Commit Graph
1338 Commits
Author SHA1 Message Date
Hanna Reitz 0bc329fbb0 block: block-status cache for data regions
As we have attempted before
(https://lists.gnu.org/archive/html/qemu-devel/2019-01/msg06451.html,
"file-posix: Cache lseek result for data regions";
https://lists.nongnu.org/archive/html/qemu-block/2021-02/msg00934.html,
"file-posix: Cache next hole"), this patch seeks to reduce the number of
SEEK_DATA/HOLE operations the file-posix driver has to perform.  The
main difference is that this time it is implemented as part of the
general block layer code.

The problem we face is that on some filesystems or in some
circumstances, SEEK_DATA/HOLE is unreasonably slow.  Given the
implementation is outside of qemu, there is little we can do about its
performance.

We have already introduced the want_zero parameter to
bdrv_co_block_status() to reduce the number of SEEK_DATA/HOLE calls
unless we really want zero information; but sometimes we do want that
information, because for files that consist largely of zero areas,
special-casing those areas can give large performance boosts.  So the
real problem is with files that consist largely of data, so that
inquiring the block status does not gain us much performance, but where
such an inquiry itself takes a lot of time.

To address this, we want to cache data regions.  Most of the time, when
bad performance is reported, it is in places where the image is iterated
over from start to end (qemu-img convert or the mirror job), so a simple
yet effective solution is to cache only the current data region.

(Note that only caching data regions but not zero regions means that
returning false information from the cache is not catastrophic: Treating
zeroes as data is fine.  While we try to invalidate the cache on zero
writes and discards, such incongruences may still occur when there are
other processes writing to the image.)

We only use the cache for nodes without children (i.e. protocol nodes),
because that is where the problem is: Drivers that rely on block-status
implementations outside of qemu (e.g. SEEK_DATA/HOLE).

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/307
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20210812084148.14458-3-hreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[hreitz: Added `local_file == bs` assertion, as suggested by Vladimir]
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2021-09-15 15:54:06 +02:00
Hanna Reitz 33ff4c9e08 block: Drop BDS comment regarding bdrv_append()
There is a comment above the BDS definition stating care must be taken
to consider handling newly added fields in bdrv_append().

Actually, this comment should have said "bdrv_swap()" as of 4ddc07cac
(nine years ago), and in any case, bdrv_swap() was dropped in
8e419aefa (six years ago).  So no such care is necessary anymore.

Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210812084148.14458-2-hreitz@redhat.com>
2021-09-15 15:54:06 +02:00
Vladimir Sementsov-OgievskiyandHanna Reitz abde8ac2a5 block/block-copy: block_copy_state_new(): drop extra arguments
The only caller pass copy_range and compress both false. Let's just
drop these arguments.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210824083856.17408-35-vsementsov@virtuozzo.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2021-09-01 14:38:08 +02:00
Vladimir Sementsov-OgievskiyandHanna Reitz b518e9e9ef block/backup: move cluster size calculation to block-copy
The main consumer of cluster-size is block-copy. Let's calculate it
here instead of passing through backup-top.

We are going to publish copy-before-write filter soon, so it will be
created through options. But we don't want for now to make explicit
option for cluster-size, let's continue to calculate it automatically.
So, now is the time to get rid of cluster_size argument for
bdrv_cbw_append().

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20210824083856.17408-10-vsementsov@virtuozzo.com>
[hreitz: Add qemu/error-report.h include to block/block-copy.c]
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2021-09-01 14:03:11 +02:00
Vladimir Sementsov-OgievskiyandHanna Reitz f8b9504bac block/block-copy: introduce block_copy_set_copy_opts()
We'll need a possibility to set compress and use_copy_range options
after initialization of the state. So make corresponding part of
block_copy_state_new() separate and public.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210824083856.17408-8-vsementsov@virtuozzo.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2021-09-01 12:57:31 +02:00
Vladimir Sementsov-OgievskiyandHanna Reitz 49577723d4 block-copy: move detecting fleecing scheme to block-copy
We want to simplify initialization interface of copy-before-write
filter as we are going to make it public. So, let's detect fleecing
scheme exactly in block-copy code, to not pass this information through
extra levels.

