Merge remote-tracking branch 'kwolf/for-anthony' into staging

* kwolf/for-anthony:
  block: remove keep_read_only flag from BlockDriverState struct
  block: convert bdrv_commit() to use bdrv_reopen()
  block: vpc image file reopen
  block: vdi image file reopen
  block: vmdk image file reopen
  block: qcow image file reopen
  block: qcow2 image file reopen
  block: qed image file reopen
  block: raw image file reopen
  block: raw-posix image file reopen
  block: purge s->aligned_buf and s->aligned_buf_size from raw-posix.c
  block: use BDRV_O_NOCACHE instead of s->aligned_buf in raw-posix.c
  block: do not parse BDRV_O_CACHE_WB in block drivers
  block: move open flag parsing in raw block drivers to helper functions
  block: move aio initialization into a helper function
  block: Framework for reopening files safely
  block: make bdrv_set_enable_write_cache() modify open_flags
  block: correctly set the keep_read_only flag
  blockdev: preserve readonly and snapshot states across media changes

12 files changed, 286 insertions, 91 deletions

diff --git a/block/iscsi.c b/block/iscsi.c
index fb001b955c..d0b1a10ee4 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -262,10 +262,6 @@ iscsi_aio_writev(BlockDriverState *bs, int64_t sector_num,
     acb->task->xfer_dir = SCSI_XFER_WRITE;
     acb->task->cdb_size = 16;
     acb->task->cdb[0] = 0x8a;
-    if (!(bs->open_flags & BDRV_O_CACHE_WB)) {
-        /* set FUA on writes when cache mode is write through */
-        acb->task->cdb[1] |= 0x04;
-    }
     lba = sector_qemu2lun(sector_num, iscsilun);
     *(uint32_t *)&acb->task->cdb[2]  = htonl(lba >> 32);
     *(uint32_t *)&acb->task->cdb[6]  = htonl(lba & 0xffffffff);
diff --git a/block/qcow.c b/block/qcow.c
index 7b5ab87d2d..b239c82ae0 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -197,6 +197,15 @@ static int qcow_open(BlockDriverState *bs, int flags)
     return ret;
 }
 
+
+/* We have nothing to do for QCOW reopen, stubs just return
+ * success */
+static int qcow_reopen_prepare(BDRVReopenState *state,
+                               BlockReopenQueue *queue, Error **errp)
+{
+    return 0;
+}
+
 static int qcow_set_key(BlockDriverState *bs, const char *key)
 {
     BDRVQcowState *s = bs->opaque;
@@ -868,6 +877,7 @@ static BlockDriver bdrv_qcow = {
     .bdrv_probe		= qcow_probe,
     .bdrv_open		= qcow_open,
     .bdrv_close		= qcow_close,
+    .bdrv_reopen_prepare = qcow_reopen_prepare,
     .bdrv_create	= qcow_create,
 
     .bdrv_co_readv          = qcow_co_readv,
diff --git a/block/qcow2.c b/block/qcow2.c
index 8f183f1465..aa5e603cd3 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -52,6 +52,7 @@ typedef struct {
     uint32_t magic;
     uint32_t len;
 } QCowExtension;
+
 #define  QCOW2_EXT_MAGIC_END 0
 #define  QCOW2_EXT_MAGIC_BACKING_FORMAT 0xE2792ACA
 #define  QCOW2_EXT_MAGIC_FEATURE_TABLE 0x6803f857
@@ -558,6 +559,14 @@ static int qcow2_set_key(BlockDriverState *bs, const char *key)
     return 0;
 }
 
+/* We have nothing to do for QCOW2 reopen, stubs just return
+ * success */
+static int qcow2_reopen_prepare(BDRVReopenState *state,
+                                BlockReopenQueue *queue, Error **errp)
+{
+    return 0;
+}
+
 static int coroutine_fn qcow2_co_is_allocated(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors, int *pnum)
 {
@@ -1679,6 +1688,7 @@ static BlockDriver bdrv_qcow2 = {
     .bdrv_probe         = qcow2_probe,
     .bdrv_open          = qcow2_open,
     .bdrv_close         = qcow2_close,
+    .bdrv_reopen_prepare  = qcow2_reopen_prepare,
     .bdrv_create        = qcow2_create,
     .bdrv_co_is_allocated = qcow2_co_is_allocated,
     .bdrv_set_key       = qcow2_set_key,
diff --git a/block/qed.c b/block/qed.c
index 21cb239870..6c182ca917 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -505,6 +505,14 @@ out:
     return ret;
 }
 
