The NBD protocol is adding an extension to let servers advertise
initialization state to the client: whether the image contains holes,
and whether it is known to read as all zeroes. With recent enough
libnbd, the nbd plugin can pass this information through.
Signed-off-by: Eric Blake <ebl...@redhat.com>
---
plugins/nbd/nbd.c | 40 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 39 insertions(+), 1 deletion(-)
diff --git a/plugins/nbd/nbd.c b/plugins/nbd/nbd.c
index d020bee..8f06420 100644
--- a/plugins/nbd/nbd.c
+++ b/plugins/nbd/nbd.c
@@ -1,5 +1,5 @@
/* nbdkit
- * Copyright (C) 2017-2019 Red Hat Inc.
+ * Copyright (C) 2017-2020 Red Hat Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
@@ -702,6 +702,42 @@ nbdplug_can_extents (void *handle)
return i;
}
+static int
+nbdplug_init_sparse (void *handle)
+{
+ struct handle *h = handle;
+ int i = 0;
+
+#if LIBNBD_HAVE_NBD_GET_INIT_FLAGS
+ i = nbd_get_init_flags (h->nbd);
+
+ if (i == -1) {
+ nbdkit_error ("failure to check init flags: %s", nbd_get_error ());
+ return -1;
+ }
+ i = !!(i & LIBNBD_INIT_SPARSE);
+#endif
+ return i;
+}
+
+static int
+nbdplug_init_zero (void *handle)
+{
+ struct handle *h = handle;
+ int i = 0;
+
+#if LIBNBD_HAVE_NBD_GET_INIT_FLAGS
+ i = nbd_get_init_flags (h->nbd);
+
+ if (i == -1) {
+ nbdkit_error ("failure to check init flags: %s", nbd_get_error ());
+ return -1;
+ }
+ i = !!(i & LIBNBD_INIT_ZERO);
+#endif
+ return i;
+}
+
/* Read data from the file. */
static int
nbdplug_pread (void *handle, void *buf, uint32_t count, uint64_t offset,
@@ -860,6 +896,8 @@ static struct nbdkit_plugin plugin = {
.can_multi_conn = nbdplug_can_multi_conn,
.can_extents = nbdplug_can_extents,
.can_cache = nbdplug_can_cache,
+ .init_sparse = nbdplug_init_sparse,
+ .init_zero = nbdplug_init_zero,
.pread = nbdplug_pread,
.pwrite = nbdplug_pwrite,
.zero = nbdplug_zero,
--
2.24.1
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