block: add bdrv_add_before_write_notifier()
The bdrv_add_before_write_notifier() function installs a callback that
is invoked before a write request is processed. This will be used to
implement copy-on-write point-in-time snapshots where we need to copy
out old data before overwriting it.
Note that BdrvTrackedRequest is moved to block_int.h since it is passed
to .notify() functions.
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block.c b/block.c
index 8e77d46..0898f6b 100644
--- a/block.c
+++ b/block.c
@@ -305,6 +305,7 @@
}
bdrv_iostatus_disable(bs);
notifier_list_init(&bs->close_notifiers);
+ notifier_with_return_list_init(&bs->before_write_notifiers);
return bs;
}
@@ -1840,16 +1841,6 @@
return 0;
}
-struct BdrvTrackedRequest {
- BlockDriverState *bs;
- int64_t sector_num;
- int nb_sectors;
- bool is_write;
- QLIST_ENTRY(BdrvTrackedRequest) list;
- Coroutine *co; /* owner, used for deadlock detection */
- CoQueue wait_queue; /* coroutines blocked on this request */
-};
-
/**
* Remove an active request from the tracked requests list
*
@@ -2620,7 +2611,11 @@
tracked_request_begin(&req, bs, sector_num, nb_sectors, true);
- if (flags & BDRV_REQ_ZERO_WRITE) {
+ ret = notifier_with_return_list_notify(&bs->before_write_notifiers, &req);
+
+ if (ret < 0) {
+ /* Do nothing, write notifier decided to fail this request */
+ } else if (flags & BDRV_REQ_ZERO_WRITE) {
ret = bdrv_co_do_write_zeroes(bs, sector_num, nb_sectors);
} else {
ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov);
@@ -4581,3 +4576,9 @@
/* Currently BlockDriverState always uses the main loop AioContext */
return qemu_get_aio_context();
}
+
+void bdrv_add_before_write_notifier(BlockDriverState *bs,
+ NotifierWithReturn *notifier)
+{
+ notifier_with_return_list_add(&bs->before_write_notifiers, notifier);
+}
