qemu/tests/qemu-iotests/223

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#!/usr/bin/env bash
#
# Test reading dirty bitmap over NBD
#
# Copyright (C) 2018-2019 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 $seq"
status=1 # failure is the default!
_cleanup()
{
nbd_server_stop
_cleanup_test_img
_cleanup_qemu
rm -f "$TEST_DIR/nbd"
}
trap "_cleanup; exit \$status" 0 1 2 3 15
# get standard environment, filters and checks
. ./common.rc
. ./common.filter
. ./common.qemu
. ./common.nbd
_supported_fmt qcow2
_supported_proto file # uses NBD as well
_supported_os Linux
# Persistent dirty bitmaps require compat=1.1
_unsupported_imgopts 'compat=0.10'
do_run_qemu()
{
echo Testing: "$@"
$QEMU -nographic -qmp stdio -serial none "$@"
echo
}
run_qemu()
{
do_run_qemu "$@" 2>&1 | _filter_testdir | _filter_qmp \
| _filter_qemu | _filter_imgfmt \
| _filter_actual_image_size
}
echo
echo "=== Create partially sparse image, then add dirty bitmaps ==="
echo
# Two bitmaps, to contrast granularity issues
nbd: Only require disabled bitmap for read-only exports Our initial implementation of x-nbd-server-add-bitmap put in a restriction because of incremental backups: in that usage, we are exporting one qcow2 file (the temporary overlay target of a blockdev-backup sync:none job) and a dirty bitmap owned by a second qcow2 file (the source of the blockdev-backup, which is the backing file of the temporary). While both qcow2 files are still writable (the target in order to capture copy-on-write of old contents, and the source in order to track live guest writes in the meantime), the NBD client expects to see constant data, including the dirty bitmap. An enabled bitmap in the source would be modified by guest writes, which is at odds with the NBD export being a read-only constant view, hence the initial code choice of enforcing a disabled bitmap (the intent is that the exposed bitmap was disabled in the same transaction that started the blockdev-backup job, although we don't want to track enough state to actually enforce that). However, consider the case of a bitmap contained in a read-only node (including when the bitmap is found in a backing layer of the active image). Because the node can't be modified, the bitmap won't change due to writes, regardless of whether it is still enabled. Forbidding the export unless the bitmap is disabled is awkward, paritcularly since we can't change the bitmap to be disabled (because the node is read-only). Alternatively, consider the case of live storage migration, where management directs the destination to create a writable NBD server, then performs a drive-mirror from the source to the target, prior to doing the rest of the live migration. Since storage migration can be time-consuming, it may be wise to let the destination include a dirty bitmap to track which portions it has already received, where even if the migration is interrupted and restarted, the source can query the destination block status in order to potentially minimize re-sending data that has not changed in the meantime on a second attempt. Such code has not been written, and might not be trivial (after all, a cluster being marked dirty in the bitmap does not necessarily guarantee it has the desired contents), but it makes sense that letting an active dirty bitmap be exposed and changing alongside writes may prove useful in the future. Solve both issues by gating the restriction against a disabled bitmap to only happen when the caller has requested a read-only export, and where the BDS that owns the bitmap (whether or not it is the BDS handed to nbd_export_new() or from its backing chain) is still writable. We could drop the check altogether (if management apps are prepared to deal with a changing bitmap even on a read-only image), but for now keeping a check for the read-only case still stands a chance of preventing management errors. Update iotest 223 to show the looser behavior by leaving a bitmap enabled the whole run; note that we have to tear down and re-export a node when handling an error. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <20190111194720.15671-4-eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
2019-01-11 22:47:15 +03:00
# Also note that b will be disabled, while b2 is left enabled, to
# check for read-only interactions
_make_test_img -o cluster_size=4k 4M
$QEMU_IO -c 'w -P 0x11 1M 2M' "$TEST_IMG" | _filter_qemu_io
run_qemu <<EOF
{ "execute": "qmp_capabilities" }
{ "execute": "blockdev-add",
"arguments": {
"driver": "$IMGFMT",
"node-name": "n",
"file": {
"driver": "file",
"filename": "$TEST_IMG"
}
}
}
{ "execute": "block-dirty-bitmap-add",
"arguments": {
"node": "n",
