This work aims to allow userspace to create and destroy device-mapper devices in a race-free way. Changes since v1: - Potentially backwards-incompatible changes to device-mapper now require userspace opt-in. - The code has been tested: I have a block script written in C that uses these changes to successfully boot a Xen VM. - The core block layer is completely untouched. Instead of exposing a block device inode directly to userspace, device-mapper ioctls that create a block device now return that device's diskseq. Userspace can then use that diskseq to safely open the device. Furthermore, ioctls that operate on an existing device-mapper device now accept a diskseq parameter, which can be used to prevent races. Demi Marie Obenour (4): dm ioctl: Allow userspace to opt-in to strict parameter checks dm ioctl: Allow userspace to provide expected diskseq dm ioctl: Allow userspace to suppress uevent generation dm ioctl: inform caller about already-existing device drivers/md/dm-core.h | 2 + drivers/md/dm-ioctl.c | 351 ++++++++++++++++++++++++++++------ drivers/md/dm.c | 5 +- include/linux/device-mapper.h | 2 +- include/uapi/linux/dm-ioctl.h | 90 ++++++++- 5 files changed, 382 insertions(+), 68 deletions(-) -- Sincerely, Demi Marie Obenour (she/her/hers) Invisible Things Lab -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel
