From clang-13:
nbd/server.c:976:22: error: variable 'bitmaps' set but not used \
[-Werror,-Wunused-but-set-variable]
which is incorrect; see //bugs.llvm.org/show_bug.cgi?id=3888.
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Before switching between AioContexts we need to make sure that we're
fully quiesced ("nb_requests == 0" for every client) when entering the
drained section.
To do this, we set "quiescing = true" for every client on
".drained_begin" to prevent new coroutines from being created, and
check if "nb_requests == 0" on ".drained_poll". Finally, once we're
exiting the drained section, on ".drained_end" we set "quiescing =
false" and call "nbd_client_receive_next_request()" to resume the
processing of new requests.
With these changes, "blk_aio_attach()" and "blk_aio_detach()" can be
reverted to be as simple as they were before f148ae7d36.
RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1960137
Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Sergio Lopez <slp@redhat.com>
Message-Id: <20210602060552.17433-3-slp@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
When querying image extents for raw image, qemu-nbd reports holes as
zero:
$ qemu-nbd -t -r -f raw empty-6g.raw
$ qemu-img map --output json nbd://localhost
[{ "start": 0, "length": 6442450944, "depth": 0, "zero": true, "data": true, "offset": 0}]
$ qemu-img map --output json empty-6g.raw
[{ "start": 0, "length": 6442450944, "depth": 0, "zero": true, "data": false, "offset": 0}]
Turns out that qemu-img map reports a hole based on BDRV_BLOCK_DATA, but
nbd server reports a hole based on BDRV_BLOCK_ALLOCATED.
The NBD protocol says:
NBD_STATE_HOLE (bit 0): if set, the block represents a hole (and
future writes to that area may cause fragmentation or encounter an
NBD_ENOSPC error); if clear, the block is allocated or the server
could not otherwise determine its status.
qemu-img manual says:
whether the sectors contain actual data or not (boolean field data;
if false, the sectors are either unallocated or stored as
optimized all-zero clusters);
To me, data=false looks compatible with NBD_STATE_HOLE. From user point
of view, getting same results from qemu-nbd and qemu-img is more
important than being more correct about allocation status.
Changing nbd server to report holes using BDRV_BLOCK_DATA makes qemu-nbd
results compatible with qemu-img map:
$ qemu-img map --output json nbd://localhost
[{ "start": 0, "length": 6442450944, "depth": 0, "zero": true, "data": false, "offset": 0}]
Signed-off-by: Nir Soffer <nsoffer@redhat.com>
Message-Id: <20210219160752.1826830-1-nsoffer@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
When switching between AIO contexts we need to me make sure that both
recv_coroutine and send_coroutine are not scheduled to run. Otherwise,
QEMU may crash while attaching the new context with an error like
this one:
aio_co_schedule: Co-routine was already scheduled in 'aio_co_schedule'
To achieve this we need a local implementation of
'qio_channel_readv_all_eof' named 'nbd_read_eof' (a trick already done
by 'nbd/client.c') that allows us to interrupt the operation and to
know when recv_coroutine is yielding.
With this in place, we delegate detaching the AIO context to the
owning context with a BH ('nbd_aio_detach_bh') scheduled using
'aio_wait_bh_oneshot'. This BH signals that we need to quiesce the
channel by setting 'client->quiescing' to 'true', and either waits for
the coroutine to finish using AIO_WAIT_WHILE or, if it's yielding in
'nbd_read_eof', actively enters the coroutine to interrupt it.
RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1900326
Signed-off-by: Sergio Lopez <slp@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20201214170519.223781-4-slp@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Coverity noticed (CID 1436125) that we check the return value of
nbd_extent_array_add in most places, but not at the end of
bitmap_to_extents(). The return value exists to break loops before a
future iteration, so there is nothing to check if we are already done
iterating. Adding a cast to void, plus a comment why, pacifies
Coverity.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20201111163510.713855-1-eblake@redhat.com>
[eblake: Prefer cast to void over odd && usage]
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Allow the server to expose an additional metacontext to be requested
by savvy clients. qemu-nbd adds a new option -A to expose the
qemu:allocation-depth metacontext through NBD_CMD_BLOCK_STATUS; this
can also be set via QMP when using block-export-add.
qemu as client is hacked into viewing the key aspects of this new
context by abusing the already-experimental x-dirty-bitmap option to
collapse all depths greater than 2, which results in a tri-state value
visible in the output of 'qemu-img map --output=json' (yes, that means
x-dirty-bitmap is now a bit of a misnomer, but I didn't feel like
renaming it as it would introduce a needless break of back-compat,
even though we make no compat guarantees with x- members):
unallocated (depth 0) => "zero":false, "data":true
local (depth 1) => "zero":false, "data":false
backing (depth 2+) => "zero":true, "data":true
libnbd as client is probably a nicer way to get at the information
without having to decipher such hacks in qemu as client. ;)
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20201027050556.269064-11-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
'qemu-img map' provides a way to determine which extents of an image
come from the top layer vs. inherited from a backing chain. This is
useful information worth exposing over NBD. There is a proposal to
add a QMP command block-dirty-bitmap-populate which can create a dirty
bitmap that reflects allocation information, at which point the
qemu:dirty-bitmap:NAME metadata context can expose that information
via the creation of a temporary bitmap, but we can shorten the effort
by adding a new qemu:allocation-depth metadata context that does the
same thing without an intermediate bitmap (this patch does not
eliminate the need for that proposal, as it will have other uses as
well).
While documenting things, remember that although the NBD protocol has
NBD_OPT_SET_META_CONTEXT, the rest of its documentation refers to
'metadata context', which is a more apt description of what is
actually being used by NBD_CMD_BLOCK_STATUS: the user is requesting
metadata by passing one or more context names. So I also touched up
some existing wording to prefer the term 'metadata context' where it
makes sense.
Note that this patch does not actually enable any way to request a
server to enable this context; that will come in the next patch.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20201027050556.269064-10-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
With this, 'qemu-nbd -B b0 -B b1 -f qcow2 img.qcow2' can let you sniff
out multiple bitmaps from one server. qemu-img as client can still
only read one bitmap per client connection, but other NBD clients
(hello libnbd) can now read multiple bitmaps in a single pass.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20201027050556.269064-8-eblake@redhat.com>
Rather than open-code the count of negotiated contexts at several
sites, embed it directly into the struct. This will make it easier
for upcoming commits to support even more simultaneous contexts.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20201027050556.269064-7-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Each dirty bitmap already knows its name; by reducing the scope of the
places where we construct "qemu:dirty-bitmap:NAME" strings, tracking
the name is more localized, and there are fewer per-export fields to
worry about. This in turn will make it easier for an upcoming patch
to export more than one bitmap at once.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20201027050556.269064-6-eblake@redhat.com>
Since 'block-export-add' is new to 5.2, we can still tweak the
interface; there, allowing 'bitmaps':['str'] is nicer than
'bitmap':'str'. This wires up the qapi and qemu-nbd changes to permit
passing multiple bitmaps as distinct metadata contexts that the NBD
client may request, but the actual support for more than one will
require a further patch to the server.