"name": "b",
"persistent": true,
"granularity": 65536
}
}
{ "execute": "block-dirty-bitmap-add",
"arguments": {
"node": "n",
"name": "b2",
"persistent": true,
"granularity": 512
}
}
{ "execute": "quit" }
EOF
echo
echo "=== Write part of the file under active bitmap ==="
echo
$QEMU_IO -c 'w -P 0x22 512 512' -c 'w -P 0x33 2M 2M' "$TEST_IMG" \
| _filter_qemu_io
echo
echo "=== End dirty bitmaps, and start serving image over NBD ==="
echo
_launch_qemu -object iothread,id=io0 2> >(_filter_nbd)
# Intentionally provoke some errors as well, to check error handling
silent=
_send_qemu_cmd $QEMU_HANDLE '{"execute":"qmp_capabilities"}' "return"
_send_qemu_cmd $QEMU_HANDLE '{"execute":"blockdev-add",
"arguments":{"driver":"qcow2", "node-name":"n",
"file":{"driver":"file", "filename":"'"$TEST_IMG"'"}}}' "return"
_send_qemu_cmd $QEMU_HANDLE '{"execute":"x-blockdev-set-iothread",
"arguments":{"node-name":"n", "iothread":"io0"}}' "return"
_send_qemu_cmd $QEMU_HANDLE '{"execute":"block-dirty-bitmap-disable",
"arguments":{"node":"n", "name":"b"}}' "return"
_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-add",
"arguments":{"device":"n"}}' "error" # Attempt add without server
_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-start",
"arguments":{"addr":{"type":"unix",
"data":{"path":"'"$TEST_DIR/nbd"'"}}}}' "return"
_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-start",
"arguments":{"addr":{"type":"unix",
"data":{"path":"'"$TEST_DIR/nbd"1'"}}}}' "error" # Attempt second server
$QEMU_NBD_PROG -L -k "$TEST_DIR/nbd"
_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-add",
nbd: Allow bitmap export during QMP nbd-server-add With the experimental x-nbd-server-add-bitmap command, there was a window of time where an NBD client could see the export but not the associated dirty bitmap, which can cause a client that planned on using the dirty bitmap to be forced to treat the entire image as dirty as a safety fallback. Furthermore, if the QMP client successfully exports a disk but then fails to add the bitmap, it has to take on the burden of removing the export. Since we don't allow changing the exposed dirty bitmap (whether to a different bitmap, or removing advertisement of the bitmap), it is nicer to make the bitmap tied to the export at the time the export is created, with automatic failure to export if the bitmap is not available. The experimental command included an optional 'bitmap-export-name' field for remapping the name exposed over NBD to be different from the bitmap name stored on disk. However, my libvirt demo code for implementing differential backups on top of persistent bitmaps did not need to take advantage of that feature (it is instead possible to create a new temporary bitmap with the desired name, use block-dirty-bitmap-merge to merge one or more persistent bitmaps into the temporary, then associate the temporary with the NBD export, if control is needed over the exported bitmap name). Hence, I'm not copying that part of the experiment over to the stable addition. For more details on the libvirt demo, see https://www.redhat.com/archives/libvir-list/2018-October/msg01254.html, https://kvmforum2018.sched.com/event/FzuB/facilitating-incremental-backup-eric-blake-red-hat This patch focuses on the user interface, and reduces (but does not completely eliminate) the window where an NBD client can see the export but not the dirty bitmap, with less work to clean up after errors. Later patches will add further cleanups now that this interface is declared stable via a single QMP command, including removing the race window. Update test 223 to use the new interface. Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <20190111194720.15671-6-eblake@redhat.com>
2019-01-11 22:47:17 +03:00
"arguments":{"device":"n", "bitmap":"b"}}' "return"
_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-add",
"arguments":{"device":"nosuch"}}' "error" # Attempt to export missing node
_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-add",
"arguments":{"device":"n"}}' "error" # Attempt to export same name twice
_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-add",
