X-Git-Url: https://repo.jachan.dev/qemu.git/blobdiff_plain/7f06d47eff9d26cca87855273f20786502f8c57e..979e9b03fc8c85d3b78a14410c64cbb16d348095:/block/block-backend.c

diff --git a/block/block-backend.c b/block/block-backend.c
index fb91680f03..9889e813b6 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -12,14 +12,54 @@
 
 #include "sysemu/block-backend.h"
 #include "block/block_int.h"
+#include "block/blockjob.h"
+#include "block/throttle-groups.h"
 #include "sysemu/blockdev.h"
+#include "sysemu/sysemu.h"
+#include "qapi-event.h"
+
+/* Number of coroutines to reserve per attached device model */
+#define COROUTINE_POOL_RESERVATION 64
+
+static AioContext *blk_aiocb_get_aio_context(BlockAIOCB *acb);
 
 struct BlockBackend {
     char *name;
     int refcnt;
     BlockDriverState *bs;
-    DriveInfo *legacy_dinfo;
+    DriveInfo *legacy_dinfo;    /* null unless created by drive_new() */
     QTAILQ_ENTRY(BlockBackend) link; /* for blk_backends */
+
+    void *dev;                  /* attached device model, if any */
+    /* TODO change to DeviceState when all users are qdevified */
+    const BlockDevOps *dev_ops;
+    void *dev_opaque;
+
+    /* the block size for which the guest device expects atomicity */
+    int guest_block_size;
+
+    /* If the BDS tree is removed, some of its options are stored here (which
+     * can be used to restore those options in the new BDS on insert) */
+    BlockBackendRootState root_state;
+
+    /* I/O stats (display with "info blockstats"). */
+    BlockAcctStats stats;
+
+    BlockdevOnError on_read_error, on_write_error;
+    bool iostatus_enabled;
+    BlockDeviceIoStatus iostatus;
+};
+
+typedef struct BlockBackendAIOCB {
+    BlockAIOCB common;
+    QEMUBH *bh;
+    BlockBackend *blk;
+    int ret;
+} BlockBackendAIOCB;
+
+static const AIOCBInfo block_backend_aiocb_info = {
+    .get_aio_context = blk_aiocb_get_aio_context,
+    .aiocb_size = sizeof(BlockBackendAIOCB),
 };
 
 static void drive_info_del(DriveInfo *dinfo);
@@ -82,21 +122,61 @@ BlockBackend *blk_new_with_bs(const char *name, Error **errp)
     return blk;
 }
 
+/*
+ * Calls blk_new_with_bs() and then calls bdrv_open() on the BlockDriverState.
+ *
+ * Just as with bdrv_open(), after having called this function the reference to
+ * @options belongs to the block layer (even on failure).
+ *
+ * TODO: Remove @filename and @flags; it should be possible to specify a whole
+ * BDS tree just by specifying the @options QDict (or @reference,
+ * alternatively). At the time of adding this function, this is not possible,
+ * though, so callers of this function have to be able to specify @filename and
+ * @flags.
+ */
+BlockBackend *blk_new_open(const char *name, const char *filename,
+                           const char *reference, QDict *options, int flags,
+                           Error **errp)
+{
+    BlockBackend *blk;
+    int ret;
+
+    blk = blk_new_with_bs(name, errp);
+    if (!blk) {
+        QDECREF(options);
+        return NULL;
+    }
+
+    ret = bdrv_open(&blk->bs, filename, reference, options, flags, errp);
+    if (ret < 0) {
+        blk_unref(blk);
+        return NULL;
+    }
+
+    return blk;
+}
+
 static void blk_delete(BlockBackend *blk)
 {
     assert(!blk->refcnt);
+    assert(!blk->dev);
     if (blk->bs) {
         assert(blk->bs->blk == blk);
         blk->bs->blk = NULL;
         bdrv_unref(blk->bs);
         blk->bs = NULL;
     }
-    /* Avoid double-remove after blk_hide_on_behalf_of_do_drive_del() */
+    if (blk->root_state.throttle_state) {
+        g_free(blk->root_state.throttle_group);
+        throttle_group_unref(blk->root_state.throttle_state);
+    }
+    /* Avoid double-remove after blk_hide_on_behalf_of_hmp_drive_del() */
     if (blk->name[0]) {
         QTAILQ_REMOVE(&blk_backends, blk, link);
     }
     g_free(blk->name);
     drive_info_del(blk->legacy_dinfo);
+    block_acct_cleanup(&blk->stats);
     g_free(blk);
 }
 
@@ -106,11 +186,15 @@ static void drive_info_del(DriveInfo *dinfo)
         return;
     }
     qemu_opts_del(dinfo->opts);
-    g_free(dinfo->id);
     g_free(dinfo->serial);
     g_free(dinfo);
 }
 
+int blk_get_refcnt(BlockBackend *blk)
+{
+    return blk ? blk->refcnt : 0;
+}
+
 /*
  * Increment @blk's reference count.
