linux.git/mm/highmem.c, branch v5.11

mm/highmem: prepare for overriding set_pte_at()

2021-01-24T18:34:52+00:00

The generic kmap_local() map function uses set_pte_at(), but MIPS requires
set_pte() and PowerPC wants __set_pte_at().

Provide arch_kmap_local_set_pte() and default it to set_pte_at().

Link: https://lkml.kernel.org/r/20210112170411.056306194@linutronix.de
Signed-off-by: Thomas Gleixner 
Cc: Andreas Larsson 
Cc: "David S. Miller" 
Cc: Michael Ellerman 
Cc: Paul Cercueil 
Cc: Peter Zijlstra 
Cc: Thomas Bogendoerfer 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'akpm' (patches from Andrew)

2020-12-15T20:53:37+00:00

Merge misc updates from Andrew Morton:

 - a few random little subsystems

 - almost all of the MM patches which are staged ahead of linux-next
   material. I'll trickle to post-linux-next work in as the dependents
   get merged up.

Subsystems affected by this patch series: kthread, kbuild, ide, ntfs,
ocfs2, arch, and mm (slab-generic, slab, slub, dax, debug, pagecache,
gup, swap, shmem, memcg, pagemap, mremap, hmm, vmalloc, documentation,
kasan, pagealloc, memory-failure, hugetlb, vmscan, z3fold, compaction,
oom-kill, migration, cma, page-poison, userfaultfd, zswap, zsmalloc,
uaccess, zram, and cleanups).

* emailed patches from Andrew Morton : (200 commits)
  mm: cleanup kstrto*() usage
  mm: fix fall-through warnings for Clang
  mm: slub: convert sysfs sprintf family to sysfs_emit/sysfs_emit_at
  mm: shmem: convert shmem_enabled_show to use sysfs_emit_at
  mm:backing-dev: use sysfs_emit in macro defining functions
  mm: huge_memory: convert remaining use of sprintf to sysfs_emit and neatening
  mm: use sysfs_emit for struct kobject * uses
  mm: fix kernel-doc markups
  zram: break the strict dependency from lzo
  zram: add stat to gather incompressible pages since zram set up
  zram: support page writeback
  mm/process_vm_access: remove redundant initialization of iov_r
  mm/zsmalloc.c: rework the list_add code in insert_zspage()
  mm/zswap: move to use crypto_acomp API for hardware acceleration
  mm/zswap: fix passing zero to 'PTR_ERR' warning
  mm/zswap: make struct kernel_param_ops definitions const
  userfaultfd/selftests: hint the test runner on required privilege
  userfaultfd/selftests: fix retval check for userfaultfd_open()
  userfaultfd/selftests: always dump something in modes
  userfaultfd: selftests: make __{s,u}64 format specifiers portable
  ...

mm: support THPs in zero_user_segments

2020-12-15T20:13:45+00:00

We can only kmap() one subpage of a THP at a time, so loop over all
relevant subpages, skipping ones which don't need to be zeroed.  This is
too large to inline when THPs are enabled and we actually need highmem, so
put it in highmem.c.

[willy@infradead.org: start1 was allowed to be less than start2]

Link: https://lkml.kernel.org/r/20201124041507.28996-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) 
Cc: Yang Shi 
Cc: Jan Kara 
Cc: Michal Hocko 
Cc: Zi Yan 
Cc: Song Liu 
Cc: Mel Gorman 
Cc: Naresh Kamboju 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/highmem: Provide kmap_local*

2020-11-24T13:42:09+00:00

Now that the kmap atomic index is stored in task struct provide a
preemptible variant. On context switch the maps of an outgoing task are
removed and the map of the incoming task are restored. That's obviously
slow, but highmem is slow anyway.

The kmap_local.*() functions can be invoked from both preemptible and
atomic context. kmap local sections disable migration to keep the resulting
virtual mapping address correct, but disable neither pagefaults nor
preemption.

A wholesale conversion of kmap_atomic to be fully preemptible is not
possible because some of the usage sites might rely on the preemption
disable for serialization or on the implicit pagefault disable. Needs to be
done on a case by case basis.

Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20201118204007.468533059@linutronix.de

sched: highmem: Store local kmaps in task struct

2020-11-24T13:42:09+00:00

Instead of storing the map per CPU provide and use per task storage. That
prepares for local kmaps which are preemptible.

The context switch code is preparatory and not yet in use because
kmap_atomic() runs with preemption disabled. Will be made usable in the
next step.

The context switch logic is safe even when an interrupt happens after
clearing or before restoring the kmaps. The kmap index in task struct is
not modified so any nesting kmap in an interrupt will use unused indices
and on return the counter is the same as before.

Also add an assert into the return to user space code. Going back to user
space with an active kmap local is a nono.

Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20201118204007.372935758@linutronix.de

mm/highmem: Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP

2020-11-24T13:42:08+00:00

CONFIG_DEBUG_KMAP_LOCAL, which is selected by CONFIG_DEBUG_HIGHMEM is only
providing guard pages, but does not provide a mechanism to enforce the
usage of the kmap_local() infrastructure.

Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP which forces the temporary
mapping even for lowmem pages. This needs to be a seperate config switch
because this only works on architectures which do not have cache aliasing
problems.

Suggested-by: Linus Torvalds 
Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20201118204007.028261233@linutronix.de

mm/highmem: Provide and use CONFIG_DEBUG_KMAP_LOCAL

2020-11-24T13:42:08+00:00

CONFIG_KMAP_LOCAL can be enabled by x86/32bit even if CONFIG_HIGHMEM is not
enabled for temporary MMIO space mappings.

Provide it as a seperate config option which depends on CONFIG_KMAP_LOCAL
and let CONFIG_DEBUG_HIGHMEM select it.

This won't increase the debug coverage of this significantly but it paves
the way to do so.

Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20201118204006.869487226@linutronix.de

mm/highmem: Take kmap_high_get() properly into account

2020-11-12T13:44:38+00:00

kunmap_local() warns when the virtual address to unmap is below
PAGE_OFFSET. This is correct except for the case that the mapping was
obtained via kmap_high_get() because the PKMAP addresses are right below
PAGE_OFFSET.

Cure it by skipping the WARN_ON() when the unmap was handled by
kunmap_high().

Fixes: 298fa1ad5571 ("highmem: Provide generic variant of kmap_atomic*")
Reported-by: vtolkm@googlemail.com
Reported-by: Marek Szyprowski 
Signed-off-by: Thomas Gleixner 
Tested-by: Marek Szyprowski 
Tested-by: Sebastian Andrzej Siewior 
Cc: Andrew Morton 
Link: https://lore.kernel.org/r/87y2j6n8mj.fsf@nanos.tec.linutronix.de

highmem: High implementation details and document API

2020-11-06T22:14:59+00:00

Move the gory details of kmap & al into a private header and only document
the interfaces which are usable by drivers.

Signed-off-by: Thomas Gleixner 
Cc: Linus Torvalds 
Cc: Christoph Hellwig 
Cc: Andrew Morton 
Link: https://lore.kernel.org/r/20201103095858.827582066@linutronix.de

mm/highmem: Remove the old kmap_atomic cruft

2020-11-06T22:14:58+00:00

All users gone.

Signed-off-by: Thomas Gleixner 
Cc: Linus Torvalds 
Cc: Christoph Hellwig 
Cc: Andrew Morton 
Cc: Arnd Bergmann 
Link: https://lore.kernel.org/r/20201103095858.516281567@linutronix.de