This makes nbd's connection_co yield during reconnects, so that
reconnect doesn't block the main thread. This is very important in
case of an unavailable nbd server host: connect() call may take a long
time, blocking the main thread (and due to reconnect, it will hang
again and again with small gaps of working time during pauses between
connection attempts).
Realization notes:
- We don't want to implement non-blocking connect() over non-blocking
socket, because getaddrinfo() doesn't have portable non-blocking
realization anyway, so let's just use a thread for both getaddrinfo()
and connect().
- We can't use qio_channel_socket_connect_async (which behaves
similarly and starts a thread to execute connect() call), as it's relying
on someone iterating main loop (g_main_loop_run() or something like
this), which is not always the case.
- We can't use thread_pool_submit_co API, as thread pool waits for all
threads to finish (but we don't want to wait for blocking reconnect
attempt on shutdown.
So, we just create the thread by hand. Some additional difficulties
are:
- We want our connect to avoid blocking drained sections and aio context
switches. To achieve this, we make it possible to "cancel" synchronous
wait for the connect (which is a coroutine yield actually), still,
the thread continues in background, and if successful, its result may be
reused on next reconnect attempt.
- We don't want to wait for reconnect on shutdown, so there is
CONNECT_THREAD_RUNNING_DETACHED thread state, which means that the block
layer is no longer interested in a result, and thread should close new
connected socket on finish and free the state.
How to reproduce the bug, fixed with this commit:
1. Create an image on node1:
qemu-img create -f qcow2 xx 100M
2. Start NBD server on node1:
qemu-nbd xx
3. Start vm with second nbd disk on node2, like this:
./x86_64-softmmu/qemu-system-x86_64 -nodefaults -drive \
file=/work/images/cent7.qcow2 -drive file=nbd+tcp://192.168.100.2 \
-vnc :0 -qmp stdio -m 2G -enable-kvm -vga std
4. Access the vm through vnc (or some other way?), and check that NBD
drive works:
dd if=/dev/sdb of=/dev/null bs=1M count=10
- the command should succeed.
5. Now, let's trigger nbd-reconnect loop in Qemu process. For this:
5.1 Kill NBD server on node1
5.2 run "dd if=/dev/sdb of=/dev/null bs=1M count=10" in the guest
again. The command should fail and a lot of error messages about
failing disk may appear as well.
Now NBD client driver in Qemu tries to reconnect.
Still, VM works well.
6. Make node1 unavailable on NBD port, so connect() from node2 will
last for a long time:
On node1 (Note, that 10809 is just a default NBD port):
sudo iptables -A INPUT -p tcp --dport 10809 -j DROP
After some time the guest hangs, and you may check in gdb that Qemu
hangs in connect() call, issued from the main thread. This is the
BUG.
7. Don't forget to drop iptables rule from your node1:
sudo iptables -D INPUT -p tcp --dport 10809 -j DROP
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20200812145237.4396-1-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: minor wording and formatting tweaks]
Signed-off-by: Eric Blake <eblake@redhat.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>
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>
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>
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>
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>
When snprintf returns the same value as the buffer size, the final
byte was truncated to ensure a NUL terminator. Fortunately, such long
export names are unusual enough, with no real impact other than what
is displayed to the user.
Fixes: 5c86bdf120
Reported-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200622210355.414941-1-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
If we want to check error after errp-function call, we need to
introduce local_err and then propagate it to errp. Instead, use
the ERRP_GUARD() macro, benefits are:
1. No need of explicit error_propagate call
2. No need of explicit local_err variable: use errp directly
3. ERRP_GUARD() leaves errp as is if it's not NULL or
&error_fatal, this means that we don't break error_abort
(we'll abort on error_set, not on error_propagate)
If we want to add some info to errp (by error_prepend() or
error_append_hint()), we must use the ERRP_GUARD() macro.
Otherwise, this info will not be added when errp == &error_fatal
(the program will exit prior to the error_append_hint() or
error_prepend() call). Fix several such cases, e.g. in nbd_read().