  * @blk must not be null.
@@ -153,7 +237,7 @@ BlockBackend *blk_next(BlockBackend *blk)
 /*
  * Return @blk's name, a non-null string.
  * Wart: the name is empty iff @blk has been hidden with
- * blk_hide_on_behalf_of_do_drive_del().
+ * blk_hide_on_behalf_of_hmp_drive_del().
  */
 const char *blk_name(BlockBackend *blk)
 {
@@ -185,6 +269,23 @@ BlockDriverState *blk_bs(BlockBackend *blk)
     return blk->bs;
 }
 
+/*
+ * Changes the BlockDriverState attached to @blk
+ */
+void blk_set_bs(BlockBackend *blk, BlockDriverState *bs)
+{
+    bdrv_ref(bs);
+
+    if (blk->bs) {
+        blk->bs->blk = NULL;
+        bdrv_unref(blk->bs);
+    }
+    assert(bs->blk == NULL);
+
+    blk->bs = bs;
+    bs->blk = blk;
+}
+
 /*
  * Return @blk's DriveInfo if any, else null.
  */
@@ -229,7 +330,7 @@ BlockBackend *blk_by_legacy_dinfo(DriveInfo *dinfo)
  * Strictly for use by do_drive_del().
  * TODO get rid of it!
  */
-void blk_hide_on_behalf_of_do_drive_del(BlockBackend *blk)
+void blk_hide_on_behalf_of_hmp_drive_del(BlockBackend *blk)
 {
     QTAILQ_REMOVE(&blk_backends, blk, link);
     blk->name[0] = 0;
@@ -237,3 +338,938 @@ void blk_hide_on_behalf_of_do_drive_del(BlockBackend *blk)
         bdrv_make_anon(blk->bs);
     }
 }
+
+/*
+ * Disassociates the currently associated BlockDriverState from @blk.
+ */
+void blk_remove_bs(BlockBackend *blk)
+{
+    blk_update_root_state(blk);
+
+    blk->bs->blk = NULL;
+    bdrv_unref(blk->bs);
+    blk->bs = NULL;
+}
+
+/*
+ * Associates a new BlockDriverState with @blk.
+ */
+void blk_insert_bs(BlockBackend *blk, BlockDriverState *bs)
+{
+    assert(!blk->bs && !bs->blk);
+    bdrv_ref(bs);
+    blk->bs = bs;
+    bs->blk = blk;
+}
+
+/*
+ * Attach device model @dev to @blk.
+ * Return 0 on success, -EBUSY when a device model is attached already.
+ */
+int blk_attach_dev(BlockBackend *blk, void *dev)
+/* TODO change to DeviceState *dev when all users are qdevified */
+{
+    if (blk->dev) {
+        return -EBUSY;
+    }
+    blk_ref(blk);
+    blk->dev = dev;
+    blk_iostatus_reset(blk);
+    return 0;
+}
+
+/*
+ * Attach device model @dev to @blk.
+ * @blk must not have a device model attached already.
+ * TODO qdevified devices don't use this, remove when devices are qdevified
+ */
+void blk_attach_dev_nofail(BlockBackend *blk, void *dev)
+{
+    if (blk_attach_dev(blk, dev) < 0) {
+        abort();
+    }
+}
+
+/*
+ * Detach device model @dev from @blk.
+ * @dev must be currently attached to @blk.
+ */
+void blk_detach_dev(BlockBackend *blk, void *dev)
+/* TODO change to DeviceState *dev when all users are qdevified */
+{
+    assert(blk->dev == dev);
+    blk->dev = NULL;
+    blk->dev_ops = NULL;
+    blk->dev_opaque = NULL;
+    blk->guest_block_size = 512;
+    blk_unref(blk);
+}
+
+/*
+ * Return the device model attached to @blk if any, else null.
+ */
+void *blk_get_attached_dev(BlockBackend *blk)
+/* TODO change to return DeviceState * when all users are qdevified */
+{
+    return blk->dev;
+}
+
+/*
+ * Set @blk's device model callbacks to @ops.
