include/block/export.h

   1 /*
   2  * Declarations for block exports
   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 #ifndef BLOCK_EXPORT_H
  15 #define BLOCK_EXPORT_H
  16
  17 #include "qapi/qapi-types-block-export.h"
  18 #include "qemu/queue.h"
  19
  20 typedef struct BlockExport BlockExport;
  21
  22 typedef struct BlockExportDriver {
  23     /* The export type that this driver services */
  24     BlockExportType type;
  25
  26     /*
  27      * The size of the driver-specific state that contains BlockExport as its
  28      * first field.
  29      */
  30     size_t instance_size;
  31
  32     /* Creates and starts a new block export */
  33     int (*create)(BlockExport *, BlockExportOptions *, Error **);
  34
  35     /*
  36      * Frees a removed block export. This function is only called after all
  37      * references have been dropped.
  38      */
  39     void (*delete)(BlockExport *);
  40
  41     /*
  42      * Start to disconnect all clients and drop other references held
  43      * internally by the export driver. When the function returns, there may
  44      * still be active references while the export is in the process of
  45      * shutting down.
  46      */
  47     void (*request_shutdown)(BlockExport *);
  48 } BlockExportDriver;
  49
  50 struct BlockExport {
  51     const BlockExportDriver *drv;
  52
  53     /* Unique identifier for the export */
  54     char *id;
  55
  56     /*
  57      * Reference count for this block export. This includes strong references
  58      * both from the owner (qemu-nbd or the monitor) and clients connected to
  59      * the export.
  60      *
  61      * Use atomics to access this field.
  62      */
  63     int refcount;
  64
  65     /*
  66      * True if one of the references in refcount belongs to the user. After the
  67      * user has dropped their reference, they may not e.g. remove the same
  68      * export a second time (which would decrease the refcount without having
  69      * it incremented first).
  70      */
  71     bool user_owned;
  72
  73     /* The AioContext whose lock protects this BlockExport object. */
  74     AioContext *ctx;
  75
  76     /* The block device to export */
  77     BlockBackend *blk;
  78
  79     /* List entry for block_exports */
  80     QLIST_ENTRY(BlockExport) next;
  81 };
  82
  83 BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp);
  84 BlockExport *blk_exp_find(const char *id);
  85 void blk_exp_ref(BlockExport *exp);
  86 void blk_exp_unref(BlockExport *exp);
  87 void blk_exp_request_shutdown(BlockExport *exp);
  88 void blk_exp_close_all(void);
  89 void blk_exp_close_all_type(BlockExportType type);
  90
  91 #endif