Why not just set BDRV_REQ_SERIALISING unconditionally: because we are
going to implement new more efficient fleecing scheme which will not
rely on backing feature.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20210824083856.17408-7-vsementsov@virtuozzo.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2021-09-01 12:57:31 +02:00
Vladimir Sementsov-OgievskiyandHanna Reitz bd8f4c42c8 block: introduce bdrv_replace_child_bs()
Add function to transactionally replace bs inside BdrvChild.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20210824083856.17408-2-vsementsov@virtuozzo.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2021-09-01 12:57:31 +02:00
Klaus Jensen a316aa50e6 hw/nvme: use symbolic names for registers
Add the NvmeBarRegs enum and use these instead of explicit register
offsets.

Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
Reviewed-by: Gollu Appalanaidu <anaidu.gollu@samsung.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
2021-07-26 21:09:38 +02:00
Klaus Jensen 5d45edbeac hw/nvme: split pmrmsc register into upper and lower
The specification uses a set of 32 bit PMRMSCL and PMRMSCU registers to
make up the 64 bit logical PMRMSC register.

Make it so.

Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
2021-07-26 21:09:38 +02:00
Stefano GarzarellaandStefan Hajnoczi 1793ad0247 iothread: add aio-max-batch parameter
The `aio-max-batch` parameter will be propagated to AIO engines
and it will be used to control the maximum number of queued requests.

When there are in queue a number of requests equal to `aio-max-batch`,
the engine invokes the system call to forward the requests to the kernel.

This parameter allows us to control the maximum batch size to reduce
the latency that requests might accumulate while queued in the AIO
engine queue.

If `aio-max-batch` is equal to 0 (default value), the AIO engine will
use its default maximum batch size value.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20210721094211.69853-3-sgarzare@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2021-07-21 13:47:50 +01:00
Peter Maydell 42e1d798a6 Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging
Block layer patches

- Make blockdev-reopen stable
- Remove deprecated qemu-img backing file without format
- rbd: Convert to coroutines and add write zeroes support
- rbd: Updated MAINTAINERS
- export/fuse: Allow other users access to the export
- vhost-user: Fix backends without multiqueue support
- Fix drive-backup transaction endless drained section

# gpg: Signature made Fri 09 Jul 2021 13:49:22 BST
# gpg:                using RSA key DC3DEB159A9AF95D3D7456FE7F09B272C88F2FD6
# gpg:                issuer "kwolf@redhat.com"
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream: (28 commits)
  block: Make blockdev-reopen stable API
  iotests: Test reopening multiple devices at the same time
  block: Support multiple reopening with x-blockdev-reopen
  block: Acquire AioContexts during bdrv_reopen_multiple()
  block: Add bdrv_reopen_queue_free()
  qcow2: Fix dangling pointer after reopen for 'file'
  qemu-img: Improve error for rebase without backing format
  qemu-img: Require -F with -b backing image
  qcow2: Prohibit backing file changes in 'qemu-img amend'
  blockdev: fix drive-backup transaction endless drained section
  vhost-user: Fix backends without multiqueue support
  MAINTAINERS: add block/rbd.c reviewer
  block/rbd: fix type of task->complete
  iotests/fuse-allow-other: Test allow-other
  iotests/308: Test +w on read-only FUSE exports
  export/fuse: Let permissions be adjustable
  export/fuse: Give SET_ATTR_SIZE its own branch
  export/fuse: Add allow-other option
  export/fuse: Pass default_permissions for mount
  util/uri: do not check argument of uri_free()
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2021-07-10 19:55:21 +01:00
Kevin Wolf 6cf42ca2f9 block: Acquire AioContexts during bdrv_reopen_multiple()
As the BlockReopenQueue can contain nodes in multiple AioContexts, only
one of which may be locked when AIO_WAIT_WHILE() can be called, we can't
let the caller lock the right contexts. Instead, individually lock the
AioContext of a single node when iterating the queue.

