As Hanna pointed out, it is not clear in the code why qemu_open()
can fail, and why blkio_set_int("fd") is not enough to discover
the `fd` property support.
Let's fix them by adding more details in the code comments.
Suggested-by: Hanna Czenczek <hreitz@redhat.com>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20230803082825.25293-3-sgarzare@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
libblkio drivers take ownership of `fd` only after a successful
blkio_connect(), so if it fails, we are still the owners.
Fixes: cad2ccc395 ("block/blkio: use qemu_open() to support fd passing for virtio-blk")
Suggested-by: Hanna Czenczek <hreitz@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
Message-id: 20230803082825.25293-2-sgarzare@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Setting the `fd` property fails with virtio-blk-* libblkio drivers
that do not support fd passing since
https://gitlab.com/libblkio/libblkio/-/merge_requests/208.
Getting the `fd` property, on the other hand, always succeeds for
virtio-blk-* libblkio drivers even when they don't support fd passing.
This patch switches to setting the `fd` property because it is a
better mechanism for probing fd passing support than getting the `fd`
property.
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20230727161020.84213-5-sgarzare@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
qemu_open() fails if called with an unix domain socket in this way:
-blockdev node-name=drive0,driver=virtio-blk-vhost-user,path=vhost-user-blk.sock,cache.direct=on: Could not open 'vhost-user-blk.sock': No such device or address
Since virtio-blk-vhost-user does not support fd passing, let`s always fall back
on using `path` if we fail the fd passing.
Fixes: cad2ccc395 ("block/blkio: use qemu_open() to support fd passing for virtio-blk")
Reported-by: Qing Wang <qinwang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20230727161020.84213-4-sgarzare@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
libblkio 1.3.0 added support of "fd" property for virtio-blk-vhost-vdpa
driver. In QEMU, starting from commit cad2ccc395 ("block/blkio: use
qemu_open() to support fd passing for virtio-blk") we are using
`blkio_get_int(..., "fd")` to check if the "fd" property is supported
for all the virtio-blk-* driver.
Unfortunately that property is also available for those driver that do
not support it, such as virtio-blk-vhost-user.
So, `blkio_get_int()` is not enough to check whether the driver supports
the `fd` property or not. This is because the virito-blk common libblkio
driver only checks whether or not `fd` is set during `blkio_connect()`
and fails with -EINVAL for those transports that do not support it
(all except vhost-vdpa for now).
So let's handle the `blkio_connect()` failure, retrying it using `path`
directly.
Fixes: cad2ccc395 ("block/blkio: use qemu_open() to support fd passing for virtio-blk")
Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20230727161020.84213-3-sgarzare@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This is in preparation for the next patch, where for virtio-blk
drivers we need to handle the failure of blkio_connect().
Let's also rename the *_open() functions to *_connect() to make
the code reflect the changes applied.
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20230727161020.84213-2-sgarzare@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
qemu_open() in blkio_virtio_blk_common_open() is used to open the
character device (e.g. /dev/vhost-vdpa-0 or /dev/vfio/vfio) or in
the future eventually the unix socket.
In all these cases we cannot open the path in read-only mode,
when the `read-only` option of blockdev is on, because the exchange
of IOCTL commands for example will fail.
In order to open the device read-only, we have to use the `read-only`
property of the libblkio driver as we already do in blkio_file_open().
Fixes: cad2ccc395 ("block/blkio: use qemu_open() to support fd passing for virtio-blk")
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2225439
Reported-by: Qing Wang <qinwang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20230726074807.14041-1-sgarzare@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Until libblkio 1.3.0, virtio-blk drivers had completion eventfd
notifications enabled from the start, but from the next releases
this is no longer the case, so we have to explicitly enable them.
In fact, the libblkio documentation says they could be disabled,
so we should always enable them at the start if we want to be
sure to get completion eventfd notifications:
By default, the driver might not generate completion events for
requests so it is necessary to explicitly enable the completion
file descriptor before use:
void blkioq_set_completion_fd_enabled(struct blkioq *q, bool enable);
I discovered this while trying a development version of libblkio:
the guest kernel hangs during boot, while probing the device.
Fixes: fd66dbd424 ("blkio: add libblkio block driver")
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20230725103744.77343-1-sgarzare@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
When QEMU is built with --enable-modules, the module_block.py script
parses block/*.c to find block drivers that are built as modules. The
script generates a table of block drivers called block_driver_modules[].
This table is used for block driver module loading.
The blkio.c driver uses macros to define its BlockDriver structs. This
was done to avoid code duplication but the module_block.py script is
unable to parse the macro. The result is that libblkio-based block
drivers can be built as modules but will not be found at runtime.
One fix is to make the module_block.py script or build system fancier so
it can parse C macros (e.g. by parsing the preprocessed source code). I
chose not to do this because it raises the complexity of the build,
making future issues harder to debug.
