[PATCH v16 00/45] sg: add v4 interface

Douglas Gilbert
2021-02-20T02:02:06Z

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.

A recent patch added support for blk_poll() and requests that
have REQ_HIPRI set. The blk_poll() additions are in patch 44 and
will compile. However, to use those additions one or more SCSI LLDs
are needed that support mq_poll(). For those, look to a patchset
from Kashyap Desai called "[PATCH v4 0/5] io_uring iopoll in scsi
layer" [20210215]. This patchset allows 'iopoll' requests to be
issued without io_uring (by setting SGV4_FLAG_HIPRI). A recent
patch to fio allows its sg engine to issue iopoll requests by
using hipri=1 in the fio script. One further note, an _async_
interface to blk_poll() is being proposed in this patchset.

For documentation 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 5.12/scsi-queue branch.

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 (sent to linux-scsi list on 20210124)
- two fixes based on report from Dan Carpenter and kernel test
robot
- fix Johannes Thumshirn's email address
- separate patch issued on fio to add 'hipri' option to its sg
engine. Enables fio to test new sg driver blk_poll() support

Changes since v13 (sent to linux-scsi list on 20210113)
- fix obscure compile error reported by "kernel test robot
<lkp@intel.com>"
- harden code around blk_poll() invocation; needed based on
fio testing
- remove SG_FFD_MMAP_CALLED bit code after Hannes Reinecke pointed
out it was redundant

Changes since v12 (sent to linux-scsi list on 20201115)
- add blk_poll() support, prefix that patch's subject with 'RFC'

Changes since v11 (sent to linux-scsi list on 20201014)
- no author originated changes since v11
- port from lk 5.9.0-rc1 to lk 5.10.0-rc1 picks up a change to
the import_iovec() which requires a change to patch 25/44
- only publish this cover letter and v12 of patch 25/44 to
the linux-scsi list. The other 43 patches remain as published
on 20201014.

Changes since v10 (sent to linux-scsi list on 20200823)
- unchanged: 0001 to 0009, 0010 to 0017
- rename sg_add_req() to sg_setup_req() [0010]
- patches 40,41,42 and 43 are new, see their commit messages
- remove SG_RS_RCV_DONE request state leaving 3.5 states
[the 0.5 state is SG_RS_BUSY]
- rework sg_rq_chg_state() code that enforces request
state changes and associated xarray marks
- track lowest used and unused indexes in the request arrays so
iterations over the request xarray are efficient. This is a
significant saving when the iodepth queue length is large

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 to v1 in earlier patchsets
- see: the v10 patchset sent to linux-scsi on 20200823

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 | 5394 +++++++++++++++++++++++++++-------------
include/scsi/sg.h | 273 +-
include/uapi/scsi/sg.h | 375 +++
3 files changed, 4117 insertions(+), 1925 deletions(-)
create mode 100644 include/uapi/scsi/sg.h

--
2.25.1