Reintroduce bdrv_reopen() as a wrapper for reopening a single node that
drains the node and temporarily drops the AioContext lock for
bdrv_reopen_multiple().

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210708114709.206487-4-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2021-07-09 13:19:11 +02:00
Alberto GarciaandKevin Wolf ab5b522879 block: Add bdrv_reopen_queue_free()
Move the code to free a BlockReopenQueue to a separate function.
It will be used in a subsequent patch.

[ kwolf: Also free explicit_options and options, and explicitly
  qobject_ref() the value when it continues to be used. This makes
  future memory leaks less likely. ]

Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210708114709.206487-3-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2021-07-09 13:19:11 +02:00
Stefan Hajnoczi 0f08586c71 util/async: add a human-readable name to BHs for debugging
It can be difficult to debug issues with BHs in production environments.
Although BHs can usually be identified by looking up their ->cb()
function pointer, this requires debug information for the program. It is
also not possible to print human-readable diagnostics about BHs because
they have no identifier.

This patch adds a name to each BH. The name is not unique per instance
but differentiates between cb() functions, which is usually enough. It's
done by changing aio_bh_new() and friends to macros that stringify cb.

The next patch will use the name field when reporting leaked BHs.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20210414200247.917496-2-stefanha@redhat.com>
2021-07-05 11:40:32 +01:00
Peter Maydell 9c2647f750 Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging
Block layer patches

- Supporting changing 'file' in x-blockdev-reopen
- ssh: add support for sha256 host key fingerprints
- vhost-user-blk: Implement reconnection during realize
- introduce QEMU_AUTO_VFREE
- Don't require password of encrypted backing file for image creation
- Code cleanups

# gpg: Signature made Wed 30 Jun 2021 17:00:55 BST
# gpg:                using RSA key DC3DEB159A9AF95D3D7456FE7F09B272C88F2FD6
# gpg:                issuer "kwolf@redhat.com"
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream: (24 commits)
  vhost-user-blk: Implement reconnection during realize
  vhost-user-blk: Factor out vhost_user_blk_realize_connect()
  vhost: Distinguish errors in vhost_dev_get_config()
  vhost-user-blk: Add Error parameter to vhost_user_blk_start()
  vhost: Return 0/-errno in vhost_dev_init()
  vhost: Distinguish errors in vhost_backend_init()
  vhost: Add Error parameter to vhost_dev_init()
  block/ssh: add support for sha256 host key fingerprints
  block/commit: use QEMU_AUTO_VFREE
  introduce QEMU_AUTO_VFREE
  iotests: Test replacing files with x-blockdev-reopen
  block: Allow changing bs->file on reopen
  block: BDRVReopenState: drop replace_backing_bs field
  block: move supports_backing check to bdrv_set_file_or_backing_noperm()
  block: bdrv_reopen_parse_backing(): simplify handling implicit filters
  block: bdrv_reopen_parse_backing(): don't check frozen child
  block: bdrv_reopen_parse_backing(): don't check aio context
  block: introduce bdrv_set_file_or_backing_noperm()
  block: introduce bdrv_remove_file_or_backing_child()
  block: comment graph-modifying function not updating permissions
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2021-07-02 11:46:32 +01:00
Peter Maydell 1ec2cd0ce2 Merge remote-tracking branch 'remotes/nvme/tags/nvme-next-pull-request' into staging
hw/nvme patches

* namespace eui64 support (Heinrich)
* aiocb refactoring (Klaus)
* controller parameter for auto zone transitioning (Niklas)
* misc fixes and additions (Gollu, Klaus, Keith)