Note that there are no changes made to the existing deprecated
'nbd-server-add' command; this required splitting the QAPI type
BlockExportOptionsNbd, which fortunately does not affect QMP
introspection.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20201027050556.269064-5-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
Make it possible to specify the iothread where the export will run. By
default the block node can be moved to other AioContexts later and the
export will follow. The fixed-iothread option forces strict behavior
that prevents changing AioContext while the export is active. See the
QAPI docs for details.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200929125516.186715-5-stefanha@redhat.com
[Fix stray '#' character in block-export.json and add missing "(since:
5.2)" as suggested by Eric Blake.
--Stefan]
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
We had a premature optimization of trying to read as little from the
wire as possible while handling NBD_OPT_SET_META_CONTEXT in phases.
But in reality, we HAVE to read the entire string from the client
before we can get to the next command, and it is easier to just read
it all at once than it is to read it in pieces. And once we do that,
several functions end up no longer performing I/O, so they can drop
length and errp parameters, and just return a bool instead of
modifying through a pointer.
Our iotests still pass; I also checked that libnbd's testsuite (which
covers more corner cases of odd meta context requests) still passes.
There are cases where the sequence of trace messages produced differs
(for example, when no bitmap is exported, a query for "qemu:" now
produces two trace lines instead of one), but trace points are for
debug and have no effect on what the client sees.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200930121105.667049-4-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: enhance commit message]
Signed-off-by: Eric Blake <eblake@redhat.com>
The NBD spec is clear that any string sent from the client must not
contain embedded NUL characters. If the client passes "a\0", we
should reject that option request rather than act on "a".
Testing this is not possible with a compliant client, but I was able
to use gdb to coerce libnbd into temporarily behaving as such a
client.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200930121105.667049-3-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
gcc 10 from Fedora 32 gives me:
Compiling C object libblock.fa.p/nbd_server.c.o
../nbd/server.c: In function ‘nbd_co_client_start’:
../nbd/server.c:625:14: error: ‘namelen’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
625 | rc = nbd_negotiate_send_info(client, NBD_INFO_NAME, namelen, name,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
626 | errp);
| ~~~~~
../nbd/server.c:564:14: note: ‘namelen’ was declared here
564 | uint32_t namelen;
| ^~~~~~~
cc1: all warnings being treated as errors
As I cannot see how this can happen, let uns silence the warning.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-Id: <20200930155859.303148-3-borntraeger@de.ibm.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
There is no real reason any more why nbd_export_new() and
nbd_export_create() should be separate functions. The latter only
performs a few checks before it calls the former.
What makes the current state stand out is that it's the only function in
BlockExportDriver that is not a static function inside nbd/server.c, but
a small wrapper in blockdev-nbd.c that then calls back into nbd/server.c
for the real functionality.
Move all the checks to nbd/server.c and make the resulting function
static to improve readability.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-27-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The 'writable' option is a basic option that will probably be applicable
to most if not all export types that we will implement. Move it from NBD
to the generic BlockExport layer.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-26-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Every export type will need a BlockBackend, so creating it centrally in
blk_exp_add() instead of the .create driver callback avoids duplication.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-24-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Every block export has a BlockBackend representing the disk that is
exported. It should live in BlockExport therefore.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-23-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Implement a new QMP command block-export-del and make nbd-server-remove
a wrapper around it.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-21-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The reference owned by the user/monitor that is created when adding the
export and dropped when removing it was tied to the 'exports' list in
nbd/server.c. Every block export will have a user reference, so move it
to the block export level and tie it to the 'block_exports' list in
block/export/export.c instead. This is necessary for introducing a QMP
command for removing exports.
Note that exports are present in block_exports even after the user has
requested shutdown. This is different from NBD's exports where exports
are immediately removed on a shutdown request, even if they are still in
the process of shutting down. In order to avoid that the user still
interacts with an export that is shutting down (and possibly removes it
a second time), we need to remember if the user actually still owns it.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-20-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This adds a function to shut down all block exports, and another one to
shut down the block exports of a single type. The latter is used for now
when stopping the NBD server. As soon as we implement support for
multiple NBD servers, we'll need a per-server list of exports and it
will be replaced by a function using that.
As a side effect, the BlockExport layer has a list tracking all existing
exports now. closed_exports loses its only user and can go away.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-18-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Instead of letting the driver allocate and return the BlockExport
object, allocate it already in blk_exp_add() and pass it. This allows us
to initialise the generic part before calling into the driver so that
the driver can just use these values instead of having to parse the
options a second time.
For symmetry, move freeing the BlockExport to blk_exp_unref().
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-17-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-15-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Having a refcount makes sense for all types of block exports. It is also
a prerequisite for keeping a list of all exports at the BlockExport
level.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-14-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Closing export is somewhat convoluted because nbd_export_close() and
nbd_export_put() call each other and the ways they actually end up being
nested is not necessarily obvious.
However, it is not really necessary to call nbd_export_close() from
nbd_export_put() when putting the last reference because it only does
three things:
1. Close all clients. We're going to refcount 0 and all clients hold a
reference, so we know there is no active client any more.
2. Close the user reference (represented by exp->name being non-NULL).
The same argument applies: If the export were still named, we would
still have a reference.
3. Freeing exp->description. This is really cleanup work to be done when
the export is finally freed. There is no reason to already clear it
while clients are still in the process of shutting down.
So after moving the cleanup of exp->description, the code can be
simplified so that only nbd_export_close() calls nbd_export_put(), but
never the other way around.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200924152717.287415-13-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The export close callback is unused by the built-in NBD server. qemu-nbd
uses it only during shutdown to wait for the unrefed export to actually
go away. It can just use nbd_export_close_all() instead and do without
the callback.
This removes the close callback from nbd_export_new() and makes both
callers of it more similar.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200924152717.287415-11-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
nbd-server-add tries to be convenient and adds two questionable
features that we don't want to share in block-export-add, even for NBD
exports:
1. When requesting a writable export of a read-only device, the export
is silently downgraded to read-only. This should be an error in the
context of block-export-add.
2. When using a BlockBackend name, unplugging the device from the guest
will automatically stop the NBD server, too. This may sometimes be
what you want, but it could also be very surprising. Let's keep
things explicit with block-export-add. If the user wants to stop the
export, they should tell us so.
Move these things into the nbd-server-add QMP command handler so that
they apply only there.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-8-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Instead of implementing qemu-nbd --offset in the NBD code, just put a
raw block node with the requested offset on top of the user image and
rely on that doing the job.