+/* We have nothing to do for QED reopen, stubs just return
+ * success */
+static int bdrv_qed_reopen_prepare(BDRVReopenState *state,
+                                   BlockReopenQueue *queue, Error **errp)
+{
+    return 0;
+}
+
 static void bdrv_qed_close(BlockDriverState *bs)
 {
     BDRVQEDState *s = bs->opaque;
@@ -1564,6 +1572,7 @@ static BlockDriver bdrv_qed = {
     .bdrv_rebind              = bdrv_qed_rebind,
     .bdrv_open                = bdrv_qed_open,
     .bdrv_close               = bdrv_qed_close,
+    .bdrv_reopen_prepare      = bdrv_qed_reopen_prepare,
     .bdrv_create              = bdrv_qed_create,
     .bdrv_co_is_allocated     = bdrv_qed_co_is_allocated,
     .bdrv_make_empty          = bdrv_qed_make_empty,
diff --git a/block/raw-posix.c b/block/raw-posix.c
index 6be20b1925..28d439fa81 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -133,13 +133,19 @@ typedef struct BDRVRawState {
     int use_aio;
     void *aio_ctx;
 #endif
-    uint8_t *aligned_buf;
-    unsigned aligned_buf_size;
 #ifdef CONFIG_XFS
     bool is_xfs : 1;
 #endif
 } BDRVRawState;
 
+typedef struct BDRVRawReopenState {
+    int fd;
+    int open_flags;
+#ifdef CONFIG_LINUX_AIO
+    int use_aio;
+#endif
+} BDRVRawReopenState;
+
 static int fd_open(BlockDriverState *bs);
 static int64_t raw_getlength(BlockDriverState *bs);
 
@@ -185,6 +191,57 @@ static int raw_normalize_devicepath(const char **filename)
 }
 #endif
 
+static void raw_parse_flags(int bdrv_flags, int *open_flags)
+{
+    assert(open_flags != NULL);
+
+    *open_flags |= O_BINARY;
+    *open_flags &= ~O_ACCMODE;
+    if (bdrv_flags & BDRV_O_RDWR) {
+        *open_flags |= O_RDWR;
+    } else {
+        *open_flags |= O_RDONLY;
+    }
+
+    /* Use O_DSYNC for write-through caching, no flags for write-back caching,
+     * and O_DIRECT for no caching. */
+    if ((bdrv_flags & BDRV_O_NOCACHE)) {
+        *open_flags |= O_DIRECT;
+    }
+}
+
+#ifdef CONFIG_LINUX_AIO
+static int raw_set_aio(void **aio_ctx, int *use_aio, int bdrv_flags)
+{
+    int ret = -1;
+    assert(aio_ctx != NULL);
+    assert(use_aio != NULL);
+    /*
+     * Currently Linux do AIO only for files opened with O_DIRECT
+     * specified so check NOCACHE flag too
+     */
+    if ((bdrv_flags & (BDRV_O_NOCACHE|BDRV_O_NATIVE_AIO)) ==
+                      (BDRV_O_NOCACHE|BDRV_O_NATIVE_AIO)) {
+
+        /* if non-NULL, laio_init() has already been run */
+        if (*aio_ctx == NULL) {
+            *aio_ctx = laio_init();
+            if (!*aio_ctx) {
+                goto error;
+            }
+        }
+        *use_aio = 1;
+    } else {
+        *use_aio = 0;
+    }
+
+    ret = 0;
+
+error:
+    return ret;
+}
+#endif
+
 static int raw_open_common(BlockDriverState *bs, const char *filename,
                            int bdrv_flags, int open_flags)
 {
@@ -196,20 +253,8 @@ static int raw_open_common(BlockDriverState *bs, const char *filename,
         return ret;
     }
 
