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-rw-r--r--qemu/block/write-threshold.c125
1 files changed, 125 insertions, 0 deletions
diff --git a/qemu/block/write-threshold.c b/qemu/block/write-threshold.c
new file mode 100644
index 000000000..a53c1f5e6
--- /dev/null
+++ b/qemu/block/write-threshold.c
@@ -0,0 +1,125 @@
+/*
+ * QEMU System Emulator block write threshold notification
+ *
+ * Copyright Red Hat, Inc. 2014
+ *
+ * Authors:
+ * Francesco Romani <fromani@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ */
+
+#include "block/block_int.h"
+#include "block/coroutine.h"
+#include "block/write-threshold.h"
+#include "qemu/notify.h"
+#include "qapi-event.h"
+#include "qmp-commands.h"
+
+
+uint64_t bdrv_write_threshold_get(const BlockDriverState *bs)
+{
+ return bs->write_threshold_offset;
+}
+
+bool bdrv_write_threshold_is_set(const BlockDriverState *bs)
+{
+ return bs->write_threshold_offset > 0;
+}
+
+static void write_threshold_disable(BlockDriverState *bs)
+{
+ if (bdrv_write_threshold_is_set(bs)) {
+ notifier_with_return_remove(&bs->write_threshold_notifier);
+ bs->write_threshold_offset = 0;
+ }
+}
+
+uint64_t bdrv_write_threshold_exceeded(const BlockDriverState *bs,
+ const BdrvTrackedRequest *req)
+{
+ if (bdrv_write_threshold_is_set(bs)) {
+ if (req->offset > bs->write_threshold_offset) {
+ return (req->offset - bs->write_threshold_offset) + req->bytes;
+ }
+ if ((req->offset + req->bytes) > bs->write_threshold_offset) {
+ return (req->offset + req->bytes) - bs->write_threshold_offset;
+ }
+ }
+ return 0;
+}
+
+static int coroutine_fn before_write_notify(NotifierWithReturn *notifier,
+ void *opaque)
+{
+ BdrvTrackedRequest *req = opaque;
+ BlockDriverState *bs = req->bs;
+ uint64_t amount = 0;
+
+ amount = bdrv_write_threshold_exceeded(bs, req);
+ if (amount > 0) {
+ qapi_event_send_block_write_threshold(
+ bs->node_name,
+ amount,
+ bs->write_threshold_offset,
+ &error_abort);
+
+ /* autodisable to avoid flooding the monitor */
+ write_threshold_disable(bs);
+ }
+
+ return 0; /* should always let other notifiers run */
+}
+
+static void write_threshold_register_notifier(BlockDriverState *bs)
+{
+ bs->write_threshold_notifier.notify = before_write_notify;
+ notifier_with_return_list_add(&bs->before_write_notifiers,
+ &bs->write_threshold_notifier);
+}
+
+static void write_threshold_update(BlockDriverState *bs,
+ int64_t threshold_bytes)
+{
+ bs->write_threshold_offset = threshold_bytes;
+}
+
+void bdrv_write_threshold_set(BlockDriverState *bs, uint64_t threshold_bytes)
+{
+ if (bdrv_write_threshold_is_set(bs)) {
+ if (threshold_bytes > 0) {
+ write_threshold_update(bs, threshold_bytes);
+ } else {
+ write_threshold_disable(bs);
+ }
+ } else {
+ if (threshold_bytes > 0) {
+ /* avoid multiple registration */
+ write_threshold_register_notifier(bs);
+ write_threshold_update(bs, threshold_bytes);
+ }
+ /* discard bogus disable request */
+ }
+}
+
+void qmp_block_set_write_threshold(const char *node_name,
+ uint64_t threshold_bytes,
+ Error **errp)
+{
+ BlockDriverState *bs;
+ AioContext *aio_context;
+
+ bs = bdrv_find_node(node_name);
+ if (!bs) {
+ error_setg(errp, "Device '%s' not found", node_name);
+ return;
+ }
+
+ aio_context = bdrv_get_aio_context(bs);
+ aio_context_acquire(aio_context);
+
+ bdrv_write_threshold_set(bs, threshold_bytes);
+
+ aio_context_release(aio_context);
+}