# gpg: Signature made Tue 29 Jun 2021 19:46:55 BST
# gpg:                using RSA key 522833AA75E2DCE6A24766C04DE1AF316D4F0DE9
# gpg: Good signature from "Klaus Jensen <its@irrelevant.dk>" [unknown]
# gpg:                 aka "Klaus Jensen <k.jensen@samsung.com>" [unknown]
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: DDCA 4D9C 9EF9 31CC 3468  4272 63D5 6FC5 E55D A838
#      Subkey fingerprint: 5228 33AA 75E2 DCE6 A247  66C0 4DE1 AF31 6D4F 0DE9

* remotes/nvme/tags/nvme-next-pull-request: (23 commits)
  hw/nvme: add 'zoned.zasl' to documentation
  hw/nvme: fix pin-based interrupt behavior (again)
  hw/nvme: fix missing check for PMR capability
  hw/nvme: documentation fix
  hw/nvme: fix endianess conversion and add controller list
  Partially revert "hw/block/nvme: drain namespaces on sq deletion"
  hw/nvme: reimplement format nvm to allow cancellation
  hw/nvme: reimplement zone reset to allow cancellation
  hw/nvme: reimplement the copy command to allow aio cancellation
  hw/nvme: add dw0/1 to the req completion trace event
  hw/nvme: use prinfo directly in nvme_check_prinfo and nvme_dif_check
  hw/nvme: remove assert from nvme_get_zone_by_slba
  hw/nvme: save reftag when generating pi
  hw/nvme: reimplement dsm to allow cancellation
  hw/nvme: add nvme_block_status_all helper
  hw/nvme: reimplement flush to allow cancellation
  hw/nvme: default for namespace EUI-64
  hw/nvme: namespace parameter for EUI-64
  hw/nvme: fix csi field for cns 0x00 and 0x11
  hw/nvme: add param to control auto zone transitioning to zone state closed
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2021-06-30 21:09:27 +01:00
Alberto GarciaandKevin Wolf ecd30d2d97 block: Allow changing bs->file on reopen
When the x-blockdev-reopen was added it allowed reconfiguring the
graph by replacing backing files, but changing the 'file' option was
forbidden. Because of this restriction some operations are not
possible, notably inserting and removing block filters.

This patch adds support for replacing the 'file' option. This is
similar to replacing the backing file and the user is likewise
responsible for the correctness of the resulting graph, otherwise this
can lead to data corruption.

Signed-off-by: Alberto Garcia <berto@igalia.com>
 [vsementsov: bdrv_reopen_parse_file_or_backing() is modified a lot]
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610120537.196183-9-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2021-06-29 16:51:00 +02:00
Vladimir Sementsov-OgievskiyandKevin Wolf 3d0e8743f0 block: BDRVReopenState: drop replace_backing_bs field
It's used only in bdrv_reopen_commit(). "backing" is covered by the
loop through all children except for case when we removed backing child
during reopen.

Make it more obvious and drop extra boolean field: qdict_del will not
fail if there is no such entry.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610120537.196183-8-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2021-06-29 16:51:00 +02:00
Gollu AppalanaiduandKlaus Jensen 5f4eb94dbb hw/nvme: fix endianess conversion and add controller list
Add the controller identifiers list CNS 0x13, available list of ctrls
in NVM Subsystem that may or may not be attached to namespaces.

In Identify Ctrl List of the CNS 0x12 and 0x13 no endian conversion
for the nsid field.

These two CNS values shows affect when there exists a Subsystem.
Added condition if there is no Subsystem return invalid field in
command.

Signed-off-by: Gollu Appalanaidu <anaidu.gollu@samsung.com>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
2021-06-29 07:16:25 +02:00
Klaus Jensen 2a132309e4 hw/nvme: use prinfo directly in nvme_check_prinfo and nvme_dif_check
The nvme_check_prinfo() and nvme_dif_check() functions operate on the
16 bit "control" member of the NvmeCmd. These functions do not otherwise
operate on an NvmeCmd or an NvmeRequest, so change them to expect the
actual 4 bit PRINFO field and add constants that work on this field as
well.

Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
2021-06-29 07:16:25 +02:00
Gollu AppalanaiduandKlaus Jensen 18de1526ba hw/nvme: add identify namespace flbas/mc enums
Add enums for the Identify Namespace FLBAS and MC fields.

