[PULL 0/9] nbd patches for -rc2, 2020-07-28

[PULL 0/9] nbd patches for -rc2, 2020-07-28

[Eric Blake]

The following changes since commit 1b242c3b1ec7c6011901b4f3b4b0876e31746afb:

  Merge remote-tracking branch 'remotes/mcayland/tags/qemu-openbios-20200727' into staging (2020-07-28 13:46:31 +0100)

are available in the Git repository at:

  https://repo.or.cz/qemu/ericb.git tags/pull-nbd-2020-07-28

for you to fetch changes up to 12c75e20a269ac917f4a76936d7142264e522233:

  block/nbd: nbd_co_reconnect_loop(): don't sleep if drained (2020-07-28 09:54:43 -0500)

Sorry this is down to the wire, Nir's patches were a pretty recent
discovery, but still counts as a bug fix worthy of having in -rc2.

----------------------------------------------------------------
nbd patches for 2020-07-28

- fix NBD handling of trim/zero requests larger than 2G
- allow no-op resizes on NBD (in turn fixing qemu-img convert -c into NBD)
- several deadlock fixes when using NBD reconnect

----------------------------------------------------------------
Eric Blake (1):
      nbd: Fix large trim/zero requests

Nir Soffer (4):
      block: nbd: Fix convert qcow2 compressed to nbd
      iotests: Make qemu_nbd_popen() a contextmanager
      iotests: Add more qemu_img helpers
      iotests: Test convert to qcow2 compressed to NBD

Vladimir Sementsov-Ogievskiy (4):
      block/nbd: split nbd_establish_connection out of nbd_client_connect
      block/nbd: allow drain during reconnect attempt
      block/nbd: on shutdown terminate connection attempt
      block/nbd: nbd_co_reconnect_loop(): don't sleep if drained

 block/nbd.c                   | 126 ++++++++++++++++++++++++++++++-----------
 nbd/server.c                  |  28 ++++++++--
 qemu-io-cmds.c                |   2 +-
 block/trace-events            |   4 +-
 tests/qemu-iotests/264        |  72 +++++++++---------------
 tests/qemu-iotests/264.out    |   2 +
 tests/qemu-iotests/302        | 127 ++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/302.out    |  31 +++++++++++
 tests/qemu-iotests/group      |   1 +
 tests/qemu-iotests/iotests.py |  34 ++++++++++-
 10 files changed, 340 insertions(+), 87 deletions(-)
 create mode 100755 tests/qemu-iotests/302
 create mode 100644 tests/qemu-iotests/302.out

-- 
2.27.0

[PULL 1/9] nbd: Fix large trim/zero requests

[Eric Blake]

Although qemu as NBD client limits requests to <2G, the NBD protocol
allows clients to send requests almost all the way up to 4G.  But
because our block layer is not yet 64-bit clean, we accidentally wrap
such requests into a negative size, and fail with EIO instead of
performing the intended operation.

The bug is visible in modern systems with something as simple as:

$ qemu-img create -f qcow2 /tmp/image.img 5G
$ sudo qemu-nbd --connect=/dev/nbd0 /tmp/image.img
$ sudo blkdiscard /dev/nbd0

or with user-space only:

$ truncate --size=3G file
$ qemu-nbd -f raw file
$ nbdsh -u nbd://localhost:10809 -c 'h.trim(3*1024*1024*1024,0)'

Although both blk_co_pdiscard and blk_pwrite_zeroes currently return 0
on success, this is also a good time to fix our code to a more robust
paradigm that treats all non-negative values as success.

Alas, our iotests do not currently make it easy to add external
dependencies on blkdiscard or nbdsh, so we have to rely on manual
testing for now.

This patch can be reverted when we later improve the overall block
layer to be 64-bit clean, but for now, a minimal fix was deemed less
risky prior to release.

CC: qemu-stable@nongnu.org
Fixes: 1f4d6d18ed
Fixes: 1c6c4bb7f0
Fixes: https://github.com/systemd/systemd/issues/16242
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200722212231.535072-1-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: rework success tests to use >=0]
---
 nbd/server.c | 28 +++++++++++++++++++++++-----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/nbd/server.c b/nbd/server.c
index 4752a6c8bc07..c5d71cff1001 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -2378,8 +2378,17 @@ static coroutine_fn int nbd_handle_request(NBDClient *client,
         if (request->flags & NBD_CMD_FLAG_FAST_ZERO) {
             flags |= BDRV_REQ_NO_FALLBACK;
         }
-        ret = blk_pwrite_zeroes(exp->blk, request->from + exp->dev_offset,
-                                request->len, flags);
+        ret = 0;
+        /* FIXME simplify this when blk_pwrite_zeroes switches to 64-bit */
+        while (ret >= 0 && request->len) {
+            int align = client->check_align ?: 1;
+            int len = MIN(request->len, QEMU_ALIGN_DOWN(BDRV_REQUEST_MAX_BYTES,
+                                                        align));
+            ret = blk_pwrite_zeroes(exp->blk, request->from + exp->dev_offset,
+                                    len, flags);
+            request->len -= len;
+            request->from += len;
+        }
         return nbd_send_generic_reply(client, request->handle, ret,
                                       "writing to file failed", errp);