This does not only simplify the nbd_export_new() interface and bring it
closer to the set of options that the nbd-server-add QMP command offers,
but in fact it also eliminates a potential source for bugs in the NBD
code which previously had to add the offset manually in all relevant
places.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200924152717.287415-7-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
We want to have a common set of commands for all types of block exports.
Currently, this is only NBD, but we're going to add more types.
This patch adds the basic BlockExport and BlockExportDriver structs and
a QMP command block-export-add that creates a new export based on the
given BlockExportOptions.
qmp_nbd_server_add() becomes a wrapper around qmp_block_export_add().
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-5-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200924152717.287415-2-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
When looking for a dirty bitmap to share, we should handle filters by
just including them in the search (so they do not break backing chains).
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
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]
Consider nbd_export_close_all(). The call-stack looks like this:
nbd_export_close_all() -> nbd_export_close -> call client_close() for
each client.
client_close() doesn't guarantee that client is closed: nbd_trip()
keeps reference to it. So, nbd_export_close_all() just reduce
reference counter on export and removes it from the list, but doesn't
guarantee that nbd_trip() finished neither export actually removed.
Let's wait for all exports actually removed.
Without this fix, the following crash is possible:
- export bitmap through internal Qemu NBD server
- connect a client
- shutdown Qemu
On shutdown nbd_export_close_all is called, but it actually don't wait
for nbd_trip() to finish and to release its references. So, export is
not release, and exported bitmap remains busy, and on try to remove the
bitmap (which is part of bdrv_close()) the assertion fails:
bdrv_release_dirty_bitmap_locked: Assertion `!bdrv_dirty_bitmap_busy(bitmap)' failed
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200714162234.13113-2-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.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.]
Ever since commit 36683283 (v2.8), the server code asserts that error
strings sent to the client are well-formed per the protocol by not
exceeding the maximum string length of 4096. At the time the server
first started sending error messages, the assertion could not be
triggered, because messages were completely under our control.
However, over the years, we have added latent scenarios where a client
could trigger the server to attempt an error message that would
include the client's information if it passed other checks first:
- requesting NBD_OPT_INFO/GO on an export name that is not present
(commit 0cfae925 in v2.12 echoes the name)
- requesting NBD_OPT_LIST/SET_META_CONTEXT on an export name that is
not present (commit e7b1948d in v2.12 echoes the name)
At the time, those were still safe because we flagged names larger
than 256 bytes with a different message; but that changed in commit
93676c88 (v4.2) when we raised the name limit to 4096 to match the NBD
string limit. (That commit also failed to change the magic number
4096 in nbd_negotiate_send_rep_err to the just-introduced named
constant.) So with that commit, long client names appended to server
text can now trigger the assertion, and thus be used as a denial of
service attack against a server. As a mitigating factor, if the
server requires TLS, the client cannot trigger the problematic paths
unless it first supplies TLS credentials, and such trusted clients are
less likely to try to intentionally crash the server.
We may later want to further sanitize the user-supplied strings we
place into our error messages, such as scrubbing out control
characters, but that is less important to the CVE fix, so it can be a
later patch to the new nbd_sanitize_name.
Consideration was given to changing the assertion in
nbd_negotiate_send_rep_verr to instead merely log a server error and
truncate the message, to avoid leaving a latent path that could
trigger a future CVE DoS on any new error message. However, this
merely complicates the code for something that is already (correctly)
flagging coding errors, and now that we are aware of the long message
pitfall, we are less likely to introduce such errors in the future,
which would make such error handling dead code.
Reported-by: Xueqiang Wei <xuwei@redhat.com>
CC: qemu-stable@nongnu.org
Fixes: https://bugzilla.redhat.com/1843684 CVE-2020-10761
Fixes: 93676c88d7
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200610163741.3745251-2-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Use bdrv_dirty_bitmap_next_dirty_area for bitmap_to_extents. Since
bdrv_dirty_bitmap_next_dirty_area is very accurate in its interface,
we'll never exceed requested region with last chunk. So, we don't need
dont_fragment, and bitmap_to_extents() interface becomes clean enough
to not require any comment.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20200205112041.6003-10-vsementsov@virtuozzo.com
Signed-off-by: John Snow <jsnow@redhat.com>
Introduce NBDExtentArray class, to handle extents list creation in more
controlled way and with fewer OUT parameters in functions.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20200205112041.6003-9-vsementsov@virtuozzo.com
Signed-off-by: John Snow <jsnow@redhat.com>
We are going to introduce bdrv_dirty_bitmap_next_dirty so that same
variable may be used to store its return value and to be its parameter,
so it would int64_t.
Similarly, we are going to refactor hbitmap_next_dirty_area to use
hbitmap_next_dirty together with hbitmap_next_zero, therefore we want
hbitmap_next_zero parameter type to be int64_t too.
So, for convenience update all parameters of *_next_zero and
*_next_dirty_area to be int64_t.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20200205112041.6003-6-vsementsov@virtuozzo.com
Signed-off-by: John Snow <jsnow@redhat.com>
Detected by a hang in the libnbd testsuite. If a client requests
multiple meta contexts (both base:allocation and qemu:dirty-bitmap:x)
at the same time, our attempt to silence a false-positive warning
about a potential uninitialized variable introduced botched logic: we
were short-circuiting the second context, and never sending the
NBD_REPLY_FLAG_DONE. Combining two 'if' into one 'if/else' in
bdf200a55 was wrong (I'm a bit embarrassed that such a change was my
initial suggestion after the v1 patch, then I did not review the v2
patch that actually got committed). Revert that, and instead silence
the false positive warning by replacing 'return ret' with 'return 0'
(the value it always has at that point in the code, even though it
eluded the deduction abilities of the robot that reported the false
positive).
Fixes: bdf200a553
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200206173832.130004-1-eblake@redhat.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Fixes:
/mnt/sdb/qemu/nbd/server.c: In function 'nbd_handle_request':
/mnt/sdb/qemu/nbd/server.c:2313:9: error: 'ret' may be used uninitialized in this function [-Werror=maybe-uninitialized]
int ret;
Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Pan Nengyuan <pannengyuan@huawei.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20200108025132.46956-1-pannengyuan@huawei.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
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>
As long as we limit NBD names to 256 bytes (the bare minimum permitted
by the standard), stack-allocation works for parsing a name received
from the client. But as mentioned in a comment, we eventually want to
permit up to the 4k maximum of the NBD standard, which is too large
for stack allocation; so switch everything in the server to use heap
allocation. For now, there is no change in actually supported name
length.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20191114024635.11363-2-eblake@redhat.com>
[eblake: fix uninit variable compile failure]
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
When iothreads are in use, the failure to grab the aio context results
in an assertion failure when trying to unlock things during blk_unref,
when trying to unlock a mutex that was not locked. In short, all
calls to nbd_export_put need to done while within the correct aio
context. But since nbd_export_put can recursively reach itself via
nbd_export_close, and recursively grabbing the context would deadlock,
we can't do the context grab directly in those functions, but must do
so in their callers.