-    s->open_flags = open_flags | O_BINARY;
-    s->open_flags &= ~O_ACCMODE;
-    if (bdrv_flags & BDRV_O_RDWR) {
-        s->open_flags |= O_RDWR;
-    } else {
-        s->open_flags |= O_RDONLY;
-    }
-
-    /* Use O_DSYNC for write-through caching, no flags for write-back caching,
-     * and O_DIRECT for no caching. */
-    if ((bdrv_flags & BDRV_O_NOCACHE))
-        s->open_flags |= O_DIRECT;
-    if (!(bdrv_flags & BDRV_O_CACHE_WB))
-        s->open_flags |= O_DSYNC;
+    s->open_flags = open_flags;
+    raw_parse_flags(bdrv_flags, &s->open_flags);
 
     s->fd = -1;
     fd = qemu_open(filename, s->open_flags, 0644);
@@ -220,45 +265,17 @@ static int raw_open_common(BlockDriverState *bs, const char *filename,
         return ret;
     }
     s->fd = fd;
-    s->aligned_buf = NULL;
-
-    if ((bdrv_flags & BDRV_O_NOCACHE)) {
-        /*
-         * Allocate a buffer for read/modify/write cycles.  Chose the size
-         * pessimistically as we don't know the block size yet.
-         */
-        s->aligned_buf_size = 32 * MAX_BLOCKSIZE;
-        s->aligned_buf = qemu_memalign(MAX_BLOCKSIZE, s->aligned_buf_size);
-        if (s->aligned_buf == NULL) {
-            goto out_close;
-        }
-    }
 
     /* We're falling back to POSIX AIO in some cases so init always */
     if (paio_init() < 0) {
-        goto out_free_buf;
+        goto out_close;
     }
 
 #ifdef CONFIG_LINUX_AIO
-    /*
-     * Currently Linux do AIO only for files opened with O_DIRECT
-     * specified so check NOCACHE flag too
-     */
-    if ((bdrv_flags & (BDRV_O_NOCACHE|BDRV_O_NATIVE_AIO)) ==
-                      (BDRV_O_NOCACHE|BDRV_O_NATIVE_AIO)) {
-
-        s->aio_ctx = laio_init();
-        if (!s->aio_ctx) {
-            goto out_free_buf;
-        }
-        s->use_aio = 1;
-    } else
-#endif
-    {
-#ifdef CONFIG_LINUX_AIO
-        s->use_aio = 0;
-#endif
+    if (raw_set_aio(&s->aio_ctx, &s->use_aio, bdrv_flags)) {
+        goto out_close;
     }
+#endif
 
 #ifdef CONFIG_XFS
     if (platform_test_xfs_fd(s->fd)) {
@@ -268,8 +285,6 @@ static int raw_open_common(BlockDriverState *bs, const char *filename,
 
     return 0;
 
-out_free_buf:
-    qemu_vfree(s->aligned_buf);
 out_close:
     qemu_close(fd);
     return -errno;
@@ -283,6 +298,109 @@ static int raw_open(BlockDriverState *bs, const char *filename, int flags)
     return raw_open_common(bs, filename, flags, 0);
 }
 