+ * @opaque is the opaque argument to pass to the callbacks.
+ * This is for use by device models.
+ */
+void blk_set_dev_ops(BlockBackend *blk, const BlockDevOps *ops,
+                     void *opaque)
+{
+    blk->dev_ops = ops;
+    blk->dev_opaque = opaque;
+}
+
+/*
+ * Notify @blk's attached device model of media change.
+ * If @load is true, notify of media load.
+ * Else, notify of media eject.
+ * Also send DEVICE_TRAY_MOVED events as appropriate.
+ */
+void blk_dev_change_media_cb(BlockBackend *blk, bool load)
+{
+    if (blk->dev_ops && blk->dev_ops->change_media_cb) {
+        bool tray_was_open, tray_is_open;
+
+        tray_was_open = blk_dev_is_tray_open(blk);
+        blk->dev_ops->change_media_cb(blk->dev_opaque, load);
+        tray_is_open = blk_dev_is_tray_open(blk);
+
+        if (tray_was_open != tray_is_open) {
+            qapi_event_send_device_tray_moved(blk_name(blk), tray_is_open,
+                                              &error_abort);
+        }
+    }
+}
+
+/*
+ * Does @blk's attached device model have removable media?
+ * %true if no device model is attached.
+ */
+bool blk_dev_has_removable_media(BlockBackend *blk)
+{
+    return !blk->dev || (blk->dev_ops && blk->dev_ops->change_media_cb);
+}
+
+/*
+ * Notify @blk's attached device model of a media eject request.
+ * If @force is true, the medium is about to be yanked out forcefully.
+ */
+void blk_dev_eject_request(BlockBackend *blk, bool force)
+{
+    if (blk->dev_ops && blk->dev_ops->eject_request_cb) {
+        blk->dev_ops->eject_request_cb(blk->dev_opaque, force);
+    }
+}
+
+/*
+ * Does @blk's attached device model have a tray, and is it open?
+ */
+bool blk_dev_is_tray_open(BlockBackend *blk)
+{
+    if (blk->dev_ops && blk->dev_ops->is_tray_open) {
+        return blk->dev_ops->is_tray_open(blk->dev_opaque);
+    }
+    return false;
+}
+
+/*
+ * Does @blk's attached device model have the medium locked?
+ * %false if the device model has no such lock.
+ */
+bool blk_dev_is_medium_locked(BlockBackend *blk)
+{
+    if (blk->dev_ops && blk->dev_ops->is_medium_locked) {
+        return blk->dev_ops->is_medium_locked(blk->dev_opaque);
+    }
+    return false;
+}
+
+/*
+ * Notify @blk's attached device model of a backend size change.
+ */
+void blk_dev_resize_cb(BlockBackend *blk)
+{
+    if (blk->dev_ops && blk->dev_ops->resize_cb) {
+        blk->dev_ops->resize_cb(blk->dev_opaque);
+    }
+}
+
+void blk_iostatus_enable(BlockBackend *blk)
+{
+    blk->iostatus_enabled = true;
+    blk->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
+}
+
+/* The I/O status is only enabled if the drive explicitly
+ * enables it _and_ the VM is configured to stop on errors */
+bool blk_iostatus_is_enabled(const BlockBackend *blk)
+{
+    return (blk->iostatus_enabled &&
+           (blk->on_write_error == BLOCKDEV_ON_ERROR_ENOSPC ||
+            blk->on_write_error == BLOCKDEV_ON_ERROR_STOP   ||
+            blk->on_read_error == BLOCKDEV_ON_ERROR_STOP));
+}
+
+BlockDeviceIoStatus blk_iostatus(const BlockBackend *blk)
+{
+    return blk->iostatus;
+}
+
+void blk_iostatus_disable(BlockBackend *blk)
+{
+    blk->iostatus_enabled = false;
+}
+
+void blk_iostatus_reset(BlockBackend *blk)
+{
+    if (blk_iostatus_is_enabled(blk)) {
+        blk->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
+        if (blk->bs && blk->bs->job) {
+            block_job_iostatus_reset(blk->bs->job);
+        }
+    }
+}
+
+void blk_iostatus_set_err(BlockBackend *blk, int error)
+{
+    assert(blk_iostatus_is_enabled(blk));
+    if (blk->iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
+        blk->iostatus = error == ENOSPC ? BLOCK_DEVICE_IO_STATUS_NOSPACE :
+                                          BLOCK_DEVICE_IO_STATUS_FAILED;
+    }
+}
+
+static int blk_check_byte_request(BlockBackend *blk, int64_t offset,
+                                  size_t size)
+{
+    int64_t len;
+