Hoist the use of the correct aio_context from nbd_export_new() to its
caller qmp_nbd_server_add(). Then tweak qmp_nbd_server_remove(),
nbd_eject_notifier(), and nbd_esport_close_all() to grab the right
context, so that all callers during qemu now own the context before
nbd_export_put() can call blk_unref().
Remaining uses in qemu-nbd don't matter (since that use case does not
support iothreads).
Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190917023917.32226-1-eblake@redhat.com>
Reviewed-by: Sergio Lopez <slp@redhat.com>
On creation, the export's AioContext is set to the same one as the
BlockBackend, while the AioContext in the client QIOChannel is left
untouched.
As a result, when using data-plane, nbd_client_receive_next_request()
schedules coroutines in the IOThread AioContext, while the client's
QIOChannel is serviced from the main_loop, potentially triggering the
assertion at qio_channel_restart_[read|write].
To fix this, as soon we have the export corresponding to the client,
we call qio_channel_attach_aio_context() to attach the QIOChannel
context to the export's AioContext. This matches with the logic at
blk_aio_attached().
RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1748253
Signed-off-by: Sergio Lopez <slp@redhat.com>
Message-Id: <20190912110032.26395-1-slp@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
The server side is fairly straightforward: we can always advertise
support for detection of fast zero, and implement it by mapping the
request to the block layer BDRV_REQ_NO_FALLBACK.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190823143726.27062-5-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: update iotests 223, 233]
Commit fe0480d6 and friends added BDRV_REQ_NO_FALLBACK as a way to
avoid wasting time on a preliminary write-zero request that will later
be rewritten by actual data, if it is known that the write-zero
request will use a slow fallback; but in doing so, could not optimize
for NBD. The NBD specification is now considering an extension that
will allow passing on those semantics; this patch updates the new
protocol bits and 'qemu-nbd --list' output to recognize the bit, as
well as the new errno value possible when using the new flag; while
upcoming patches will improve the client to use the feature when
present, and the server to advertise support for it.
The NBD spec recommends (but not requires) that ENOTSUP be avoided for
all but failures of a fast zero (the only time it is mandatory to
avoid an ENOTSUP failure is when fast zero is supported but not
requested during write zeroes; the questionable use is for ENOTSUP to
other actions like a normal write request). However, clients that get
an unexpected ENOTSUP will either already be treating it the same as
EINVAL, or may appreciate the extra bit of information. We were
equally loose for returning EOVERFLOW in more situations than
recommended by the spec, so if it turns out to be a problem in
practice, a later patch can tighten handling for both error codes.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190823143726.27062-3-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: tweak commit message, also handle EOPNOTSUPP]
When creating a read-only image, we are still advertising support for
TRIM and WRITE_ZEROES to the client, even though the client should not
be issuing those commands. But seeing this requires looking across
multiple functions:
All callers to nbd_export_new() passed a single flag based solely on
whether the export allows writes. Later, we then pass a constant set
of flags to nbd_negotiate_options() (namely, the set of flags which we
always support, at least for writable images), which is then further
dynamically modified with NBD_FLAG_SEND_DF based on client requests
for structured options. Finally, when processing NBD_OPT_EXPORT_NAME
or NBD_OPT_EXPORT_GO we bitwise-or the original caller's flag with the
runtime set of flags we've built up over several functions.
Let's refactor things to instead compute a baseline of flags as soon
as possible which gets shared between multiple clients, in
nbd_export_new(), and changing the signature for the callers to pass
in a simpler bool rather than having to figure out flags. We can then
get rid of the 'myflags' parameter to various functions, and instead
refer to client for everything we need (we still have to perform a
bitwise-OR for NBD_FLAG_SEND_DF during NBD_OPT_EXPORT_NAME and
NBD_OPT_EXPORT_GO, but it's easier to see what is being computed).
This lets us quit advertising senseless flags for read-only images, as
well as making the next patch for exposing FAST_ZERO support easier to
write.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190823143726.27062-2-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: improve commit message, update iotest 223]
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>
The NBD specification defines NBD_FLAG_CAN_MULTI_CONN, which can be
advertised when the server promises cache consistency between
simultaneous clients (basically, rules that determine what FUA and
flush from one client are able to guarantee for reads from another
client). When we don't permit simultaneous clients (such as qemu-nbd
without -e), the bit makes no sense; and for writable images, we
probably have a lot more work before we can declare that actions from
one client are cache-consistent with actions from another. But for
read-only images, where flush isn't changing any data, we might as
well advertise multi-conn support. What's more, advertisement of the
bit makes it easier for clients to determine if 'qemu-nbd -e' was in
use, where a second connection will succeed rather than hang until the
first client goes away.
This patch affects qemu as server in advertising the bit. We may want
to consider patches to qemu as client to attempt parallel connections
for higher throughput by spreading the load over those connections
when a server advertises multi-conn, but for now sticking to one
connection per nbd:// BDS is okay.
See also: https://bugzilla.redhat.com/1708300
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190815185024.7010-1-eblake@redhat.com>
[eblake: tweak blockdev-nbd.c to not request shared when writable,
fix iotest 233]
Reviewed-by: John Snow <jsnow@redhat.com>
Add a public interface for get. While we're at it,
rename "bdrv_get_dirty_bitmap_locked" to "bdrv_dirty_bitmap_get_locked".
(There are more functions to rename to the bdrv_dirty_bitmap_VERB form,
but they will wait until the conclusion of this series.)
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190709232550.10724-11-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190812052359.30071-20-armbru@redhat.com>
This helps to avoid extra io, allocations and memory copying.
We assume here that CMD_CACHE is always used with copy-on-read, as
otherwise it's a noop.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20190725100550.33801-4-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Commit 3d068aff (3.0) introduced NBD_MAX_BITMAP_EXTENTS as a limit on
how large we would allow a reply to NBD_CMD_BLOCK_STATUS to grow when
it is visiting a qemu:dirty-bitmap: context. Later, commit fb7afc79
(3.1) reused the constant to limit base:allocation context replies,
although the name is now less appropriate in that situation.
Rename things, and improve the macro to use units.h for better
legibility. Then reformat the comment to comply with checkpatch rules
added in the meantime. No semantic change.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190510151735.29687-1-eblake@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
This adds a new parameter to blk_new() which requires its callers to
declare from which AioContext this BlockBackend is going to be used (or
the locks of which AioContext need to be taken anyway).
