Merge tag 'mm-stable-2022-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull MM updates from Andrew Morton:
 "Most of the MM queue. A few things are still pending.

  Liam's maple tree rework didn't make it. This has resulted in a few
  other minor patch series being held over for next time.

  Multi-gen LRU still isn't merged as we were waiting for mapletree to
  stabilize. The current plan is to merge MGLRU into -mm soon and to
  later reintroduce mapletree, with a view to hopefully getting both
  into 6.1-rc1.

  Summary:

   - The usual batches of cleanups from Baoquan He, Muchun Song, Miaohe
     Lin, Yang Shi, Anshuman Khandual and Mike Rapoport

   - Some kmemleak fixes from Patrick Wang and Waiman Long

   - DAMON updates from SeongJae Park

   - memcg debug/visibility work from Roman Gushchin

   - vmalloc speedup from Uladzislau Rezki

   - more folio conversion work from Matthew Wilcox

   - enhancements for coherent device memory mapping from Alex Sierra

   - addition of shared pages tracking and CoW support for fsdax, from
     Shiyang Ruan

   - hugetlb optimizations from Mike Kravetz

   - Mel Gorman has contributed some pagealloc changes to improve
     latency and realtime behaviour.

   - mprotect soft-dirty checking has been improved by Peter Xu

   - Many other singleton patches all over the place"

 [ XFS merge from hell as per Darrick Wong in

   https://lore.kernel.org/all/YshKnxb4VwXycPO8@magnolia/ ]

* tag 'mm-stable-2022-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (282 commits)
  tools/testing/selftests/vm/hmm-tests.c: fix build
  mm: Kconfig: fix typo
  mm: memory-failure: convert to pr_fmt()
  mm: use is_zone_movable_page() helper
  hugetlbfs: fix inaccurate comment in hugetlbfs_statfs()
  hugetlbfs: cleanup some comments in inode.c
  hugetlbfs: remove unneeded header file
  hugetlbfs: remove unneeded hugetlbfs_ops forward declaration
  hugetlbfs: use helper macro SZ_1{K,M}
  mm: cleanup is_highmem()
  mm/hmm: add a test for cross device private faults
  selftests: add soft-dirty into run_vmtests.sh
  selftests: soft-dirty: add test for mprotect
  mm/mprotect: fix soft-dirty check in can_change_pte_writable()
  mm: memcontrol: fix potential oom_lock recursion deadlock
  mm/gup.c: fix formatting in check_and_migrate_movable_page()
  xfs: fail dax mount if reflink is enabled on a partition
  mm/memcontrol.c: remove the redundant updating of stats_flush_threshold
  userfaultfd: don't fail on unrecognized features
  hugetlb_cgroup: fix wrong hugetlb cgroup numa stat
  ...