+    if (size > INT_MAX) {
+        return -EIO;
+    }
+
+    if (!blk_is_available(blk)) {
+        return -ENOMEDIUM;
+    }
+
+    len = blk_getlength(blk);
+    if (len < 0) {
+        return len;
+    }
+
+    if (offset < 0) {
+        return -EIO;
+    }
+
+    if (offset > len || len - offset < size) {
+        return -EIO;
+    }
+
+    return 0;
+}
+
+static int blk_check_request(BlockBackend *blk, int64_t sector_num,
+                             int nb_sectors)
+{
+    if (sector_num < 0 || sector_num > INT64_MAX / BDRV_SECTOR_SIZE) {
+        return -EIO;
+    }
+
+    if (nb_sectors < 0 || nb_sectors > INT_MAX / BDRV_SECTOR_SIZE) {
+        return -EIO;
+    }
+
+    return blk_check_byte_request(blk, sector_num * BDRV_SECTOR_SIZE,
+                                  nb_sectors * BDRV_SECTOR_SIZE);
+}
+
+int blk_read(BlockBackend *blk, int64_t sector_num, uint8_t *buf,
+             int nb_sectors)
+{
+    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return bdrv_read(blk->bs, sector_num, buf, nb_sectors);
+}
+
+int blk_read_unthrottled(BlockBackend *blk, int64_t sector_num, uint8_t *buf,
+                         int nb_sectors)
+{
+    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return bdrv_read_unthrottled(blk->bs, sector_num, buf, nb_sectors);
+}
+
+int blk_write(BlockBackend *blk, int64_t sector_num, const uint8_t *buf,
+              int nb_sectors)
+{
+    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return bdrv_write(blk->bs, sector_num, buf, nb_sectors);
+}
+
+int blk_write_zeroes(BlockBackend *blk, int64_t sector_num,
+                     int nb_sectors, BdrvRequestFlags flags)
+{
+    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return bdrv_write_zeroes(blk->bs, sector_num, nb_sectors, flags);
+}
+
+static void error_callback_bh(void *opaque)
+{
+    struct BlockBackendAIOCB *acb = opaque;
+    qemu_bh_delete(acb->bh);
+    acb->common.cb(acb->common.opaque, acb->ret);
+    qemu_aio_unref(acb);
+}
+
+static BlockAIOCB *abort_aio_request(BlockBackend *blk, BlockCompletionFunc *cb,
+                                     void *opaque, int ret)
+{
+    struct BlockBackendAIOCB *acb;
+    QEMUBH *bh;
+
+    acb = blk_aio_get(&block_backend_aiocb_info, blk, cb, opaque);
+    acb->blk = blk;
+    acb->ret = ret;
+
+    bh = aio_bh_new(blk_get_aio_context(blk), error_callback_bh, acb);
+    acb->bh = bh;
+    qemu_bh_schedule(bh);
+
+    return &acb->common;
+}
+
+BlockAIOCB *blk_aio_write_zeroes(BlockBackend *blk, int64_t sector_num,
+                                 int nb_sectors, BdrvRequestFlags flags,
+                                 BlockCompletionFunc *cb, void *opaque)
+{
+    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    if (ret < 0) {
+        return abort_aio_request(blk, cb, opaque, ret);
+    }
+
+    return bdrv_aio_write_zeroes(blk->bs, sector_num, nb_sectors, flags,
+                                 cb, opaque);
+}
+
+int blk_pread(BlockBackend *blk, int64_t offset, void *buf, int count)
+{
+    int ret = blk_check_byte_request(blk, offset, count);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return bdrv_pread(blk->bs, offset, buf, count);
+}
+
+int blk_pwrite(BlockBackend *blk, int64_t offset, const void *buf, int count)
+{
+    int ret = blk_check_byte_request(blk, offset, count);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return bdrv_pwrite(blk->bs, offset, buf, count);
+}
+
+int64_t blk_getlength(BlockBackend *blk)
+{
+    if (!blk_is_available(blk)) {
+        return -ENOMEDIUM;
+    }
+
+    return bdrv_getlength(blk->bs);
+}
+
+void blk_get_geometry(BlockBackend *blk, uint64_t *nb_sectors_ptr)
+{
+    if (!blk->bs) {
+        *nb_sectors_ptr = 0;
+    } else {
+        bdrv_get_geometry(blk->bs, nb_sectors_ptr);
+    }
+}
+
+int64_t blk_nb_sectors(BlockBackend *blk)
+{
+    if (!blk_is_available(blk)) {
+        return -ENOMEDIUM;
+    }
+
+    return bdrv_nb_sectors(blk->bs);