nbd: Allow bitmap export during QMP nbd-server-add With the experimental x-nbd-server-add-bitmap command, there was a window of time where an NBD client could see the export but not the associated dirty bitmap, which can cause a client that planned on using the dirty bitmap to be forced to treat the entire image as dirty as a safety fallback. Furthermore, if the QMP client successfully exports a disk but then fails to add the bitmap, it has to take on the burden of removing the export. Since we don't allow changing the exposed dirty bitmap (whether to a different bitmap, or removing advertisement of the bitmap), it is nicer to make the bitmap tied to the export at the time the export is created, with automatic failure to export if the bitmap is not available. The experimental command included an optional 'bitmap-export-name' field for remapping the name exposed over NBD to be different from the bitmap name stored on disk. However, my libvirt demo code for implementing differential backups on top of persistent bitmaps did not need to take advantage of that feature (it is instead possible to create a new temporary bitmap with the desired name, use block-dirty-bitmap-merge to merge one or more persistent bitmaps into the temporary, then associate the temporary with the NBD export, if control is needed over the exported bitmap name). Hence, I'm not copying that part of the experiment over to the stable addition. For more details on the libvirt demo, see https://www.redhat.com/archives/libvir-list/2018-October/msg01254.html, https://kvmforum2018.sched.com/event/FzuB/facilitating-incremental-backup-eric-blake-red-hat This patch focuses on the user interface, and reduces (but does not completely eliminate) the window where an NBD client can see the export but not the dirty bitmap, with less work to clean up after errors. Later patches will add further cleanups now that this interface is declared stable via a single QMP command, including removing the race window. Update test 223 to use the new interface. Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <20190111194720.15671-6-eblake@redhat.com>
2019-01-11 22:47:17 +03:00
"arguments":{"device":"n", "name":"n2",
"bitmap":"b2"}}' "error" # enabled vs. read-only
nbd: Only require disabled bitmap for read-only exports Our initial implementation of x-nbd-server-add-bitmap put in a restriction because of incremental backups: in that usage, we are exporting one qcow2 file (the temporary overlay target of a blockdev-backup sync:none job) and a dirty bitmap owned by a second qcow2 file (the source of the blockdev-backup, which is the backing file of the temporary). While both qcow2 files are still writable (the target in order to capture copy-on-write of old contents, and the source in order to track live guest writes in the meantime), the NBD client expects to see constant data, including the dirty bitmap. An enabled bitmap in the source would be modified by guest writes, which is at odds with the NBD export being a read-only constant view, hence the initial code choice of enforcing a disabled bitmap (the intent is that the exposed bitmap was disabled in the same transaction that started the blockdev-backup job, although we don't want to track enough state to actually enforce that). However, consider the case of a bitmap contained in a read-only node (including when the bitmap is found in a backing layer of the active image). Because the node can't be modified, the bitmap won't change due to writes, regardless of whether it is still enabled. Forbidding the export unless the bitmap is disabled is awkward, paritcularly since we can't change the bitmap to be disabled (because the node is read-only). Alternatively, consider the case of live storage migration, where management directs the destination to create a writable NBD server, then performs a drive-mirror from the source to the target, prior to doing the rest of the live migration. Since storage migration can be time-consuming, it may be wise to let the destination include a dirty bitmap to track which portions it has already received, where even if the migration is interrupted and restarted, the source can query the destination block status in order to potentially minimize re-sending data that has not changed in the meantime on a second attempt. Such code has not been written, and might not be trivial (after all, a cluster being marked dirty in the bitmap does not necessarily guarantee it has the desired contents), but it makes sense that letting an active dirty bitmap be exposed and changing alongside writes may prove useful in the future. Solve both issues by gating the restriction against a disabled bitmap to only happen when the caller has requested a read-only export, and where the BDS that owns the bitmap (whether or not it is the BDS handed to nbd_export_new() or from its backing chain) is still writable. We could drop the check altogether (if management apps are prepared to deal with a changing bitmap even on a read-only image), but for now keeping a check for the read-only case still stands a chance of preventing management errors. Update iotest 223 to show the looser behavior by leaving a bitmap enabled the whole run; note that we have to tear down and re-export a node when handling an error. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <20190111194720.15671-4-eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