Keep things simple: use the macro to avoid duplicating BlockDriver
function pointers but define .format_name and .protocol_name manually
for each BlockDriver. This way the module_block.py is able to parse the
code.
Also get rid of the block driver name macros (e.g. DRIVER_IO_URING)
because module_block.py cannot parse them either.
Fixes: fd66dbd424 ("blkio: add libblkio block driver")
Reported-by: Qing Wang <qinwang@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20230704123436.187761-1-stefanha@redhat.com
Cc: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Some virtio-blk drivers (e.g. virtio-blk-vhost-vdpa) supports the fd
passing. Let's expose this to the user, so the management layer
can pass the file descriptor of an already opened path.
If the libblkio virtio-blk driver supports fd passing, let's always
use qemu_open() to open the `path`, so we can handle fd passing
from the management layer through the "/dev/fdset/N" special path.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20230530071941.8954-2-sgarzare@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Stop using the .bdrv_co_io_plug() API because it is not multi-queue
block layer friendly. Use the new blk_io_plug_call() API to batch I/O
submission instead.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 20230530180959.1108766-4-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
All callers now pass is_external=false to aio_set_fd_handler() and
aio_set_event_notifier(). The aio_disable_external() API that
temporarily disables fd handlers that were registered is_external=true
is therefore dead code.
Remove aio_disable_external(), aio_enable_external(), and the
is_external arguments to aio_set_fd_handler() and
aio_set_event_notifier().
The entire test-fdmon-epoll test is removed because its sole purpose was
testing aio_disable_external().
Parts of this patch were generated using the following coccinelle
(https://coccinelle.lip6.fr/) semantic patch:
@@
expression ctx, fd, is_external, io_read, io_write, io_poll, io_poll_ready, opaque;
@@
- aio_set_fd_handler(ctx, fd, is_external, io_read, io_write, io_poll, io_poll_ready, opaque)
+ aio_set_fd_handler(ctx, fd, io_read, io_write, io_poll, io_poll_ready, opaque)
@@
expression ctx, notifier, is_external, io_read, io_poll, io_poll_ready;
@@
- aio_set_event_notifier(ctx, notifier, is_external, io_read, io_poll, io_poll_ready)
+ aio_set_event_notifier(ctx, notifier, io_read, io_poll, io_poll_ready)
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20230516190238.8401-21-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
bdrv_get_info() is categorized as an I/O function, and it currently
doesn't run in a coroutine. We should let it take a graph rdlock since
it traverses the block nodes graph, which however is only possible in a
coroutine.
Therefore turn it into a co_wrapper to move the actual function into a
coroutine where the lock can be taken.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230113204212.359076-11-kwolf@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
BlockDriver->bdrv_getlength is categorized as IO callback, and it
currently doesn't run in a coroutine. We should let it take a graph
rdlock since the callback traverses the block nodes graph, which however
is only possible in a coroutine.
Therefore turn it into a co_wrapper to move the actual function into a
coroutine where the lock can be taken.
Because now this function creates a new coroutine and polls, we need to
take the AioContext lock where it is missing, for the only reason that
internally co_wrapper calls AIO_WAIT_WHILE and it expects to release the
AioContext lock.
This is especially messy when a co_wrapper creates a coroutine and polls
in bdrv_open_driver, because this function has so many callers in so
many context that it can easily lead to deadlocks. Therefore the new
rule for bdrv_open_driver is that the caller must always hold the
AioContext lock of the given bs (except if it is a coroutine), because
the function calls bdrv_refresh_total_sectors() which is now a
co_wrapper.
Once the rwlock is ultimated and placed in every place it needs to be,
we will poll using AIO_WAIT_WHILE_UNLOCKED and remove the AioContext
lock.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230113204212.359076-7-kwolf@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
BlockDriver->bdrv_io_unplug is categorized as IO callback, and it
currently doesn't run in a coroutine. We should let it take a graph
rdlock since the callback traverses the block nodes graph, which however
is only possible in a coroutine.
