]> Git Repo - qemu.git/blobdiff - block/block-backend.c
block: Introduce BdrvChild.opaque
[qemu.git] / block / block-backend.c
index efd61464da5136925a32e114bd582e4bdd615e8b..52b7b922c23428e2a89efb990be30559e7d20c14 100644 (file)
@@ -1,7 +1,7 @@
 /*
  * QEMU Block backends
  *
- * Copyright (C) 2014 Red Hat, Inc.
+ * Copyright (C) 2014-2016 Red Hat, Inc.
  *
  * Authors:
  *  Markus Armbruster <[email protected]>,
 #include "sysemu/blockdev.h"
 #include "sysemu/sysemu.h"
 #include "qapi-event.h"
+#include "qemu/id.h"
 
 /* Number of coroutines to reserve per attached device model */
 #define COROUTINE_POOL_RESERVATION 64
 
+#define NOT_DONE 0x7fffffff /* used while emulated sync operation in progress */
+
 static AioContext *blk_aiocb_get_aio_context(BlockAIOCB *acb);
 
 struct BlockBackend {
     char *name;
     int refcnt;
-    BlockDriverState *bs;
+    BdrvChild *root;
     DriveInfo *legacy_dinfo;    /* null unless created by drive_new() */
-    QTAILQ_ENTRY(BlockBackend) link; /* for blk_backends */
+    QTAILQ_ENTRY(BlockBackend) link;         /* for block_backends */
+    QTAILQ_ENTRY(BlockBackend) monitor_link; /* for monitor_block_backends */
+    BlockBackendPublic public;
 
     void *dev;                  /* attached device model, if any */
     /* TODO change to DeviceState when all users are qdevified */
@@ -43,12 +48,18 @@ struct BlockBackend {
      * can be used to restore those options in the new BDS on insert) */
     BlockBackendRootState root_state;
 
+    bool enable_write_cache;
+
     /* I/O stats (display with "info blockstats"). */
     BlockAcctStats stats;
 
     BlockdevOnError on_read_error, on_write_error;
     bool iostatus_enabled;
     BlockDeviceIoStatus iostatus;
+
+    bool allow_write_beyond_eof;
+
+    NotifierList remove_bs_notifiers, insert_bs_notifiers;
 };
 
 typedef struct BlockBackendAIOCB {
@@ -65,41 +76,44 @@ static const AIOCBInfo block_backend_aiocb_info = {
 
 static void drive_info_del(DriveInfo *dinfo);
 
-/* All the BlockBackends (except for hidden ones) */
-static QTAILQ_HEAD(, BlockBackend) blk_backends =
-    QTAILQ_HEAD_INITIALIZER(blk_backends);
+/* All BlockBackends */
+static QTAILQ_HEAD(, BlockBackend) block_backends =
+    QTAILQ_HEAD_INITIALIZER(block_backends);
+
+/* All BlockBackends referenced by the monitor and which are iterated through by
+ * blk_next() */
+static QTAILQ_HEAD(, BlockBackend) monitor_block_backends =
+    QTAILQ_HEAD_INITIALIZER(monitor_block_backends);
+
+static void blk_root_inherit_options(int *child_flags, QDict *child_options,
+                                     int parent_flags, QDict *parent_options)
+{
+    /* We're not supposed to call this function for root nodes */
+    abort();
+}
+
+static const BdrvChildRole child_root = {
+    .inherit_options = blk_root_inherit_options,
+};
 
 /*
- * Create a new BlockBackend with @name, with a reference count of one.
- * @name must not be null or empty.
- * Fail if a BlockBackend with this name already exists.
+ * Create a new BlockBackend with a reference count of one.
  * Store an error through @errp on failure, unless it's null.
  * Return the new BlockBackend on success, null on failure.
  */
-BlockBackend *blk_new(const char *name, Error **errp)
+BlockBackend *blk_new(Error **errp)
 {
     BlockBackend *blk;
 
-    assert(name && name[0]);
-    if (!id_wellformed(name)) {
-        error_setg(errp, "Invalid device name");
-        return NULL;
-    }
-    if (blk_by_name(name)) {
-        error_setg(errp, "Device with id '%s' already exists", name);
-        return NULL;
-    }
-    if (bdrv_find_node(name)) {
-        error_setg(errp,
-                   "Device name '%s' conflicts with an existing node name",
-                   name);
-        return NULL;
-    }
-
     blk = g_new0(BlockBackend, 1);
-    blk->name = g_strdup(name);
     blk->refcnt = 1;
-    QTAILQ_INSERT_TAIL(&blk_backends, blk, link);
+    qemu_co_queue_init(&blk->public.throttled_reqs[0]);
+    qemu_co_queue_init(&blk->public.throttled_reqs[1]);
+
+    notifier_list_init(&blk->remove_bs_notifiers);
+    notifier_list_init(&blk->insert_bs_notifiers);
+
+    QTAILQ_INSERT_TAIL(&block_backends, blk, link);
     return blk;
 }
 
@@ -107,18 +121,19 @@ BlockBackend *blk_new(const char *name, Error **errp)
  * Create a new BlockBackend with a new BlockDriverState attached.
  * Otherwise just like blk_new(), which see.
  */
-BlockBackend *blk_new_with_bs(const char *name, Error **errp)
+BlockBackend *blk_new_with_bs(Error **errp)
 {
     BlockBackend *blk;
     BlockDriverState *bs;
 
-    blk = blk_new(name, errp);
+    blk = blk_new(errp);
     if (!blk) {
         return NULL;
     }
 
     bs = bdrv_new_root();
-    blk->bs = bs;
+    blk->root = bdrv_root_attach_child(bs, "root", &child_root);
+    blk->root->opaque = blk;
     bs->blk = blk;
     return blk;
 }
@@ -135,47 +150,44 @@ BlockBackend *blk_new_with_bs(const char *name, Error **errp)
  * 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_new_open(const char *filename, const char *reference,
+                           QDict *options, int flags, Error **errp)
 {
     BlockBackend *blk;
     int ret;
 
