This is necessary for efficient block-status export, for clients which
support it.
Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---
nbd/server.c | 77 +++++++++++++++++++++++++++++++++++++++++++++---------------
1 file changed, 58 insertions(+), 19 deletions(-)
diff --git a/nbd/server.c b/nbd/server.c
index ea5fe0eb33..a6d013aec4 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1844,11 +1844,22 @@ static int coroutine_fn
nbd_co_send_sparse_read(NBDClient *client,
return ret;
}
-static int blockstatus_to_extent_be(BlockDriverState *bs, uint64_t offset,
- uint64_t bytes, NBDExtent *extent)
+/*
+ * Populate @extents from block status. Store in @bytes the byte length encoded
+ * (which may be smaller but (unlike bitmap_to_extents) _never_ larger than the
+ * original), and store in @nb_extents the number of extents used.
+ *
+ * Returns zero on success and -errno on bdrv_block_status_above failure.
+ */
+static int blockstatus_to_extents(BlockDriverState *bs, uint64_t offset,
+ uint64_t *bytes, NBDExtent *extents,
+ unsigned int *nb_extents)
{
- uint64_t remaining_bytes = bytes;
+ uint64_t remaining_bytes = *bytes;
+ NBDExtent *extent = extents, *extents_end = extents + *nb_extents;
+ bool first_extent = true;
+ assert(*nb_extents);
while (remaining_bytes) {
uint32_t flags;
int64_t num;
@@ -1860,21 +1871,40 @@ static int blockstatus_to_extent_be(BlockDriverState
*bs, uint64_t offset,
flags = (ret & BDRV_BLOCK_ALLOCATED ? 0 : NBD_STATE_HOLE) |
(ret & BDRV_BLOCK_ZERO ? NBD_STATE_ZERO : 0);
+ offset += num;
+ remaining_bytes -= num;
- if (remaining_bytes == bytes) {
+ if (first_extent) {
extent->flags = flags;
+ extent->length = num;
+ first_extent = false;
+ continue;
}
- if (flags != extent->flags) {
- break;
+ if (flags == extent->flags) {
+ /* extend current extent */
+ extent->length += num;
+ } else {
+ if (extent + 1 == extents_end) {
+ break;
+ }
+
+ /* start new extent */
+ extent++;
+ extent->flags = flags;
+ extent->length = num;
}
+ }
- offset += num;
- remaining_bytes -= num;
+ extents_end = extent + 1;
+
+ for (extent = extents; extent < extents_end; extent++) {
+ cpu_to_be32s(&extent->flags);
+ cpu_to_be32s(&extent->length);
}
- cpu_to_be32s(&extent->flags);
- extent->length = cpu_to_be32(bytes - remaining_bytes);
+ *bytes -= remaining_bytes;
+ *nb_extents = extents_end - extents;
return 0;
}
@@ -1910,21 +1940,29 @@ static int nbd_co_send_extents(NBDClient *client,
uint64_t handle,
/* Get block status from the exported device and send it to the client */
static int nbd_co_send_block_status(NBDClient *client, uint64_t handle,
BlockDriverState *bs, uint64_t offset,
- uint32_t length, bool last,
- uint32_t context_id, Error **errp)
+ uint32_t length, bool dont_fragment,
+ bool last, uint32_t context_id,
+ Error **errp)
{
int ret;
- NBDExtent extent;
+ unsigned int nb_extents = dont_fragment ? 1 : NBD_MAX_BITMAP_EXTENTS;
+ NBDExtent *extents = g_new(NBDExtent, nb_extents);
+ uint64_t final_length = length;
- ret = blockstatus_to_extent_be(bs, offset, length, &extent);
+ ret = blockstatus_to_extents(bs, offset, &final_length, extents,
+ &nb_extents);
if (ret < 0) {
+ g_free(extents);
return nbd_co_send_structured_error(
client, handle, -ret, "can't get block status", errp);
}
- return nbd_co_send_extents(client, handle, &extent, 1,
- be32_to_cpu(extent.length), last,
- context_id, errp);
+ ret = nbd_co_send_extents(client, handle, extents, nb_extents,
+ final_length, last, context_id, errp);
+
+ g_free(extents);
+
+ return ret;
}
/*
@@ -2228,10 +2266,11 @@ static coroutine_fn int nbd_handle_request(NBDClient
*client,
(client->export_meta.base_allocation ||
client->export_meta.bitmap))
{
+ bool dont_fragment = request->flags & NBD_CMD_FLAG_REQ_ONE;
if (client->export_meta.base_allocation) {
ret = nbd_co_send_block_status(client, request->handle,
blk_bs(exp->blk),
request->from,
- request->len,
+ request->len, dont_fragment,
!client->export_meta.bitmap,
NBD_META_ID_BASE_ALLOCATION,
errp);
@@ -2244,7 +2283,7 @@ static coroutine_fn int nbd_handle_request(NBDClient
*client,
ret = nbd_co_send_bitmap(client, request->handle,
client->exp->export_bitmap,
request->from, request->len,
- request->flags & NBD_CMD_FLAG_REQ_ONE,
+ dont_fragment,
true, NBD_META_ID_DIRTY_BITMAP,
errp);
if (ret < 0) {
return ret;