This work aims to allow userspace to create and destroy block devices in a race-free and leak-free way, and to allow them to be exposed to other Xen VMs via blkback without leaks or races. It’s marked as RFC for a few reasons: - The code has been only lightly tested. It might be unstable or insecure. - The DM_DEV_CREATE ioctl gains a new flag. Unknown flags were previously ignored, so this could theoretically break buggy userspace tools. - I have no idea if I got the block device reference counting and locking correct. Demi Marie Obenour (7): block: Support creating a struct file from a block device Allow userspace to get an FD to a newly-created DM device Implement diskseq checks in blkback Increment diskseq when releasing a loop device If autoclear is set, delete a no-longer-used loop device Minor blkback cleanups xen/blkback: Inform userspace that device has been opened block/bdev.c | 77 +++++++++++-- block/genhd.c | 1 + drivers/block/loop.c | 17 ++- drivers/block/xen-blkback/blkback.c | 8 +- drivers/block/xen-blkback/xenbus.c | 171 ++++++++++++++++++++++------ drivers/md/dm-ioctl.c | 67 +++++++++-- include/linux/blkdev.h | 5 + include/uapi/linux/dm-ioctl.h | 16 ++- 8 files changed, 298 insertions(+), 64 deletions(-) -- Sincerely, Demi Marie Obenour (she/her/hers) Invisible Things Lab