-    blk = blk_new_with_bs(name, errp);
+    blk = blk_new_with_bs(errp);
     if (!blk) {
         QDECREF(options);
         return NULL;
     }
 
-    ret = bdrv_open(&blk->bs, filename, reference, options, flags, errp);
+    ret = bdrv_open(&blk->root->bs, filename, reference, options, flags, errp);
     if (ret < 0) {
         blk_unref(blk);
         return NULL;
     }
 
+    blk_set_enable_write_cache(blk, true);
+
     return blk;
 }
 
 static void blk_delete(BlockBackend *blk)
 {
     assert(!blk->refcnt);
+    assert(!blk->name);
     assert(!blk->dev);
-    if (blk->bs) {
-        assert(blk->bs->blk == blk);
-        blk->bs->blk = NULL;
-        bdrv_unref(blk->bs);
-        blk->bs = NULL;
+    if (blk->root) {
+        blk_remove_bs(blk);
     }
+    assert(QLIST_EMPTY(&blk->remove_bs_notifiers.notifiers));
+    assert(QLIST_EMPTY(&blk->insert_bs_notifiers.notifiers));
     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);
+    QTAILQ_REMOVE(&block_backends, blk, link);
     drive_info_del(blk->legacy_dinfo);
     block_acct_cleanup(&blk->stats);
     g_free(blk);
@@ -221,7 +233,32 @@ void blk_unref(BlockBackend *blk)
 }
 
 /*
- * Return the BlockBackend after @blk.
+ * Behaves similarly to blk_next() but iterates over all BlockBackends, even the
+ * ones which are hidden (i.e. are not referenced by the monitor).
+ */
+static BlockBackend *blk_all_next(BlockBackend *blk)
+{
+    return blk ? QTAILQ_NEXT(blk, link)
+               : QTAILQ_FIRST(&block_backends);
+}
+
+void blk_remove_all_bs(void)
+{
+    BlockBackend *blk = NULL;
+
+    while ((blk = blk_all_next(blk)) != NULL) {
+        AioContext *ctx = blk_get_aio_context(blk);
+
+        aio_context_acquire(ctx);
+        if (blk->root) {
+            blk_remove_bs(blk);
+        }
+        aio_context_release(ctx);
+    }
+}
+
+/*
+ * Return the monitor-owned BlockBackend after @blk.
  * If @blk is null, return the first one.
  * Else, return @blk's next sibling, which may be null.
  *
@@ -232,17 +269,91 @@ void blk_unref(BlockBackend *blk)
  */
 BlockBackend *blk_next(BlockBackend *blk)
 {
-    return blk ? QTAILQ_NEXT(blk, link) : QTAILQ_FIRST(&blk_backends);
+    return blk ? QTAILQ_NEXT(blk, monitor_link)
+               : QTAILQ_FIRST(&monitor_block_backends);
+}
+
+/*
+ * Iterates over all BlockDriverStates which are attached to a BlockBackend.
+ * This function is for use by bdrv_next().
+ *
+ * @bs must be NULL or a BDS that is attached to a BB.
+ */
+BlockDriverState *blk_next_root_bs(BlockDriverState *bs)
+{
+    BlockBackend *blk;
+
+    if (bs) {
+        assert(bs->blk);
+        blk = bs->blk;
+    } else {
+        blk = NULL;
+    }
+
+    do {
+        blk = blk_all_next(blk);
+    } while (blk && !blk->root);
+
+    return blk ? blk->root->bs : NULL;
+}
+
+/*
+ * Add a BlockBackend into the list of backends referenced by the monitor, with
+ * the given @name acting as the handle for the monitor.
+ * Strictly for use by blockdev.c.
+ *
+ * @name must not be null or empty.
+ *
+ * Returns true on success and false on failure. In the latter case, an Error
+ * object is returned through @errp.
+ */
+bool monitor_add_blk(BlockBackend *blk, const char *name, Error **errp)
+{
+    assert(!blk->name);
+    assert(name && name[0]);
+
+    if (!id_wellformed(name)) {
+        error_setg(errp, "Invalid device name");
+        return false;
+    }
+    if (blk_by_name(name)) {
+        error_setg(errp, "Device with id '%s' already exists", name);
+        return false;
+    }
+    if (bdrv_find_node(name)) {
+        error_setg(errp,
+                   "Device name '%s' conflicts with an existing node name",
+                   name);
+        return false;
+    }
+
+    blk->name = g_strdup(name);
+    QTAILQ_INSERT_TAIL(&monitor_block_backends, blk, monitor_link);
+    return true;
+}
+
+/*
+ * Remove a BlockBackend from the list of backends referenced by the monitor.
+ * Strictly for use by blockdev.c.
+ */
+void monitor_remove_blk(BlockBackend *blk)
+{
+    if (!blk->name) {
+        return;
+    }
+
+    QTAILQ_REMOVE(&monitor_block_backends, blk, monitor_link);
+    g_free(blk->name);
+    blk->name = NULL;
 }
 
 /*
  * Return @blk's name, a non-null string.
- * Wart: the name is empty iff @blk has been hidden with
- * blk_hide_on_behalf_of_hmp_drive_del().
+ * Returns an empty string iff @blk is not referenced by the monitor.
  */
 const char *blk_name(BlockBackend *blk)
 {
-    return blk->name;
+    return blk->name ?: "";
 }
 
 /*
@@ -251,10 +362,10 @@ const char *blk_name(BlockBackend *blk)
  */
 BlockBackend *blk_by_name(const char *name)
 {
-    BlockBackend *blk;
+    BlockBackend *blk = NULL;
 
     assert(name);
-    QTAILQ_FOREACH(blk, &blk_backends, link) {
+    while ((blk = blk_next(blk)) != NULL) {
         if (!strcmp(name, blk->name)) {
             return blk;
         }
@@ -267,24 +378,7 @@ BlockBackend *blk_by_name(const char *name)
  */
 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->root ? blk->root->bs : NULL;
 }
 