The only caller of this function is blk_io_unplug(), therefore make
blk_io_unplug() a co_wrapper, so that we're always running in a
coroutine where the lock can be taken.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230113204212.359076-4-kwolf@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
After recent header file inclusion rework the build fails when the blkio
module is enabled:
../block/blkio.c: In function ‘blkio_detach_aio_context’:
../block/blkio.c:321:24: error: implicit declaration of function ‘bdrv_get_aio_context’; did you mean ‘qemu_get_aio_context’? [-Werror=implicit-function-declaration]
321 | aio_set_fd_handler(bdrv_get_aio_context(bs),
| ^~~~~~~~~~~~~~~~~~~~
| qemu_get_aio_context
../block/blkio.c:321:24: error: nested extern declaration of ‘bdrv_get_aio_context’ [-Werror=nested-externs]
../block/blkio.c:321:24: error: passing argument 1 of ‘aio_set_fd_handler’ makes pointer from integer without a cast [-Werror=int-conversion]
321 | aio_set_fd_handler(bdrv_get_aio_context(bs),
| ^~~~~~~~~~~~~~~~~~~~~~~~
| |
| int
In file included from /home/pipo/git/qemu.git/include/qemu/job.h:33,
from /home/pipo/git/qemu.git/include/block/blockjob.h:30,
from /home/pipo/git/qemu.git/include/block/block_int-global-state.h:28,
from /home/pipo/git/qemu.git/include/block/block_int.h:27,
from ../block/blkio.c:13:
/home/pipo/git/qemu.git/include/block/aio.h:476:37: note: expected ‘AioContext *’ but argument is of type ‘int’
476 | void aio_set_fd_handler(AioContext *ctx,
| ~~~~~~~~~~~~^~~
../block/blkio.c: In function ‘blkio_file_open’:
../block/blkio.c:821:34: error: passing argument 2 of ‘blkio_attach_aio_context’ makes pointer from integer without a cast [-Werror=int-conversion]
821 | blkio_attach_aio_context(bs, bdrv_get_aio_context(bs));
| ^~~~~~~~~~~~~~~~~~~~~~~~
| |
| int
Fix it by including 'block/block-io.h' which contains the required
declarations.
Fixes: e2c1c34f13
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-id: 2bc956011404a1ab03342aefde0087b5b4762562.1674477350.git.pkrempa@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Setting it to true can cause the device size to be queried from libblkio
in otherwise fast paths, degrading performance. Set it to false and
require users to refresh the device size explicitly instead.
Fixes: 4c8f4fda05 ("block/blkio: Tolerate device size changes")
Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Alberto Faria <afaria@redhat.com>
Message-Id: <20221108144433.1334074-1-afaria@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The nvme-io_uring driver expects a character special file such as
/dev/ng0n1. Follow the convention of having a "filename" option when a
regular file is expected, and a "path" option otherwise.
This makes io_uring the only libblkio-based driver with a "filename"
option, as it accepts a regular file (even though it can also take a
block special file).
Signed-off-by: Alberto Faria <afaria@redhat.com>
Message-id: 20221028233854.839933-1-afaria@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Some libblkio drivers may be able to work with regular files (e.g.,
io_uring) or otherwise resizable devices. Conservatively set
BlockDriver::has_variable_length to true to ensure bdrv_nb_sectors()
always gives up-to-date results.
Also implement BlockDriver::bdrv_co_truncate for the case where no
preallocation is needed and the device already has a size compatible
with what was requested.
Signed-off-by: Alberto Faria <afaria@redhat.com>
Message-id: 20221029122031.975273-1-afaria@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Avoid bounce buffers when QEMUIOVector elements are within previously
registered bdrv_register_buf() buffers.
The idea is that emulated storage controllers will register guest RAM
using bdrv_register_buf() and set the BDRV_REQ_REGISTERED_BUF on I/O
requests. Therefore no blkio_map_mem_region() calls are necessary in the
performance-critical I/O code path.
This optimization doesn't apply if the I/O buffer is internally
allocated by QEMU (e.g. qcow2 metadata). There we still take the slow
path because BDRV_REQ_REGISTERED_BUF is not set.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20221013185908.1297568-13-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
libblkio (https://gitlab.com/libblkio/libblkio/) is a library for
high-performance disk I/O. It currently supports io_uring,
virtio-blk-vhost-user, and virtio-blk-vhost-vdpa with additional drivers
under development.
One of the reasons for developing libblkio is that other applications
besides QEMU can use it. This will be particularly useful for
virtio-blk-vhost-user which applications may wish to use for connecting
to qemu-storage-daemon.
libblkio also gives us an opportunity to develop in Rust behind a C API
that is easy to consume from QEMU.
This commit adds io_uring, nvme-io_uring, virtio-blk-vhost-user, and
virtio-blk-vhost-vdpa BlockDrivers to QEMU using libblkio. It will be
easy to add other libblkio drivers since they will share the majority of
code.
For now I/O buffers are copied through bounce buffers if the libblkio
driver requires it. Later commits add an optimization for
pre-registering guest RAM to avoid bounce buffers.
The syntax is:
--blockdev io_uring,node-name=drive0,filename=test.img,readonly=on|off,cache.direct=on|off
--blockdev nvme-io_uring,node-name=drive0,filename=/dev/ng0n1,readonly=on|off,cache.direct=on
--blockdev virtio-blk-vhost-vdpa,node-name=drive0,path=/dev/vdpa...,readonly=on|off,cache.direct=on
--blockdev virtio-blk-vhost-user,node-name=drive0,path=vhost-user-blk.sock,readonly=on|off,cache.direct=on
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20221013185908.1297568-3-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