This commit is generated by command
sed -n '/^Network Block Device (NBD)$/,/^$/{s/^F: //p}' \
MAINTAINERS | \
xargs git ls-files | grep '\.[hc]$' | \
xargs spatch \
--sp-file scripts/coccinelle/errp-guard.cocci \
--macro-file scripts/cocci-macro-file.h \
--in-place --no-show-diff --max-width 80
Reported-by: Kevin Wolf <kwolf@redhat.com>
Reported-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Commit message tweaked]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20200707165037.1026246-8-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[ERRP_AUTO_PROPAGATE() renamed to ERRP_GUARD(), and
auto-propagated-errp.cocci to errp-guard.cocci. Commit message
tweaked again.]
When all we do with an Error we receive into a local variable is
propagating to somewhere else, we can just as well receive it there
right away. The previous commit did that with a Coccinelle script I
consider fairly trustworthy. This commit uses the same script with
the matching of return taken out, i.e. we convert
if (!foo(..., &err)) {
...
error_propagate(errp, err);
...
}
to
if (!foo(..., errp)) {
...
...
}
This is unsound: @err could still be read between afterwards. I don't
know how to express "no read of @err without an intervening write" in
Coccinelle. Instead, I manually double-checked for uses of @err.
Suboptimal line breaks tweaked manually. qdev_realize() simplified
further to placate scripts/checkpatch.pl.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200707160613.848843-36-armbru@redhat.com>
The previous commit enables conversion of
visit_foo(..., &err);
if (err) {
...
}
to
if (!visit_foo(..., errp)) {
...
}
for visitor functions that now return true / false on success / error.
Coccinelle script:
@@
identifier fun =~ "check_list|input_type_enum|lv_start_struct|lv_type_bool|lv_type_int64|lv_type_str|lv_type_uint64|output_type_enum|parse_type_bool|parse_type_int64|parse_type_null|parse_type_number|parse_type_size|parse_type_str|parse_type_uint64|print_type_bool|print_type_int64|print_type_null|print_type_number|print_type_size|print_type_str|print_type_uint64|qapi_clone_start_alternate|qapi_clone_start_list|qapi_clone_start_struct|qapi_clone_type_bool|qapi_clone_type_int64|qapi_clone_type_null|qapi_clone_type_number|qapi_clone_type_str|qapi_clone_type_uint64|qapi_dealloc_start_list|qapi_dealloc_start_struct|qapi_dealloc_type_anything|qapi_dealloc_type_bool|qapi_dealloc_type_int64|qapi_dealloc_type_null|qapi_dealloc_type_number|qapi_dealloc_type_str|qapi_dealloc_type_uint64|qobject_input_check_list|qobject_input_check_struct|qobject_input_start_alternate|qobject_input_start_list|qobject_input_start_struct|qobject_input_type_any|qobject_input_type_bool|qobject_input_type_bool_keyval|qobject_input_type_int64|qobject_input_type_int64_keyval|qobject_input_type_null|qobject_input_type_number|qobject_input_type_number_keyval|qobject_input_type_size_keyval|qobject_input_type_str|qobject_input_type_str_keyval|qobject_input_type_uint64|qobject_input_type_uint64_keyval|qobject_output_start_list|qobject_output_start_struct|qobject_output_type_any|qobject_output_type_bool|qobject_output_type_int64|qobject_output_type_null|qobject_output_type_number|qobject_output_type_str|qobject_output_type_uint64|start_list|visit_check_list|visit_check_struct|visit_start_alternate|visit_start_list|visit_start_struct|visit_type_.*";
expression list args;
typedef Error;
Error *err;
@@
- fun(args, &err);
- if (err)
+ if (!fun(args, &err))
{
...