@@ -2393,9 +2402,18 @@ static coroutine_fn int nbd_handle_request(NBDClient *client,
                                       "flush failed", errp);

     case NBD_CMD_TRIM:
-        ret = blk_co_pdiscard(exp->blk, request->from + exp->dev_offset,
-                              request->len);
-        if (ret == 0 && request->flags & NBD_CMD_FLAG_FUA) {
+        ret = 0;
+        /* FIXME simplify this when blk_co_pdiscard switches to 64-bit */
+        while (ret >= 0 && request->len) {
+            int align = client->check_align ?: 1;
+            int len = MIN(request->len, QEMU_ALIGN_DOWN(BDRV_REQUEST_MAX_BYTES,
+                                                        align));
+            ret = blk_co_pdiscard(exp->blk, request->from + exp->dev_offset,
+                                  len);
+            request->len -= len;
+            request->from += len;
+        }
+        if (ret >= 0 && request->flags & NBD_CMD_FLAG_FUA) {
             ret = blk_co_flush(exp->blk);
         }
         return nbd_send_generic_reply(client, request->handle, ret,
-- 
2.27.0

[PULL 2/9] block: nbd: Fix convert qcow2 compressed to nbd

[Eric Blake]

From: Nir Soffer <nirsof@gmail.com>

When converting to qcow2 compressed format, the last step is a special
zero length compressed write, ending in a call to bdrv_co_truncate(). This
call always fails for the nbd driver since it does not implement
bdrv_co_truncate().

For block devices, which have the same limits, the call succeeds since
the file driver implements bdrv_co_truncate(). If the caller asked to
truncate to the same or smaller size with exact=false, the truncate
succeeds. Implement the same logic for nbd.

Example failing without this change:

In one shell start qemu-nbd:

$ truncate -s 1g test.tar
$ qemu-nbd --socket=/tmp/nbd.sock --persistent --format=raw --offset 1536 test.tar

In another shell convert an image to qcow2 compressed via NBD:

$ echo "disk data" > disk.raw
$ truncate -s 1g disk.raw
$ qemu-img convert -f raw -O qcow2 -c disk1.raw nbd+unix:///?socket=/tmp/nbd.sock; echo $?
1

qemu-img failed, but the conversion was successful:

$ qemu-img info nbd+unix:///?socket=/tmp/nbd.sock
image: nbd+unix://?socket=/tmp/nbd.sock
file format: qcow2
virtual size: 1 GiB (1073741824 bytes)
...

$ qemu-img check nbd+unix:///?socket=/tmp/nbd.sock
No errors were found on the image.
1/16384 = 0.01% allocated, 100.00% fragmented, 100.00% compressed clusters
Image end offset: 393216

$ qemu-img compare disk.raw nbd+unix:///?socket=/tmp/nbd.sock
Images are identical.

Fixes: https://bugzilla.redhat.com/1860627
Signed-off-by: Nir Soffer <nsoffer@redhat.com>
Message-Id: <20200727215846.395443-2-nsoffer@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: typo fixes]
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c    | 30 ++++++++++++++++++++++++++++++
 qemu-io-cmds.c |  2 +-
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/block/nbd.c b/block/nbd.c
index 65a4f56924ec..8934bcb47901 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -1966,6 +1966,33 @@ static void nbd_close(BlockDriverState *bs)
     nbd_clear_bdrvstate(s);
 }

+/*
+ * NBD cannot truncate, but if the caller asks to truncate to the same size, or
+ * to a smaller size with exact=false, there is no reason to fail the
+ * operation.
+ *
+ * Preallocation mode is ignored since it does not seems useful to fail when
+ * we never change anything.
+ */
+static int coroutine_fn nbd_co_truncate(BlockDriverState *bs, int64_t offset,
+                                        bool exact, PreallocMode prealloc,
+                                        BdrvRequestFlags flags, Error **errp)
+{
+    BDRVNBDState *s = bs->opaque;
+
+    if (offset != s->info.size && exact) {
+        error_setg(errp, "Cannot resize NBD nodes");
+        return -ENOTSUP;
+    }
+
+    if (offset > s->info.size) {
+        error_setg(errp, "Cannot grow NBD nodes");
+        return -EINVAL;
+    }
+
+    return 0;
+}
+
 static int64_t nbd_getlength(BlockDriverState *bs)
 {
     BDRVNBDState *s = bs->opaque;
@@ -2045,6 +2072,7 @@ static BlockDriver bdrv_nbd = {
     .bdrv_co_flush_to_os        = nbd_co_flush,
     .bdrv_co_pdiscard           = nbd_client_co_pdiscard,
     .bdrv_refresh_limits        = nbd_refresh_limits,
+    .bdrv_co_truncate           = nbd_co_truncate,
     .bdrv_getlength             = nbd_getlength,
     .bdrv_detach_aio_context    = nbd_client_detach_aio_context,
     .bdrv_attach_aio_context    = nbd_client_attach_aio_context,
@@ -2072,6 +2100,7 @@ static BlockDriver bdrv_nbd_tcp = {
     .bdrv_co_flush_to_os        = nbd_co_flush,
     .bdrv_co_pdiscard           = nbd_client_co_pdiscard,
     .bdrv_refresh_limits        = nbd_refresh_limits,
+    .bdrv_co_truncate           = nbd_co_truncate,
     .bdrv_getlength             = nbd_getlength,
     .bdrv_detach_aio_context    = nbd_client_detach_aio_context,
     .bdrv_attach_aio_context    = nbd_client_attach_aio_context,
@@ -2099,6 +2128,7 @@ static BlockDriver bdrv_nbd_unix = {
     .bdrv_co_flush_to_os        = nbd_co_flush,
     .bdrv_co_pdiscard           = nbd_client_co_pdiscard,
     .bdrv_refresh_limits        = nbd_refresh_limits,
+    .bdrv_co_truncate           = nbd_co_truncate,
     .bdrv_getlength             = nbd_getlength,
     .bdrv_detach_aio_context    = nbd_client_detach_aio_context,
     .bdrv_attach_aio_context    = nbd_client_attach_aio_context,
diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index 851f07e8f8b9..baeae86d8c85 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -1715,7 +1715,7 @@ static int truncate_f(BlockBackend *blk, int argc, char **argv)
      * exact=true.  It is better to err on the "emit more errors" side
      * than to be overly permissive.
      */
-    ret = blk_truncate(blk, offset, true, PREALLOC_MODE_OFF, 0, &local_err);
+    ret = blk_truncate(blk, offset, false, PREALLOC_MODE_OFF, 0, &local_err);
     if (ret < 0) {
         error_report_err(local_err);
         return ret;
-- 
2.27.0