The given context is only stored and kept up to date when changing
AioContexts. Actually applying the stored AioContext to the root node
is saved for another commit.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The NBD server uses an AioContext notifier, so it can tolerate that its
BlockBackend is switched to a different AioContext. Before we start
actually calling bdrv_try_set_aio_context(), which checks for
consistency, outside of test cases, we need to make sure that the NBD
server actually allows this.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
In commit 0c1d50bd, I added a couple of TODO comments about whether we
consult bl.request_alignment when responding to NBD_OPT_INFO. At the
time, qemu as server was hard-coding an advertised alignment of 512 to
clients that promised to obey constraints, and there was no function
for getting at a device's preferred alignment. But in hindsight,
advertising 512 when the block device prefers 1 caused other
compliance problems, and commit b0245d64 changed one of the two TODO
comments to advertise a more accurate alignment. Time to fix the other
TODO. Doesn't really impact qemu as client (our normal client doesn't
use NBD_OPT_INFO, and qemu-nbd --list promises to obey block sizes),
but it might prove useful to other clients.
Fixes: b0245d64
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190403030526.12258-4-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
We've recently added traces for clients to flag server non-compliance;
let's do the same for servers to flag client non-compliance. According
to the spec, if the client requests NBD_INFO_BLOCK_SIZE, it is
promising to send all requests aligned to those boundaries. Of
course, if the client does not request NBD_INFO_BLOCK_SIZE, then it
made no promises so we shouldn't flag anything; and because we are
willing to handle clients that made no promises (the spec allows us to
use NBD_REP_ERR_BLOCK_SIZE_REQD if we had been unwilling), we already
have to handle unaligned requests (which the block layer already does
on our behalf). So even though the spec allows us to return EINVAL
for clients that promised to behave, it's easier to always answer
unaligned requests. Still, flagging non-compliance can be useful in
debugging a client that is trying to be maximally portable.
Qemu as client used to have one spot where it sent non-compliant
requests: if the server sends an unaligned reply to
NBD_CMD_BLOCK_STATUS, and the client was iterating over the entire
disk, the next request would start at that unaligned point; this was
fixed in commit a39286dd when the client was taught to work around
server non-compliance; but is equally fixed if the server is patched
to not send unaligned replies in the first place (yes, qemu 4.0 as
server still has few such bugs, although they will be patched in
4.1). Fortunately, I did not find any more spots where qemu as client
was non-compliant. I was able to test the patch by using the following
hack to convince qemu-io to run various unaligned commands, coupled
with serving 512-byte alignment by intentionally omitting '-f raw' on
the server while viewing server traces.
| diff --git i/nbd/client.c w/nbd/client.c
| index 427980bdd22..1858b2aac35 100644
| --- i/nbd/client.c
| +++ w/nbd/client.c
| @@ -449,6 +449,7 @@ static int nbd_opt_info_or_go(QIOChannel *ioc, uint32_t opt,
| nbd_send_opt_abort(ioc);
| return -1;
| }
| + info->min_block = 1;//hack
| if (!is_power_of_2(info->min_block)) {
| error_setg(errp, "server minimum block size %" PRIu32
| " is not a power of two", info->min_block);
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190403030526.12258-3-eblake@redhat.com>
[eblake: address minor review nits]
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Don't increment remaining_bytes until we know that we will actually be
including the current block status extent in the reply; otherwise, the
value traced will include a bytes value that is oversized by the
length of the next block status extent which did not get sent because
it instead ended the loop.
Fixes: fb7afc79
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190403030526.12258-2-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Both NBD_CMD_BLOCK_STATUS and structured NBD_CMD_READ will split their
reply according to bdrv_block_status() boundaries. If the block device
has a request_alignment smaller than 512, but we advertise a block
alignment of 512 to the client, then this can result in the server
reply violating client expectations by reporting a smaller region of
the export than what the client is permitted to address (although this
is less of an issue for qemu 4.0 clients, given recent client patches
to overlook our non-compliance at EOF). Since it's always better to
be strict in what we send, it is worth advertising the actual minimum
block limit rather than blindly rounding it up to 512.
Note that this patch is not foolproof - it is still possible to
provoke non-compliant server behavior using:
$ qemu-nbd --image-opts driver=blkdebug,align=512,image.driver=file,image.filename=/path/to/non-aligned-file
That is arguably a bug in the blkdebug driver (it should never pass
back block status smaller than its alignment, even if it has to make
multiple bdrv_get_status calls and determine the
least-common-denominator status among the group to return). It may
also be possible to observe issues with a backing layer with smaller
alignment than the active layer, although so far I have been unable to
write a reliable iotest for that scenario (but again, an issue like
that could be argued to be a bug in the block layer, or something
where we need a flag to bdrv_block_status() to state whether the
result must be aligned to the current layer's limits or can be
subdivided for accuracy when chasing backing files).
Anyways, as blkdebug is not normally used, and as this patch makes our
server more interoperable with qemu 3.1 clients, it is worth applying
now, even while we still work on a larger patch series for the 4.1
timeframe to have byte-accurate file lengths.
Note that the iotests output changes - for 223 and 233, we can see the
server's better granularity advertisement; and for 241, the three test
cases have the following effects:
- natural alignment: the server's smaller alignment is now advertised,
and the hole reported at EOF is now the right result; we've gotten rid
of the server's non-compliance
- forced server alignment: the server still advertises 512 bytes, but
still sends a mid-sector hole. This is still a server compliance bug,
which needs to be fixed in the block layer in a later patch; output
does not change because the client is already being tolerant of the
non-compliance
- forced client alignment: the server's smaller alignment means that
the client now sees the server's status change mid-sector without any
protocol violations, but the fact that the map shows an unaligned
mid-sector hole is evidence of the block layer problems with aligned
block status, to be fixed in a later patch
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190329042750.14704-7-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: rebase to enhanced iotest 241 coverage]
Instead of checking against busy, inconsistent, or read only directly,
use a check function with permissions bits that let us streamline the
checks without reproducing them in many places.
Included in this patch are permissions changes that simply add the
inconsistent check to existing permissions call spots, without
addressing existing bugs.
In general, this means that busy+readonly checks become BDRV_BITMAP_DEFAULT,
which checks against all three conditions. busy-only checks become
BDRV_BITMAP_ALLOW_RO.
Notably, remove allows inconsistent bitmaps, so it doesn't follow the pattern.
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20190301191545.8728-4-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
These mean the same thing now. Unify them and rename the merged call
bdrv_dirty_bitmap_busy to indicate semantically what we are describing,
as well as help disambiguate from the various _locked and _unlocked
versions of bitmap helpers that refer to mutex locks.
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20190223000614.13894-8-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
Check that the bitmap is not in use prior to it checking if it is
not enabled/recording guest writes. The bitmap being busy was likely
at the behest of the user, so this error has a greater chance of being
understood by the user.
