diff mbox series

[3/3] nbd: Add 'qemu-nbd -A' to expose allocation depth

Message ID 20200925203249.155705-4-eblake@redhat.com
State New
Headers show
Series Exposing backing-chain allocation over NBD | expand

Commit Message

Eric Blake Sept. 25, 2020, 8:32 p.m. UTC
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 nbd-server-add.

qemu as client can be hacked into viewing this new context by using
the now-misnamed x-dirty-bitmap option when creating an NBD blockdev;
although it is worth noting the decoding of how such context
information will appear in 'qemu-img map --output=json':

NBD_STATE_DEPTH_UNALLOC => "zero":false, "data":true
NBD_STATE_DEPTH_LOCAL => "zero":false, "data":false
NBD_STATE_DEPTH_BACKING => "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>
---
 docs/tools/qemu-nbd.rst    |  6 ++++
 qapi/block-core.json       |  7 ++--
 include/block/nbd.h        |  7 ++--
 blockdev-nbd.c             |  3 +-
 nbd/server.c               |  8 +++--
 qemu-nbd.c                 | 16 ++++++---
 tests/qemu-iotests/309     | 73 ++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/309.out | 22 ++++++++++++
 tests/qemu-iotests/group   |  1 +
 9 files changed, 129 insertions(+), 14 deletions(-)
 create mode 100755 tests/qemu-iotests/309
 create mode 100644 tests/qemu-iotests/309.out

Comments

Richard W.M. Jones Sept. 26, 2020, 7:34 a.m. UTC | #1
On Fri, Sep 25, 2020 at 03:32:49PM -0500, Eric Blake wrote:
> 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 nbd-server-add.

> 

> qemu as client can be hacked into viewing this new context by using

> the now-misnamed x-dirty-bitmap option when creating an NBD blockdev;

> although it is worth noting the decoding of how such context

> information will appear in 'qemu-img map --output=json':

> 

> NBD_STATE_DEPTH_UNALLOC => "zero":false, "data":true

> NBD_STATE_DEPTH_LOCAL => "zero":false, "data":false

> NBD_STATE_DEPTH_BACKING => "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. ;)


I've been meaning to add extents information to nbdinfo, or
perhaps a new tool ("nbdmap").

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-builder quickly builds VMs from scratch
http://libguestfs.org/virt-builder.1.html
Vladimir Sementsov-Ogievskiy Sept. 26, 2020, 1:32 p.m. UTC | #2
25.09.2020 23:32, Eric Blake wrote:
> 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 nbd-server-add.
> 
> qemu as client can be hacked into viewing this new context by using
> the now-misnamed x-dirty-bitmap option when creating an NBD blockdev;

may be rename it to x-block-status ?

> although it is worth noting the decoding of how such context
> information will appear in 'qemu-img map --output=json':
> 
> NBD_STATE_DEPTH_UNALLOC => "zero":false, "data":true
> NBD_STATE_DEPTH_LOCAL => "zero":false, "data":false
> NBD_STATE_DEPTH_BACKING => "zero":true, "data":true

It wouldn't be so simple if we decide to export exact depth number..
Eric Blake Sept. 28, 2020, 2:35 p.m. UTC | #3
On 9/26/20 8:32 AM, Vladimir Sementsov-Ogievskiy wrote:
> 25.09.2020 23:32, Eric Blake wrote:
>> 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 nbd-server-add.
>>
>> qemu as client can be hacked into viewing this new context by using
>> the now-misnamed x-dirty-bitmap option when creating an NBD blockdev;
> 
> may be rename it to x-block-status ?

I thought about it.  We don't promise any back-compat with x- prefix, 
but at the same time, if there's not a strong reason to change it, 
scripts written against older qemu will not break as long as we still 
have the hack.

> 
>> although it is worth noting the decoding of how such context
>> information will appear in 'qemu-img map --output=json':
>>
>> NBD_STATE_DEPTH_UNALLOC => "zero":false, "data":true
>> NBD_STATE_DEPTH_LOCAL => "zero":false, "data":false
>> NBD_STATE_DEPTH_BACKING => "zero":true, "data":true
> 
> It wouldn't be so simple if we decide to export exact depth number..

It's still simple to do tri-state results if we separate the exact depth 
number to bits 31-4, leaving bits 1-0 as the tri-state summary...
diff mbox series

Patch

diff --git a/docs/tools/qemu-nbd.rst b/docs/tools/qemu-nbd.rst
index 667861cb22e9..0e545a97cfa3 100644
--- a/docs/tools/qemu-nbd.rst
+++ b/docs/tools/qemu-nbd.rst
@@ -72,6 +72,12 @@  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`` context accessible through
+  NBD_OPT_SET_META_CONTEXT.
+
 .. option:: -B, --bitmap=NAME

   If *filename* has a qcow2 persistent bitmap *NAME*, expose
diff --git a/qapi/block-core.json b/qapi/block-core.json
index b3ec30a83cd7..84f7a7a34dc1 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -3874,9 +3874,12 @@ 
 #
 # @tls-creds: TLS credentials ID
 #
-# @x-dirty-bitmap: A "qemu:dirty-bitmap:NAME" string to query in place of
+# @x-dirty-bitmap: A metacontext 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
diff --git a/include/block/nbd.h b/include/block/nbd.h
index 71a2623f7842..f660e0274ce3 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -336,9 +336,10 @@  typedef struct NBDClient NBDClient;

 NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
                           uint64_t size, const char *name, const char *desc,
-                          const char *bitmap, bool readonly, bool shared,
-                          void (*close)(NBDExport *), bool writethrough,
-                          BlockBackend *on_eject_blk, Error **errp);
+                          bool alloc_depth, const char *bitmap, bool readonly,
+                          bool shared, void (*close)(NBDExport *),
+                          bool writethrough, BlockBackend *on_eject_blk,
+                          Error **errp);
 void nbd_export_close(NBDExport *exp);
 void nbd_export_remove(NBDExport *exp, NbdServerRemoveMode mode, Error **errp);
 void nbd_export_get(NBDExport *exp);
diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index 1a95d89f0096..562ea3751b85 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -203,7 +203,8 @@  void qmp_nbd_server_add(BlockExportNbd *arg, Error **errp)
         arg->writable = false;
     }

-    exp = nbd_export_new(bs, 0, len, arg->name, arg->description, arg->bitmap,
+    exp = nbd_export_new(bs, 0, len, arg->name, arg->description,
+                         arg->alloc, arg->bitmap,
                          !arg->writable, !arg->writable,
                          NULL, false, on_eject_blk, errp);
     if (!exp) {
diff --git a/nbd/server.c b/nbd/server.c
index 02d5fb375b24..f5e0e115b703 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1450,9 +1450,10 @@  static void nbd_eject_notifier(Notifier *n, void *data)

 NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
                           uint64_t size, const char *name, const char *desc,
-                          const char *bitmap, bool readonly, bool shared,
-                          void (*close)(NBDExport *), bool writethrough,
-                          BlockBackend *on_eject_blk, Error **errp)
+                          bool alloc_depth, const char *bitmap, bool readonly,
+                          bool shared, void (*close)(NBDExport *),
+                          bool writethrough, BlockBackend *on_eject_blk,
+                          Error **errp)
 {
     AioContext *ctx;
     BlockBackend *blk;
@@ -1545,6 +1546,7 @@  NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
         assert(strlen(exp->export_bitmap_context) < NBD_MAX_STRING_SIZE);
     }

+    exp->alloc_context = alloc_depth;
     exp->close = close;
     exp->ctx = ctx;
     blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
diff --git a/qemu-nbd.c b/qemu-nbd.c
index e39d3b23c121..5aeef60b0a5a 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -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"
@@ -527,7 +528,7 @@  int main(int argc, char **argv)
     int64_t fd_size;
     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' },
@@ -536,6 +537,7 @@  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' },
@@ -577,6 +579,7 @@  int main(int argc, char **argv)
     QDict *options = NULL;
     const char *export_name = NULL; /* defaults to "" later for server mode */
     const char *export_description = NULL;
+    bool alloc_depth = false;
     const char *bitmap = NULL;
     const char *tlscredsid = NULL;
     bool imageOpts = false;
@@ -700,6 +703,9 @@  int main(int argc, char **argv)
             readonly = true;
             flags &= ~BDRV_O_RDWR;
             break;
+        case 'A':
+            alloc_depth = true;
+            break;
         case 'B':
             bitmap = optarg;
             break;
@@ -797,8 +803,8 @@  int main(int argc, char **argv)
             exit(EXIT_FAILURE);
         }
         if (export_name || export_description || dev_offset ||
-            device || disconnect || fmt || sn_id_or_name || bitmap ||
-            seen_aio || seen_discard || seen_cache) {
+            device || disconnect || fmt || sn_id_or_name || alloc_depth ||
+            bitmap || seen_aio || seen_discard || seen_cache) {
             error_report("List mode is incompatible with per-device settings");
             exit(EXIT_FAILURE);
         }
@@ -1069,8 +1075,8 @@  int main(int argc, char **argv)
     fd_size -= dev_offset;

     export = nbd_export_new(bs, dev_offset, fd_size, export_name,
-                            export_description, bitmap, readonly, shared > 1,
-                            nbd_export_closed, writethrough, NULL,
+                            export_description, alloc_depth, bitmap, readonly,
+                            shared > 1, nbd_export_closed, writethrough, NULL,
                             &error_fatal);

     if (device) {
diff --git a/tests/qemu-iotests/309 b/tests/qemu-iotests/309
new file mode 100755
index 000000000000..fda3be9abbd2
--- /dev/null
+++ b/tests/qemu-iotests/309
@@ -0,0 +1,73 @@ 
+#!/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
+
+# Normal -f raw NBD block status loses access to allocation information
+$QEMU_IMG map --output=json -f qcow2 "$TEST_IMG"
+IMG="driver=nbd,server.type=unix,server.path=$nbd_unix_socket"
+nbd_server_start_unix_socket -r -f qcow2 -A "$TEST_IMG"
+$QEMU_IMG map --output=json --image-opts \
+    "$IMG" | _filter_qemu_img_map
+# But since we used -A, and use x-dirty-bitmap as a hack for reading bitmaps,
+# we can reconstruct it, by abusing block status to report:
+#    NBD_STATE_DEPTH_UNALLOC => "zero":false, "data":true
+#    NBD_STATE_DEPTH_LOCAL => "zero":false, "data":false
+#    NBD_STATE_DEPTH_BACKING => "zero":true, "data":true
+$QEMU_IMG map --output=json --image-opts \
+    "$IMG,x-dirty-bitmap=qemu:allocation-depth" | _filter_qemu_img_map
+
+# success, all done
+echo '*** done'
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/309.out b/tests/qemu-iotests/309.out
new file mode 100644
index 000000000000..db75bb6b0df9
--- /dev/null
+++ b/tests/qemu-iotests/309.out
@@ -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
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index ff59cfd2d4c4..57182e4b3169 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -314,3 +314,4 @@ 
 303 rw quick
 304 rw quick
 305 rw quick
+309 rw auto quick