OpenE2K/qemu-e2k
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nbd: Add 'qemu-nbd -A' to expose allocation depth

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Allow the server to expose an additional metacontext to be requested
by savvy clients.  qemu-nbd adds a new option -A to expose the
qemu:allocation-depth metacontext through NBD_CMD_BLOCK_STATUS; this
can also be set via QMP when using block-export-add.

qemu as client is hacked into viewing the key aspects of this new
context by abusing the already-experimental x-dirty-bitmap option to
collapse all depths greater than 2, which results in a tri-state value
visible in the output of 'qemu-img map --output=json' (yes, that means
x-dirty-bitmap is now a bit of a misnomer, but I didn't feel like
renaming it as it would introduce a needless break of back-compat,
even though we make no compat guarantees with x- members):

unallocated (depth 0) => "zero":false, "data":true
local (depth 1)       => "zero":false, "data":false
backing (depth 2+)    => "zero":true,  "data":true

libnbd as client is probably a nicer way to get at the information
without having to decipher such hacks in qemu as client. ;)

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20201027050556.269064-11-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
This commit is contained in:
Eric Blake 2020-10-27 00:05:55 -05:00
parent 71719cd57f
commit dbc7b01492
9 changed files with 151 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
block/nbd.c
View File

@ -135,6 +135,7 @@ typedef struct BDRVNBDState {
QCryptoTLSCreds *tlscreds;
const char *hostname;
char *x_dirty_bitmap;
bool alloc_depth;
bool wait_connect;
NBDConnectThread *connect_thread;
@ -961,6 +962,16 @@ static int nbd_parse_blockstatus_payload(BDRVNBDState *s,
trace_nbd_parse_blockstatus_compliance("extent length too large");
}
/*
* HACK: if we are using x-dirty-bitmaps to access
* qemu:allocation-depth, treat all depths > 2 the same as 2,
* since nbd_client_co_block_status is only expecting the low two
* bits to be set.
*/
if (s->alloc_depth && extent->flags > 2) {
extent->flags = 2;
}
return 0;
}
@ -1795,11 +1806,16 @@ static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
s->sioc = NULL;
return ret;
}
if (s->x_dirty_bitmap && !s->info.base_allocation) {
error_setg(errp, "requested x-dirty-bitmap %s not found",
s->x_dirty_bitmap);
ret = -EINVAL;
goto fail;
if (s->x_dirty_bitmap) {
if (!s->info.base_allocation) {
error_setg(errp, "requested x-dirty-bitmap %s not found",
s->x_dirty_bitmap);
ret = -EINVAL;
goto fail;
}
if (strcmp(s->x_dirty_bitmap, "qemu:allocation-depth") == 0) {
s->alloc_depth = true;
}
}
if (s->info.flags & NBD_FLAG_READ_ONLY) {
ret = bdrv_apply_auto_read_only(bs, "NBD export is read-only", errp);

8
docs/tools/qemu-nbd.rst
View File

@ -72,10 +72,16 @@ driver options if ``--image-opts`` is specified.
Export the disk as read-only.
.. option:: -A, --allocation-depth
Expose allocation depth information via the
``qemu:allocation-depth`` metadata context accessible through
NBD_OPT_SET_META_CONTEXT.
.. option:: -B, --bitmap=NAME
If *filename* has a qcow2 persistent bitmap *NAME*, expose
that bitmap via the ``qemu:dirty-bitmap:NAME`` context
that bitmap via the ``qemu:dirty-bitmap:NAME`` metadata context
accessible through NBD_OPT_SET_META_CONTEXT.
.. option:: -s, --snapshot

2
nbd/server.c
View File

@ -1641,6 +1641,8 @@ static int nbd_export_create(BlockExport *blk_exp, BlockExportOptions *exp_args,
bdrv_dirty_bitmap_set_busy(exp->export_bitmaps[i], true);
}
exp->allocation_depth = arg->allocation_depth;
blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
QTAILQ_INSERT_TAIL(&exports, exp, next);