+}
+
+BlockAIOCB *blk_aio_readv(BlockBackend *blk, int64_t sector_num,
+                          QEMUIOVector *iov, int nb_sectors,
+                          BlockCompletionFunc *cb, void *opaque)
+{
+    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    if (ret < 0) {
+        return abort_aio_request(blk, cb, opaque, ret);
+    }
+
+    return bdrv_aio_readv(blk->bs, sector_num, iov, nb_sectors, cb, opaque);
+}
+
+BlockAIOCB *blk_aio_writev(BlockBackend *blk, int64_t sector_num,
+                           QEMUIOVector *iov, int nb_sectors,
+                           BlockCompletionFunc *cb, void *opaque)
+{
+    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    if (ret < 0) {
+        return abort_aio_request(blk, cb, opaque, ret);
+    }
+
+    return bdrv_aio_writev(blk->bs, sector_num, iov, nb_sectors, cb, opaque);
+}
+
+BlockAIOCB *blk_aio_flush(BlockBackend *blk,
+                          BlockCompletionFunc *cb, void *opaque)
+{
+    if (!blk_is_available(blk)) {
+        return abort_aio_request(blk, cb, opaque, -ENOMEDIUM);
+    }
+
+    return bdrv_aio_flush(blk->bs, cb, opaque);
+}
+
+BlockAIOCB *blk_aio_discard(BlockBackend *blk,
+                            int64_t sector_num, int nb_sectors,
+                            BlockCompletionFunc *cb, void *opaque)
+{
+    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    if (ret < 0) {
+        return abort_aio_request(blk, cb, opaque, ret);
+    }
+
+    return bdrv_aio_discard(blk->bs, sector_num, nb_sectors, cb, opaque);
+}
+
+void blk_aio_cancel(BlockAIOCB *acb)
+{
+    bdrv_aio_cancel(acb);
+}
+
+void blk_aio_cancel_async(BlockAIOCB *acb)
+{
+    bdrv_aio_cancel_async(acb);
+}
+
+int blk_aio_multiwrite(BlockBackend *blk, BlockRequest *reqs, int num_reqs)
+{
+    int i, ret;
+
+    for (i = 0; i < num_reqs; i++) {
+        ret = blk_check_request(blk, reqs[i].sector, reqs[i].nb_sectors);
+        if (ret < 0) {
+            return ret;
+        }
+    }
+
+    return bdrv_aio_multiwrite(blk->bs, reqs, num_reqs);
+}
+
+int blk_ioctl(BlockBackend *blk, unsigned long int req, void *buf)
+{
+    if (!blk_is_available(blk)) {
+        return -ENOMEDIUM;
+    }
+
+    return bdrv_ioctl(blk->bs, req, buf);
+}
+
+BlockAIOCB *blk_aio_ioctl(BlockBackend *blk, unsigned long int req, void *buf,
+                          BlockCompletionFunc *cb, void *opaque)
+{
+    if (!blk_is_available(blk)) {
+        return abort_aio_request(blk, cb, opaque, -ENOMEDIUM);
+    }
+
+    return bdrv_aio_ioctl(blk->bs, req, buf, cb, opaque);
+}
+
+int blk_co_discard(BlockBackend *blk, int64_t sector_num, int nb_sectors)
+{
+    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return bdrv_co_discard(blk->bs, sector_num, nb_sectors);
+}
+
+int blk_co_flush(BlockBackend *blk)
+{
+    if (!blk_is_available(blk)) {
+        return -ENOMEDIUM;
+    }
+
+    return bdrv_co_flush(blk->bs);
+}
+
+int blk_flush(BlockBackend *blk)
+{
+    if (!blk_is_available(blk)) {
+        return -ENOMEDIUM;
+    }
+
+    return bdrv_flush(blk->bs);
+}
+
+int blk_flush_all(void)
+{
+    return bdrv_flush_all();
+}
+
+void blk_drain(BlockBackend *blk)
+{
+    if (blk->bs) {
+        bdrv_drain(blk->bs);
+    }
+}
+
+void blk_drain_all(void)
+{
+    bdrv_drain_all();
+}
+
+void blk_set_on_error(BlockBackend *blk, BlockdevOnError on_read_error,
+                      BlockdevOnError on_write_error)
+{
+    blk->on_read_error = on_read_error;
+    blk->on_write_error = on_write_error;
+}
+
+BlockdevOnError blk_get_on_error(BlockBackend *blk, bool is_read)
+{
+    return is_read ? blk->on_read_error : blk->on_write_error;
+}
+
+BlockErrorAction blk_get_error_action(BlockBackend *blk, bool is_read,
+                                      int error)
+{
+    BlockdevOnError on_err = blk_get_on_error(blk, is_read);
+
+    switch (on_err) {
+    case BLOCKDEV_ON_ERROR_ENOSPC:
+        return (error == ENOSPC) ?
