On Mon, Jan 25, 2021 at 01:01:09PM -0500, Vivek Goyal wrote: > Hi, > > We are working on DAX support in virtiofs and have some patches out of > the tree hosted here. > > https://gitlab.com/virtio-fs/qemu/-/commits/virtio-fs-dev
ping anyone wants to pick this up and post a non-rfc version? > These patches have not been proposed for merge yet, becasue David > Gilbert noticed that we can run into a deadlock during an emergency > reboot of guest kernel. (echo b > /proc/sysrq-trigger). > > I have provided details of deadlock in 4th path of the series with > subject "qemu, vhost-user: Extend protocol to start/stop/flush slave > channel". > > Basic problem seems to be that we don't have a proper mechanism to > shutdown slave channel when vhost-user device is stopping. This means > there might be pending messages in slave channel and slave is blocked > and waiting for response. > > This is an RFC patch series to enhance vhost-user protocol to > properly shutdown/flush slave channel and avoid the deadlock. Though > we faced the issue in the context of virtiofs, any vhost-user > device using slave channel can potentially run into issues and > can benefit from these patches. > > Any feedback is welcome. Currently patches are based on out of > tree code but after I get some feedback, I can only take pieces > which are relevant to upstream and post separately. > > Thanks > Vivek > > Vivek Goyal (6): > virtiofsd: Drop ->vu_dispatch_rwlock while waiting for thread to exit > libvhost-user: Use slave_mutex in all slave messages > vhost-user: Return error code from slave_read() > qemu, vhost-user: Extend protocol to start/stop/flush slave channel > libvhost-user: Add support to start/stop/flush slave channel > virtiofsd: Opt in for slave start/stop/shutdown functionality > > hw/virtio/vhost-user.c | 151 +++++++++++++++++++++- > subprojects/libvhost-user/libvhost-user.c | 147 +++++++++++++++++---- > subprojects/libvhost-user/libvhost-user.h | 8 +- > tools/virtiofsd/fuse_virtio.c | 20 +++ > 4 files changed, 294 insertions(+), 32 deletions(-) > > -- > 2.25.4