[PULL 3/9] iotests: Make qemu_nbd_popen() a contextmanager

[Eric Blake]

From: Nir Soffer <nirsof@gmail.com>

Instead of duplicating the code to wait until the server is ready and
remember to terminate the server and wait for it, make it possible to
use like this:

    with qemu_nbd_popen('-k', sock, image):
        # Access image via qemu-nbd socket...

Only test 264 used this helper, but I had to modify the output since it
did not consistently when starting and stopping qemu-nbd.

Signed-off-by: Nir Soffer <nsoffer@redhat.com>
Message-Id: <20200727215846.395443-3-nsoffer@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 tests/qemu-iotests/264        | 72 +++++++++++++----------------------
 tests/qemu-iotests/264.out    |  2 +
 tests/qemu-iotests/iotests.py | 28 +++++++++++++-
 3 files changed, 54 insertions(+), 48 deletions(-)

diff --git a/tests/qemu-iotests/264 b/tests/qemu-iotests/264
index 304a7443d77f..666f164ed8f4 100755
--- a/tests/qemu-iotests/264
+++ b/tests/qemu-iotests/264
@@ -36,48 +36,32 @@ wait_step = 0.2

 qemu_img_create('-f', iotests.imgfmt, disk_a, str(size))
 qemu_img_create('-f', iotests.imgfmt, disk_b, str(size))
-srv = qemu_nbd_popen('-k', nbd_sock, '-f', iotests.imgfmt, disk_b)

-# Wait for NBD server availability
-t = 0
-ok = False
-while t < wait_limit:
-    ok = qemu_io_silent_check('-f', 'raw', '-c', 'read 0 512', nbd_uri)
-    if ok:
-        break
-    time.sleep(wait_step)
-    t += wait_step
+with qemu_nbd_popen('-k', nbd_sock, '-f', iotests.imgfmt, disk_b):
+    vm = iotests.VM().add_drive(disk_a)
+    vm.launch()
+    vm.hmp_qemu_io('drive0', 'write 0 {}'.format(size))

-assert ok
+    vm.qmp_log('blockdev-add', filters=[iotests.filter_qmp_testfiles],
+               **{'node_name': 'backup0',
+                  'driver': 'raw',
+                  'file': {'driver': 'nbd',
+                           'server': {'type': 'unix', 'path': nbd_sock},
+                           'reconnect-delay': 10}})
+    vm.qmp_log('blockdev-backup', device='drive0', sync='full', target='backup0',
+               speed=(1 * 1024 * 1024))

-vm = iotests.VM().add_drive(disk_a)
-vm.launch()
-vm.hmp_qemu_io('drive0', 'write 0 {}'.format(size))
+    # Wait for some progress
+    t = 0
+    while t < wait_limit:
+        jobs = vm.qmp('query-block-jobs')['return']
+        if jobs and jobs[0]['offset'] > 0:
+            break
+        time.sleep(wait_step)
+        t += wait_step

-vm.qmp_log('blockdev-add', filters=[iotests.filter_qmp_testfiles],
-           **{'node_name': 'backup0',
-              'driver': 'raw',
-              'file': {'driver': 'nbd',
-                       'server': {'type': 'unix', 'path': nbd_sock},
-                       'reconnect-delay': 10}})
-vm.qmp_log('blockdev-backup', device='drive0', sync='full', target='backup0',
-           speed=(1 * 1024 * 1024))
-
-# Wait for some progress
-t = 0
-while t < wait_limit:
-    jobs = vm.qmp('query-block-jobs')['return']
     if jobs and jobs[0]['offset'] > 0:
-        break
-    time.sleep(wait_step)
-    t += wait_step
-
-if jobs and jobs[0]['offset'] > 0:
-    log('Backup job is started')
-
-log('Kill NBD server')
-srv.kill()
-srv.wait()
+        log('Backup job is started')

 jobs = vm.qmp('query-block-jobs')['return']
 if jobs and jobs[0]['offset'] < jobs[0]['len']:
@@ -88,12 +72,8 @@ vm.qmp_log('block-job-set-speed', device='drive0', speed=0)
 # Emulate server down time for 1 second
 time.sleep(1)