+               BLOCK_ERROR_ACTION_STOP : BLOCK_ERROR_ACTION_REPORT;
+    case BLOCKDEV_ON_ERROR_STOP:
+        return BLOCK_ERROR_ACTION_STOP;
+    case BLOCKDEV_ON_ERROR_REPORT:
+        return BLOCK_ERROR_ACTION_REPORT;
+    case BLOCKDEV_ON_ERROR_IGNORE:
+        return BLOCK_ERROR_ACTION_IGNORE;
+    default:
+        abort();
+    }
+}
+
+static void send_qmp_error_event(BlockBackend *blk,
+                                 BlockErrorAction action,
+                                 bool is_read, int error)
+{
+    IoOperationType optype;
+
+    optype = is_read ? IO_OPERATION_TYPE_READ : IO_OPERATION_TYPE_WRITE;
+    qapi_event_send_block_io_error(blk_name(blk), optype, action,
+                                   blk_iostatus_is_enabled(blk),
+                                   error == ENOSPC, strerror(error),
+                                   &error_abort);
+}
+
+/* This is done by device models because, while the block layer knows
+ * about the error, it does not know whether an operation comes from
+ * the device or the block layer (from a job, for example).
+ */
+void blk_error_action(BlockBackend *blk, BlockErrorAction action,
+                      bool is_read, int error)
+{
+    assert(error >= 0);
+
+    if (action == BLOCK_ERROR_ACTION_STOP) {
+        /* First set the iostatus, so that "info block" returns an iostatus
+         * that matches the events raised so far (an additional error iostatus
+         * is fine, but not a lost one).
+         */
+        blk_iostatus_set_err(blk, error);
+
+        /* Then raise the request to stop the VM and the event.
+         * qemu_system_vmstop_request_prepare has two effects.  First,
+         * it ensures that the STOP event always comes after the
+         * BLOCK_IO_ERROR event.  Second, it ensures that even if management
+         * can observe the STOP event and do a "cont" before the STOP
+         * event is issued, the VM will not stop.  In this case, vm_start()
+         * also ensures that the STOP/RESUME pair of events is emitted.
+         */
+        qemu_system_vmstop_request_prepare();
+        send_qmp_error_event(blk, action, is_read, error);
+        qemu_system_vmstop_request(RUN_STATE_IO_ERROR);
+    } else {
+        send_qmp_error_event(blk, action, is_read, error);
+    }
+}
+
+int blk_is_read_only(BlockBackend *blk)
+{
+    if (blk->bs) {
+        return bdrv_is_read_only(blk->bs);
+    } else {
+        return blk->root_state.read_only;
+    }
+}
+
+int blk_is_sg(BlockBackend *blk)
+{
+    if (!blk->bs) {
+        return 0;
+    }
+
+    return bdrv_is_sg(blk->bs);
+}
+
+int blk_enable_write_cache(BlockBackend *blk)
+{
+    if (blk->bs) {
+        return bdrv_enable_write_cache(blk->bs);
+    } else {
+        return !!(blk->root_state.open_flags & BDRV_O_CACHE_WB);
+    }
+}
+
+void blk_set_enable_write_cache(BlockBackend *blk, bool wce)
+{
+    if (blk->bs) {
+        bdrv_set_enable_write_cache(blk->bs, wce);
+    } else {
+        if (wce) {
+            blk->root_state.open_flags |= BDRV_O_CACHE_WB;
+        } else {
+            blk->root_state.open_flags &= ~BDRV_O_CACHE_WB;
+        }
+    }
+}
+
+void blk_invalidate_cache(BlockBackend *blk, Error **errp)
+{
+    if (!blk->bs) {
+        error_setg(errp, "Device '%s' has no medium", blk->name);
+        return;
+    }
+
+    bdrv_invalidate_cache(blk->bs, errp);
+}
+
+bool blk_is_inserted(BlockBackend *blk)
+{
+    return blk->bs && bdrv_is_inserted(blk->bs);
+}
+
+bool blk_is_available(BlockBackend *blk)
+{
+    return blk_is_inserted(blk) && !blk_dev_is_tray_open(blk);
