 337     }
 338
 339     if (!has_mode) {
 340         mode = BLOCK_EXPORT_REMOVE_MODE_SAFE;
 341     }
 342     if (mode == BLOCK_EXPORT_REMOVE_MODE_SAFE && exp->refcount > 1) {
 343         error_setg(errp, "export '%s' still in use", exp->id);
 344         error_append_hint(errp, "Use mode='hard' to force client "
 345                           "disconnect\n");
 346         return;
 347     }
 348
 349     blk_exp_request_shutdown(exp);
 350 }
 351
 352 BlockExportInfoList *qmp_query_block_exports(Error **errp)
 353 {
 354     BlockExportInfoList *head = NULL, **tail = &head;
 355     BlockExport *exp;
 356
 357     QLIST_FOREACH(exp, &block_exports, next) {
 358         BlockExportInfo *info = g_new(BlockExportInfo, 1);
 359         *info = (BlockExportInfo) {
 360             .id             = g_strdup(exp->id),
 361             .type           = exp->drv->type,
 362             .node_name      = g_strdup(bdrv_get_node_name(blk_bs(exp->blk))),
 363             .shutting_down  = !exp->user_owned,
 364         };
 365
 366         QAPI_LIST_APPEND(tail, info);
 367     }
 368
 369     return head;
 370 }