[v10,00/40] sg: add v4 interface

This patchset is the first stage of a two stage rewrite of the scsi
generic (sg) driver. The main goal of the first stage is to introduce
the sg v4 interface that uses 'struct sg_io_v4' as well as keeping and
modernizing the sg v3 interface (based on 'struct sg_io_hdr'). The
async interface formerly requiring the use of write() and read()
system calls now have ioctl(SG_IOSUBMIT) and ioctl(SG_IORECEIVE)
replacements. See:
    http://sg.danny.cz/sg/sg_v40.html
for more details. If accessing http pages is a problem, a temporary
rendering of this page can be found here:
    https://doug-gilbert.github.io/sg_v40.html

This patchset is against Martin Petersen's 5.10/scsi-queue branch.

Changes since v9 (sent to linux-scsi list on 20200421)
  - rebase on MKP's 5.10/scsi-queue branch
  - remove some master/slave terminology that had bled in from
    the part 2 patchset
  - change sg_request::start_ns type from ktime_t to u64
  - pick up several error path correction fixes applied to the
    sg driver by other authors

Changes since v8 (sent to linux-scsi list on 20200301)
  - add new patch to ignore the /proc/scsi/sg/allow_dio setting.
    Now direct IO will be attempted whenever the SG_FLAG_DIRECT_IO
    flag is given
  - add new patch to track mmap_sz from previous mmap() call.
    Allows catching mmap-ed requests that exceed that value
  - change warning about using the v3 interface with the write()
    system call from WARN_ONCE() to pr_warn_once()
  - remove __KERNEL__ conditionals in include/scsi/sg.h
  - change struct sg_fd::start_ns from u64 to ktime_t type
  - introduce a new small sg_rq_state_mul2arr array to avoid
    a multiplication at runtime in the state machine engine
  - tweak mempool introduced in v7 for sense buffers
  - rework sg_mk_sgat() to better handle low memory situations;
    similar work on sg_remove_sgat_helper()

Changes since v7 (sent to linux-scsi list on 20200227)
  - improve direct IO code, remove the SG_FRQ_DIO_IN_USE
    sg_request::frq_bm flag as it is no longer needed
  - simplify state changing code. Many state changes (rq_st) do not
    need changes to the xarray "marks"; only lock those that do
    (reviewer queried the locking)
  - remove some misplaced likely()/unlikely() macros. They are gathered
    together in a separate patch (in a second patchset)
  - change a cast that the kbuild robot complained about. It also
    flagged a stack size problem in sg_ioctl_common() for reasons not
    given nor obvious. That function (and its parents) declare only
    simple scalars on the stack.
  - add 'Reviewed-by' where appropriate

Changes since v6 (sent to linux-scsi list on 20200112)
  - based on Martin Petersen's 5.7/scsi-queue branch in his
    linux-scsi repository
  - major work on mmap support: when mmap(2) is used the reserve
    request scatter gather list is rebuilt to have order=0
    elements (i.e. each is PAGE_SIZE bytes).
  - address one kbuild robot issue: add include defining size_t
  - nearly all patches that have been reviewed have been changed,
    usually in minor ways. Those patches have "***" before the
    "Reviewed-by" line.

Changes since v5 (sent to linux-scsi list on 20191008)
  - replace linked lists with xarray mechanism
  - use the locking in the xarray implementation to
    replace several discrete locks
  - some patches that were previously reviewed by
    Hannes Reinecke have had small changes made to
    them usually associated with xarrays. Those have
    been marked with "***" prepended to the
    "Reviewed-by" line
  - bump the driver version number to 4.0.08

Changes since v4 (sent to linux-scsi list on 20190829)
  - remove much of the logic in the previous patchset
    series from and including:
        [PATCH v4 11/22] sg: replace rq array with lists
    to
        [PATCH v4 22/22] sg: bump version to 4.0.03
  - bump the driver version number from 3.5.36 to 3.9.01
    [20190606] reflecting that the v4 interface has not
    been implemented (in this patchset)
  - patches 13/23 through to 22/23 reduce the complexity
    of "[PATCH v4 11/22] sg: replace rq array with lists"
    measured in KiloBytes from about 130 KB to 80 KB.
  - various changes suggested by reviewers of the v4
    patchset have been implemented
  - change all %p descriptors (mainly in SG_LOG() macros)
    to %pK so that the debug output remains useful in
    recent kernels. Evidently sys admins can selectively
    turn on pointer obfuscation on %pK as required on
    secure systems.

Changes since v3 (sent to linux-scsi list on 20190807):
  - move __must_hold attributes into separate patch
  - move procfs and debugfs file scope definitions toward
    the end of sg.c to avoid forward declarations
  - move module_param* and MODULE_* macros to end of sg.c
  - expand debugfs support with snapshot_devs which allows
    filtering of snapshot output by sg device(s)
  - add a WARN_ONCE when write(2) is used with the sg v3
    interface. Suggest using SG_IOSUBMIT_V3 instead.
  - address more of the review comments from Hannes Reinecke
    and Christoph Hellwig
  - add various reviewed-by tags where appropriate

Changes since v2 (sent to linux-scsi list on 20190727):
  - address issues "Reported-by: kbuild test robot <lkp@intel.com>".
    The main one was to change the bsg header included to:
    include/uapi/linux/bsg.h rather than include/linux/bsg.h
  - address some of the review comments from Hannes Reinecke;
    email responses have been sent for review comments that
    did not result in code changes

Changes since v1 (sent to linux-scsi list on 20190616):
  - change ktime_get_boot_ns() to ktime_get_boottime_ns() to reflect
    kernel API change first seen in lk 5.3.0-rc1

Douglas Gilbert (40):
  sg: move functions around
  sg: remove typedefs, type+formatting cleanup
  sg: sg_log and is_enabled
  sg: rework sg_poll(), minor changes
  sg: bitops in sg_device
  sg: make open count an atomic
  sg: move header to uapi section
  sg: speed sg_poll and sg_get_num_waiting
  sg: sg_allow_if_err_recovery and renames
  sg: improve naming
  sg: change rwlock to spinlock
  sg: ioctl handling
  sg: split sg_read
  sg: sg_common_write add structure for arguments
  sg: rework sg_vma_fault
  sg: rework sg_mmap
  sg: replace sg_allow_access
  sg: rework scatter gather handling
  sg: introduce request state machine
  sg: sg_find_srp_by_id
  sg: sg_fill_request_element
  sg: printk change %p to %pK
  sg: xarray for fds in device
  sg: xarray for reqs in fd
  sg: replace rq array with lists
  sg: sense buffer rework
  sg: add sg v4 interface support
  sg: rework debug info
  sg: add 8 byte SCSI LUN to sg_scsi_id
  sg: expand sg_comm_wr_t
  sg: add sg_iosubmit_v3 and sg_ioreceive_v3 ioctls
  sg: add some __must_hold macros
  sg: move procfs objects to avoid forward decls
  sg: protect multiple receivers
  sg: first debugfs support
  sg: rework mmap support
  sg: defang allow_dio
  sg: warn v3 write system call users
  sg: add mmap_sz tracking
  sg: bump version to 4.0.09

 drivers/scsi/sg.c      | 5183 +++++++++++++++++++++++++++-------------
 include/scsi/sg.h      |  273 +--
 include/uapi/scsi/sg.h |  374 +++
 3 files changed, 3917 insertions(+), 1913 deletions(-)
 create mode 100644 include/uapi/scsi/sg.h