The following patches were made over Linus's tree but also apply over Jens's for-next io_uring branch and Michaels' vhost/next branch.
This is V3 of the patchset. It should handle all the review comments posted in V1 and V2. If I missed a comment, please let me know. This patchset allows the vhost layer to do a copy_process on the thread that does the VHOST_SET_OWNER ioctl like how io_uring does a copy_process against its userspace app (Jens, the patches make create_io_thread more generic so that's why you are cc'd). This allows the vhost layer's worker threads to inherit cgroups, namespaces, address space, etc and this worker thread will also be accounted for against that owner/parent process's RLIMIT_NPROC limit. If you are not familiar with qemu and vhost here is more detailed problem description: Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups. The problem with this approach is that we then have to add new functions/ args/functionality for every thing we want to inherit. I started doing that here: https://lkml.org/lkml/2021/6/23/1233 for the RLIMIT_NPROC check, but it seems it might be easier to just inherit everything from the beginning, becuase I'd need to do something like that patch several times. For example, the current approach does not support cgroups v2 so commands like virsh emulatorpin do not work. The qemu process can go over its RLIMIT_NPROC. And for future vhost interfaces where we export the vhost thread pid we will want the namespace info. V3: - Add parentheses in p->flag and work_flags check in copy_thread. - Fix check in arm/arm64 and xtensa which were doing the reverse of other archs in their check for PF_IO_WORKER. V2: - Rename kernel_copy_process to kernel_worker. - Instead of exporting functions, make kernel_worker() a proper function/API that does common work for the caller. - Instead of adding new fields to kernel_clone_args for each option make it flag based similar to CLONE_*. - Drop unused completion struct in vhost. - Fix compile warnings by merging vhost cgroup cleanup patch and vhost conversion patch. _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