 /*
@@ -312,9 +406,9 @@ DriveInfo *blk_set_legacy_dinfo(BlockBackend *blk, DriveInfo *dinfo)
  */
 BlockBackend *blk_by_legacy_dinfo(DriveInfo *dinfo)
 {
-    BlockBackend *blk;
+    BlockBackend *blk = NULL;
 
-    QTAILQ_FOREACH(blk, &blk_backends, link) {
+    while ((blk = blk_next(blk)) != NULL) {
         if (blk->legacy_dinfo == dinfo) {
             return blk;
         }
@@ -323,21 +417,19 @@ BlockBackend *blk_by_legacy_dinfo(DriveInfo *dinfo)
 }
 
 /*
- * Hide @blk.
- * @blk must not have been hidden already.
- * Make attached BlockDriverState, if any, anonymous.
- * Once hidden, @blk is invisible to all functions that don't receive
- * it as argument.  For example, blk_by_name() won't return it.
- * Strictly for use by do_drive_del().
- * TODO get rid of it!
+ * Returns a pointer to the publicly accessible fields of @blk.
  */
-void blk_hide_on_behalf_of_hmp_drive_del(BlockBackend *blk)
+BlockBackendPublic *blk_get_public(BlockBackend *blk)
 {
-    QTAILQ_REMOVE(&blk_backends, blk, link);
-    blk->name[0] = 0;
-    if (blk->bs) {
-        bdrv_make_anon(blk->bs);
-    }
+    return &blk->public;
+}
+
+/*
+ * Returns a BlockBackend given the associated @public fields.
+ */
+BlockBackend *blk_by_public(BlockBackendPublic *public)
+{
+    return container_of(public, BlockBackend, public);
 }
 
 /*
@@ -345,11 +437,18 @@ void blk_hide_on_behalf_of_hmp_drive_del(BlockBackend *blk)
  */
 void blk_remove_bs(BlockBackend *blk)
 {
+    assert(blk->root->bs->blk == blk);
+
+    notifier_list_notify(&blk->remove_bs_notifiers, blk);
+
     blk_update_root_state(blk);
+    if (blk->public.throttle_state) {
+        blk_io_limits_disable(blk);
+    }
 
-    blk->bs->blk = NULL;
-    bdrv_unref(blk->bs);
-    blk->bs = NULL;
+    blk->root->bs->blk = NULL;
+    bdrv_root_unref_child(blk->root);
+    blk->root = NULL;
 }
 
 /*
@@ -357,10 +456,13 @@ void blk_remove_bs(BlockBackend *blk)
  */
 void blk_insert_bs(BlockBackend *blk, BlockDriverState *bs)
 {
-    assert(!blk->bs && !bs->blk);
+    assert(!blk->root && !bs->blk);
     bdrv_ref(bs);
-    blk->bs = bs;
+    blk->root = bdrv_root_attach_child(bs, "root", &child_root);
+    blk->root->opaque = blk;
     bs->blk = blk;
+
+    notifier_list_notify(&blk->insert_bs_notifiers, blk);
 }
 
 /*
@@ -458,6 +560,14 @@ bool blk_dev_has_removable_media(BlockBackend *blk)
     return !blk->dev || (blk->dev_ops && blk->dev_ops->change_media_cb);
 }
 
+/*
+ * Does @blk's attached device model have a tray?
+ */
+bool blk_dev_has_tray(BlockBackend *blk)
+{
+    return blk->dev_ops && blk->dev_ops->is_tray_open;
+}
+
 /*
  * Notify @blk's attached device model of a media eject request.
  * If @force is true, the medium is about to be yanked out forcefully.
@@ -474,7 +584,7 @@ void blk_dev_eject_request(BlockBackend *blk, bool force)
  */
 bool blk_dev_is_tray_open(BlockBackend *blk)
 {
-    if (blk->dev_ops && blk->dev_ops->is_tray_open) {
+    if (blk_dev_has_tray(blk)) {
         return blk->dev_ops->is_tray_open(blk->dev_opaque);
     }
     return false;
@@ -531,9 +641,10 @@ void blk_iostatus_disable(BlockBackend *blk)
 void blk_iostatus_reset(BlockBackend *blk)
 {
     if (blk_iostatus_is_enabled(blk)) {
+        BlockDriverState *bs = blk_bs(blk);
         blk->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
-        if (blk->bs && blk->bs->job) {
-            block_job_iostatus_reset(blk->bs->job);
+        if (bs && bs->job) {
+            block_job_iostatus_reset(bs->job);
         }
     }
 }
@@ -547,6 +658,11 @@ void blk_iostatus_set_err(BlockBackend *blk, int error)
     }
 }
 
+void blk_set_allow_write_beyond_eof(BlockBackend *blk, bool allow)
+{
+    blk->allow_write_beyond_eof = allow;
+}
+
 static int blk_check_byte_request(BlockBackend *blk, int64_t offset,
                                   size_t size)
 {
@@ -560,17 +676,19 @@ static int blk_check_byte_request(BlockBackend *blk, int64_t offset,
         return -ENOMEDIUM;
     }
 
-    len = blk_getlength(blk);
-    if (len < 0) {
-        return len;
-    }
-
     if (offset < 0) {
         return -EIO;
     }
 
-    if (offset > len || len - offset < size) {
-        return -EIO;
+    if (!blk->allow_write_beyond_eof) {
+        len = blk_getlength(blk);
+        if (len < 0) {
+            return len;
+        }
+
+        if (offset > len || len - offset < size) {
+            return -EIO;
+        }
     }
 
     return 0;
@@ -591,48 +709,126 @@ static int blk_check_request(BlockBackend *blk, int64_t sector_num,
                                   nb_sectors * BDRV_SECTOR_SIZE);
 }
 
-int blk_read(BlockBackend *blk, int64_t sector_num, uint8_t *buf,
-             int nb_sectors)
+static int coroutine_fn blk_co_preadv(BlockBackend *blk, int64_t offset,
+                                      unsigned int bytes, QEMUIOVector *qiov,
+                                      BdrvRequestFlags flags)
 {
-    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    int ret = blk_check_byte_request(blk, offset, bytes);
     if (ret < 0) {
         return ret;
     }
 