+static int raw_reopen_prepare(BDRVReopenState *state,
+                              BlockReopenQueue *queue, Error **errp)
+{
+    BDRVRawState *s;
+    BDRVRawReopenState *raw_s;
+    int ret = 0;
+
+    assert(state != NULL);
+    assert(state->bs != NULL);
+
+    s = state->bs->opaque;
+
+    state->opaque = g_malloc0(sizeof(BDRVRawReopenState));
+    raw_s = state->opaque;
+
+#ifdef CONFIG_LINUX_AIO
+    raw_s->use_aio = s->use_aio;
+
+    /* we can use s->aio_ctx instead of a copy, because the use_aio flag is
+     * valid in the 'false' condition even if aio_ctx is set, and raw_set_aio()
+     * won't override aio_ctx if aio_ctx is non-NULL */
+    if (raw_set_aio(&s->aio_ctx, &raw_s->use_aio, state->flags)) {
+        return -1;
+    }
+#endif
+
+    raw_parse_flags(state->flags, &raw_s->open_flags);
+
+    raw_s->fd = -1;
+
+    int fcntl_flags = O_APPEND | O_ASYNC | O_NONBLOCK;
+#ifdef O_NOATIME
+    fcntl_flags |= O_NOATIME;
+#endif
+
+    if ((raw_s->open_flags & ~fcntl_flags) == (s->open_flags & ~fcntl_flags)) {
+        /* dup the original fd */
+        /* TODO: use qemu fcntl wrapper */
+#ifdef F_DUPFD_CLOEXEC
+        raw_s->fd = fcntl(s->fd, F_DUPFD_CLOEXEC, 0);
+#else
+        raw_s->fd = dup(s->fd);
+        if (raw_s->fd != -1) {
+            qemu_set_cloexec(raw_s->fd);
+        }
+#endif
+        if (raw_s->fd >= 0) {
+            ret = fcntl_setfl(raw_s->fd, raw_s->open_flags);
+            if (ret) {
+                qemu_close(raw_s->fd);
+                raw_s->fd = -1;
+            }
+        }
+    }
+
+    /* If we cannot use fcntl, or fcntl failed, fall back to qemu_open() */
+    if (raw_s->fd == -1) {
+        assert(!(raw_s->open_flags & O_CREAT));
+        raw_s->fd = qemu_open(state->bs->filename, raw_s->open_flags);
+        if (raw_s->fd == -1) {
+            ret = -1;
+        }
+    }
+    return ret;
+}
+
+
+static void raw_reopen_commit(BDRVReopenState *state)
+{
+    BDRVRawReopenState *raw_s = state->opaque;
+    BDRVRawState *s = state->bs->opaque;
+
+    s->open_flags = raw_s->open_flags;
+
+    qemu_close(s->fd);
+    s->fd = raw_s->fd;
+#ifdef CONFIG_LINUX_AIO
+    s->use_aio = raw_s->use_aio;
+#endif
+
+    g_free(state->opaque);
+    state->opaque = NULL;
+}
+
+
+static void raw_reopen_abort(BDRVReopenState *state)
+{
+    BDRVRawReopenState *raw_s = state->opaque;
+
+     /* nothing to do if NULL, we didn't get far enough */
+    if (raw_s == NULL) {
+        return;
+    }
+
+    if (raw_s->fd >= 0) {
+        qemu_close(raw_s->fd);
+        raw_s->fd = -1;
+    }
+    g_free(state->opaque);
+    state->opaque = NULL;
+}
+
+
 /* XXX: use host sector size if necessary with:
 #ifdef DIOCGSECTORSIZE
         {
@@ -330,7 +448,7 @@ static BlockDriverAIOCB *raw_aio_submit(BlockDriverState *bs,
      * boundary.  Check if this is the case or tell the low-level
      * driver that it needs to copy the buffer.
      */
-    if (s->aligned_buf) {
+    if ((bs->open_flags & BDRV_O_NOCACHE)) {
         if (!qiov_is_aligned(bs, qiov)) {
             type |= QEMU_AIO_MISALIGNED;
 #ifdef CONFIG_LINUX_AIO
@@ -378,8 +496,6 @@ static void raw_close(BlockDriverState *bs)
     if (s->fd >= 0) {
         qemu_close(s->fd);
         s->fd = -1;
-        if (s->aligned_buf != NULL)
-            qemu_vfree(s->aligned_buf);
     }
 }
 
@@ -735,6 +851,9 @@ static BlockDriver bdrv_file = {
     .instance_size = sizeof(BDRVRawState),
     .bdrv_probe = NULL, /* no probe for protocols */
     .bdrv_file_open = raw_open,
+    .bdrv_reopen_prepare = raw_reopen_prepare,
+    .bdrv_reopen_commit = raw_reopen_commit,
+    .bdrv_reopen_abort = raw_reopen_abort,
     .bdrv_close = raw_close,
     .bdrv_create = raw_create,
     .bdrv_co_discard = raw_co_discard,
diff --git a/block/raw-win32.c b/block/raw-win32.c
index c56bf83375..78c830648b 100644
--- a/block/raw-win32.c
+++ b/block/raw-win32.c
@@ -77,6 +77,23 @@ static int set_sparse(int fd)
 				 NULL, 0, NULL, 0, &returned, NULL);
 }
 
