virtiofsd: Add support for FUSE_SYNCFS request

FUSE_SYNCFS allows the client to flush the host page cache.

v4: - based on upstream linux FUSE_SYNCFS
    - added support for the '-o announce_submounts' case, i.e. client sends
      a FUSE_SYNCFS request for each submount (identified by its root inode)
    - adapted the case without '-o announce_submounts' so that syncfs() is
      no longer called with lo->mutex held

v3: - track submounts and do per-submount syncfs() (Vivek)
    - based on new version of FUSE_SYNCFS (still not upstream)
      https://listman.redhat.com/archives/virtio-fs/2021-May/msg00025.html

v2: - based on new version of FUSE_SYNCFS
      https://listman.redhat.com/archives/virtio-fs/2021-April/msg00166.html
    - propagate syncfs() errors to client (Vivek)

v6.1.1 release

v6.2.0 release

v6.2.0-rc4 release

v6.2.0-rc3 release

v6.2.0-rc2 release

v6.2.0-rc1 release

accel/tcg: Fix monitor deadlock

Commit 7bed89958bfb ("device_core: use drain_call_rcu in in qmp_device_add")
introduced a regression in QEMU 6.0 : passing device_add without argument
hangs the monitor. This was reported against qemu-system-mips64 with TGC,
but I could consistently reproduce it with other targets (x86 and ppc64).

See https://gitlab.com/qemu-project/qemu/-/issues/650 for details.

The problem is that an emulated busy-looping vCPU can stay forever in
its RCU read-side critical section and prevent drain_call_rcu() to return.
This series fixes the issue by letting RCU kick vCPU threads out of the
read-side critical section when drain_call_rcu() is in progress. This is
achieved through notifiers, as suggested by Paolo Bonzini.

I've pushed this series to:

https://gitlab.com/gkurz/qemu/-/commits/fix-drain-call-rcu

v4:
- use rr_kick_next_cpu() instead of async_run_on_cpu(first_cpu)

v3:
- new separate implementations of force RCU notifiers for MTTCG and RR

v2:
- moved notifier list to RCU reader data
- separate API for notifier registration
- CPUState passed as an opaque pointer

v6.2.0-rc0 release

accel/tcg: Fix monitor deadlock

Commit 7bed89958bfb ("device_core: use drain_call_rcu in in qmp_device_add")
introduced a regression in QEMU 6.0 : passing device_add without argument
hangs the monitor. This was reported against qemu-system-mips64 with TGC,
but I could consistently reproduce it with other targets (x86 and ppc64).

See https://gitlab.com/qemu-project/qemu/-/issues/650 for details.

The problem is that an emulated busy-looping vCPU can stay forever in
its RCU read-side critical section and prevent drain_call_rcu() to return.
This series fixes the issue by letting RCU kick vCPU threads out of the
read-side critical section when drain_call_rcu() is in progress. This is
achieved through notifiers, as suggested by Paolo Bonzini.

I've pushed this series to:

https://gitlab.com/gkurz/qemu/-/commits/fix-drain-call-rcu

v3:
- new separate implementations of force RCU notifiers for MTTCG and RR

v2:
- moved notifier list to RCU reader data
- separate API for notifier registration
- CPUState passed as an opaque pointer

v6.0.1 release

9pfs: performance fix and cleanup

* First patch fixes suboptimal I/O performance on guest due to previously
  incorrect block size being transmitted to 9p client.

* Subsequent patches are cleanup ones intended to reduce code complexity.

accel/tcg: Fix monitor deadlock

Commit 7bed89958bfb ("device_core: use drain_call_rcu in in qmp_device_add")
introduced a regression in QEMU 6.0 : passing device_add without argument
hangs the monitor. This was reported against qemu-system-mips64 with TGC,
but I could consistently reproduce it with other targets (x86 and ppc64).

See https://gitlab.com/qemu-project/qemu/-/issues/650 for details.

The problem is that an emulated busy-looping vCPU can stay forever in
its RCU read-side critical section and prevent drain_call_rcu() to return.
This series fixes the issue by letting RCU kick vCPUs out of the read-side
critical section when drain_call_rcu() is in progress. This is achieved
through notifiers, as suggested by Paolo Bonzini.

v2:
- moved notifier list to RCU reader data
- separate API for notifier registration
- CPUState passed as an opaque pointer

accel/tcg: Fix monitor deadlock

Commit 7bed89958bfb ("device_core: use drain_call_rcu in in qmp_device_add")
introduced a regression in QEMU 6.0 : passing device_add without argument
hangs the monitor. This was reported against qemu-system-mips64 with TGC,
but I could consistently reproduce it with other targets (x86 and ppc64).

See https://gitlab.com/qemu-project/qemu/-/issues/650 for details.

The problem is that an emulated busy-looping vCPU can stay forever in
its RCU read-side critical section and prevent drain_call_rcu() to return.
This series fixes the issue by letting RCU kick vCPUs out of the read-side
critical section when drain_call_rcu() is in progress. This is achieved
through notifiers, as suggested by Paolo Bonzini.

9pfs: misc patches

* Fix an occasional crash when handling 'Twalk' requests.

* Two code cleanup patches.

v6.1.0 release

v6.1.0-rc4 release

v6.1.0-rc3 release

v6.1.0-rc2 release

v6.1.0-rc1 release