-log('Start NBD server')
-srv = qemu_nbd_popen('-k', nbd_sock, '-f', iotests.imgfmt, disk_b)
-
-e = vm.event_wait('BLOCK_JOB_COMPLETED')
-log('Backup completed: {}'.format(e['data']['offset']))
-
-vm.qmp_log('blockdev-del', node_name='backup0')
-srv.kill()
-vm.shutdown()
+with qemu_nbd_popen('-k', nbd_sock, '-f', iotests.imgfmt, disk_b):
+    e = vm.event_wait('BLOCK_JOB_COMPLETED')
+    log('Backup completed: {}'.format(e['data']['offset']))
+    vm.qmp_log('blockdev-del', node_name='backup0')
+    vm.shutdown()
diff --git a/tests/qemu-iotests/264.out b/tests/qemu-iotests/264.out
index 3000944b099a..c45b1e81ef26 100644
--- a/tests/qemu-iotests/264.out
+++ b/tests/qemu-iotests/264.out
@@ -1,3 +1,4 @@
+Start NBD server
 {"execute": "blockdev-add", "arguments": {"driver": "raw", "file": {"driver": "nbd", "reconnect-delay": 10, "server": {"path": "TEST_DIR/PID-nbd-sock", "type": "unix"}}, "node-name": "backup0"}}
 {"return": {}}
 {"execute": "blockdev-backup", "arguments": {"device": "drive0", "speed": 1048576, "sync": "full", "target": "backup0"}}
@@ -11,3 +12,4 @@ Start NBD server
 Backup completed: 5242880
 {"execute": "blockdev-del", "arguments": {"node-name": "backup0"}}
 {"return": {}}
+Kill NBD server
diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 3590ed78a0e4..8f79668435a0 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -28,10 +28,13 @@ import signal
 import struct
 import subprocess
 import sys
+import time
 from typing import (Any, Callable, Dict, Iterable,
                     List, Optional, Sequence, Tuple, TypeVar)
 import unittest

+from contextlib import contextmanager
+
 # pylint: disable=import-error, wrong-import-position
 sys.path.append(os.path.join(os.path.dirname(__file__), '..', '..', 'python'))
 from qemu import qtest
@@ -270,9 +273,30 @@ def qemu_nbd_early_pipe(*args):

     return subp.returncode, output if subp.returncode else ''

+@contextmanager
 def qemu_nbd_popen(*args):
-    '''Run qemu-nbd in daemon mode and return the parent's exit code'''
-    return subprocess.Popen(qemu_nbd_args + ['--persistent'] + list(args))
+    '''Context manager running qemu-nbd within the context'''
+    pid_file = file_path("pid")
+
+    cmd = list(qemu_nbd_args)
+    cmd.extend(('--persistent', '--pid-file', pid_file))
+    cmd.extend(args)
+
+    log('Start NBD server')
+    p = subprocess.Popen(cmd)
+    try:
+        while not os.path.exists(pid_file):
+            if p.poll() is not None:
+                raise RuntimeError(
+                    "qemu-nbd terminated with exit code {}: {}"
+                    .format(p.returncode, ' '.join(cmd)))
+
+            time.sleep(0.01)
+        yield
+    finally:
+        log('Kill NBD server')
+        p.kill()
+        p.wait()

 def compare_images(img1, img2, fmt1=imgfmt, fmt2=imgfmt):
     '''Return True if two image files are identical'''
-- 
2.27.0

[PULL 4/9] iotests: Add more qemu_img helpers

[Eric Blake]

From: Nir Soffer <nirsof@gmail.com>

Add 2 helpers for measuring and checking images:
- qemu_img_measure()
- qemu_img_check()

Both use --output-json and parse the returned json to make easy to use
in other tests. I'm going to use them in a new test, and I hope they
will be useful in may other tests.

Signed-off-by: Nir Soffer <nsoffer@redhat.com>
Message-Id: <20200727215846.395443-4-nsoffer@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 tests/qemu-iotests/iotests.py | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 8f79668435a0..717b5b652c45 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -141,6 +141,12 @@ def qemu_img_create(*args):

     return qemu_img(*args)

+def qemu_img_measure(*args):
+    return json.loads(qemu_img_pipe("measure", "--output", "json", *args))
+
+def qemu_img_check(*args):
+    return json.loads(qemu_img_pipe("check", "--output", "json", *args))
+
 def qemu_img_verbose(*args):
     '''Run qemu-img without suppressing its output and return the exit code'''
     exitcode = subprocess.call(qemu_img_args + list(args))
-- 
2.27.0

[PULL 5/9] iotests: Test convert to qcow2 compressed to NBD

[Eric Blake]

From: Nir Soffer <nirsof@gmail.com>

Add test for "qemu-img convert -O qcow2 -c" to NBD target. The tests    
create a OVA file and write compressed qcow2 disk content directly into
the OVA file via qemu-nbd.

Signed-off-by: Nir Soffer <nsoffer@redhat.com>
Message-Id: <20200727215846.395443-5-nsoffer@redhat.com>
Tested-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 tests/qemu-iotests/302     | 127 +++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/302.out |  31 +++++++++
 tests/qemu-iotests/group   |   1 +
 3 files changed, 159 insertions(+)
 create mode 100755 tests/qemu-iotests/302
 create mode 100644 tests/qemu-iotests/302.out