+}
+
+void blk_lock_medium(BlockBackend *blk, bool locked)
+{
+    if (blk->bs) {
+        bdrv_lock_medium(blk->bs, locked);
+    }
+}
+
+void blk_eject(BlockBackend *blk, bool eject_flag)
+{
+    if (blk->bs) {
+        bdrv_eject(blk->bs, eject_flag);
+    }
+}
+
+int blk_get_flags(BlockBackend *blk)
+{
+    if (blk->bs) {
+        return bdrv_get_flags(blk->bs);
+    } else {
+        return blk->root_state.open_flags;
+    }
+}
+
+int blk_get_max_transfer_length(BlockBackend *blk)
+{
+    if (blk->bs) {
+        return blk->bs->bl.max_transfer_length;
+    } else {
+        return 0;
+    }
+}
+
+void blk_set_guest_block_size(BlockBackend *blk, int align)
+{
+    blk->guest_block_size = align;
+}
+
+void *blk_blockalign(BlockBackend *blk, size_t size)
+{
+    return qemu_blockalign(blk ? blk->bs : NULL, size);
+}
+
+bool blk_op_is_blocked(BlockBackend *blk, BlockOpType op, Error **errp)
+{
+    if (!blk->bs) {
+        return false;
+    }
+
+    return bdrv_op_is_blocked(blk->bs, op, errp);
+}
+
+void blk_op_unblock(BlockBackend *blk, BlockOpType op, Error *reason)
+{
+    if (blk->bs) {
+        bdrv_op_unblock(blk->bs, op, reason);
+    }
+}
+
+void blk_op_block_all(BlockBackend *blk, Error *reason)
+{
+    if (blk->bs) {
+        bdrv_op_block_all(blk->bs, reason);
+    }
+}
+
+void blk_op_unblock_all(BlockBackend *blk, Error *reason)
+{
+    if (blk->bs) {
+        bdrv_op_unblock_all(blk->bs, reason);
+    }
+}
+
+AioContext *blk_get_aio_context(BlockBackend *blk)
+{
+    if (blk->bs) {
+        return bdrv_get_aio_context(blk->bs);
+    } else {
+        return qemu_get_aio_context();
+    }
+}
+
+static AioContext *blk_aiocb_get_aio_context(BlockAIOCB *acb)
+{
+    BlockBackendAIOCB *blk_acb = DO_UPCAST(BlockBackendAIOCB, common, acb);
+    return blk_get_aio_context(blk_acb->blk);
+}
+
+void blk_set_aio_context(BlockBackend *blk, AioContext *new_context)
+{
+    if (blk->bs) {
+        bdrv_set_aio_context(blk->bs, new_context);
+    }
+}
+
+void blk_add_aio_context_notifier(BlockBackend *blk,
+        void (*attached_aio_context)(AioContext *new_context, void *opaque),
+        void (*detach_aio_context)(void *opaque), void *opaque)
+{
+    if (blk->bs) {
+        bdrv_add_aio_context_notifier(blk->bs, attached_aio_context,
+                                      detach_aio_context, opaque);
+    }
+}
+
+void blk_remove_aio_context_notifier(BlockBackend *blk,
+                                     void (*attached_aio_context)(AioContext *,
+                                                                  void *),
+                                     void (*detach_aio_context)(void *),
+                                     void *opaque)
+{
+    if (blk->bs) {
+        bdrv_remove_aio_context_notifier(blk->bs, attached_aio_context,
+                                         detach_aio_context, opaque);
+    }
+}
+
+void blk_add_close_notifier(BlockBackend *blk, Notifier *notify)
+{
+    if (blk->bs) {
+        bdrv_add_close_notifier(blk->bs, notify);
+    }
+}
+
+void blk_io_plug(BlockBackend *blk)
+{
+    if (blk->bs) {
+        bdrv_io_plug(blk->bs);
+    }
+}
+
+void blk_io_unplug(BlockBackend *blk)
+{
+    if (blk->bs) {
+        bdrv_io_unplug(blk->bs);
+    }
+}
+
+BlockAcctStats *blk_get_stats(BlockBackend *blk)
+{
+    return &blk->stats;
+}
+
+void *blk_aio_get(const AIOCBInfo *aiocb_info, BlockBackend *blk,
+                  BlockCompletionFunc *cb, void *opaque)
+{
+    return qemu_aio_get(aiocb_info, blk_bs(blk), cb, opaque);
+}
+