}
A few line breaks tidied up manually.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20200707160613.848843-19-armbru@redhat.com>
Commit 93676c88 relaxed our NBD client code to request export names up
to the NBD protocol maximum of 4096 bytes without NUL terminator, even
though the block layer can't store anything longer than 4096 bytes
including NUL terminator for display to the user. Since this means
there are some export names where we have to truncate things, we can
at least try to make the truncation a bit more obvious for the user.
Note that in spite of the truncated display name, we can still
communicate with an NBD server using such a long export name; this was
deemed nicer than refusing to even connect to such a server (since the
server may not be under our control, and since determining our actual
length limits gets tricky when nbd://host:port/export and
nbd+unix:///export?socket=/path are themselves variable-length
expansions beyond the export name but count towards the block layer
name length).
Reported-by: Xueqiang Wei <xuwei@redhat.com>
Fixes: https://bugzilla.redhat.com/1843684
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20200610163741.3745251-3-eblake@redhat.com>
The NBD spec was updated (see nbd.git commit 9f30fedb) so that
max_block doesn't relate to NBD_CMD_TRIM. So, drop the restriction.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20200401150112.9557-3-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: tweak commit message to call out NBD commit]
Signed-off-by: Eric Blake <eblake@redhat.com>
The NBD spec was updated (see nbd.git commit 9f30fedb) so that
max_block doesn't relate to NBD_CMD_BLOCK_STATUS. So, drop the
restriction.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200401150112.9557-2-vsementsov@virtuozzo.com>
[eblake: tweak commit message to call out NBD commit]
Signed-off-by: Eric Blake <eblake@redhat.com>
Instead of checking the .bdrv_co_create_opts to see if we need the
fallback, just implement the .bdrv_co_create_opts in the drivers that
need it.
This way we don't break various places that need to know if the
underlying protocol/format really supports image creation, and this way
we still allow some drivers to not support image creation.
Fixes: fd17146cd9
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1816007
Note that technically this driver reverts the image creation fallback
for the vxhs driver since I don't have a means to test it, and IMHO it
is better to leave it not supported as it was prior to generic image
creation patches.
Also drop iscsi_create_opts which was left accidentally.
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20200326011218.29230-3-mlevitsk@redhat.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
[mreitz: Fixed alignment, and moved bdrv_co_create_opts_simple() and
bdrv_create_opts_simple from block.h into block_int.h]
Signed-off-by: Max Reitz <mreitz@redhat.com>
In currently implementation there will be a memory leak when
nbd_client_connect() returns error status. Here is an easy way to
reproduce:
1. run qemu-iotests as follow and check the result with asan:
./check -raw 143
Following is the asan output backtrack:
Direct leak of 40 byte(s) in 1 object(s) allocated from:
#0 0x7f629688a560 in calloc (/usr/lib64/libasan.so.3+0xc7560)
#1 0x7f6295e7e015 in g_malloc0 (/usr/lib64/libglib-2.0.so.0+0x50015)
#2 0x56281dab4642 in qobject_input_start_struct /mnt/sdb/qemu-4.2.0-rc0/qapi/qobject-input-visitor.c:295
#3 0x56281dab1a04 in visit_start_struct /mnt/sdb/qemu-4.2.0-rc0/qapi/qapi-visit-core.c:49
#4 0x56281dad1827 in visit_type_SocketAddress qapi/qapi-visit-sockets.c:386
#5 0x56281da8062f in nbd_config /mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1716
#6 0x56281da8062f in nbd_process_options /mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1829
#7 0x56281da8062f in nbd_open /mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1873
Direct leak of 15 byte(s) in 1 object(s) allocated from:
#0 0x7f629688a3a0 in malloc (/usr/lib64/libasan.so.3+0xc73a0)
#1 0x7f6295e7dfbd in g_malloc (/usr/lib64/libglib-2.0.so.0+0x4ffbd)
#2 0x7f6295e96ace in g_strdup (/usr/lib64/libglib-2.0.so.0+0x68ace)
#3 0x56281da804ac in nbd_process_options /mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1834