-    return bdrv_read(blk->bs, sector_num, buf, nb_sectors);
+    /* throttling disk I/O */
+    if (blk->public.throttle_state) {
+        throttle_group_co_io_limits_intercept(blk, bytes, false);
+    }
+
+    return bdrv_co_preadv(blk_bs(blk), offset, bytes, qiov, flags);
 }
 
-int blk_read_unthrottled(BlockBackend *blk, int64_t sector_num, uint8_t *buf,
-                         int nb_sectors)
+static int coroutine_fn blk_co_pwritev(BlockBackend *blk, int64_t offset,
+                                      unsigned int bytes, QEMUIOVector *qiov,
+                                      BdrvRequestFlags flags)
 {
-    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    int ret;
+
+    ret = blk_check_byte_request(blk, offset, bytes);
     if (ret < 0) {
         return ret;
     }
 
-    return bdrv_read_unthrottled(blk->bs, sector_num, buf, nb_sectors);
+    /* throttling disk I/O */
+    if (blk->public.throttle_state) {
+        throttle_group_co_io_limits_intercept(blk, bytes, true);
+    }
+
+    if (!blk->enable_write_cache) {
+        flags |= BDRV_REQ_FUA;
+    }
+
+    return bdrv_co_pwritev(blk_bs(blk), offset, bytes, qiov, flags);
 }
 
-int blk_write(BlockBackend *blk, int64_t sector_num, const uint8_t *buf,
-              int nb_sectors)
+typedef struct BlkRwCo {
+    BlockBackend *blk;
+    int64_t offset;
+    QEMUIOVector *qiov;
+    int ret;
+    BdrvRequestFlags flags;
+} BlkRwCo;
+
+static void blk_read_entry(void *opaque)
 {
-    int ret = blk_check_request(blk, sector_num, nb_sectors);
-    if (ret < 0) {
-        return ret;
+    BlkRwCo *rwco = opaque;
+
+    rwco->ret = blk_co_preadv(rwco->blk, rwco->offset, rwco->qiov->size,
+                              rwco->qiov, rwco->flags);
+}
+
+static void blk_write_entry(void *opaque)
+{
+    BlkRwCo *rwco = opaque;
+
+    rwco->ret = blk_co_pwritev(rwco->blk, rwco->offset, rwco->qiov->size,
+                               rwco->qiov, rwco->flags);
+}
+
+static int blk_prw(BlockBackend *blk, int64_t offset, uint8_t *buf,
+                   int64_t bytes, CoroutineEntry co_entry,
+                   BdrvRequestFlags flags)
+{
+    AioContext *aio_context;
+    QEMUIOVector qiov;
+    struct iovec iov;
+    Coroutine *co;
+    BlkRwCo rwco;
+
+    iov = (struct iovec) {
+        .iov_base = buf,
+        .iov_len = bytes,
+    };
+    qemu_iovec_init_external(&qiov, &iov, 1);
+
+    rwco = (BlkRwCo) {
+        .blk    = blk,
+        .offset = offset,
+        .qiov   = &qiov,
+        .flags  = flags,
+        .ret    = NOT_DONE,
+    };
+
+    co = qemu_coroutine_create(co_entry);
+    qemu_coroutine_enter(co, &rwco);
+
+    aio_context = blk_get_aio_context(blk);
+    while (rwco.ret == NOT_DONE) {
+        aio_poll(aio_context, true);
     }
 
-    return bdrv_write(blk->bs, sector_num, buf, nb_sectors);
+    return rwco.ret;
 }
 
-int blk_write_zeroes(BlockBackend *blk, int64_t sector_num,
-                     int nb_sectors, BdrvRequestFlags flags)
+int blk_pread_unthrottled(BlockBackend *blk, int64_t offset, uint8_t *buf,
+                          int count)
 {
-    int ret = blk_check_request(blk, sector_num, nb_sectors);
+    int ret;
+
+    ret = blk_check_byte_request(blk, offset, count);
     if (ret < 0) {
         return ret;
     }
 
-    return bdrv_write_zeroes(blk->bs, sector_num, nb_sectors, flags);
+    bdrv_no_throttling_begin(blk_bs(blk));
+    ret = blk_pread(blk, offset, buf, count);
+    bdrv_no_throttling_end(blk_bs(blk));
+    return ret;
+}
+
+int blk_write_zeroes(BlockBackend *blk, int64_t offset,
+                     int count, BdrvRequestFlags flags)
+{
+    return blk_prw(blk, offset, NULL, count, blk_write_entry,
+                   flags | BDRV_REQ_ZERO_WRITE);
 }
 
 static void error_callback_bh(void *opaque)
@@ -661,37 +857,115 @@ BlockAIOCB *blk_abort_aio_request(BlockBackend *blk,
     return &acb->common;
 }
 
-BlockAIOCB *blk_aio_write_zeroes(BlockBackend *blk, int64_t sector_num,
-                                 int nb_sectors, BdrvRequestFlags flags,
-                                 BlockCompletionFunc *cb, void *opaque)
+typedef struct BlkAioEmAIOCB {
+    BlockAIOCB common;
+    BlkRwCo rwco;
+    int bytes;
+    bool has_returned;
+    QEMUBH* bh;
+} BlkAioEmAIOCB;
+
+static const AIOCBInfo blk_aio_em_aiocb_info = {
+    .aiocb_size         = sizeof(BlkAioEmAIOCB),
+};
+
+static void blk_aio_complete(BlkAioEmAIOCB *acb)
 {
-    int ret = blk_check_request(blk, sector_num, nb_sectors);
-    if (ret < 0) {
-        return blk_abort_aio_request(blk, cb, opaque, ret);
+    if (acb->bh) {
+        assert(acb->has_returned);
+        qemu_bh_delete(acb->bh);
+    }
+    if (acb->has_returned) {
+        acb->common.cb(acb->common.opaque, acb->rwco.ret);
+        qemu_aio_unref(acb);
+    }
+}
+
+static void blk_aio_complete_bh(void *opaque)
+{
+    blk_aio_complete(opaque);
+}
+
+static BlockAIOCB *blk_aio_prwv(BlockBackend *blk, int64_t offset, int bytes,
+                                QEMUIOVector *qiov, CoroutineEntry co_entry,
+                                BdrvRequestFlags flags,
+                                BlockCompletionFunc *cb, void *opaque)
+{
+    BlkAioEmAIOCB *acb;
+    Coroutine *co;
+
+    acb = blk_aio_get(&blk_aio_em_aiocb_info, blk, cb, opaque);
+    acb->rwco = (BlkRwCo) {
+        .blk    = blk,
+        .offset = offset,
+        .qiov   = qiov,
+        .flags  = flags,
+        .ret    = NOT_DONE,
+    };
+    acb->bytes = bytes;
+    acb->bh = NULL;
+    acb->has_returned = false;
+
+    co = qemu_coroutine_create(co_entry);
+    qemu_coroutine_enter(co, acb);
+
+    acb->has_returned = true;
+    if (acb->rwco.ret != NOT_DONE) {
+        acb->bh = aio_bh_new(blk_get_aio_context(blk), blk_aio_complete_bh, acb);
+        qemu_bh_schedule(acb->bh);
     }
 