diff --git a/tests/qemu-iotests/302 b/tests/qemu-iotests/302
new file mode 100755
index 000000000000..a8506bda1592
--- /dev/null
+++ b/tests/qemu-iotests/302
@@ -0,0 +1,127 @@
+#!/usr/bin/env python3
+#
+# Tests converting qcow2 compressed to NBD
+#
+# Copyright (c) 2020 Nir Soffer <nirsof@gmail.com>
+#
+# 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/>.
+#
+# owner=nirsof@gmail.com
+
+import io
+import tarfile
+
+import iotests
+
+from iotests import (
+    file_path,
+    qemu_img,
+    qemu_img_check,
+    qemu_img_create,
+    qemu_img_log,
+    qemu_img_measure,
+    qemu_io,
+    qemu_nbd_popen,
+)
+
+iotests.script_initialize(supported_fmts=["qcow2"])
+
+# Create source disk. Using qcow2 to enable strict comparing later, and
+# avoid issues with random filesystem on CI environment.
+src_disk = file_path("disk.qcow2")
+qemu_img_create("-f", iotests.imgfmt, src_disk, "1g")
+qemu_io("-f", iotests.imgfmt, "-c", "write 1m 64k", src_disk)
+
+# The use case is writing qcow2 image directly into an ova file, which
+# is a tar file with specific layout. This is tricky since we don't know the
+# size of the image before compressing, so we have to do:
+# 1. Add an ovf file.
+# 2. Find the offset of the next member data.
+# 3. Make room for image data, allocating for the worst case.
+# 4. Write compressed image data into the tar.
+# 5. Add a tar entry with the actual image size.
+# 6. Shrink the tar to the actual size, aligned to 512 bytes.
+
+tar_file = file_path("test.ova")
+
+with tarfile.open(tar_file, "w") as tar:
+
+    # 1. Add an ovf file.
+
+    ovf_data = b"<xml/>"
+    ovf = tarfile.TarInfo("vm.ovf")
+    ovf.size = len(ovf_data)
+    tar.addfile(ovf, io.BytesIO(ovf_data))
+
+    # 2. Find the offset of the next member data.
+
+    offset = tar.fileobj.tell() + 512
+
+    # 3. Make room for image data, allocating for the worst case.
+
+    measure = qemu_img_measure("-O", "qcow2", src_disk)
+    tar.fileobj.truncate(offset + measure["required"])
+
+    # 4. Write compressed image data into the tar.
+
+    nbd_sock = file_path("nbd-sock", base_dir=iotests.sock_dir)
+    nbd_uri = "nbd+unix:///exp?socket=" + nbd_sock
+
+    # Use raw format to allow creating qcow2 directly into tar file.
+    with qemu_nbd_popen(
+            "--socket", nbd_sock,
+            "--export-name", "exp",
+            "--format", "raw",
+            "--offset", str(offset),
+            tar_file):
+
+        iotests.log("=== Target image info ===")
+        qemu_img_log("info", nbd_uri)
+
+        qemu_img(
+            "convert",
+            "-f", iotests.imgfmt,
+            "-O", "qcow2",
+            "-c",
+            src_disk,
+            nbd_uri)
+
+        iotests.log("=== Converted image info ===")
+        qemu_img_log("info", nbd_uri)
+
+        iotests.log("=== Converted image check ===")
+        qemu_img_log("check", nbd_uri)
+
+        iotests.log("=== Comparing to source disk ===")
+        qemu_img_log("compare", src_disk, nbd_uri)
+
+        actual_size = qemu_img_check(nbd_uri)["image-end-offset"]
+
+    # 5. Add a tar entry with the actual image size.
+
+    disk = tarfile.TarInfo("disk")
+    disk.size = actual_size
+    tar.addfile(disk)
+
+    # 6. Shrink the tar to the actual size, aligned to 512 bytes.
+
+    tar_size = offset + (disk.size + 511) & ~511
+    tar.fileobj.seek(tar_size)
+    tar.fileobj.truncate(tar_size)
+
+with tarfile.open(tar_file) as tar:
+    members = [{"name": m.name, "size": m.size, "offset": m.offset_data}
+               for m in tar]
+    iotests.log("=== OVA file contents ===")
+    iotests.log(members)
diff --git a/tests/qemu-iotests/302.out b/tests/qemu-iotests/302.out
new file mode 100644
index 000000000000..e37d3a103082
--- /dev/null
+++ b/tests/qemu-iotests/302.out
@@ -0,0 +1,31 @@
+Start NBD server
+=== Target image info ===
+image: nbd+unix:///exp?socket=SOCK_DIR/PID-nbd-sock
+file format: raw
+virtual size: 448 KiB (458752 bytes)
+disk size: unavailable
+
+=== Converted image info ===
+image: nbd+unix:///exp?socket=SOCK_DIR/PID-nbd-sock
+file format: qcow2
+virtual size: 1 GiB (1073741824 bytes)
+disk size: unavailable
+cluster_size: 65536
+Format specific information:
+    compat: 1.1
+    compression type: zlib
+    lazy refcounts: false
+    refcount bits: 16
+    corrupt: false
+
+=== Converted image check ===
+No errors were found on the image.
+1/16384 = 0.01% allocated, 100.00% fragmented, 100.00% compressed clusters
+Image end offset: 393216
+
+=== Comparing to source disk ===
+Images are identical.
+
+Kill NBD server
+=== OVA file contents ===
+[{"name": "vm.ovf", "offset": 512, "size": 6}, {"name": "disk", "offset": 1536, "size": 393216}]
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 1d0252e1f051..1e1cb27bc8e3 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -308,3 +308,4 @@
 297 meta
 299 auto quick
 301 backing quick
+302 quick
-- 
2.27.0

[PULL 6/9] block/nbd: split nbd_establish_connection out of nbd_client_connect

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We are going to implement non-blocking version of
nbd_establish_connection, which for a while will be used only for
nbd_reconnect_attempt, not for nbd_open, so we need to call it
separately.

