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nbd/server: send more than one extent of base:allocation context 

This is necessary for efficient block-status export, for clients which
support it.  (qemu is not yet such a client, but could become one.)

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180704112302.471456-3-vsementsov@virtuozzo.com>
[eblake: grammar tweaks]
Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2018-07-04 14:23:02 +03:00 committed by Eric Blake
parent cb9f871e80
commit fb7afc797e
1 changed files with 64 additions and 23 deletions
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87
nbd/server.c
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@ -1844,37 +1844,68 @@ 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. Update @bytes to be the actual
* length encoded (which may be smaller than the original), and update
* @nb_extents to 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;
int ret = bdrv_block_status_above(bs, NULL, offset, remaining_bytes,
&num, NULL, NULL);
if (ret < 0) {
return ret;
}
flags = (ret & BDRV_BLOCK_ALLOCATED ? 0 : NBD_STATE_HOLE) |
(ret & BDRV_BLOCK_ZERO ? NBD_STATE_ZERO : 0);
if (remaining_bytes == bytes) {
extent->flags = flags;
}
if (flags != extent->flags) {
break;
}
offset += num;
remaining_bytes -= num;
if (first_extent) {
extent->flags = flags;
extent->length = num;
first_extent = false;
continue;
}
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;
}
}
cpu_to_be32s(&extent->flags);
extent->length = cpu_to_be32(bytes - remaining_bytes);
extents_end = extent + 1;
for (extent = extents; extent < extents_end; extent++) {
cpu_to_be32s(&extent->flags);
cpu_to_be32s(&extent->length);
}
*bytes -= remaining_bytes;
*nb_extents = extents_end - extents;
return 0;
}
@ -1910,21 +1941,29 @@ 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;
}
/*
@ -2231,10 +2270,12 @@ 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);
@ -2247,7 +2288,7 @@ 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;