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20190223000614.13894-6-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
Currently any client which can complete the TLS handshake is able to use
the NBD server. The server admin can turn on the 'verify-peer' option
for the x509 creds to require the client to provide a x509 certificate.
This means the client will have to acquire a certificate from the CA
before they are permitted to use the NBD server. This is still a fairly
low bar to cross.
This adds a '--tls-authz OBJECT-ID' option to the qemu-nbd command which
takes the ID of a previously added 'QAuthZ' object instance. This will
be used to validate the client's x509 distinguished name. Clients
failing the authorization check will not be permitted to use the NBD
server.
For example to setup authorization that only allows connection from a client
whose x509 certificate distinguished name is
CN=laptop.example.com,O=Example Org,L=London,ST=London,C=GB
escape the commas in the name and use:
qemu-nbd --object tls-creds-x509,id=tls0,dir=/home/berrange/qemutls,\
endpoint=server,verify-peer=yes \
--object 'authz-simple,id=auth0,identity=CN=laptop.example.com,,\
O=Example Org,,L=London,,ST=London,,C=GB' \
--tls-creds tls0 \
--tls-authz authz0 \
....other qemu-nbd args...
NB: a real shell command line would not have leading whitespace after
the line continuation, it is just included here for clarity.
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <20190227162035.18543-2-berrange@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: split long line in --help text, tweak 233 to show that whitespace
after ,, in identity= portion is actually okay]
Signed-off-by: Eric Blake <eblake@redhat.com>
lgtm.com pointed out that commit 678ba275 introduced a shadowed
declaration of local variable 'bs'; thankfully, the inner 'bs'
obtained by 'blk_bs(blk)' matches the outer one given that we had
'blk_insert_bs(blk, bs, errp)' a few lines earlier, and there are
no later uses of 'bs' beyond the scope of the 'if (bitmap)' to
care if we change the value stored in 'bs' while traveling the
backing chain to find a bitmap. So simply get rid of the extra
declaration.
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190207191357.6665-1-eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
We generally do very similar things around nbd_read: error_prepend
specifying what we have tried to read, and be_to_cpu conversion of
integers.
So, it seems reasonable to move common things to helper functions,
which:
1. simplify code a bit
2. generalize nbd_read error descriptions, all starting with
"Failed to read"
3. make it more difficult to forget to convert things from BE
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190128165830.165170-1-vsementsov@virtuozzo.com>
[eblake: rename macro to DEF_NBD_READ_N and formatting tweaks;
checkpatch has false positive complaint]
Signed-off-by: Eric Blake <eblake@redhat.com>
Although our compile-time environment is set up so that we always
support long files with 64-bit off_t, we have no guarantee whether
off_t is the same type as int64_t. This requires casts when
printing values, and prevents us from directly using qemu_strtoi64()
(which will be done in the next patch). Let's just flip to uint64_t
where possible, and stick to int64_t for detecting failure of
blk_getlength(); we also keep the assertions added in the previous
patch that the resulting values fit in 63 bits. The overflow check
in nbd_co_receive_request() was already sane (request->from is
validated to fit in 63 bits, and request->len is 32 bits, so the
addition can't overflow 64 bits), but rewrite it in a form easier
to recognize as a typical overflow check.
Rename the variable 'description' to keep line lengths reasonable.
Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190117193658.16413-7-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
We only had two callers to nbd_export_new; qemu-nbd.c always
passed a valid offset/length pair (because it already checked
the file length, to ensure that offset was in bounds), while
blockdev-nbd.c always passed 0/-1. Then nbd_export_new reduces
the size to a multiple of BDRV_SECTOR_SIZE (can only happen
when offset is not sector-aligned, since bdrv_getlength()
currently rounds up) (someday, it would be nice to have
byte-accurate lengths - but not today).
However, I'm finding it easier to work with the code if we are
consistent on having both callers pass in a valid length, and
just assert that things are sane in nbd_export_new, meaning
that no negative values were passed, and that offset+size does
not exceed 63 bits (as that really is a fundamental limit to
later operations, whether we use off_t or uint64_t).
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190117193658.16413-6-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
We only have one caller that wants to export a bitmap name,
which it does right after creation of the export. But there is
still a brief window of time where an NBD client could see the
export but not the dirty bitmap, which a robust client would
have to interpret as meaning the entire image should be treated
as dirty. Better is to eliminate the window entirely, by
inlining nbd_export_bitmap() into nbd_export_new(), and refusing
to create the bitmap in the first place if the requested bitmap
can't be located.
We also no longer need logic for setting a different bitmap
name compared to the bitmap being exported.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20190111194720.15671-8-eblake@redhat.com>
The existing NBD code had a weird split where nbd_export_new()
created an export but did not add it to the list of exported
names until a later nbd_export_set_name() came along and grabbed
a second reference on the object; later, the first call to
nbd_export_close() drops the second reference while removing
the export from the list. This is in part because the QAPI
NbdServerRemoveNode enum documents the possibility of adding a
mode where we could do a soft disconnect: preventing new clients,
but waiting for existing clients to gracefully quit, based on
the mode used when calling nbd_export_close().
But in spite of all that, note that we never change the name of
an NBD export while it is exposed, which means it is easier to
just inline the process of setting the name as part of creating
the export.
Inline the contents of nbd_export_set_name() and
nbd_export_set_description() into the two points in an export
lifecycle where they matter, then adjust both callers to pass
the name up front. Note that for creation, all callers pass a
non-NULL name, (passing NULL at creation was for old style
servers, but we removed support for that in commit 7f7dfe2a),
so we can add an assert and do things unconditionally; but for
cleanup, because of the dual nature of nbd_export_close(), we
still have to be careful to avoid use-after-free. Along the
way, add a comment reminding ourselves of the potential of
adding a middle mode disconnect.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20190111194720.15671-5-eblake@redhat.com>
Our initial implementation of x-nbd-server-add-bitmap put
in a restriction because of incremental backups: in that
usage, we are exporting one qcow2 file (the temporary overlay
target of a blockdev-backup sync:none job) and a dirty bitmap
owned by a second qcow2 file (the source of the
blockdev-backup, which is the backing file of the temporary).
While both qcow2 files are still writable (the target in
order to capture copy-on-write of old contents, and the
source in order to track live guest writes in the meantime),
the NBD client expects to see constant data, including the
dirty bitmap. An enabled bitmap in the source would be
modified by guest writes, which is at odds with the NBD
export being a read-only constant view, hence the initial
code choice of enforcing a disabled bitmap (the intent is
that the exposed bitmap was disabled in the same transaction
that started the blockdev-backup job, although we don't want
to track enough state to actually enforce that).
However, consider the case of a bitmap contained in a read-only
node (including when the bitmap is found in a backing layer of
the active image). Because the node can't be modified, the
bitmap won't change due to writes, regardless of whether it is
still enabled. Forbidding the export unless the bitmap is
disabled is awkward, paritcularly since we can't change the
bitmap to be disabled (because the node is read-only).