-    return bdrv_aio_write_zeroes(blk->bs, sector_num, nb_sectors, flags,
-                                 cb, opaque);
+    return &acb->common;
+}
+
+static void blk_aio_read_entry(void *opaque)
+{
+    BlkAioEmAIOCB *acb = opaque;
+    BlkRwCo *rwco = &acb->rwco;
+
+    assert(rwco->qiov->size == acb->bytes);
+    rwco->ret = blk_co_preadv(rwco->blk, rwco->offset, acb->bytes,
+                              rwco->qiov, rwco->flags);
+    blk_aio_complete(acb);
+}
+
+static void blk_aio_write_entry(void *opaque)
+{
+    BlkAioEmAIOCB *acb = opaque;
+    BlkRwCo *rwco = &acb->rwco;
+
+    assert(!rwco->qiov || rwco->qiov->size == acb->bytes);
+    rwco->ret = blk_co_pwritev(rwco->blk, rwco->offset, acb->bytes,
+                               rwco->qiov, rwco->flags);
+    blk_aio_complete(acb);
+}
+
+BlockAIOCB *blk_aio_write_zeroes(BlockBackend *blk, int64_t offset,
+                                 int count, BdrvRequestFlags flags,
+                                 BlockCompletionFunc *cb, void *opaque)
+{
+    return blk_aio_prwv(blk, offset, count, NULL, blk_aio_write_entry,
+                        flags | BDRV_REQ_ZERO_WRITE, cb, opaque);
 }
 
 int blk_pread(BlockBackend *blk, int64_t offset, void *buf, int count)
 {
-    int ret = blk_check_byte_request(blk, offset, count);
+    int ret = blk_prw(blk, offset, buf, count, blk_read_entry, 0);
     if (ret < 0) {
         return ret;
     }
-
-    return bdrv_pread(blk->bs, offset, buf, count);
+    return count;
 }
 
-int blk_pwrite(BlockBackend *blk, int64_t offset, const void *buf, int count)
+int blk_pwrite(BlockBackend *blk, int64_t offset, const void *buf, int count,
+               BdrvRequestFlags flags)
 {
-    int ret = blk_check_byte_request(blk, offset, count);
+    int ret = blk_prw(blk, offset, (void *) buf, count, blk_write_entry,
+                      flags);
     if (ret < 0) {
         return ret;
     }
-
-    return bdrv_pwrite(blk->bs, offset, buf, count);
+    return count;
 }
 
 int64_t blk_getlength(BlockBackend *blk)
@@ -700,15 +974,15 @@ int64_t blk_getlength(BlockBackend *blk)
         return -ENOMEDIUM;
     }
 
-    return bdrv_getlength(blk->bs);
+    return bdrv_getlength(blk_bs(blk));
 }
 
 void blk_get_geometry(BlockBackend *blk, uint64_t *nb_sectors_ptr)
 {
-    if (!blk->bs) {
+    if (!blk_bs(blk)) {
         *nb_sectors_ptr = 0;
     } else {
-        bdrv_get_geometry(blk->bs, nb_sectors_ptr);
+        bdrv_get_geometry(blk_bs(blk), nb_sectors_ptr);
     }
 }
 
@@ -718,31 +992,23 @@ int64_t blk_nb_sectors(BlockBackend *blk)
         return -ENOMEDIUM;
     }
 
-    return bdrv_nb_sectors(blk->bs);
+    return bdrv_nb_sectors(blk_bs(blk));
 }
 
-BlockAIOCB *blk_aio_readv(BlockBackend *blk, int64_t sector_num,
-                          QEMUIOVector *iov, int nb_sectors,
-                          BlockCompletionFunc *cb, void *opaque)
+BlockAIOCB *blk_aio_preadv(BlockBackend *blk, int64_t offset,
+                           QEMUIOVector *qiov, BdrvRequestFlags flags,
+                           BlockCompletionFunc *cb, void *opaque)
 {
-    int ret = blk_check_request(blk, sector_num, nb_sectors);
-    if (ret < 0) {
-        return blk_abort_aio_request(blk, cb, opaque, ret);
-    }
-
-    return bdrv_aio_readv(blk->bs, sector_num, iov, nb_sectors, cb, opaque);
+    return blk_aio_prwv(blk, offset, qiov->size, qiov,
+                        blk_aio_read_entry, flags, cb, opaque);
 }
 
-BlockAIOCB *blk_aio_writev(BlockBackend *blk, int64_t sector_num,
-                           QEMUIOVector *iov, int nb_sectors,
-                           BlockCompletionFunc *cb, void *opaque)
+BlockAIOCB *blk_aio_pwritev(BlockBackend *blk, int64_t offset,
+                            QEMUIOVector *qiov, BdrvRequestFlags flags,
+                            BlockCompletionFunc *cb, void *opaque)
 {
-    int ret = blk_check_request(blk, sector_num, nb_sectors);
-    if (ret < 0) {
-        return blk_abort_aio_request(blk, cb, opaque, ret);
-    }
-
-    return bdrv_aio_writev(blk->bs, sector_num, iov, nb_sectors, cb, opaque);
+    return blk_aio_prwv(blk, offset, qiov->size, qiov,
+                        blk_aio_write_entry, flags, cb, opaque);
 }
 