#4 0x56281da804ac in nbd_open /mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1873
Indirect leak of 24 byte(s) in 1 object(s) allocated from:
#0 0x7f629688a3a0 in malloc (/usr/lib64/libasan.so.3+0xc73a0)
#1 0x7f6295e7dfbd in g_malloc (/usr/lib64/libglib-2.0.so.0+0x4ffbd)
#2 0x7f6295e96ace in g_strdup (/usr/lib64/libglib-2.0.so.0+0x68ace)
#3 0x56281dab41a3 in qobject_input_type_str_keyval /mnt/sdb/qemu-4.2.0-rc0/qapi/qobject-input-visitor.c:536
#4 0x56281dab2ee9 in visit_type_str /mnt/sdb/qemu-4.2.0-rc0/qapi/qapi-visit-core.c:297
#5 0x56281dad0fa1 in visit_type_UnixSocketAddress_members qapi/qapi-visit-sockets.c:141
#6 0x56281dad17b6 in visit_type_SocketAddress_members qapi/qapi-visit-sockets.c:366
#7 0x56281dad186a in visit_type_SocketAddress qapi/qapi-visit-sockets.c:393
#8 0x56281da8062f in nbd_config /mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1716
#9 0x56281da8062f in nbd_process_options /mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1829
#10 0x56281da8062f in nbd_open /mnt/sdb/qemu-4.2.0-rc0/block/nbd.c:1873
Fixes: 8f071c9db5
Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Pan Nengyuan <pannengyuan@huawei.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Cc: qemu-stable <qemu-stable@nongnu.org>
Cc: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <1575517528-44312-3-git-send-email-pannengyuan@huawei.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
The BDRVNBDState cleanup code is common in two places, add
nbd_clear_bdrvstate() function to do these cleanups.
Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Pan Nengyuan <pannengyuan@huawei.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <1575517528-44312-2-git-send-email-pannengyuan@huawei.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: fix compilation error and commit message]
Signed-off-by: Eric Blake <eblake@redhat.com>
The NBD URI specification [1] states that only one leading slash at
the beginning of the URI path component is stripped, not all such
slashes. This becomes important to a patch I just proposed to nbdkit
[2], which would allow the exportname to select a file embedded within
an ext2 image: ext2fs demands an absolute pathname beginning with '/',
and because qemu was inadvertantly stripping it, my nbdkit patch had
to work around the behavior.
[1] https://github.com/NetworkBlockDevice/nbd/blob/master/doc/uri.md
[2] https://www.redhat.com/archives/libguestfs/2020-February/msg00109.html
Note that the qemu bug only affects handling of URIs such as
nbd://host:port//abs/path (where '/abs/path' should be the export
name); it is still possible to use --image-opts and pass the desired
export name with a leading slash directly through JSON even without
this patch.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200212023101.1162686-1-eblake@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
When nbd_close() is called from a coroutine, the connection_co never
gets to run, and thus nbd_teardown_connection() hangs.
This is because aio_co_enter() only puts the connection_co into the main
coroutine's wake-up queue, so this main coroutine needs to yield and
wait for connection_co to terminate.
Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200122164532.178040-2-mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
All callers of nbd_iter_channel_error() pass the address of a
local_err variable, and only call this function if an error has
already occurred, using this function to propagate that error.
This is already implied by its name (local_err instead of the classic
errp), but it is worth additionally stressing this by adding an
assertion to make it part of the function contract.
The local_err parameter is not here to return information about
nbd_iter_channel_error failure. Instead it's assumed to be filled when
passed to the function. This is already stressed by its name
(local_err, instead of classic errp). Stress it additionally by
assertion.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20191205174635.18758-22-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Qemu as server currently won't accept export names larger than 256
bytes, nor create dirty bitmap names longer than 1023 bytes, so most
uses of qemu as client or server have no reason to get anywhere near
the NBD spec maximum of a 4k limit per string.