7
qapi/block-core.json
View File

@ -3905,9 +3905,12 @@
#
# @tls-creds: TLS credentials ID
#
# @x-dirty-bitmap: A "qemu:dirty-bitmap:NAME" string to query in place of
# @x-dirty-bitmap: A metadata context name such as "qemu:dirty-bitmap:NAME"
# or "qemu:allocation-depth" to query in place of the
# traditional "base:allocation" block status (see
# NBD_OPT_LIST_META_CONTEXT in the NBD protocol) (since 3.0)
# NBD_OPT_LIST_META_CONTEXT in the NBD protocol; and
# yes, naming this option x-context would have made
# more sense) (since 3.0)
#
# @reconnect-delay: On an unexpected disconnect, the nbd client tries to
# connect again until succeeding or encountering a serious

7
qapi/block-export.json
View File

@ -90,11 +90,16 @@
# the metadata context name "qemu:dirty-bitmap:BITMAP" to inspect
# each bitmap.
#
# @allocation-depth: Also export the allocation depth map for @device, so
# the NBD client can use NBD_OPT_SET_META_CONTEXT with
# the metadata context name "qemu:allocation-depth" to
# inspect allocation details. (since 5.2)
#
# Since: 5.2
##
{ 'struct': 'BlockExportOptionsNbd',
'base': 'BlockExportOptionsNbdBase',
'data': { '*bitmaps': ['str'] } }
'data': { '*bitmaps': ['str'], '*allocation-depth': 'bool' } }
##
# @BlockExportOptionsVhostUserBlk:

12
qemu-nbd.c
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@ -100,6 +100,7 @@ static void usage(const char *name)
"\n"
"Exposing part of the image:\n"
" -o, --offset=OFFSET offset into the image\n"
" -A, --allocation-depth expose the allocation depth\n"
" -B, --bitmap=NAME expose a persistent dirty bitmap\n"
"\n"
"General purpose options:\n"
@ -524,7 +525,7 @@ int main(int argc, char **argv)
char *device = NULL;
QemuOpts *sn_opts = NULL;
const char *sn_id_or_name = NULL;
const char *sopt = "hVb:o:p:rsnc:dvk:e:f:tl:x:T:D:B:L";
const char *sopt = "hVb:o:p:rsnc:dvk:e:f:tl:x:T:D:AB:L";
struct option lopt[] = {
{ "help", no_argument, NULL, 'h' },
{ "version", no_argument, NULL, 'V' },
@ -533,6 +534,7 @@ int main(int argc, char **argv)
{ "socket", required_argument, NULL, 'k' },
{ "offset", required_argument, NULL, 'o' },
{ "read-only", no_argument, NULL, 'r' },
{ "allocation-depth", no_argument, NULL, 'A' },
{ "bitmap", required_argument, NULL, 'B' },
{ "connect", required_argument, NULL, 'c' },
{ "disconnect", no_argument, NULL, 'd' },
@ -575,6 +577,7 @@ int main(int argc, char **argv)
const char *export_name = NULL; /* defaults to "" later for server mode */
const char *export_description = NULL;
strList *bitmaps = NULL;
bool alloc_depth = false;
const char *tlscredsid = NULL;
bool imageOpts = false;
bool writethrough = true;
@ -689,6 +692,9 @@ int main(int argc, char **argv)
readonly = true;
flags &= ~BDRV_O_RDWR;
break;
case 'A':
alloc_depth = true;
break;
case 'B':
QAPI_LIST_PREPEND(bitmaps, g_strdup(optarg));
break;
@ -787,7 +793,7 @@ int main(int argc, char **argv)
}
if (export_name || export_description || dev_offset ||
device || disconnect || fmt || sn_id_or_name || bitmaps ||
seen_aio || seen_discard || seen_cache) {
alloc_depth || seen_aio || seen_discard || seen_cache) {
error_report("List mode is incompatible with per-device settings");
exit(EXIT_FAILURE);
}
@ -1073,6 +1079,8 @@ int main(int argc, char **argv)
.description = g_strdup(export_description),
.has_bitmaps = !!bitmaps,
.bitmaps = bitmaps,
.has_allocation_depth = alloc_depth,
.allocation_depth = alloc_depth,
},
};
blk_exp_add(export_opts, &error_fatal);

