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.

For documentation see either url:
    https://sg.danny.cz/sg/sg_v40.html
    https://doug-gilbert.github.io/sg_v40.html

This patchset is against Martin Petersen's 5.14/scsi-queue branch.


Changes since v18 (sent to linux-scsi list on 20210407)
  - a request queue's QUEUE_FLAG_POLL flag can be cleared via
    sysfs, overriding the ability to use blk_poll() even when the
    associated LLD allows it. Check that flag and, only when it
    is set and the sg user gives SGV4_FLAG_HIPRI, set REQ_HIPRI
    on a request.
  - simplify the functions supporting ioctl(SG_SET_RESERVED_SIZE)
  - replace blk_rq_append_bio() calls with the simpler
    blk_rq_bio_prep() calls
    [see lk: a4fe2d3afe3ce77edeadb567c0d0a8d102c6b159]
  - rebase on 5.14/scsi-queue branch [lk 5.13-0-rc1]
    - unchecked_isa_dma removed
    - BIO_MAX_PAGES renamed to BIO_MAX_VECS

Changes since v17 (sent to linux-scsi list on 20210407)
  - make clearer distinction between user pollable (i.e. async)
    requests and (user) non-pollable requests (e.g. those injected
    with ioctl(SG_IO), IOWs sync requests)
  - fix crash is sg_start_req() when blk_get_request() yields an
    error (e.g. -EAGAIN when low on resources)
  - sg_finish_scsi_blk_rq(): remove now_zero variable as suggested
    by Hannes R.
  - change deprecation warning url reference from http to https

Changes since v16 (sent to linux-scsi list on 20210208)
  - sg_start_req() fix double free on error path [KASAN]
  - sg_rq_map_kern() fix uninitialized variable [coverity]
  - sg_add_sfp() fix use after free [coverity]
  - sg_remove_sfp_usercontext(): remove pointless NULL check [coverity]
  - fix misuse of WARN_ONCE in sg_rq_end_io_usercontext() [D. Carpenter]
  - remove unused error checks: tracking blk_put_request() calls and
    multiple SG_XA_RQ_FREE calls
  - hipri: as blk_poll() can return > 0 for requests other than the one
    that is being checked for, need to re-check that request is ready
  - rebased on MKP's 5.13/scsi-queue

Changes since v15 (sent to linux-scsi list on 20210125)
  - tweak state machine which sets INFLIGHT state _before_
    blk_execute_rq_nowait() is called. Add a bit flag that indicates
    the logic flow has returned from that call. This guards against
    blk_poll() being called before the block layer has really
    launched the request.
  - fix bug clearing SG_FFD_HIPRI_SEEN bit as
    atomic_dec_and_test() returns true when the post-decrement value
    is zero, the opposite of what a C conditional does.

Changes since v14 and earlier
  - see: the v18 patchset sent to linux-scsi on 20210427


Douglas Gilbert (45):
  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 xarray
  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: remove rcv_done request state
  sg: track lowest inactive and await indexes
  sg: remove unit attention check for device changed
  sg: no_dxfer: move to/from kernel buffers
  sg: add blk_poll support
  sg: bump version to 4.0.12

 drivers/scsi/sg.c      | 5353 +++++++++++++++++++++++++++-------------
 include/scsi/sg.h      |  273 +-
 include/uapi/scsi/sg.h |  375 +++
 3 files changed, 4065 insertions(+), 1936 deletions(-)
 create mode 100644 include/uapi/scsi/sg.h

-- 
2.25.1