[PATCH v3 0/4] block: add IOC_PR_READ_KEYS and IOC_PR_READ_RESERVATION ioctls

[Stefan Hajnoczi <stefanha@redhat.com>]

v3:
- Use checked_mul_overflow(), struct_size(), etc to avoid duplicating size calculations [Christoph]
- Don't use __free() from cleanup.h [Christoph, Krzysztof]
- Drop one-time use num_copy_keys local variable [Christoph]
- Rename inout local variable to read_keys [Christoph]

v2:
- Fix num_keys validation in patches 1-3 [Hannes]
- Declare local variables at beginning of scope [Hannes]

This series exposes struct pr_ops pr_read_keys() and pr_read_reservations() to
userspace as ioctls, making it possible to list registered reservation keys and
report the current reservation on a block device.

The new ioctls are needed by applications or cluster managers that rely on
inspecting the PR state. This is something that has been possible with SCSI-
and NVME-specific commands but not with the PR ioctls. I hope to move QEMU from
SG_IO to PR ioctls so that NVMe host block devices can be supported alongside
SCSI devices without protocol-specific commands.

These ioctls will also make troubleshooting possible with the blkpr(8)
util-linux tool, for which I have prepared a separate patch series.

Stefan Hajnoczi (4):
  scsi: sd: reject invalid pr_read_keys() num_keys values
  nvme: reject invalid pr_read_keys() num_keys values
  block: add IOC_PR_READ_KEYS ioctl
  block: add IOC_PR_READ_RESERVATION ioctl

 include/uapi/linux/pr.h | 14 +++++++
 block/ioctl.c           | 84 +++++++++++++++++++++++++++++++++++++++++
 drivers/nvme/host/pr.c  |  6 ++-
 drivers/scsi/sd.c       | 12 +++++-
 4 files changed, 114 insertions(+), 2 deletions(-)

-- 
2.52.0