linux.git/mm/highmem.c, branch v5.13

mm: fix typos in comments

2021-05-07T07:26:35+00:00

Fix ~94 single-word typos in locking code comments, plus a few
very obvious grammar mistakes.

Link: https://lkml.kernel.org/r/20210322212624.GA1963421@gmail.com
Link: https://lore.kernel.org/r/20210322205203.GB1959563@gmail.com
Signed-off-by: Ingo Molnar 
Reviewed-by: Matthew Wilcox (Oracle) 
Reviewed-by: Randy Dunlap 
Cc: Bhaskar Chowdhury 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/highmem.c: fix coding style issue

2021-05-05T18:27:27+00:00

Delete/add some blank lines and some blank spaces

Link: https://lkml.kernel.org/r/20210311095015.14277-1-songqiang@uniontech.com
Signed-off-by: songqiang 
Reviewed-by: David Hildenbrand 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/highmem: fix CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP

2021-03-25T16:22:55+00:00

The kernel test robot found that __kmap_local_sched_out() was not
correctly skipping the guard pages when DEBUG_KMAP_LOCAL_FORCE_MAP was
set.[1] This was due to DEBUG_HIGHMEM check being used.

Change the configuration check to be correct.

[1] https://lore.kernel.org/lkml/20210304083825.GB17830@xsang-OptiPlex-9020/

Link: https://lkml.kernel.org/r/20210318230657.1497881-1-ira.weiny@intel.com
Fixes: 0e91a0c6984c ("mm/highmem: Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP")
Signed-off-by: Ira Weiny 
Reported-by: kernel test robot 
Reviewed-by: Thomas Gleixner 
Cc: Thomas Gleixner 
Cc: Oliver Sang 
Cc: Chaitanya Kulkarni 
Cc: David Sterba 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/highmem.c: fix zero_user_segments() with start > end

2021-03-13T19:27:30+00:00

zero_user_segments() is used from __block_write_begin_int(), for example
like the following

	zero_user_segments(page, 4096, 1024, 512, 918)

But new the zero_user_segments() implementation for for HIGHMEM +
TRANSPARENT_HUGEPAGE doesn't handle "start > end" case correctly, and hits
BUG_ON().  (we can fix __block_write_begin_int() instead though, it is the
old and multiple usage)

Also it calls kmap_atomic() unnecessarily while start == end == 0.

Link: https://lkml.kernel.org/r/87v9ab60r4.fsf@mail.parknet.co.jp
Fixes: 0060ef3b4e6d ("mm: support THPs in zero_user_segments")
Signed-off-by: OGAWA Hirofumi 
Cc: Matthew Wilcox 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

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