+static void raw_parse_flags(int flags, int *access_flags, DWORD *overlapped)
+{
+    assert(access_flags != NULL);
+    assert(overlapped != NULL);
+
+    if (flags & BDRV_O_RDWR) {
+        *access_flags = GENERIC_READ | GENERIC_WRITE;
+    } else {
+        *access_flags = GENERIC_READ;
+    }
+
+    *overlapped = FILE_ATTRIBUTE_NORMAL;
+    if (flags & BDRV_O_NOCACHE) {
+        *overlapped |= FILE_FLAG_NO_BUFFERING;
+    }
+}
+
 static int raw_open(BlockDriverState *bs, const char *filename, int flags)
 {
     BDRVRawState *s = bs->opaque;
@@ -85,17 +102,8 @@ static int raw_open(BlockDriverState *bs, const char *filename, int flags)
 
     s->type = FTYPE_FILE;
 
-    if (flags & BDRV_O_RDWR) {
-        access_flags = GENERIC_READ | GENERIC_WRITE;
-    } else {
-        access_flags = GENERIC_READ;
-    }
+    raw_parse_flags(flags, &access_flags, &overlapped);
 
-    overlapped = FILE_ATTRIBUTE_NORMAL;
-    if (flags & BDRV_O_NOCACHE)
-        overlapped |= FILE_FLAG_NO_BUFFERING;
-    if (!(flags & BDRV_O_CACHE_WB))
-        overlapped |= FILE_FLAG_WRITE_THROUGH;
     s->hfile = CreateFile(filename, access_flags,
                           FILE_SHARE_READ, NULL,
                           OPEN_EXISTING, overlapped, NULL);
@@ -374,18 +382,10 @@ static int hdev_open(BlockDriverState *bs, const char *filename, int flags)
     }
     s->type = find_device_type(bs, filename);
 
-    if (flags & BDRV_O_RDWR) {
-        access_flags = GENERIC_READ | GENERIC_WRITE;
-    } else {
-        access_flags = GENERIC_READ;
-    }
+    raw_parse_flags(flags, &access_flags, &overlapped);
+
     create_flags = OPEN_EXISTING;
 
-    overlapped = FILE_ATTRIBUTE_NORMAL;
-    if (flags & BDRV_O_NOCACHE)
-        overlapped |= FILE_FLAG_NO_BUFFERING;
-    if (!(flags & BDRV_O_CACHE_WB))
-        overlapped |= FILE_FLAG_WRITE_THROUGH;
     s->hfile = CreateFile(filename, access_flags,
                           FILE_SHARE_READ, NULL,
                           create_flags, overlapped, NULL);
diff --git a/block/raw.c b/block/raw.c
index ff34ea41e7..253e949b8c 100644
--- a/block/raw.c
+++ b/block/raw.c
@@ -9,6 +9,14 @@ static int raw_open(BlockDriverState *bs, int flags)
     return 0;
 }
 
+/* We have nothing to do for raw reopen, stubs just return
+ * success */
+static int raw_reopen_prepare(BDRVReopenState *state,
+                              BlockReopenQueue *queue,  Error **errp)
+{
+    return 0;
+}
+
 static int coroutine_fn raw_co_readv(BlockDriverState *bs, int64_t sector_num,
                                      int nb_sectors, QEMUIOVector *qiov)
 {
@@ -115,6 +123,8 @@ static BlockDriver bdrv_raw = {
     .bdrv_open          = raw_open,
     .bdrv_close         = raw_close,
 
+    .bdrv_reopen_prepare  = raw_reopen_prepare,
+
     .bdrv_co_readv          = raw_co_readv,
     .bdrv_co_writev         = raw_co_writev,
     .bdrv_co_is_allocated   = raw_co_is_allocated,
diff --git a/block/rbd.c b/block/rbd.c
index 5a0f79fc8f..015a9db0ad 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -487,12 +487,6 @@ static int qemu_rbd_open(BlockDriverState *bs, const char *filename, int flags)
         rados_conf_set(s->cluster, "rbd_cache", "false");
     } else {
         rados_conf_set(s->cluster, "rbd_cache", "true");
-        if (!(flags & BDRV_O_CACHE_WB)) {
-            r = rados_conf_set(s->cluster, "rbd_cache_max_dirty", "0");
-            if (r < 0) {
-                rados_conf_set(s->cluster, "rbd_cache", "false");
-            }
-        }
     }
 
     if (strstr(conf, "conf=") == NULL) {
diff --git a/block/sheepdog.c b/block/sheepdog.c
index e0753ee9e5..4742f8ae6f 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -1114,14 +1114,12 @@ static int sd_open(BlockDriverState *bs, const char *filename, int flags)
         goto out;
     }
 