2019-01-11 22:47:15 +03:00
_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-add",
nbd: Allow bitmap export during QMP nbd-server-add With the experimental x-nbd-server-add-bitmap command, there was a window of time where an NBD client could see the export but not the associated dirty bitmap, which can cause a client that planned on using the dirty bitmap to be forced to treat the entire image as dirty as a safety fallback. Furthermore, if the QMP client successfully exports a disk but then fails to add the bitmap, it has to take on the burden of removing the export. Since we don't allow changing the exposed dirty bitmap (whether to a different bitmap, or removing advertisement of the bitmap), it is nicer to make the bitmap tied to the export at the time the export is created, with automatic failure to export if the bitmap is not available. The experimental command included an optional 'bitmap-export-name' field for remapping the name exposed over NBD to be different from the bitmap name stored on disk. However, my libvirt demo code for implementing differential backups on top of persistent bitmaps did not need to take advantage of that feature (it is instead possible to create a new temporary bitmap with the desired name, use block-dirty-bitmap-merge to merge one or more persistent bitmaps into the temporary, then associate the temporary with the NBD export, if control is needed over the exported bitmap name). Hence, I'm not copying that part of the experiment over to the stable addition. For more details on the libvirt demo, see https://www.redhat.com/archives/libvir-list/2018-October/msg01254.html, https://kvmforum2018.sched.com/event/FzuB/facilitating-incremental-backup-eric-blake-red-hat This patch focuses on the user interface, and reduces (but does not completely eliminate) the window where an NBD client can see the export but not the dirty bitmap, with less work to clean up after errors. Later patches will add further cleanups now that this interface is declared stable via a single QMP command, including removing the race window. Update test 223 to use the new interface. Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <20190111194720.15671-6-eblake@redhat.com>
2019-01-11 22:47:17 +03:00
"arguments":{"device":"n", "name":"n2",
"bitmap":"b3"}}' "error" # Missing bitmap
_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-add",
"arguments":{"device":"n", "name":"n2", "writable":true,
"bitmap":"b2"}}' "return"
$QEMU_NBD_PROG -L -k "$TEST_DIR/nbd"
echo
echo "=== Contrast normal status to large granularity dirty-bitmap ==="
echo
QEMU_IO_OPTIONS=$QEMU_IO_OPTIONS_NO_FMT
IMG="driver=nbd,export=n,server.type=unix,server.path=$TEST_DIR/nbd"
$QEMU_IO -r -c 'r -P 0x22 512 512' -c 'r -P 0 512k 512k' -c 'r -P 0x11 1m 1m' \
-c 'r -P 0x33 2m 2m' --image-opts "$IMG" | _filter_qemu_io
$QEMU_IMG map --output=json --image-opts \
"$IMG" | _filter_qemu_img_map
$QEMU_IMG map --output=json --image-opts \
"$IMG,x-dirty-bitmap=qemu:dirty-bitmap:b" | _filter_qemu_img_map
echo
echo "=== Contrast to small granularity dirty-bitmap ==="
echo
IMG="driver=nbd,export=n2,server.type=unix,server.path=$TEST_DIR/nbd"
$QEMU_IMG map --output=json --image-opts \
"$IMG,x-dirty-bitmap=qemu:dirty-bitmap:b2" | _filter_qemu_img_map
echo
echo "=== End qemu NBD server ==="
echo
_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-remove",
"arguments":{"name":"n"}}' "return"
_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-remove",
"arguments":{"name":"n2"}}' "return"
_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-remove",
"arguments":{"name":"n2"}}' "error" # Attempt duplicate clean
_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-stop"}' "return"
_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-stop"}' "error" # Again
_send_qemu_cmd $QEMU_HANDLE '{"execute":"quit"}' "return"
wait=yes _cleanup_qemu
echo
echo "=== Use qemu-nbd as server ==="
echo
nbd_server_start_unix_socket -r -f $IMGFMT -B b "$TEST_IMG"
IMG="driver=nbd,server.type=unix,server.path=$nbd_unix_socket"
$QEMU_IMG map --output=json --image-opts \
"$IMG,x-dirty-bitmap=qemu:dirty-bitmap:b" | _filter_qemu_img_map
nbd_server_start_unix_socket -f $IMGFMT -B b2 "$TEST_IMG"
IMG="driver=nbd,server.type=unix,server.path=$nbd_unix_socket"
$QEMU_IMG map --output=json --image-opts \
"$IMG,x-dirty-bitmap=qemu:dirty-bitmap:b2" | _filter_qemu_img_map
# success, all done
echo '*** done'
rm -f $seq.full
status=0