Pull Kbuild fixes from Masahiro Yamada:

 - ignore compiler stubs for PPC to fix builds

 - fix the usage of --target mentioned in the LLVM document

* tag 'kbuild-fixes-v5.9-4' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  Documentation/llvm: Fix clang target examples
  scripts/kallsyms: skip ppc compiler stub *.long_branch.* / *.plt_branch.*

Pull x86 fixes from Thomas Gleixner:
 "Two fixes for the x86 interrupt code:

   - Unbreak the magic 'search the timer interrupt' logic in IO/APIC
     code which got wreckaged when the core interrupt code made the
     state tracking logic stricter.

     That caused the interrupt line to stay masked after switching from
     IO/APIC to PIC delivery mode, which obviously prevents interrupts
     from being delivered.

   - Make run_on_irqstack_code() typesafe. The function argument is a
     void pointer which is then cast to 'void (*fun)(void *).

     This breaks Control Flow Integrity checking in clang. Use proper
     helper functions for the three variants reuqired"

* tag 'x86-urgent-2020-09-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/ioapic: Unbreak check_timer()
  x86/irq: Make run_on_irqstack_cond() typesafe

Pull timer updates from Thomas Gleixner:
 "A set of clocksource/clockevents updates:

   - Reset the TI/DM timer before enabling it instead of doing it the
     other way round.

   - Initialize the reload value for the GX6605s timer correctly so the
     hardware counter starts at 0 again after overrun.

   - Make error return value negative in the h8300 timer init function"

* tag 'timers-urgent-2020-09-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  clocksource/drivers/timer-gx6605s: Fixup counter reload
  clocksource/drivers/timer-ti-dm: Do reset before enable
  clocksource/drivers/h8300_timer8: Fix wrong return value in h8300_8timer_init()

Pinned pages shouldn't be write-protected when fork() happens, because
follow up copy-on-write on these pages could cause the pinned pages to
be replaced by random newly allocated pages.

For huge PMDs, we split the huge pmd if pinning is detected.  So that
future handling will be done by the PTE level (with our latest changes,
each of the small pages will be copied).  We can achieve this by let
copy_huge_pmd() return -EAGAIN for pinned pages, so that we'll
fallthrough in copy_pmd_range() and finally land the next
copy_pte_range() call.

Huge PUDs will be even more special - so far it does not support
anonymous pages.  But it can actually be done the same as the huge PMDs
even if the split huge PUDs means to erase the PUD entries.  It'll
guarantee the follow up fault ins will remap the same pages in either
parent/child later.

This might not be the most efficient way, but it should be easy and
clean enough.  It should be fine, since we're tackling with a very rare
case just to make sure userspaces that pinned some thps will still work
even without MADV_DONTFORK and after they fork()ed.

Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This allows copy_pte_range() to do early cow if the pages were pinned on
the source mm.

Currently we don't have an accurate way to know whether a page is pinned
or not.  The only thing we have is page_maybe_dma_pinned().  However
that's good enough for now.  Especially, with the newly added
mm->has_pinned flag to make sure we won't affect processes that never
pinned any pages.

It would be easier if we can do GFP_KERNEL allocation within
copy_one_pte().  Unluckily, we can't because we're with the page table
locks held for both the parent and child processes.  So the page
allocation needs to be done outside copy_one_pte().

Some trick is there in copy_present_pte(), majorly the wrprotect trick
to block concurrent fast-gup.  Comments in the function should explain
better in place.

Oleg Nesterov reported a (probably harmless) bug during review that we
didn't reset entry.val properly in copy_pte_range() so that potentially
there's chance to call add_swap_count_continuation() multiple times on
the same swp entry.  However that should be harmless since even if it
happens, the same function (add_swap_count_continuation()) will return
directly noticing that there're enough space for the swp counter.  So
instead of a standalone stable patch, it is touched up in this patch
directly.

Link: https://lore.kernel.org/lkml/20200914143829.GA1424636@nvidia.com/
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This prepares for the future work to trigger early cow on pinned pages
during fork().

No functional change intended.

Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

(Commit message majorly collected from Jason Gunthorpe)

Reduce the chance of false positive from page_maybe_dma_pinned() by
keeping track if the mm_struct has ever been used with pin_user_pages().
This allows cases that might drive up the page ref_count to avoid any
penalty from handling dma_pinned pages.

Future work is planned, to provide a more sophisticated solution, likely
to turn it into a real counter.  For now, make it atomic_t but use it as
a boolean for simplicity.

Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull clocksource/clockevent fixes from Daniel Lezcano:

 - Fix wrong signed return value when checking of_iomap in the probe
   function for the h8300 timer (Tianjia Zhang)

 - Fix reset sequence when setting up the timer on the dm_timer (Tony
   Lindgren)

 - Fix counter reload when the interrupt fires on gx6605s (Guo Ren)

Pull SCSI fixes from James Bottomley:
 "Three fixes: one in drivers (lpfc) and two for zoned block devices.

  The latter also impinges on the block layer but only to introduce a
  new block API for setting the zone model rather than fiddling with the
  queue directly in the zoned block driver"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  scsi: sd: sd_zbc: Fix ZBC disk initialization
  scsi: sd: sd_zbc: Fix handling of host-aware ZBC disks
  scsi: lpfc: Fix initial FLOGI failure due to BBSCN not supported