77
tests/qemu-iotests/309 Executable file
View File

@ -0,0 +1,77 @@
#!/usr/bin/env bash
#
# Test qemu-nbd -A
#
# Copyright (C) 2018-2020 Red Hat, Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
seq="$(basename $0)"
echo "QA output created by $seq"
status=1 # failure is the default!
_cleanup()
{
_cleanup_test_img
nbd_server_stop
}
trap "_cleanup; exit \$status" 0 1 2 3 15
# get standard environment, filters and checks
. ./common.rc
. ./common.filter
. ./common.nbd
_supported_fmt qcow2
_supported_proto file
_supported_os Linux
_require_command QEMU_NBD
echo
echo "=== Initial image setup ==="
echo
TEST_IMG="$TEST_IMG.base" _make_test_img 4M
$QEMU_IO -c 'w 0 2M' -f $IMGFMT "$TEST_IMG.base" | _filter_qemu_io
_make_test_img -b "$TEST_IMG.base" -F $IMGFMT 4M
$QEMU_IO -c 'w 1M 2M' -f $IMGFMT "$TEST_IMG" | _filter_qemu_io
echo
echo "=== Check allocation over NBD ==="
echo
$QEMU_IMG map --output=json -f qcow2 "$TEST_IMG"
IMG="driver=nbd,server.type=unix,server.path=$nbd_unix_socket"
nbd_server_start_unix_socket -r -f qcow2 -A "$TEST_IMG"
# Normal -f raw NBD block status loses access to allocation information
$QEMU_IMG map --output=json --image-opts \
"$IMG" | _filter_qemu_img_map
# But when we use -A, coupled with x-dirty-bitmap in the client for feeding
# 2-bit block status from an alternative NBD metadata context (note that
# the client code for x-dirty-bitmap intentionally collapses all depths
# beyond 2 into a single value), we can determine:
# unallocated (depth 0) => "zero":false, "data":true
# local (depth 1) => "zero":false, "data":false
# backing (depth 2+) => "zero":true, "data":true
$QEMU_IMG map --output=json --image-opts \
"$IMG,x-dirty-bitmap=qemu:allocation-depth" | _filter_qemu_img_map
# More accurate results can be obtained by other NBD clients such as
# libnbd, but this test works without such external dependencies.
# success, all done
echo '*** done'
rm -f $seq.full
status=0

22
tests/qemu-iotests/309.out Normal file
View File

@ -0,0 +1,22 @@
QA output created by 309
=== Initial image setup ===
Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=4194304
wrote 2097152/2097152 bytes at offset 0
2 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4194304 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
wrote 2097152/2097152 bytes at offset 1048576
2 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
=== Check allocation over NBD ===
[{ "start": 0, "length": 1048576, "depth": 1, "zero": false, "data": true, "offset": 327680},
{ "start": 1048576, "length": 2097152, "depth": 0, "zero": false, "data": true, "offset": 327680},
{ "start": 3145728, "length": 1048576, "depth": 1, "zero": true, "data": false}]
[{ "start": 0, "length": 3145728, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
{ "start": 3145728, "length": 1048576, "depth": 0, "zero": true, "data": false, "offset": OFFSET}]
[{ "start": 0, "length": 1048576, "depth": 0, "zero": true, "data": true, "offset": OFFSET},
{ "start": 1048576, "length": 2097152, "depth": 0, "zero": false, "data": false},
{ "start": 3145728, "length": 1048576, "depth": 0, "zero": false, "data": true, "offset": OFFSET}]
*** done

1
tests/qemu-iotests/group
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@ -315,3 +315,4 @@
304 rw quick
305 rw quick
307 rw quick export
309 rw auto quick