This is a relatively new feature in libfuse (available since 3.8.0,
which was released in November 2019), so we have to add a dedicated
check whether it is available before making use of it.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20201027190600.192171-7-mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

This allows allocating areas after the (old) EOF as part of a growing
resize, writing zeroes, and discarding.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20201027190600.192171-6-mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

These will behave more like normal files in that writes beyond the EOF
will automatically grow the export size.

As an optimization, keep the RESIZE permission for growable exports so
we do not have to take it for every post-EOF write.  (This permission is
not released when the export is destroyed, because at that point the
BlockBackend is destroyed altogether anyway.)

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20201027190600.192171-5-mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

This makes the export actually useful instead of only producing errors
whenever it is accessed.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20201027190600.192171-4-mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block-export-add type=fuse allows mounting block graph nodes via FUSE on
some existing regular file.  That file should then appears like a raw
disk image, and accesses to it result in accesses to the exported BDS.

Right now, we only implement the necessary block export functions to set
it up and shut it down.  We do not implement any access functions, so
accessing the mount point only results in errors.  This will be
addressed by a followup patch.

We keep a hash table of exported mount points, because we want to be
able to detect when users try to use a mount point twice.  This is
because we invoke stat() to check whether the given mount point is a
regular file, but if that file is served by ourselves (because it is
already used as a mount point), then this stat() would have to be served
by ourselves, too, which is impossible to do while we (as the caller)
are waiting for it to settle.  Therefore, keep track of mount point
paths to at least catch the most obvious instances of that problem.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20201027190600.192171-3-mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

Do not validate input with g_return_val_if(). This API is intended for
checking programming errors and is compiled out with -DG_DISABLE_CHECKS.

Use an explicit if statement for input validation so it cannot
accidentally be compiled out.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20201118091644.199527-5-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

By making libvhost-user a subproject, check it builds
standalone (without the global QEMU cflags etc).

Note that the library still relies on QEMU include/qemu/atomic.h and
linux_headers/.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20201125100640.366523-6-marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

The --enable/disable-vhost-user-blk-server options were implemented in
./configure. There has been confusion about them and part of the problem
is that the shell syntax used for setting the default value is not easy
to read. Move the option over to meson where the conditions are easier
to understand:

  have_vhost_user_blk_server = (targetos == 'linux')

  if get_option('vhost_user_blk_server').enabled()
      if targetos != 'linux'
          error('vhost_user_blk_server requires linux')
      endif
  elif get_option('vhost_user_blk_server').disabled() or not have_system
      have_vhost_user_blk_server = false
  endif

This patch does not change behavior.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20201110171121.1265142-2-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Refuse get_config() requests in excess of sizeof(struct virtio_blk_config).

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20201027173528.213464-5-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

VIRTIO 1.0 devices have little-endian configuration space. The
vhost-user-blk-server.c code already uses little-endian for virtqueue
processing but not for the configuration space fields. Fix this so the
vhost-user-blk export works on big-endian hosts.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20201027173528.213464-4-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Make it possible to compile out the vhost-user-blk server. It is enabled
by default on Linux.

Note that vhost-user-server.c depends on libvhost-user, which requires
CONFIG_LINUX. The CONFIG_VHOST_USER dependency was erroneous since that
option controls vhost-user frontends (previously known as "master") and
not device backends (previously known as "slave").

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20201027173528.213464-3-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Allow the number of queues to be configured using --export
vhost-user-blk,num-queues=N. This setting should match the QEMU --device
vhost-user-blk-pci,num-queues=N setting but QEMU vhost-user-blk.c lowers
its own value if the vhost-user-blk backend offers fewer queues than
QEMU.

The vhost-user-blk-server.c code is already capable of multi-queue. All
virtqueue processing runs in the same AioContext. No new locking is
needed.

Add the num-queues=N option and set the VIRTIO_BLK_F_MQ feature bit.
Note that the feature bit only announces the presence of the num_queues
configuration space field. It does not promise that there is more than 1
virtqueue, so we can set it unconditionally.

I tested multi-queue by running a random read fio test with numjobs=4 on
an -smp 4 guest. After the benchmark finished the guest /proc/interrupts
file showed activity on all 4 virtio-blk MSI-X. The /sys/block/vda/mq/
directory shows that Linux blk-mq has 4 queues configured.

An automated test is included in the next commit.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-id: 20201001144604.559733-2-stefanha@redhat.com
[Fixed accidental tab characters as suggested by Markus Armbruster
--Stefan]
Signed-off-by: Stefan Hajnoczi <stefanha@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>

Block exports are used by softmmu, qemu-storage-daemon, and qemu-nbd.
They are not used by other programs and are not otherwise needed in
libblock.