However, we weren't actually enforcing things, ignoring when the
remote side violates the protocol on input, and also having several
code paths where we send oversize strings on output (for example,
qemu-nbd --description could easily send more than 4k). Tighten
things up as follows:
client:
- Perform bounds check on export name and dirty bitmap request prior
to handing it to server
- Validate that copied server replies are not too long (ignoring
NBD_INFO_* replies that are not copied is not too bad)
server:
- Perform bounds check on export name and description prior to
advertising it to client
- Reject client name or metadata query that is too long
- Adjust things to allow full 4k name limit rather than previous
256 byte limit
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20191114024635.11363-4-eblake@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Implement reconnect. To achieve this:
1. add new modes:
connecting-wait: means, that reconnecting is in progress, and there
were small number of reconnect attempts, so all requests are
waiting for the connection.
connecting-nowait: reconnecting is in progress, there were a lot of
attempts of reconnect, all requests will return errors.
two old modes are used too:
connected: normal state
quit: exiting after fatal error or on close
Possible transitions are:
* -> quit
connecting-* -> connected
connecting-wait -> connecting-nowait (transition is done after
reconnect-delay seconds in connecting-wait mode)
connected -> connecting-wait
2. Implement reconnect in connection_co. So, in connecting-* mode,
connection_co, tries to reconnect unlimited times.
3. Retry nbd queries on channel error, if we are in connecting-wait
state.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20191009084158.15614-3-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
The client side is fairly straightforward: if the server advertised
fast zero support, then we can map that to BDRV_REQ_NO_FALLBACK
support. A server that advertises FAST_ZERO but not WRITE_ZEROES
is technically broken, but we can ignore that situation as it does
not change our behavior.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190823143726.27062-4-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Thanks to our recent move to use glib's g_autofree, I can join the
bandwagon. Getting rid of gotos is fun ;)
There are probably more places where we could register cleanup
functions and get rid of more gotos; this patch just focuses on the
labels that existed merely to call g_free.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190824172813.29720-2-eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
In my "build everything" tree, changing qemu/main-loop.h triggers a
recompile of some 5600 out of 6600 objects (not counting tests and
objects that don't depend on qemu/osdep.h). It includes block/aio.h,
which in turn includes qemu/event_notifier.h, qemu/notify.h,
qemu/processor.h, qemu/qsp.h, qemu/queue.h, qemu/thread-posix.h,
qemu/thread.h, qemu/timer.h, and a few more.
Include qemu/main-loop.h only where it's needed. Touching it now
recompiles only some 1700 objects. For block/aio.h and
qemu/event_notifier.h, these numbers drop from 5600 to 2800. For the
others, they shrink only slightly.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190812052359.30071-21-armbru@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
We'll need some connection parameters to be available all the time to
implement nbd reconnect. So, let's refactor them: define additional
parameters in BDRVNBDState, drop them from function parameters, drop
nbd_client_init and separate options parsing instead from nbd_open.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20190618114328.55249-6-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: Drop useless 'if' before object_unref]
Signed-off-by: Eric Blake <eblake@redhat.com>
Reconnect will be implemented in the following commit, so for now,
in semantics below, disconnect itself is a "serious error".
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190618114328.55249-5-vsementsov@virtuozzo.com>
[eblake: slipped from 4.1 to 4.2]
Signed-off-by: Eric Blake <eblake@redhat.com>
To implement reconnect we need several states for the client:
CONNECTED, QUIT and two different CONNECTING states. CONNECTING states
will be added in the following patches. This patch implements CONNECTED
and QUIT.
QUIT means, that we should close the connection and fail all current
and further requests (like old quit = true).
CONNECTED means that connection is ok, we can send requests (like old
quit = false).
For receiving loop we use a comparison of the current state with QUIT,
because reconnect will be in the same loop, so it should be looping
until the end.