+int coroutine_fn blk_co_write_zeroes(BlockBackend *blk, int64_t sector_num,
+                                     int nb_sectors, BdrvRequestFlags flags)
+{
+    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return bdrv_co_write_zeroes(blk->bs, sector_num, nb_sectors, flags);
+}
+
+int blk_write_compressed(BlockBackend *blk, int64_t sector_num,
+                         const uint8_t *buf, int nb_sectors)
+{
+    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return bdrv_write_compressed(blk->bs, sector_num, buf, nb_sectors);
+}
+
+int blk_truncate(BlockBackend *blk, int64_t offset)
+{
+    if (!blk_is_available(blk)) {
+        return -ENOMEDIUM;
+    }
+
+    return bdrv_truncate(blk->bs, offset);
+}
+
+int blk_discard(BlockBackend *blk, int64_t sector_num, int nb_sectors)
+{
+    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return bdrv_discard(blk->bs, sector_num, nb_sectors);
+}
+
+int blk_save_vmstate(BlockBackend *blk, const uint8_t *buf,
+                     int64_t pos, int size)
+{
+    if (!blk_is_available(blk)) {
+        return -ENOMEDIUM;
+    }
+
+    return bdrv_save_vmstate(blk->bs, buf, pos, size);
+}
+
+int blk_load_vmstate(BlockBackend *blk, uint8_t *buf, int64_t pos, int size)
+{
+    if (!blk_is_available(blk)) {
+        return -ENOMEDIUM;
+    }
+
+    return bdrv_load_vmstate(blk->bs, buf, pos, size);
+}
+
+int blk_probe_blocksizes(BlockBackend *blk, BlockSizes *bsz)
+{
+    if (!blk_is_available(blk)) {
+        return -ENOMEDIUM;
+    }
+
+    return bdrv_probe_blocksizes(blk->bs, bsz);
+}
+
+int blk_probe_geometry(BlockBackend *blk, HDGeometry *geo)
+{
+    if (!blk_is_available(blk)) {
+        return -ENOMEDIUM;
+    }
+
+    return bdrv_probe_geometry(blk->bs, geo);
+}
+
+/*
+ * Updates the BlockBackendRootState object with data from the currently
+ * attached BlockDriverState.
+ */
+void blk_update_root_state(BlockBackend *blk)
+{
+    assert(blk->bs);
+
+    blk->root_state.open_flags    = blk->bs->open_flags;
+    blk->root_state.read_only     = blk->bs->read_only;
+    blk->root_state.detect_zeroes = blk->bs->detect_zeroes;
+
+    if (blk->root_state.throttle_group) {
+        g_free(blk->root_state.throttle_group);
+        throttle_group_unref(blk->root_state.throttle_state);
+    }
+    if (blk->bs->throttle_state) {
+        const char *name = throttle_group_get_name(blk->bs);
+        blk->root_state.throttle_group = g_strdup(name);
+        blk->root_state.throttle_state = throttle_group_incref(name);
+    } else {
+        blk->root_state.throttle_group = NULL;
+        blk->root_state.throttle_state = NULL;
+    }
+}
+
+/*
+ * Applies the information in the root state to the given BlockDriverState. This
+ * does not include the flags which have to be specified for bdrv_open(), use
+ * blk_get_open_flags_from_root_state() to inquire them.
+ */
+void blk_apply_root_state(BlockBackend *blk, BlockDriverState *bs)
+{
+    bs->detect_zeroes = blk->root_state.detect_zeroes;
+    if (blk->root_state.throttle_group) {
+        bdrv_io_limits_enable(bs, blk->root_state.throttle_group);
+    }
+}
+
+/*
+ * Returns the flags to be used for bdrv_open() of a BlockDriverState which is
+ * supposed to inherit the root state.
+ */
+int blk_get_open_flags_from_root_state(BlockBackend *blk)
+{
+    int bs_flags;
+
+    bs_flags = blk->root_state.read_only ? 0 : BDRV_O_RDWR;
+    bs_flags |= blk->root_state.open_flags & ~BDRV_O_RDWR;
+
+    return bs_flags;
+}
+
+BlockBackendRootState *blk_get_root_state(BlockBackend *blk)
+{
+    return &blk->root_state;
+}