Refactor nbd_reconnect_attempt in a way which makes next commit
simpler.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20200727184751.15704-2-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c        | 60 +++++++++++++++++++++++++++-------------------
 block/trace-events |  4 ++--
 2 files changed, 38 insertions(+), 26 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 8934bcb47901..3558c173e34b 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -93,7 +93,10 @@ typedef struct BDRVNBDState {
     char *x_dirty_bitmap;
 } BDRVNBDState;

-static int nbd_client_connect(BlockDriverState *bs, Error **errp);
+static QIOChannelSocket *nbd_establish_connection(SocketAddress *saddr,
+                                                  Error **errp);
+static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
+                                Error **errp);

 static void nbd_clear_bdrvstate(BDRVNBDState *s)
 {
@@ -241,7 +244,9 @@ static bool nbd_client_connecting_wait(BDRVNBDState *s)

 static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
 {
+    int ret;
     Error *local_err = NULL;
+    QIOChannelSocket *sioc;

     if (!nbd_client_connecting(s)) {
         return;
@@ -280,19 +285,25 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
         s->ioc = NULL;
     }

-    s->connect_status = nbd_client_connect(s->bs, &local_err);
+    sioc = nbd_establish_connection(s->saddr, &local_err);
+    if (!sioc) {
+        ret = -ECONNREFUSED;
+        goto out;
+    }
+
+    ret = nbd_client_handshake(s->bs, sioc, &local_err);
+
+out:
+    s->connect_status = ret;
     error_free(s->connect_err);
     s->connect_err = NULL;
     error_propagate(&s->connect_err, local_err);

-    if (s->connect_status < 0) {
-        /* failed attempt */
-        return;
+    if (ret >= 0) {
+        /* successfully connected */
+        s->state = NBD_CLIENT_CONNECTED;
+        qemu_co_queue_restart_all(&s->free_sema);
     }
-
-    /* successfully connected */
-    s->state = NBD_CLIENT_CONNECTED;
-    qemu_co_queue_restart_all(&s->free_sema);
 }

 static coroutine_fn void nbd_co_reconnect_loop(BDRVNBDState *s)
@@ -1425,24 +1436,15 @@ static QIOChannelSocket *nbd_establish_connection(SocketAddress *saddr,
     return sioc;
 }

-static int nbd_client_connect(BlockDriverState *bs, Error **errp)
+/* nbd_client_handshake takes ownership on sioc. On failure it is unref'ed. */
+static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
+                                Error **errp)
 {
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
     AioContext *aio_context = bdrv_get_aio_context(bs);
     int ret;

-    /*
-     * establish TCP connection, return error if it fails
-     * TODO: Configurable retry-until-timeout behaviour.
-     */
-    QIOChannelSocket *sioc = nbd_establish_connection(s->saddr, errp);
-
-    if (!sioc) {
-        return -ECONNREFUSED;
-    }
-
-    /* NBD handshake */
-    trace_nbd_client_connect(s->export);
+    trace_nbd_client_handshake(s->export);
     qio_channel_set_blocking(QIO_CHANNEL(sioc), false, NULL);
     qio_channel_attach_aio_context(QIO_CHANNEL(sioc), aio_context);

@@ -1489,7 +1491,7 @@ static int nbd_client_connect(BlockDriverState *bs, Error **errp)
         object_ref(OBJECT(s->ioc));
     }

-    trace_nbd_client_connect_success(s->export);
+    trace_nbd_client_handshake_success(s->export);

     return 0;

@@ -1894,6 +1896,7 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
 {
     int ret;
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
+    QIOChannelSocket *sioc;

     ret = nbd_process_options(bs, options, errp);
     if (ret < 0) {
@@ -1904,7 +1907,16 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
     qemu_co_mutex_init(&s->send_mutex);
     qemu_co_queue_init(&s->free_sema);

-    ret = nbd_client_connect(bs, errp);
+    /*
+     * establish TCP connection, return error if it fails
+     * TODO: Configurable retry-until-timeout behaviour.
+     */
+    sioc = nbd_establish_connection(s->saddr, errp);
+    if (!sioc) {
+        return -ECONNREFUSED;
+    }
+
+    ret = nbd_client_handshake(bs, sioc, errp);
     if (ret < 0) {
         nbd_clear_bdrvstate(s);
         return ret;
diff --git a/block/trace-events b/block/trace-events
index d3533ca8963c..915833506189 100644
--- a/block/trace-events
+++ b/block/trace-events
@@ -168,8 +168,8 @@ nbd_parse_blockstatus_compliance(const char *err) "ignoring extra data from non-
 nbd_structured_read_compliance(const char *type) "server sent non-compliant unaligned read %s chunk"
 nbd_read_reply_entry_fail(int ret, const char *err) "ret = %d, err: %s"
 nbd_co_request_fail(uint64_t from, uint32_t len, uint64_t handle, uint16_t flags, uint16_t type, const char *name, int ret, const char *err) "Request failed { .from = %" PRIu64", .len = %" PRIu32 ", .handle = %" PRIu64 ", .flags = 0x%" PRIx16 ", .type = %" PRIu16 " (%s) } ret = %d, err: %s"
-nbd_client_connect(const char *export_name) "export '%s'"
-nbd_client_connect_success(const char *export_name) "export '%s'"
+nbd_client_handshake(const char *export_name) "export '%s'"
+nbd_client_handshake_success(const char *export_name) "export '%s'"

 # ssh.c
 ssh_restart_coroutine(void *co) "co=%p"
-- 
2.27.0

[PULL 7/9] block/nbd: allow drain during reconnect attempt

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

It should be safe to reenter qio_channel_yield() on io/channel read/write
path, so it's safe to reduce in_flight and allow attaching new aio
context. And no problem to allow drain itself: connection attempt is
not a guest request. Moreover, if remote server is down, we can hang
in negotiation, blocking drain section and provoking a dead lock.