Opposite, for requests we use a comparison of the current state with
CONNECTED, as we don't want to send requests in future CONNECTING
states.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190618114328.55249-4-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
No reason to use blocking channel for negotiation and we'll benefit in
further reconnect feature, as qio_channel reads and writes will do
qemu_coroutine_yield while waiting for io completion.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190618114328.55249-3-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
nbd_client_connect is going to be used from connection_co, so, let's
refactor nbd_client_connect in advance, leaving io channel
configuration all in nbd_client_connect.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190618114328.55249-2-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
We've had two separate reports of different callers running into use
of uninitialized data if s->quit is set (one detected by gcc -O3,
another by valgrind), due to checking 'nbd_reply_is_simple(reply) ||
s->quit' in the wrong order. Rather than chasing down which callers
need to pre-initialize reply, and whether there are any other
uninitialized uses, it's easier to guarantee that reply will always be
set by nbd_co_receive_one_chunk() even on failure.
The uninitialized use happens to be harmless (the only time the
variable is uninitialized is if s->quit is set, so the conditional
results in the same action regardless of what was read from reply),
and was introduced in commit 65e01d47.
In fixing the problem, it can also be seen that all (one) callers pass
in a non-NULL reply, so there is a dead conditional to also be cleaned
up.
Reported-by: Thomas Huth <thuth@redhat.com>
Reported-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190719172001.19770-1-eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
No reason to keep it separate, it differs from others block driver
behavior and therefore confuses. Instead of generic
'state = (State*)bs->opaque' we have to use special helper.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20190611102720.86114-4-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
No reason for keeping driver handlers realization separate from driver
structure. We can get rid of extra header file.
While being here, fix comments style, restore forgotten comments for
NBD_FOREACH_REPLY_CHUNK and nbd_reply_chunk_iter_receive, remove extra
includes.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20190611102720.86114-3-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
We have a latent bug in our NBD client code, tickled by the brand new
nbdkit 1.11.10 block status support:
$ nbdkit --filter=log --filter=truncate -U - \
data data="1" size=511 truncate=64K logfile=/dev/stdout \
--run 'qemu-img convert $nbd /var/tmp/out'
...
qemu-img: block/io.c:2122: bdrv_co_block_status: Assertion `*pnum && QEMU_IS_ALIGNED(*pnum, align) && align > offset - aligned_offset' failed.
The culprit? Our implementation of .bdrv_co_block_status can return
unaligned block status for any server that operates with a lower
actual alignment than what we tell the block layer in
request_alignment, in violation of the block layer's constraints. To
date, we've been unable to trip the bug, because qemu as NBD server
always advertises block sizing (at which point it is a server bug if
the server sends unaligned status - although qemu 3.1 is such a server
and I've sent separate patches for 4.0 both to get the server to obey
the spec, and to let the client to tolerate server oddities at EOF).
But nbdkit does not (yet) advertise block sizing, and therefore is not
in violation of the spec for returning block status at whatever
boundaries it wants, and those unaligned results can occur anywhere
rather than just at EOF. While we are still wise to avoid sending
sub-sector read/write requests to a server of unknown origin, we MUST
consider that a server telling us block status without an advertised
block size is correct. So, we either have to munge unaligned answers
from the server into aligned ones that we hand back to the block
layer, or we have to tell the block layer about a smaller alignment.
Similarly, if the server advertises an image size that is not
sector-aligned, we might as well assume that the server intends to let
us access those tail bytes, and therefore supports a minimum block
size of 1, regardless of whether the server supports block status
(although we still need more patches to fix the problem that with an
unaligned image, we can send read or block status requests that exceed
EOF to the server). Again, qemu as server cannot trip this problem
(because it rounds images to sector alignment), but nbdkit advertised
unaligned size even before it gained block status support.
Solve both alignment problems at once by using better heuristics on
what alignment to report to the block layer when the server did not
give us something to work with. Note that very few NBD servers
implement block status (to date, only qemu and nbdkit are known to do
so); and as the NBD spec mentioned block sizing constraints prior to
documenting block status, it can be assumed that any future
implementations of block status are aware that they must advertise
block size if they want a minimum size other than 1.
We've had a long history of struggles with picking the right alignment
to use in the block layer, as evidenced by the commit message of
fd8d372d (v2.12) that introduced the current choice of forced 512-byte
alignment.