Alternatively, consider the case of live storage migration,
where management directs the destination to create a writable
NBD server, then performs a drive-mirror from the source to
the target, prior to doing the rest of the live migration.
Since storage migration can be time-consuming, it may be wise
to let the destination include a dirty bitmap to track which
portions it has already received, where even if the migration
is interrupted and restarted, the source can query the
destination block status in order to potentially minimize
re-sending data that has not changed in the meantime on a
second attempt. Such code has not been written, and might not
be trivial (after all, a cluster being marked dirty in the
bitmap does not necessarily guarantee it has the desired
contents), but it makes sense that letting an active dirty
bitmap be exposed and changing alongside writes may prove
useful in the future.
Solve both issues by gating the restriction against a
disabled bitmap to only happen when the caller has requested
a read-only export, and where the BDS that owns the bitmap
(whether or not it is the BDS handed to nbd_export_new() or
from its backing chain) is still writable. We could drop
the check altogether (if management apps are prepared to
deal with a changing bitmap even on a read-only image), but
for now keeping a check for the read-only case still stands
a chance of preventing management errors.
Update iotest 223 to show the looser behavior by leaving
a bitmap enabled the whole run; note that we have to tear
down and re-export a node when handling an error.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190111194720.15671-4-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
The NBD spec, and even our code comment, says that if the client
asks for NBD_OPT_LIST_META_CONTEXT with 0 queries, then we should
reply with (a possibly-compressed representation of) ALL contexts
that we are willing to let them try. But commit 3d068aff forgot
to advertise qemu:dirty-bitmap:FOO.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20181130023232.3079982-2-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Commit 37ec36f6 intentionally ignores errors when trying to reply
to an NBD_OPT_ABORT request for plaintext clients, but did not make
the same change for a TLS server. Since NBD_OPT_ABORT is
documented as being a potential for an EPIPE when the client hangs
up without waiting for our reply, we don't need to pollute the
server's output with that failure.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20181117223221.2198751-1-eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
A space was missing after the option number was printed:
Option 0x8not permitted before TLS
becomes
Option 0x8 not permitted before TLS
This fixes
commit 3668328303
Author: Eric Blake <eblake@redhat.com>
Date: Fri Oct 14 13:33:09 2016 -0500
nbd: Send message along with server NBD_REP_ERR errors
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20181116155325.22428-2-berrange@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: move lone space to next line]
Signed-off-by: Eric Blake <eblake@redhat.com>
Whether it's "locked" or "frozen", it's in use and should
not be allowed for the purposes of this operation.
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20181002230218.13949-7-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
After the previous commit, nbd_client_new's first parameter is always
NULL. Let's drop it with all corresponding old-style negotiation code
path which is unreachable now.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20181003170228.95973-3-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: re-wrap short line]
Signed-off-by: Eric Blake <eblake@redhat.com>
We should not go to structured-read branch on CACHE command, fix that.
Bug introduced in bc37b06a5c "nbd/server: introduce NBD_CMD_CACHE"
with the whole feature and affects 3.0.0 release.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
CC: qemu-stable@nongnu.org
Message-Id: <20181003144738.70670-1-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: commit message typo fix]
Signed-off-by: Eric Blake <eblake@redhat.com>
Taking the address of a field in a packed struct is a bad idea, because
it might not be actually aligned enough for that pointer type (and
thus cause a crash on dereference on some host architectures). Newer
versions of clang warn about this. Avoid the bug by not using the
"modify in place" byte swapping functions.
This patch was produced with the following spatch script:
@@
expression E;
@@
-be16_to_cpus(&E);
+E = be16_to_cpu(E);
@@
expression E;
@@
-be32_to_cpus(&E);
+E = be32_to_cpu(E);
@@
expression E;
@@
-be64_to_cpus(&E);
+E = be64_to_cpu(E);
@@
expression E;
@@
-cpu_to_be16s(&E);
+E = cpu_to_be16(E);
@@
expression E;
@@
-cpu_to_be32s(&E);
+E = cpu_to_be32(E);
@@
expression E;
@@
-cpu_to_be64s(&E);
+E = cpu_to_be64(E);
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20180927164200.15097-1-peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: rebase, and squash in missed changes]
Signed-off-by: Eric Blake <eblake@redhat.com>
This is necessary for efficient block-status export, for clients which
support it. (qemu is not yet such a client, but could become one.)
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180704112302.471456-3-vsementsov@virtuozzo.com>
[eblake: grammar tweaks]
Signed-off-by: Eric Blake <eblake@redhat.com>
bitmap_to_extents function is broken: it switches dirty variable after
every iteration, however it can process only part of dirty (or zero)
area during one iteration in case when this area is too large for one
extent.
Fortunately, the bug doesn't produce wrong extent flags: it just inserts
a zero-length extent between sequential extents representing large dirty
(or zero) area. However, zero-length extents are forbidden by the NBD
protocol. So, a careful client should consider such a reply as a server
fault, while a less-careful will likely ignore zero-length extents.
The bug can only be triggered by a client that requests block status
for nearly 4G at once (a request of 4G and larger is impossible per
the protocol, and requests smaller than 4G less the bitmap granularity
cause the loop to quit iterating rather than revisit the tail of the
large area); it also cannot trigger if the client used the
NBD_CMD_FLAG_REQ_ONE flag. Since qemu 3.0 as client (using the
x-dirty-bitmap extension) always passes the flag, it is immune; and
we are not aware of other open-source clients that know how to request
qemu:dirty-bitmap:FOO contexts. Clients that want to avoid the bug
could cap block status requests to a smaller length, such as 2G or 3G.
Fix this by more careful handling of dirty variable.
Bug was introduced in 3d068aff16
"nbd/server: implement dirty bitmap export", with the whole function.
and is present in v3.0.0 release.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180914165116.23182-1-vsementsov@virtuozzo.com>
CC: qemu-stable@nongnu.org
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: improved commit message]
Signed-off-by: Eric Blake <eblake@redhat.com>
Call nbd_co_send_extents() with correct length parameter
(extent.length may be smaller than original length).
Also, switch length parameter type to uint32_t, to correspond with
request->len and similar nbd_co_send_bitmap().
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180704112302.471456-2-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
In my hurry to fix a build failure, I introduced a logic bug.
The assertion conditional is backwards, meaning that qemu will
now abort instead of reporting dirty bitmap status.
The bug can only be tickled by an NBD client using an exported
dirty bitmap (which is still an experimental QMP command), so
it's not the end of the world for supported usage (and neither
'make check' nor qemu-iotests fails); but it also shows that we
really want qemu-io support for reading dirty bitmaps if only
so that I can add iotests coverage to prevent future
brown-bag-of-shame events like this one.
