[PATCH RESEND v2 00/26] proc: convert the driver entries (Part 4/7)

[Christian Brauner <brauner@kernel.org>]

Part 4/7 of "proc: move procfs to what kernfs does", on top of part 2
and independent of parts 3, 5 and 6:

  https://patch.msgid.link/20261104-work-procfs-v2-0-b45cd5789ac5@brauner

This converts the proc entries of nubus, zorro, PCI, md, dasd and cio,
scsi, dell-smm, viafb, rndis, ipw2x00, sysrq, the input devices file and
ALSA to what "proc: let procfs own the data path" set up. Afterwards the
entries' code only runs with the entry pinned and never touches
userspace memory. One patch per subsystem and method.

- procfs owns the seq_file of the nubus resource files, /proc/mdstat,
  the scsi host files, sg's allow_dio and def_reserved_size and ALSA's
  text entries. Their open and release hooks only do what is left,
  private data or the event count, and reading a scsi host file or an
  ALSA entry no longer holds up the removal of the host or the card.
- procfs copies in the writes of the PCI config space,
  /proc/dasd/statistics, cio_ignore and cio_settle, /proc/scsi/scsi,
  device_info and the host files, sg, viafb, rndis, ipw2x00's debug
  level, /proc/sysrq-trigger and ALSA's entries. Most of them just parse
  procfs' copy. Where a write larger than anything the entry parses now
  fails with -EINVAL from procfs the commit says so.
- procfs copies out the reads of /proc/bus/zorro, the PCI config space
  and ALSA's data entries.
- the PCI config space and ALSA's data entries take binary data at
  positions and keep doing that, PROC_ENTRY_SHORT_WRITES for writes in
  pieces, and ALSA's data entries ask for PROC_ENTRY_FULL_READS so that
  reading all of one at once keeps working. They hand procfs' buffer to
  the drivers, so struct snd_info_entry_ops changes along with them.
- procfs copies the ioctl arguments of PCI, esas2r's ATTONode file and
  dell-smm's i8k in and out. The PCI commands only pass values and the
  i8k ones encode the wrong sizes, both tables list what is really
  copied. ALSA's ioctl hook that no driver implements goes away.
- /proc/mdstat and /proc/bus/input/devices move their pollers to the
  wait queue procfs owns for the entry, which ends md's wakeup loop at
  unload, and the poll op of an ALSA info entry, which nothing
  implements, loses its poll_table.

The selftest writes to the file of a scsi_debug host from a buffer
backed by userfaultfd and removes the host while procfs copies in. On a
KASAN and lockdep kernel it fails without the series and passes with it.
Build tested per commit on x86_64 and with W=1 on the touched objects on
their own architectures. The entries I could get at in a VM behave the
same with and without the series.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
Changes in v2:
- md and Input let procfs own the wait queues of /proc/mdstat and
  /proc/bus/input/devices, md's wakeup loop at unload is gone and
  /proc/mdstat is removed last, Input forgets the entry when it is
  removed, and the poll op of an ALSA info entry loses its poll_table
- the scsi_debug selftest skips without /proc/scsi and removes the host
  it added when its file can't be found
- Reviewed-by from Jiri on sysrq
- rebased onto v7.4-rc1
- Link to v1: https://patch.msgid.link/20261102-work-procfs-drivers-v1-0-a994bd4d3b1a@kernel.org

---
Christian Brauner (26):
      nubus: let procfs own the seq_file of the resource files
      zorro: let procfs copy out reads
      PCI/proc: let procfs copy in config space writes
      PCI/proc: let procfs copy out config space reads
      PCI/proc: let procfs handle the ioctls
      md: let procfs own the seq_file of /proc/mdstat
      md: let procfs own the wait queue of /proc/mdstat
      s390/dasd: let procfs copy in writes to /proc/dasd/statistics
      s390/cio: let procfs copy in writes
      scsi: let procfs own the seq_file of the host files
      scsi: core: let procfs copy in writes
      selftests/proc: check that a faulting writer doesn't hold up removal
      scsi: sg: let procfs own the seq_file of allow_dio and def_reserved_size
      scsi: sg: let procfs copy in writes
      scsi: esas2r: let procfs copy the ioctl argument of the ATTONode file
      hwmon: (dell-smm) let procfs copy the i8k ioctl arguments
      fbdev: viafb: let procfs copy in writes
      usb: gadget: function: rndis: let procfs copy in writes
      wifi: ipw2x00: let procfs copy in writes to the debug level
      tty: sysrq: let procfs copy in writes to /proc/sysrq-trigger
      Input: let procfs own the wait queue of /proc/bus/input/devices
      ALSA: info: let procfs own the seq_file of text entries
      ALSA: info: let procfs copy in writes
      ALSA: info: let procfs copy out reads of data entries
      ALSA: info: drop the ioctl hook of data entries
      ALSA: info: drop the poll_table from the info entry poll op

 .../sound/kernel-api/writing-an-alsa-driver.rst    |  10 +-
 drivers/hwmon/dell-smm-hwmon.c                     |  48 ++---
 drivers/input/input.c                              |  13 +-
 drivers/md/md.c                                    |  44 ++---
 drivers/net/wireless/intel/ipw2x00/libipw_module.c |   7 +-
 drivers/nubus/proc.c                               |  12 +-
 drivers/pci/proc.c                                 |  69 +++----
 drivers/s390/block/dasd_proc.c                     |  17 +-
 drivers/s390/cio/blacklist.c                       |  33 +---
 drivers/s390/cio/css.c                             |   4 +-
 drivers/scsi/esas2r/esas2r.h                       |   2 +
 drivers/scsi/esas2r/esas2r_ioctl.c                 |  58 +++---
 drivers/scsi/esas2r/esas2r_main.c                  |  44 ++++-
 drivers/scsi/scsi_devinfo.c                        |  29 +--
 drivers/scsi/scsi_proc.c                           |  55 ++----
 drivers/scsi/sg.c                                  |  44 ++---
 drivers/tty/sysrq.c                                |   9 +-
 drivers/usb/gadget/function/rndis.c                |   9 +-
 drivers/video/fbdev/via/viafbdev.c                 |  46 +++--
 drivers/zorro/proc.c                               |   7 +-
 include/sound/gus.h                                |   2 +-
 include/sound/info.h                               |   9 +-
 sound/core/info.c                                  |  59 +++---
 sound/drivers/opl4/opl4_proc.c                     |  23 +--
 sound/isa/gus/gus_dram.c                           |   7 +-
 sound/isa/gus/gus_mem_proc.c                       |   2 +-
 sound/pci/cs4281.c                                 |  10 +-
 sound/pci/cs46xx/cs46xx_lib.c                      |   5 +-
 sound/pci/emu10k1/emuproc.c                        |   8 +-
 sound/pci/mixart/mixart.c                          |  10 +-
 sound/usb/mixer_scarlett2.c                        |   9 +-
 tools/testing/selftests/proc/.gitignore            |   1 +
 tools/testing/selftests/proc/Makefile              |   1 +
 tools/testing/selftests/proc/config                |   3 +
 .../selftests/proc/proc-remove-slow-writer.c       | 209 +++++++++++++++++++++
 35 files changed, 503 insertions(+), 415 deletions(-)
---
base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
change-id: 20261101-work-procfs-drivers-58cd83649658
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