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 "block/export.h"
  19 #include "block/nbd.h"
  20 #include "qapi/error.h"
  21 #include "qapi/qapi-commands-block-export.h"
  22
  23 static const BlockExportDriver *blk_exp_drivers[] = {
  24     &blk_exp_nbd,
  25 };
  26
  27 static const BlockExportDriver *blk_exp_find_driver(BlockExportType type)
  28 {
  29     int i;
  30
  31     for (i = 0; i < ARRAY_SIZE(blk_exp_drivers); i++) {
  32         if (blk_exp_drivers[i]->type == type) {
  33             return blk_exp_drivers[i];
  34         }
  35     }
  36     return NULL;
  37 }
  38
  39 BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
  40 {
  41     const BlockExportDriver *drv;
  42     BlockExport *exp;
  43     int ret;
  44
  45     drv = blk_exp_find_driver(export->type);
  46     if (!drv) {
  47         error_setg(errp, "No driver found for the requested export type");
  48         return NULL;
  49     }
  50
  51     assert(drv->instance_size >= sizeof(BlockExport));
  52     exp = g_malloc0(drv->instance_size);
  53     *exp = (BlockExport) {
  54         .drv        = drv,
  55         .refcount   = 1,
  56     };
  57
  58     ret = drv->create(exp, export, errp);
  59     if (ret < 0) {
  60         g_free(exp);
  61         return NULL;
  62     }
  63
  64     return exp;
  65 }
  66
  67 /* Callers must hold exp->ctx lock */
  68 void blk_exp_ref(BlockExport *exp)
  69 {
  70     assert(exp->refcount > 0);
  71     exp->refcount++;
  72 }
  73
  74 /* Callers must hold exp->ctx lock */
  75 void blk_exp_unref(BlockExport *exp)
  76 {
  77     assert(exp->refcount > 0);
  78     if (--exp->refcount == 0) {
  79         exp->drv->delete(exp);
  80         g_free(exp);
  81     }
  82 }
  83
  84 void qmp_block_export_add(BlockExportOptions *export, Error **errp)
  85 {
  86     blk_exp_add(export, errp);
  87 }