 BlockAIOCB *blk_aio_flush(BlockBackend *blk,
@@ -752,7 +1018,7 @@ BlockAIOCB *blk_aio_flush(BlockBackend *blk,
         return blk_abort_aio_request(blk, cb, opaque, -ENOMEDIUM);
     }
 
-    return bdrv_aio_flush(blk->bs, cb, opaque);
+    return bdrv_aio_flush(blk_bs(blk), cb, opaque);
 }
 
 BlockAIOCB *blk_aio_discard(BlockBackend *blk,
@@ -764,7 +1030,7 @@ BlockAIOCB *blk_aio_discard(BlockBackend *blk,
         return blk_abort_aio_request(blk, cb, opaque, ret);
     }
 
-    return bdrv_aio_discard(blk->bs, sector_num, nb_sectors, cb, opaque);
+    return bdrv_aio_discard(blk_bs(blk), sector_num, nb_sectors, cb, opaque);
 }
 
 void blk_aio_cancel(BlockAIOCB *acb)
@@ -788,7 +1054,7 @@ int blk_aio_multiwrite(BlockBackend *blk, BlockRequest *reqs, int num_reqs)
         }
     }
 
-    return bdrv_aio_multiwrite(blk->bs, reqs, num_reqs);
+    return bdrv_aio_multiwrite(blk_bs(blk), reqs, num_reqs);
 }
 
 int blk_ioctl(BlockBackend *blk, unsigned long int req, void *buf)
@@ -797,7 +1063,7 @@ int blk_ioctl(BlockBackend *blk, unsigned long int req, void *buf)
         return -ENOMEDIUM;
     }
 
-    return bdrv_ioctl(blk->bs, req, buf);
+    return bdrv_ioctl(blk_bs(blk), req, buf);
 }
 
 BlockAIOCB *blk_aio_ioctl(BlockBackend *blk, unsigned long int req, void *buf,
@@ -807,7 +1073,7 @@ BlockAIOCB *blk_aio_ioctl(BlockBackend *blk, unsigned long int req, void *buf,
         return blk_abort_aio_request(blk, cb, opaque, -ENOMEDIUM);
     }
 
-    return bdrv_aio_ioctl(blk->bs, req, buf, cb, opaque);
+    return bdrv_aio_ioctl(blk_bs(blk), req, buf, cb, opaque);
 }
 
 int blk_co_discard(BlockBackend *blk, int64_t sector_num, int nb_sectors)
@@ -817,7 +1083,7 @@ int blk_co_discard(BlockBackend *blk, int64_t sector_num, int nb_sectors)
         return ret;
     }
 
-    return bdrv_co_discard(blk->bs, sector_num, nb_sectors);
+    return bdrv_co_discard(blk_bs(blk), sector_num, nb_sectors);
 }
 
 int blk_co_flush(BlockBackend *blk)
@@ -826,7 +1092,7 @@ int blk_co_flush(BlockBackend *blk)
         return -ENOMEDIUM;
     }
 
-    return bdrv_co_flush(blk->bs);
+    return bdrv_co_flush(blk_bs(blk));
 }
 
 int blk_flush(BlockBackend *blk)
@@ -835,18 +1101,13 @@ int blk_flush(BlockBackend *blk)
         return -ENOMEDIUM;
     }
 
-    return bdrv_flush(blk->bs);
-}
-
-int blk_flush_all(void)
-{
-    return bdrv_flush_all();
+    return bdrv_flush(blk_bs(blk));
 }
 
 void blk_drain(BlockBackend *blk)
 {
-    if (blk->bs) {
-        bdrv_drain(blk->bs);
+    if (blk_bs(blk)) {
+        bdrv_drain(blk_bs(blk));
     }
 }
 
@@ -934,8 +1195,10 @@ void blk_error_action(BlockBackend *blk, BlockErrorAction action,
 
 int blk_is_read_only(BlockBackend *blk)
 {
-    if (blk->bs) {
-        return bdrv_is_read_only(blk->bs);
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (bs) {
+        return bdrv_is_read_only(bs);
     } else {
         return blk->root_state.read_only;
     }
@@ -943,48 +1206,42 @@ int blk_is_read_only(BlockBackend *blk)
 
 int blk_is_sg(BlockBackend *blk)
 {
-    if (!blk->bs) {
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (!bs) {
         return 0;
     }
 
-    return bdrv_is_sg(blk->bs);
+    return bdrv_is_sg(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);
-    }
+    return blk->enable_write_cache;
 }
 
 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;
-        }
-    }
+    blk->enable_write_cache = wce;
 }
 
 void blk_invalidate_cache(BlockBackend *blk, Error **errp)
 {
-    if (!blk->bs) {
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (!bs) {
         error_setg(errp, "Device '%s' has no medium", blk->name);
         return;
     }
 
-    bdrv_invalidate_cache(blk->bs, errp);
+    bdrv_invalidate_cache(bs, errp);
 }
 
 bool blk_is_inserted(BlockBackend *blk)
 {
-    return blk->bs && bdrv_is_inserted(blk->bs);
+    BlockDriverState *bs = blk_bs(blk);
+
+    return bs && bdrv_is_inserted(bs);
 }
 
 bool blk_is_available(BlockBackend *blk)
@@ -994,22 +1251,28 @@ bool blk_is_available(BlockBackend *blk)
 
 void blk_lock_medium(BlockBackend *blk, bool locked)
 {
-    if (blk->bs) {
-        bdrv_lock_medium(blk->bs, locked);
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (bs) {
+        bdrv_lock_medium(bs, locked);
     }
 }
 
 void blk_eject(BlockBackend *blk, bool eject_flag)
 {
-    if (blk->bs) {
-        bdrv_eject(blk->bs, eject_flag);
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (bs) {
+        bdrv_eject(bs, eject_flag);
     }
 }
 