How to reproduce the dead lock:

1. Create nbd-fault-injector.conf with the following contents:

[inject-error "mega1"]
event=data
io=readwrite
when=before

2. In one terminal run nbd-fault-injector in a loop, like this:

n=1; while true; do
    echo $n; ((n++));
    ./nbd-fault-injector.py 127.0.0.1:10000 nbd-fault-injector.conf;
done

3. In another terminal run qemu-io in a loop, like this:

n=1; while true; do
    echo $n; ((n++));
    ./qemu-io -c 'read 0 512' nbd://127.0.0.1:10000;
done

After some time, qemu-io will hang trying to drain, for example, like
this:

 #3 aio_poll (ctx=0x55f006bdd890, blocking=true) at
    util/aio-posix.c:600
 #4 bdrv_do_drained_begin (bs=0x55f006bea710, recursive=false,
    parent=0x0, ignore_bds_parents=false, poll=true) at block/io.c:427
 #5 bdrv_drained_begin (bs=0x55f006bea710) at block/io.c:433
 #6 blk_drain (blk=0x55f006befc80) at block/block-backend.c:1710
 #7 blk_unref (blk=0x55f006befc80) at block/block-backend.c:498
 #8 bdrv_open_inherit (filename=0x7fffba1563bc
    "nbd+tcp://127.0.0.1:10000", reference=0x0, options=0x55f006be86d0,
    flags=24578, parent=0x0, child_class=0x0, child_role=0,
    errp=0x7fffba154620) at block.c:3491
 #9 bdrv_open (filename=0x7fffba1563bc "nbd+tcp://127.0.0.1:10000",
    reference=0x0, options=0x0, flags=16386, errp=0x7fffba154620) at
    block.c:3513
 #10 blk_new_open (filename=0x7fffba1563bc "nbd+tcp://127.0.0.1:10000",
    reference=0x0, options=0x0, flags=16386, errp=0x7fffba154620) at
    block/block-backend.c:421

And connection_co stack like this:

 #0 qemu_coroutine_switch (from_=0x55f006bf2650, to_=0x7fe96e07d918,
    action=COROUTINE_YIELD) at util/coroutine-ucontext.c:302
 #1 qemu_coroutine_yield () at util/qemu-coroutine.c:193
 #2 qio_channel_yield (ioc=0x55f006bb3c20, condition=G_IO_IN) at
    io/channel.c:472
 #3 qio_channel_readv_all_eof (ioc=0x55f006bb3c20, iov=0x7fe96d729bf0,
    niov=1, errp=0x7fe96d729eb0) at io/channel.c:110
 #4 qio_channel_readv_all (ioc=0x55f006bb3c20, iov=0x7fe96d729bf0,
    niov=1, errp=0x7fe96d729eb0) at io/channel.c:143
 #5 qio_channel_read_all (ioc=0x55f006bb3c20, buf=0x7fe96d729d28
    "\300.\366\004\360U", buflen=8, errp=0x7fe96d729eb0) at
    io/channel.c:247
 #6 nbd_read (ioc=0x55f006bb3c20, buffer=0x7fe96d729d28, size=8,
    desc=0x55f004f69644 "initial magic", errp=0x7fe96d729eb0) at
    /work/src/qemu/master/include/block/nbd.h:365
 #7 nbd_read64 (ioc=0x55f006bb3c20, val=0x7fe96d729d28,
    desc=0x55f004f69644 "initial magic", errp=0x7fe96d729eb0) at
    /work/src/qemu/master/include/block/nbd.h:391
 #8 nbd_start_negotiate (aio_context=0x55f006bdd890,
    ioc=0x55f006bb3c20, tlscreds=0x0, hostname=0x0,
    outioc=0x55f006bf19f8, structured_reply=true,
    zeroes=0x7fe96d729dca, errp=0x7fe96d729eb0) at nbd/client.c:904
 #9 nbd_receive_negotiate (aio_context=0x55f006bdd890,
    ioc=0x55f006bb3c20, tlscreds=0x0, hostname=0x0,
    outioc=0x55f006bf19f8, info=0x55f006bf1a00, errp=0x7fe96d729eb0) at
    nbd/client.c:1032
 #10 nbd_client_connect (bs=0x55f006bea710, errp=0x7fe96d729eb0) at
    block/nbd.c:1460
 #11 nbd_reconnect_attempt (s=0x55f006bf19f0) at block/nbd.c:287
 #12 nbd_co_reconnect_loop (s=0x55f006bf19f0) at block/nbd.c:309
 #13 nbd_connection_entry (opaque=0x55f006bf19f0) at block/nbd.c:360
 #14 coroutine_trampoline (i0=113190480, i1=22000) at
    util/coroutine-ucontext.c:173

Note, that the hang may be
triggered by another bug, so the whole case is fixed only together with
commit "block/nbd: on shutdown terminate connection attempt".

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20200727184751.15704-3-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/block/nbd.c b/block/nbd.c
index 3558c173e34b..ee9ab7512b65 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -291,8 +291,22 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
         goto out;
     }

+    bdrv_dec_in_flight(s->bs);
+
     ret = nbd_client_handshake(s->bs, sioc, &local_err);

+    if (s->drained) {
+        s->wait_drained_end = true;
+        while (s->drained) {
+            /*
+             * We may be entered once from nbd_client_attach_aio_context_bh
+             * and then from nbd_client_co_drain_end. So here is a loop.
+             */
+            qemu_coroutine_yield();
+        }
+    }
+    bdrv_inc_in_flight(s->bs);
+
 out:
     s->connect_status = ret;
     error_free(s->connect_err);
-- 
2.27.0

[PULL 8/9] block/nbd: on shutdown terminate connection attempt

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

On shutdown nbd driver may be in a connecting state. We should shutdown
it as well, otherwise we may hang in
nbd_teardown_connection, waiting for conneciton_co to finish in
BDRV_POLL_WHILE(bs, s->connection_co) loop if remote server is down.