1 files changed, 184 insertions, 0 deletions

diff --git a/Documentation/mm/hwpoison.rst b/Documentation/mm/hwpoison.rst
new file mode 100644
index 000000000000..b9d5253c1305
--- /dev/null
+++ b/Documentation/mm/hwpoison.rst
@@ -0,0 +1,184 @@
+.. hwpoison:
+
+========
+hwpoison
+========
+
+What is hwpoison?
+=================
+
+Upcoming Intel CPUs have support for recovering from some memory errors
+(``MCA recovery``). This requires the OS to declare a page "poisoned",
+kill the processes associated with it and avoid using it in the future.
+
+This patchkit implements the necessary infrastructure in the VM.
+
+To quote the overview comment::
+
+	High level machine check handler. Handles pages reported by the
+	hardware as being corrupted usually due to a 2bit ECC memory or cache
+	failure.
+
+	This focusses on pages detected as corrupted in the background.
+	When the current CPU tries to consume corruption the currently
+	running process can just be killed directly instead. This implies
+	that if the error cannot be handled for some reason it's safe to
+	just ignore it because no corruption has been consumed yet. Instead
+	when that happens another machine check will happen.
+
+	Handles page cache pages in various states. The tricky part
+	here is that we can access any page asynchronous to other VM
+	users, because memory failures could happen anytime and anywhere,
+	possibly violating some of their assumptions. This is why this code
+	has to be extremely careful. Generally it tries to use normal locking
+	rules, as in get the standard locks, even if that means the
+	error handling takes potentially a long time.
+
+	Some of the operations here are somewhat inefficient and have non
+	linear algorithmic complexity, because the data structures have not
+	been optimized for this case. This is in particular the case
+	for the mapping from a vma to a process. Since this case is expected
+	to be rare we hope we can get away with this.
+
+The code consists of a the high level handler in mm/memory-failure.c,
+a new page poison bit and various checks in the VM to handle poisoned
+pages.
+
+The main target right now is KVM guests, but it works for all kinds
+of applications. KVM support requires a recent qemu-kvm release.
+
+For the KVM use there was need for a new signal type so that
+KVM can inject the machine check into the guest with the proper
+address. This in theory allows other applications to handle
+memory failures too. The expection is that near all applications
+won't do that, but some very specialized ones might.
+
+Failure recovery modes
+======================
+
+There are two (actually three) modes memory failure recovery can be in:
+
+vm.memory_failure_recovery sysctl set to zero:
+	All memory failures cause a panic. Do not attempt recovery.
+
+early kill
+	(can be controlled globally and per process)
+	Send SIGBUS to the application as soon as the error is detected
+	This allows applications who can process memory errors in a gentle
+	way (e.g. drop affected object)
+	This is the mode used by KVM qemu.
+
+late kill
+	Send SIGBUS when the application runs into the corrupted page.
+	This is best for memory error unaware applications and default
+	Note some pages are always handled as late kill.
+
+User control
+============
+
+vm.memory_failure_recovery
+	See sysctl.txt
+
+vm.memory_failure_early_kill
+	Enable early kill mode globally
+
+PR_MCE_KILL
+	Set early/late kill mode/revert to system default
+
+	arg1: PR_MCE_KILL_CLEAR:
+		Revert to system default
+	arg1: PR_MCE_KILL_SET:
+		arg2 defines thread specific mode
+
+		PR_MCE_KILL_EARLY:
+			Early kill
+		PR_MCE_KILL_LATE:
+			Late kill
+		PR_MCE_KILL_DEFAULT
+			Use system global default
+
+	Note that if you want to have a dedicated thread which handles
+	the SIGBUS(BUS_MCEERR_AO) on behalf of the process, you should
+	call prctl(PR_MCE_KILL_EARLY) on the designated thread. Otherwise,
+	the SIGBUS is sent to the main thread.
+
+PR_MCE_KILL_GET
+	return current mode
+
+Testing
+=======
+
+* madvise(MADV_HWPOISON, ....) (as root) - Poison a page in the
+  process for testing
+
+* hwpoison-inject module through debugfs ``/sys/kernel/debug/hwpoison/``
+
+  corrupt-pfn
+	Inject hwpoison fault at PFN echoed into this file. This does
+	some early filtering to avoid corrupted unintended pages in test suites.
+
+  unpoison-pfn
+	Software-unpoison page at PFN echoed into this file. This way
+	a page can be reused again.  This only works for Linux
+	injected failures, not for real memory failures. Once any hardware
+	memory failure happens, this feature is disabled.
+
+  Note these injection interfaces are not stable and might change between
+  kernel versions
+
+  corrupt-filter-dev-major, corrupt-filter-dev-minor
+	Only handle memory failures to pages associated with the file
+	system defined by block device major/minor.  -1U is the
+	wildcard value.  This should be only used for testing with
+	artificial injection.
+
+  corrupt-filter-memcg
+	Limit injection to pages owned by memgroup. Specified by inode
+	number of the memcg.
+
+	Example::
+
+		mkdir /sys/fs/cgroup/mem/hwpoison
+
+	        usemem -m 100 -s 1000 &
+		echo `jobs -p` > /sys/fs/cgroup/mem/hwpoison/tasks
+
+		memcg_ino=$(ls -id /sys/fs/cgroup/mem/hwpoison | cut -f1 -d' ')
+		echo $memcg_ino > /debug/hwpoison/corrupt-filter-memcg
+
+		page-types -p `pidof init`   --hwpoison  # shall do nothing
+		page-types -p `pidof usemem` --hwpoison  # poison its pages
+
+  corrupt-filter-flags-mask, corrupt-filter-flags-value
+	When specified, only poison pages if ((page_flags & mask) ==
+	value).  This allows stress testing of many kinds of
+	pages. The page_flags are the same as in /proc/kpageflags. The
+	flag bits are defined in include/linux/kernel-page-flags.h and
+	documented in Documentation/admin-guide/mm/pagemap.rst
+
+* Architecture specific MCE injector
+
+  x86 has mce-inject, mce-test
+
+  Some portable hwpoison test programs in mce-test, see below.
+
+References
+==========
+
+http://halobates.de/mce-lc09-2.pdf
+	Overview presentation from LinuxCon 09
+
+git://git.kernel.org/pub/scm/utils/cpu/mce/mce-test.git
+	Test suite (hwpoison specific portable tests in tsrc)
+
+git://git.kernel.org/pub/scm/utils/cpu/mce/mce-inject.git
+	x86 specific injector
+
+
+Limitations
+===========
+- Not all page types are supported and never will. Most kernel internal
+  objects cannot be recovered, only LRU pages for now.
+
+---
+Andi Kleen, Oct 2009