 int blk_get_flags(BlockBackend *blk)
 {
-    if (blk->bs) {
-        return bdrv_get_flags(blk->bs);
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (bs) {
+        return bdrv_get_flags(bs);
     } else {
         return blk->root_state.open_flags;
     }
@@ -1017,8 +1280,10 @@ int blk_get_flags(BlockBackend *blk)
 
 int blk_get_max_transfer_length(BlockBackend *blk)
 {
-    if (blk->bs) {
-        return blk->bs->bl.max_transfer_length;
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (bs) {
+        return bs->bl.max_transfer_length;
     } else {
         return 0;
     }
@@ -1026,7 +1291,7 @@ int blk_get_max_transfer_length(BlockBackend *blk)
 
 int blk_get_max_iov(BlockBackend *blk)
 {
-    return blk->bs->bl.max_iov;
+    return blk->root->bs->bl.max_iov;
 }
 
 void blk_set_guest_block_size(BlockBackend *blk, int align)
@@ -1036,48 +1301,58 @@ void blk_set_guest_block_size(BlockBackend *blk, int align)
 
 void *blk_try_blockalign(BlockBackend *blk, size_t size)
 {
-    return qemu_try_blockalign(blk ? blk->bs : NULL, size);
+    return qemu_try_blockalign(blk ? blk_bs(blk) : NULL, size);
 }
 
 void *blk_blockalign(BlockBackend *blk, size_t size)
 {
-    return qemu_blockalign(blk ? blk->bs : NULL, size);
+    return qemu_blockalign(blk ? blk_bs(blk) : NULL, size);
 }
 
 bool blk_op_is_blocked(BlockBackend *blk, BlockOpType op, Error **errp)
 {
-    if (!blk->bs) {
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (!bs) {
         return false;
     }
 
-    return bdrv_op_is_blocked(blk->bs, op, errp);
+    return bdrv_op_is_blocked(bs, op, errp);
 }
 
 void blk_op_unblock(BlockBackend *blk, BlockOpType op, Error *reason)
 {
-    if (blk->bs) {
-        bdrv_op_unblock(blk->bs, op, reason);
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (bs) {
+        bdrv_op_unblock(bs, op, reason);
     }
 }
 
 void blk_op_block_all(BlockBackend *blk, Error *reason)
 {
-    if (blk->bs) {
-        bdrv_op_block_all(blk->bs, reason);
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (bs) {
+        bdrv_op_block_all(bs, reason);
     }
 }
 
 void blk_op_unblock_all(BlockBackend *blk, Error *reason)
 {
-    if (blk->bs) {
-        bdrv_op_unblock_all(blk->bs, reason);
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (bs) {
+        bdrv_op_unblock_all(bs, reason);
     }
 }
 
 AioContext *blk_get_aio_context(BlockBackend *blk)
 {
-    if (blk->bs) {
-        return bdrv_get_aio_context(blk->bs);
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (bs) {
+        return bdrv_get_aio_context(bs);
     } else {
         return qemu_get_aio_context();
     }
@@ -1091,8 +1366,10 @@ static AioContext *blk_aiocb_get_aio_context(BlockAIOCB *acb)
 
 void blk_set_aio_context(BlockBackend *blk, AioContext *new_context)
 {
-    if (blk->bs) {
-        bdrv_set_aio_context(blk->bs, new_context);
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (bs) {
+        bdrv_set_aio_context(bs, new_context);
     }
 }
 
@@ -1100,8 +1377,10 @@ 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,
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (bs) {
+        bdrv_add_aio_context_notifier(bs, attached_aio_context,
                                       detach_aio_context, opaque);
     }
 }
@@ -1112,30 +1391,39 @@ void blk_remove_aio_context_notifier(BlockBackend *blk,
                                      void (*detach_aio_context)(void *),
                                      void *opaque)
 {
-    if (blk->bs) {
-        bdrv_remove_aio_context_notifier(blk->bs, attached_aio_context,
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (bs) {
+        bdrv_remove_aio_context_notifier(bs, attached_aio_context,
                                          detach_aio_context, opaque);
     }
 }
 
-void blk_add_close_notifier(BlockBackend *blk, Notifier *notify)
+void blk_add_remove_bs_notifier(BlockBackend *blk, Notifier *notify)
 {
-    if (blk->bs) {
-        bdrv_add_close_notifier(blk->bs, notify);
-    }
+    notifier_list_add(&blk->remove_bs_notifiers, notify);
+}
+
+void blk_add_insert_bs_notifier(BlockBackend *blk, Notifier *notify)
+{
+    notifier_list_add(&blk->insert_bs_notifiers, notify);
 }
 
 void blk_io_plug(BlockBackend *blk)
 {
-    if (blk->bs) {
-        bdrv_io_plug(blk->bs);
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (bs) {
+        bdrv_io_plug(bs);
     }
 }
 
 void blk_io_unplug(BlockBackend *blk)
 {
-    if (blk->bs) {
-        bdrv_io_unplug(blk->bs);
+    BlockDriverState *bs = blk_bs(blk);
+
+    if (bs) {
+        bdrv_io_unplug(bs);
     }
 }
 
@@ -1150,15 +1438,11 @@ void *blk_aio_get(const AIOCBInfo *aiocb_info, BlockBackend *blk,
     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 coroutine_fn blk_co_write_zeroes(BlockBackend *blk, int64_t offset,
+                                     int count, 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);
+    return blk_co_pwritev(blk, offset, count, NULL,
+                          flags | BDRV_REQ_ZERO_WRITE);
 }
 
 int blk_write_compressed(BlockBackend *blk, int64_t sector_num,
@@ -1169,7 +1453,7 @@ int blk_write_compressed(BlockBackend *blk, int64_t sector_num,
         return ret;
     }
 
-    return bdrv_write_compressed(blk->bs, sector_num, buf, nb_sectors);
+    return bdrv_write_compressed(blk_bs(blk), sector_num, buf, nb_sectors);
 }
 
 int blk_truncate(BlockBackend *blk, int64_t offset)
@@ -1178,7 +1462,7 @@ int blk_truncate(BlockBackend *blk, int64_t offset)
         return -ENOMEDIUM;
     }
 