How to reproduce the dead lock:

1. Create nbd-fault-injector.conf with the following contents:

[inject-error "mega1"]
event=data
io=readwrite
when=before

2. In one terminal run nbd-fault-injector in a loop, like this:

n=1; while true; do
    echo $n; ((n++));
    ./nbd-fault-injector.py 127.0.0.1:10000 nbd-fault-injector.conf;
done

3. In another terminal run qemu-io in a loop, like this:

n=1; while true; do
    echo $n; ((n++));
    ./qemu-io -c 'read 0 512' nbd://127.0.0.1:10000;
done

After some time, qemu-io will hang. Note, that this hang may be
triggered by another bug, so the whole case is fixed only together with
commit "block/nbd: allow drain during reconnect attempt".

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200727184751.15704-4-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index ee9ab7512b65..620c97be6ba2 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -209,11 +209,15 @@ static void nbd_teardown_connection(BlockDriverState *bs)
 {
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;

-    if (s->state == NBD_CLIENT_CONNECTED) {
+    if (s->ioc) {
         /* finish any pending coroutines */
-        assert(s->ioc);
         qio_channel_shutdown(s->ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
+    } else if (s->sioc) {
+        /* abort negotiation */
+        qio_channel_shutdown(QIO_CHANNEL(s->sioc), QIO_CHANNEL_SHUTDOWN_BOTH,
+                             NULL);
     }
+
     s->state = NBD_CLIENT_QUIT;
     if (s->connection_co) {
         if (s->connection_co_sleep_ns_state) {
@@ -1459,6 +1463,9 @@ static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
     int ret;

     trace_nbd_client_handshake(s->export);
+
+    s->sioc = sioc;
+
     qio_channel_set_blocking(QIO_CHANNEL(sioc), false, NULL);
     qio_channel_attach_aio_context(QIO_CHANNEL(sioc), aio_context);

@@ -1473,6 +1480,7 @@ static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
     g_free(s->info.name);
     if (ret < 0) {
         object_unref(OBJECT(sioc));
+        s->sioc = NULL;
         return ret;
     }
     if (s->x_dirty_bitmap && !s->info.base_allocation) {
@@ -1498,8 +1506,6 @@ static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
         }
     }

-    s->sioc = sioc;
-
     if (!s->ioc) {
         s->ioc = QIO_CHANNEL(sioc);
         object_ref(OBJECT(s->ioc));
@@ -1520,6 +1526,7 @@ static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
         nbd_send_request(s->ioc ?: QIO_CHANNEL(sioc), &request);

         object_unref(OBJECT(sioc));
+        s->sioc = NULL;

         return ret;
     }
-- 
2.27.0

[PULL 9/9] block/nbd: nbd_co_reconnect_loop(): don't sleep if drained

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We try to go to wakeable sleep, so that, if drain begins it will break
the sleep. But what if nbd_client_co_drain_begin() already called and
s->drained is already true? We'll go to sleep, and drain will have to
wait for the whole timeout. Let's improve it.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200727184751.15704-5-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 620c97be6ba2..7bb881fef49c 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -341,8 +341,6 @@ static coroutine_fn void nbd_co_reconnect_loop(BDRVNBDState *s)
             qemu_co_queue_restart_all(&s->free_sema);
         }

-        qemu_co_sleep_ns_wakeable(QEMU_CLOCK_REALTIME, timeout,
-                                  &s->connection_co_sleep_ns_state);
         if (s->drained) {
             bdrv_dec_in_flight(s->bs);
             s->wait_drained_end = true;
@@ -354,9 +352,12 @@ static coroutine_fn void nbd_co_reconnect_loop(BDRVNBDState *s)
                 qemu_coroutine_yield();
             }
             bdrv_inc_in_flight(s->bs);
-        }
-        if (timeout < max_timeout) {
-            timeout *= 2;
+        } else {
+            qemu_co_sleep_ns_wakeable(QEMU_CLOCK_REALTIME, timeout,
+                                      &s->connection_co_sleep_ns_state);
+            if (timeout < max_timeout) {
+                timeout *= 2;
+            }
         }

         nbd_reconnect_attempt(s);
-- 
2.27.0

Re: [PULL 0/9] nbd patches for -rc2, 2020-07-28

[Peter Maydell]

On Tue, 28 Jul 2020 at 16:06, Eric Blake <eblake@redhat.com> wrote:
>
> The following changes since commit 1b242c3b1ec7c6011901b4f3b4b0876e31746afb:
>
>   Merge remote-tracking branch 'remotes/mcayland/tags/qemu-openbios-20200727' into staging (2020-07-28 13:46:31 +0100)
>
> are available in the Git repository at:
>
>   https://repo.or.cz/qemu/ericb.git tags/pull-nbd-2020-07-28
>
> for you to fetch changes up to 12c75e20a269ac917f4a76936d7142264e522233:
>
>   block/nbd: nbd_co_reconnect_loop(): don't sleep if drained (2020-07-28 09:54:43 -0500)
>
> Sorry this is down to the wire, Nir's patches were a pretty recent
> discovery, but still counts as a bug fix worthy of having in -rc2.
>
> ----------------------------------------------------------------
> nbd patches for 2020-07-28
>
> - fix NBD handling of trim/zero requests larger than 2G
> - allow no-op resizes on NBD (in turn fixing qemu-img convert -c into NBD)
> - several deadlock fixes when using NBD reconnect


Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/5.1
for any user-visible changes.

-- PMM