Signed-off-by: Gollu Appalanaidu <anaidu.gollu@samsung.com>
[k.jensen: squashed separate flbas/mc commits into one]
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
2021-06-29 07:16:25 +02:00
Peter Maydell 6512fa497c Merge remote-tracking branch 'remotes/bonzini-gitlab/tags/for-upstream' into staging
* Some Meson test conversions
* KVM dirty page ring buffer fix
* KVM TSC scaling support
* Fixes for SG_IO with /dev/sdX devices
* (Non)support for host devices on iOS
* -smp cleanups

# gpg: Signature made Fri 25 Jun 2021 15:16:18 BST
# gpg:                using RSA key F13338574B662389866C7682BFFBD25F78C7AE83
# gpg:                issuer "pbonzini@redhat.com"
# gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>" [full]
# gpg:                 aka "Paolo Bonzini <pbonzini@redhat.com>" [full]
# Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4  E2F7 7E15 100C CD36 69B1
#      Subkey fingerprint: F133 3857 4B66 2389 866C  7682 BFFB D25F 78C7 AE83

* remotes/bonzini-gitlab/tags/for-upstream: (28 commits)
  machine: reject -smp dies!=1 for non-PC machines
  machine: pass QAPI struct to mc->smp_parse
  machine: add error propagation to mc->smp_parse
  machine: move common smp_parse code to caller
  machine: move dies from X86MachineState to CpuTopology
  file-posix: handle EINTR during ioctl
  block: detect DKIOCGETBLOCKCOUNT/SIZE before use
  block: try BSD disk size ioctls one after another
  block: check for sys/disk.h
  block: feature detection for host block support
  file-posix: try BLKSECTGET on block devices too, do not round to power of 2
  block: add max_hw_transfer to BlockLimits
  block-backend: align max_transfer to request alignment
  osdep: provide ROUND_DOWN macro
  scsi-generic: pass max_segments via max_iov field in BlockLimits
  file-posix: fix max_iov for /dev/sg devices
  KVM: Fix dirty ring mmap incorrect size due to renaming accident
  configure, meson: convert libusbredir detection to meson
  configure, meson: convert libcacard detection to meson
  configure, meson: convert libusb detection to meson
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2021-06-28 21:04:22 +01:00
Emanuele Giuseppe EspositoandVladimir Sementsov-Ogievskiy 149009bef4 block-copy: atomic .cancelled and .finished fields in BlockCopyCallState
By adding acquire/release pairs, we ensure that .ret and .error_is_read
fields are written by block_copy_dirty_clusters before .finished is true,
and that they are read by API user after .finished is true.

The atomic here are necessary because the fields are concurrently modified
in coroutines, and read outside.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20210624072043.180494-6-eesposit@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
2021-06-25 14:33:51 +03:00
Paolo Bonzini 24b36e9813 block: add max_hw_transfer to BlockLimits
For block host devices, I/O can happen through either the kernel file
descriptor I/O system calls (preadv/pwritev, io_submit, io_uring)
or the SCSI passthrough ioctl SG_IO.

In the latter case, the size of each transfer can be limited by the
HBA, while for file descriptor I/O the kernel is able to split and
merge I/O in smaller pieces as needed.  Applying the HBA limits to
file descriptor I/O results in more system calls and suboptimal
performance, so this patch splits the max_transfer limit in two:
max_transfer remains valid and is used in general, while max_hw_transfer
is limited to the maximum hardware size.  max_hw_transfer can then be
included by the scsi-generic driver in the block limits page, to ensure
that the stricter hardware limit is used.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-25 10:54:13 +02:00
Vladimir Sementsov-OgievskiyandEric Blake 97cf89259e nbd/client-connection: add option for non-blocking connection attempt
We'll need a possibility of non-blocking nbd_co_establish_connection(),
so that it returns immediately, and it returns success only if a
connections was previously established in background.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-30-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
2021-06-18 12:21:22 -05:00