Undo the recent move of blockdev-nbd.c from blockdev_ss into block_ss.
Since bdrv_close_all() (libblock) calls blk_exp_close_all()
(libblockdev) a stub function is required..

Make qemu-nbd.c use signal handling utility functions instead of
duplicating the code. This helps because os-posix.c is in libblockdev
and it depends on a qemu_system_killed() symbol that qemu-nbd.c lacks.
Once we use the signal handling utility functions we also end up
providing the necessary symbol.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20200929125516.186715-4-stefanha@redhat.com
[Fixed s/ndb/nbd/ typo in commit description as suggested by Eric Blake
--Stefan]
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Don't compile contrib/libvhost-user/libvhost-user.c again. Instead build
the static library once and then reuse it throughout QEMU.

Also switch from CONFIG_LINUX to CONFIG_VHOST_USER, which is what the
vhost-user tools (vhost-user-gpu, etc) do.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200924151549.913737-14-stefanha@redhat.com
[Added CONFIG_LINUX again because libvhost-user doesn't build on macOS.
--Stefan]
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Headers used by other subsystems are located in include/. Also add the
vhost-user-server and vhost-user-blk-server headers to MAINTAINERS.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200924151549.913737-13-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Use the new QAPI block exports API instead of defining our own QOM
objects.

This is a large change because the lifecycle of VuBlockDev needs to
follow BlockExportDriver. QOM properties are replaced by QAPI options
objects.

VuBlockDev is renamed VuBlkExport and contains a BlockExport field.
Several fields can be dropped since BlockExport already has equivalents.

The file names and meson build integration will be adjusted in a future
patch. libvhost-user should probably be built as a static library that
is linked into QEMU instead of as a .c file that results in duplicate
compilation.

The new command-line syntax is:

  $ qemu-storage-daemon \
      --blockdev file,node-name=drive0,filename=test.img \
      --export vhost-user-blk,node-name=drive0,id=export0,unix-socket=/tmp/vhost-user-blk.sock

Note that unix-socket is optional because we may wish to accept chardevs
too in the future.

Markus noted that supported address families are not explicit in the
QAPI schema. It is unlikely that support for more address families will
be added since file descriptor passing is required and few address
families support it. If a new address family needs to be added, then the
QAPI 'features' syntax can be used to advertize them.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-id: 20200924151549.913737-12-stefanha@redhat.com
[Skip test on big-endian host architectures because this device doesn't
support them yet (as already mentioned in a code comment).
--Stefan]
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Propagate the flush return value since errors are possible.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200924151549.913737-11-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

The vu_client_trip() coroutine is leaked during AioContext switching. It
is also unsafe to destroy the vu_dev in panic_cb() since its callers
still access it in some cases.

Rework the lifecycle to solve these safety issues.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200924151549.913737-10-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

The device panic notifier callback is not used. Drop it.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200924151549.913737-7-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Only one struct is needed per request. Drop req_data and the separate
VuBlockReq instance. Instead let vu_queue_pop() allocate everything at
once.

This fixes the req_data memory leak in vu_block_virtio_process_req().

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200924151549.913737-6-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

By making use of libvhost-user, block device drive can be shared to
the connected vhost-user client. Only one client can connect to the
server one time.

Since vhost-user-server needs a block drive to be created first, delay
the creation of this object.

Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Coiby Xu <coiby.xu@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20200918080912.321299-6-coiby.xu@gmail.com
[Shorten "vhost_user_blk_server" string to "vhost_user_blk" to avoid the
following compiler warning:
../block/export/vhost-user-blk-server.c:178:50: error: ‘%s’ directive output truncated writing 21 bytes into a region of size 20 [-Werror=format-truncation=]
and fix "Invalid size %ld ..." ssize_t format string arguments for
32-bit hosts.
--Stefan]
Signed-off-by: Stefan Hajnoczi <stefanha@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>

This adds a simple QMP command to query the list of block exports.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-25-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>

Clients may want to know when an export has finally disappeard
(block-export-del returns earlier than that in the general case), so add
a QAPI event for it.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20200924152717.287415-22-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Max Reitz <mreitz@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>

We'll need an id to identify block exports in monitor commands. This
adds one.

Note that this is different from the 'name' option in the NBD server,
which is the externally visible export name. While block export ids need
to be unique in the whole process, export names must be unique only for
the same server. Different export types or (potentially in the future)
multiple NBD servers can have the same export name externally, but still
need different block export ids internally.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-19-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>

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>

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>