-    return bdrv_truncate(blk->bs, offset);
+    return bdrv_truncate(blk_bs(blk), offset);
 }
 
 int blk_discard(BlockBackend *blk, int64_t sector_num, int nb_sectors)
@@ -1188,17 +1472,28 @@ int blk_discard(BlockBackend *blk, int64_t sector_num, int nb_sectors)
         return ret;
     }
 
-    return bdrv_discard(blk->bs, sector_num, nb_sectors);
+    return bdrv_discard(blk_bs(blk), sector_num, nb_sectors);
 }
 
 int blk_save_vmstate(BlockBackend *blk, const uint8_t *buf,
                      int64_t pos, int size)
 {
+    int ret;
+
     if (!blk_is_available(blk)) {
         return -ENOMEDIUM;
     }
 
-    return bdrv_save_vmstate(blk->bs, buf, pos, size);
+    ret = bdrv_save_vmstate(blk_bs(blk), buf, pos, size);
+    if (ret < 0) {
+        return ret;
+    }
+
+    if (ret == size && !blk->enable_write_cache) {
+        ret = bdrv_flush(blk_bs(blk));
+    }
+
+    return ret < 0 ? ret : size;
 }
 
 int blk_load_vmstate(BlockBackend *blk, uint8_t *buf, int64_t pos, int size)
@@ -1207,7 +1502,7 @@ int blk_load_vmstate(BlockBackend *blk, uint8_t *buf, int64_t pos, int size)
         return -ENOMEDIUM;
     }
 
-    return bdrv_load_vmstate(blk->bs, buf, pos, size);
+    return bdrv_load_vmstate(blk_bs(blk), buf, pos, size);
 }
 
 int blk_probe_blocksizes(BlockBackend *blk, BlockSizes *bsz)
@@ -1216,7 +1511,7 @@ int blk_probe_blocksizes(BlockBackend *blk, BlockSizes *bsz)
         return -ENOMEDIUM;
     }
 
-    return bdrv_probe_blocksizes(blk->bs, bsz);
+    return bdrv_probe_blocksizes(blk_bs(blk), bsz);
 }
 
 int blk_probe_geometry(BlockBackend *blk, HDGeometry *geo)
@@ -1225,7 +1520,7 @@ int blk_probe_geometry(BlockBackend *blk, HDGeometry *geo)
         return -ENOMEDIUM;
     }
 
-    return bdrv_probe_geometry(blk->bs, geo);
+    return bdrv_probe_geometry(blk_bs(blk), geo);
 }
 
 /*
@@ -1234,18 +1529,18 @@ int blk_probe_geometry(BlockBackend *blk, HDGeometry *geo)
  */
 void blk_update_root_state(BlockBackend *blk)
 {
-    assert(blk->bs);
+    assert(blk->root);
 
-    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;
+    blk->root_state.open_flags    = blk->root->bs->open_flags;
+    blk->root_state.read_only     = blk->root->bs->read_only;
+    blk->root_state.detect_zeroes = blk->root->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);
+    if (blk->public.throttle_state) {
+        const char *name = throttle_group_get_name(blk);
         blk->root_state.throttle_group = g_strdup(name);
         blk->root_state.throttle_state = throttle_group_incref(name);
     } else {
@@ -1263,7 +1558,7 @@ 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);
+        blk_io_limits_enable(blk, blk->root_state.throttle_group);
     }
 }
 
@@ -1285,3 +1580,84 @@ BlockBackendRootState *blk_get_root_state(BlockBackend *blk)
 {
     return &blk->root_state;
 }
+
+int blk_commit_all(void)
+{
+    BlockBackend *blk = NULL;
+
+    while ((blk = blk_all_next(blk)) != NULL) {
+        AioContext *aio_context = blk_get_aio_context(blk);
+
+        aio_context_acquire(aio_context);
+        if (blk_is_inserted(blk) && blk->root->bs->backing) {
+            int ret = bdrv_commit(blk->root->bs);
+            if (ret < 0) {
+                aio_context_release(aio_context);
+                return ret;
+            }
+        }
+        aio_context_release(aio_context);
+    }
+    return 0;
+}
+
+int blk_flush_all(void)
+{
+    BlockBackend *blk = NULL;
+    int result = 0;
+
+    while ((blk = blk_all_next(blk)) != NULL) {
+        AioContext *aio_context = blk_get_aio_context(blk);
+        int ret;
+
+        aio_context_acquire(aio_context);
+        if (blk_is_inserted(blk)) {
+            ret = blk_flush(blk);
+            if (ret < 0 && !result) {
+                result = ret;
+            }
+        }
+        aio_context_release(aio_context);
+    }
+
+    return result;
+}
+
+
+/* throttling disk I/O limits */
+void blk_set_io_limits(BlockBackend *blk, ThrottleConfig *cfg)
+{
+    throttle_group_config(blk, cfg);
+}
+
+void blk_io_limits_disable(BlockBackend *blk)
+{
+    assert(blk->public.throttle_state);
+    bdrv_no_throttling_begin(blk_bs(blk));
+    throttle_group_unregister_blk(blk);
+    bdrv_no_throttling_end(blk_bs(blk));
+}
+
+/* should be called before blk_set_io_limits if a limit is set */
+void blk_io_limits_enable(BlockBackend *blk, const char *group)
+{
+    assert(!blk->public.throttle_state);
+    throttle_group_register_blk(blk, group);
+}
+
+void blk_io_limits_update_group(BlockBackend *blk, const char *group)
+{
+    /* this BB is not part of any group */
+    if (!blk->public.throttle_state) {
+        return;
+    }
+
+    /* this BB is a part of the same group than the one we want */
+    if (!g_strcmp0(throttle_group_get_name(blk), group)) {
+        return;
+    }
+
+    /* need to change the group this bs belong to */
+    blk_io_limits_disable(blk);
+    blk_io_limits_enable(blk, group);
+}
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