There is no iotest coverage for this fix, because qemu can't provoke
it, and I didn't want to make test 241 dependent on nbdkit.
Fixes: fd8d372d
Reported-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190329042750.14704-3-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Currently, BlockDriver.bdrv_refresh_filename() is supposed to both
refresh the filename (BDS.exact_filename) and set BDS.full_open_options.
Now that we have generic code in the central bdrv_refresh_filename() for
creating BDS.full_open_options, we can drop the latter part from all
BlockDriver.bdrv_refresh_filename() implementations.
This also means that we can drop all of the existing default code for
this from the global bdrv_refresh_filename() itself.
Furthermore, we now have to call BlockDriver.bdrv_refresh_filename()
after having set BDS.full_open_options, because the block driver's
implementation should now be allowed to depend on BDS.full_open_options
being set correctly.
Finally, with this patch we can drop the @options parameter from
BlockDriver.bdrv_refresh_filename(); also, add a comment on this
function's purpose in block/block_int.h while touching its interface.
This completely obsoletes blklogwrite's implementation of
.bdrv_refresh_filename().
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190201192935.18394-25-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This new field can be set by block drivers to list the runtime options
they accept that may influence the contents of the respective BDS. As of
a follow-up patch, this list will be used by the common
bdrv_refresh_filename() implementation to decide which options to put
into BDS.full_open_options (and consequently whether a JSON filename has
to be created), thus freeing the drivers of having to implement that
logic themselves.
Additionally, this patch adds the field to all of the block drivers that
need it and sets it accordingly.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 20190201192935.18394-22-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
The generic bdrv_dirname() implementation would be able to generate some
form of directory name for many NBD nodes, but it would be always wrong.
Therefore, we have to explicitly make it an error (until NBD has some
form of specification for export paths, if it ever will).
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20190201192935.18394-18-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
Keep all connection code in one file, to be able to implement reconnect
in further patches.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20190201130138.94525-3-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: format tweak]
Signed-off-by: Eric Blake <eblake@redhat.com>
qstring_from_substr() takes the index of the substring's first and
last character. qstring_from_substr(s, 0, SIZE_MAX) denotes an empty
substring. Awkward.
Shift the end index one to the right. This simplifies both
qstring_from_substr() and its callers.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180727062204.10401-3-armbru@redhat.com>
In order to test that the NBD server is properly advertising
dirty bitmaps, we need a bare minimum client that can request
and read the context. Since feature freeze for 3.0 is imminent,
this is the smallest workable patch, which replaces the qemu
block status report with the results of the NBD server's dirty
bitmap (making it very easy to use 'qemu-img map --output=json'
to learn where the dirty portions are). Note that the NBD
protocol defines a dirty section with the same bit but opposite
sense that normal "base:allocation" uses to report an allocated
section; so in qemu-img map output, "data":true corresponds to
clean, "data":false corresponds to dirty.
A more complete solution that allows dirty bitmaps to be queried
at the same time as normal block status will be required before
this addition can lose the x- prefix. Until then, the fact that
this replaces normal status with dirty status means actions
like 'qemu-img convert' will likely misbehave due to treating
dirty regions of the file as if they are unallocated.
The next patch adds an iotest to exercise this new code.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180702191458.28741-2-eblake@redhat.com>
The previous commit fixed -blockdev breakage due to misuse of the
qobject input visitor's keyval flavor in bdrv_file_open(). The commit
message explain why using the plain flavor would be just as wrong; it
would break -drive. Turns out we break it in three places:
nbd_open(), sd_open() and ssh_file_open(). They are even marked
FIXME. Example breakage:
$ qemu-system-x86 -drive node-name=n1,driver=nbd,server.type=inet,server.host=localhost,server.port=1234,server.numeric=off
qemu-system-x86: -drive node-name=n1,driver=nbd,server.type=inet,server.host=localhost,server.port=1234,server.numeric=off: Invalid parameter type for 'numeric', expected: boolean
Fix it the same way: replace qdict_crumple() by
qdict_crumple_for_keyval_qiv(), and switch from plain to the keyval
flavor.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
There are numerous QDict functions that have been introduced for and are
used only by the block layer. Move their declarations into an own
header file to reflect that.