-    if (flags & BDRV_O_CACHE_WB) {
-        s->cache_enabled = 1;
-        s->flush_fd = connect_to_sdog(s->addr, s->port);
-        if (s->flush_fd < 0) {
-            error_report("failed to connect");
-            ret = s->flush_fd;
-            goto out;
-        }
+    s->cache_enabled = 1;
+    s->flush_fd = connect_to_sdog(s->addr, s->port);
+    if (s->flush_fd < 0) {
+        error_report("failed to connect");
+        ret = s->flush_fd;
+        goto out;
     }
 
     if (snapid || tag[0] != '\0') {
diff --git a/block/vdi.c b/block/vdi.c
index 550cf58a39..f35b12ec98 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -454,6 +454,12 @@ static int vdi_open(BlockDriverState *bs, int flags)
     return -1;
 }
 
+static int vdi_reopen_prepare(BDRVReopenState *state,
+                              BlockReopenQueue *queue, Error **errp)
+{
+    return 0;
+}
+
 static int coroutine_fn vdi_co_is_allocated(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors, int *pnum)
 {
@@ -761,6 +767,7 @@ static BlockDriver bdrv_vdi = {
     .bdrv_probe = vdi_probe,
     .bdrv_open = vdi_open,
     .bdrv_close = vdi_close,
+    .bdrv_reopen_prepare = vdi_reopen_prepare,
     .bdrv_create = vdi_create,
     .bdrv_co_is_allocated = vdi_co_is_allocated,
     .bdrv_make_empty = vdi_make_empty,
diff --git a/block/vmdk.c b/block/vmdk.c
index bba4c61a74..f2e861b074 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -300,6 +300,40 @@ static int vmdk_is_cid_valid(BlockDriverState *bs)
     return 1;
 }
 
+/* Queue extents, if any, for reopen() */
+static int vmdk_reopen_prepare(BDRVReopenState *state,
+                               BlockReopenQueue *queue, Error **errp)
+{
+    BDRVVmdkState *s;
+    int ret = -1;
+    int i;
+    VmdkExtent *e;
+
+    assert(state != NULL);
+    assert(state->bs != NULL);
+
+    if (queue == NULL) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                 "No reopen queue for VMDK extents");
+        goto exit;
+    }
+
+    s = state->bs->opaque;
+
+    assert(s != NULL);
+
+    for (i = 0; i < s->num_extents; i++) {
+        e = &s->extents[i];
+        if (e->file != state->bs->file) {
+            bdrv_reopen_queue(queue, e->file, state->flags);
+        }
+    }
+    ret = 0;
+
+exit:
+    return ret;
+}
+
 static int vmdk_parent_open(BlockDriverState *bs)
 {
     char *p_name;
@@ -1646,6 +1680,7 @@ static BlockDriver bdrv_vmdk = {
     .instance_size  = sizeof(BDRVVmdkState),
     .bdrv_probe     = vmdk_probe,
     .bdrv_open      = vmdk_open,
+    .bdrv_reopen_prepare = vmdk_reopen_prepare,
     .bdrv_read      = vmdk_co_read,
     .bdrv_write     = vmdk_co_write,
     .bdrv_close     = vmdk_close,
diff --git a/block/vpc.c b/block/vpc.c
index c0b82c4f57..b6bf52f140 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -265,6 +265,12 @@ static int vpc_open(BlockDriverState *bs, int flags)
     return err;
 }
 
+static int vpc_reopen_prepare(BDRVReopenState *state,
+                              BlockReopenQueue *queue, Error **errp)
+{
+    return 0;
+}
+
 /*
  * Returns the absolute byte offset of the given sector in the image file.
  * If the sector is not allocated, -1 is returned instead.
@@ -783,6 +789,7 @@ static BlockDriver bdrv_vpc = {
     .bdrv_probe     = vpc_probe,
     .bdrv_open      = vpc_open,
     .bdrv_close     = vpc_close,
+    .bdrv_reopen_prepare = vpc_reopen_prepare,
     .bdrv_create    = vpc_create,
 
     .bdrv_read              = vpc_co_read,