Fixes: 45eb6fb6
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180622153509.375130-1-eblake@redhat.com>
The code has a while() loop that always initialized 'end', and
the loop always executes at least once (as evidenced by the assert()
just prior to the loop). But some versions of gcc still complain
that 'end' is used uninitialized, so silence them.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20180622125814.345274-1-eblake@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Handle nbd CACHE command. Just do read, without sending read data back.
Cache mechanism should be done by exported node driver chain.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180413143156.11409-1-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: fix two missing case labels in switch statements]
Signed-off-by: Eric Blake <eblake@redhat.com>
Handle a new NBD meta namespace: "qemu", and corresponding queries:
"qemu:dirty-bitmap:<export bitmap name>".
With the new metadata context negotiated, BLOCK_STATUS query will reply
with dirty-bitmap data, converted to extents. The new public function
nbd_export_bitmap selects which bitmap to export. For now, only one bitmap
may be exported.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180609151758.17343-5-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: wording tweaks, minor cleanups, additional tracing]
Signed-off-by: Eric Blake <eblake@redhat.com>
Add nbd_meta_pattern() and nbd_meta_empty_or_pattern() helpers for
metadata query parsing. nbd_meta_pattern() will be reused for the
"qemu" namespace in following patches.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180609151758.17343-4-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: comment tweaks]
Signed-off-by: Eric Blake <eblake@redhat.com>
Use NBDExport pointer instead of just export name: there is no need to
store a duplicated name in the struct; moreover, NBDExport will be used
further.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180609151758.17343-3-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: commit message grammar tweak]
Signed-off-by: Eric Blake <eblake@redhat.com>
Return code = 1 doesn't mean that we parsed base:allocation. Use
correct traces in both -parsed and -skipped cases.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180609151758.17343-2-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: comment tweaks]
Signed-off-by: Eric Blake <eblake@redhat.com>
The NBD spec says that behavior is unspecified if the client
requests 0 length for block status; but since the structured
reply is documenting as returning a non-zero length, it's
easier to just diagnose this with an EINVAL error than to
figure out what to return.
CC: qemu-stable@nongnu.org
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180621124937.166549-1-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Having a more detailed log of the interaction between client and
server is invaluable in debugging how meta context negotiation
actually works.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180330130950.1931229-1-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Minimal realization: only one extent in server answer is supported.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180312152126.286890-4-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: tweak whitespace, move constant from .h to .c, improve
logic of check_meta_export_name, simplify nbd_negotiate_options
by doing more in nbd_negotiate_meta_queries]
Signed-off-by: Eric Blake <eblake@redhat.com>
Add helper to read name in format:
uint32 len (<= NBD_MAX_NAME_SIZE)
len bytes string (not 0-terminated)
The helper will be reused in following patch.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180312152126.286890-3-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: grammar fixes, actually check error]
Signed-off-by: Eric Blake <eblake@redhat.com>
NBD_REP_ERR_INVALID is often parameter to nbd_opt_drop and it would
be used more in following patches. So, let's add a helper.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180312152126.286890-2-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
The NBD spec states that since trim requests can affect disk contents,
then they should allow for FUA semantics just like writes for ensuring
the disk has settled before returning. As bdrv_[co_]pdiscard() does
not support a flags argument, we can't pass FUA down the block layer
stack, and must therefore emulate it with a flush at the NBD layer.
Note that in all reality, generic well-behaved clients will never
send TRIM+FUA (in fact, qemu as a client never does, and we have no
intention to plumb flags into bdrv_pdiscard). This is because the
NBD protocol states that it is unspecified to READ a trimmed area
(you might read stale data, all zeroes, or even random unrelated
data) without first rewriting it, and even the experimental
BLOCK_STATUS extension states that TRIM need not affect reported
status. Thus, in the general case, a client cannot tell the
difference between an arbitrary server that ignores TRIM, a server
that had a power outage without flushing to disk, and a server that
actually affected the disk before returning; so waiting for the
trim actions to flush to disk makes little sense. However, for a
specific client and server pair, where the client knows the server
treats TRIM'd areas as guaranteed reads-zero, waiting for a flush
makes sense, hence why the protocol documents that FUA is valid on
trim. So, even though the NBD protocol doesn't have a way for the
server to advertise what effects (if any) TRIM will actually have,
and thus any client that relies on specific effects is probably
in error, we can at least support a client that requests TRIM+FUA.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180307225732.155835-1-eblake@redhat.com>
Split out request handling logic.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180308184636.178534-6-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: touch up blank line placement]
Signed-off-by: Eric Blake <eblake@redhat.com>
nbd_trip has difficult logic when sending replies: it tries to use one
code path for all replies. It is ok for simple replies, but is not
comfortable for structured replies. Also, two types of error (and
corresponding messages in local_err) - fatal (leading to disconnect)
and not-fatal (just to be sent to the client) are difficult to follow.
To make things a bit clearer, the following is done:
- split CMD_READ logic to separate function. It is the most difficult
command for now, and it is definitely cramped inside nbd_trip. Also,
it is difficult to follow CMD_READ logic, shared between
"case NBD_CMD_READ" and "if"s under "reply:" label.
- create separate helper function nbd_send_generic_reply() and use it
both in new nbd_do_cmd_read and for other commands in nbd_trip instead
of common code-path under "reply:" label in nbd_trip. The helper
supports an error message, so logic with local_err in nbd_trip is
simplified.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180308184636.178534-5-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: grammar tweaks and blank line placement]
Signed-off-by: Eric Blake <eblake@redhat.com>
Since the unchanged code has just set client->recv_coroutine to
NULL before calling nbd_client_receive_next_request(), we are
spawning a new coroutine unconditionally, but the first thing
that coroutine will do is check for client->closing, making it
a no-op if we have already detected that the client is going
away. Furthermore, for any error other than EIO (where we
disconnect, which itself sets client->closing), if the client
has already gone away, we'll probably encounter EIO later
in the function and attempt disconnect at that point. Logically,
as soon as we know the connection is closing, there is no need
to try a likely-to-fail a response or spawn a no-op coroutine.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180308184636.178534-4-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: squash in further reordering: hoist check before spawning
next coroutine, and document rationale in commit message]
Signed-off-by: Eric Blake <eblake@redhat.com>
In case of io error in nbd_co_send_sparse_read we should not
"goto reply:", as it was a fatal error and the common behavior
is to disconnect in this case. We should not try to send the
client an additional error reply, since we already hit a
channel-io error on our previous attempt to send one.
Fix this by handling block-status error in nbd_co_send_sparse_read,
so nbd_co_send_sparse_read fails only on io error. Then just skip
common "reply:" code path in nbd_trip.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180308184636.178534-3-vsementsov@virtuozzo.com>
[eblake: grammar tweaks]
Signed-off-by: Eric Blake <eblake@redhat.com>