While qdict_extract_subqdict() is in fact used outside of the block
layer (in util/qemu-config.c), it is still a function related very
closely to how the block layer works with nested QDicts, namely by
sometimes flattening them. Therefore, its declaration is put into this
header as well and util/qemu-config.c includes it with a comment stating
exactly which function it needs.
Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20180509165530.29561-7-mreitz@redhat.com>
[Copyright note tweaked, superfluous includes dropped]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
When pulling in headers that are in the same directory as the C file (as
opposed to one in include/), we should use its relative path, without a
directory.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Now that we can safely call QOBJECT() on QObject * as well as its
subtypes, we can have macros qobject_ref() / qobject_unref() that work
everywhere instead of having to use QINCREF() / QDECREF() for QObject
and qobject_incref() / qobject_decref() for its subtypes.
The replacement is mechanical, except I broke a long line, and added a
cast in monitor_qmp_cleanup_req_queue_locked(). Unlike
qobject_decref(), qobject_unref() doesn't accept void *.
Note that the new macros evaluate their argument exactly once, thus no
need to shout them.
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180419150145.24795-4-marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Rebased, semantic conflict resolved, commit message improved]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Minimal realization: only one extent in server answer is supported.
Flag NBD_CMD_FLAG_REQ_ONE is used to force this behavior.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180312152126.286890-6-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: grammar tweaks, fix min_block check and 32-bit cap, use -1
instead of errno on failure in nbd_negotiate_simple_meta_context,
ensure that block status makes progress on success]
Signed-off-by: Eric Blake <eblake@redhat.com>
In my "build everything" tree, a change to the types in
qapi-schema.json triggers a recompile of about 4800 out of 5100
objects.
The previous commit split up qmp-commands.h, qmp-event.h, qmp-visit.h,
qapi-types.h. Each of these headers still includes all its shards.
Reduce compile time by including just the shards we actually need.
To illustrate the benefits: adding a type to qapi/migration.json now
recompiles some 2300 instead of 4800 objects. The next commit will
improve it further.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20180211093607.27351-24-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
[eblake: rebase to master]
Signed-off-by: Eric Blake <eblake@redhat.com>
Commit 79ba8c98 (v2.7) changed the setting of request_alignment
to occur only during bdrv_refresh_limits(), rather than at at
bdrv_open() time; but at the time, NBD was unaffected, because
it still used sector-based callbacks, so the block layer
defaulted NBD to use 512 request_alignment.
Later, commit 70c4fb26 (also v2.7) changed NBD to use byte-based
callbacks, without setting request_alignment. This resulted in
NBD using request_alignment of 1, which works great when the
server supports it (as is the case for qemu-nbd), but falls apart
miserably if the server requires alignment (but only if qemu
actually sends a sub-sector request; qemu-io can do it, but
most qemu operations still perform on sectors or larger).
Even later, the NBD protocol was updated to document that clients
should learn the server's minimum alignment during NBD_OPT_GO;
and recommended that clients should assume a minimum size of 512
unless the server understands NBD_OPT_GO and replied with a smaller
size. Commit 081dd1fe (v2.10) attempted to do that, by assigning
request_alignment to whatever was learned from the server; but
it has two flaws: the assignment is done during bdrv_open() so
it gets unconditionally wiped out back to 1 during any later
bdrv_refresh_limits(); and the code is not using a default of 512
when the server did not report a minimum size.
Fix these issues by moving the assignment to request_alignment
to the right function, and by using a sane default when the
server does not advertise a minimum size.
CC: qemu-stable@nongnu.org
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180215032905.27146-1-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy<vsementsov@virtuozzo.com>
