After reviewing driver submissions with new cdev + ioctl usages one
common stumbling block is coordinating the shutdown of the ioctl path,
or other file operations, at driver ->remove() time. While cdev_del()
guarantees that no new file descriptors will be established, operations
on existing file descriptors can proceed indefinitely.
Given the observation that the kernel spends the resources for a percpu_ref
per request_queue shared with all block_devices on a gendisk, do the
same for all the cdev instances that share the same
cdev_add()-to-cdev_del() lifetime.
With this in place cdev_del() not only guarantees 'no new opens', but it
also guarantees 'no new operations invocations' and 'all threads running
in an operation handler have exited that handler'.
As a proof point of the way driver implementations open-code around this
gap in the api the libnvdimm ioctl path is reworked with a result of:
4 files changed, 101 insertions(+), 153 deletions(-)
---
Dan Williams (3):
cdev: Finish the cdev api with queued mode support
libnvdimm/ida: Switch to non-deprecated ida helpers
libnvdimm/ioctl: Switch to cdev_register_queued()
drivers/nvdimm/btt_devs.c | 6 +
drivers/nvdimm/bus.c | 177 +++++++++------------------------------
drivers/nvdimm/core.c | 14 ++-
drivers/nvdimm/dax_devs.c | 4 -
drivers/nvdimm/dimm_devs.c | 53 +++++++++---
drivers/nvdimm/namespace_devs.c | 14 +--
drivers/nvdimm/nd-core.h | 14 ++-
drivers/nvdimm/pfn_devs.c | 4 -
fs/char_dev.c | 108 ++++++++++++++++++++++--
include/linux/cdev.h | 21 ++++-
10 files changed, 238 insertions(+), 177 deletions(-)
