path: root/Documentation
diff options
authorLinus Torvalds <>2021-02-24 16:20:38 -0800
committerLinus Torvalds <>2021-02-24 16:20:38 -0800
commit4c48faba5b7f18fb53e4aeeb768932f17c9da1ed (patch)
tree9d9d2ca881a670b5df55a663ee506f212c9514c3 /Documentation
parent062c84fccc4444805738d76a2699c4d3c95184ec (diff)
parenta553e3cd2053501b658feec2be9a3b662eb1b22b (diff)
Merge branch 'akpm' (patches from Andrew)
Merge misc updates from Andrew Morton: "A few small subsystems and some of MM. 172 patches. Subsystems affected by this patch series: hexagon, scripts, ntfs, ocfs2, vfs, and mm (slab-generic, slab, slub, debug, pagecache, swap, memcg, pagemap, mprotect, mremap, page-reporting, vmalloc, kasan, pagealloc, memory-failure, hugetlb, vmscan, z3fold, compaction, mempolicy, oom-kill, hugetlbfs, and migration)" * emailed patches from Andrew Morton <>: (172 commits) mm/migrate: remove unneeded semicolons hugetlbfs: remove unneeded return value of hugetlb_vmtruncate() hugetlbfs: fix some comment typos hugetlbfs: correct some obsolete comments about inode i_mutex hugetlbfs: make hugepage size conversion more readable hugetlbfs: remove meaningless variable avoid_reserve hugetlbfs: correct obsolete function name in hugetlbfs_read_iter() hugetlbfs: use helper macro default_hstate in init_hugetlbfs_fs hugetlbfs: remove useless BUG_ON(!inode) in hugetlbfs_setattr() hugetlbfs: remove special hugetlbfs_set_page_dirty() mm/hugetlb: change hugetlb_reserve_pages() to type bool mm, oom: fix a comment in dump_task() mm/mempolicy: use helper range_in_vma() in queue_pages_test_walk() numa balancing: migrate on fault among multiple bound nodes mm, compaction: make fast_isolate_freepages() stay within zone mm/compaction: fix misbehaviors of fast_find_migrateblock() mm/compaction: correct deferral logic for proactive compaction mm/compaction: remove duplicated VM_BUG_ON_PAGE !PageLocked mm/compaction: remove rcu_read_lock during page compaction z3fold: simplify the zhdr initialization code in init_z3fold_page() ...
Diffstat (limited to 'Documentation')
6 files changed, 30 insertions, 31 deletions
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index c513eafaddea..9acc57f68f31 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1299,6 +1299,10 @@ PAGE_SIZE multiple when read back.
Amount of cached filesystem data that was modified and
is currently being written back to disk
+ swapcached
+ Amount of swap cached in memory. The swapcache is accounted
+ against both memory and swap usage.
Amount of memory used in anonymous mappings backed by
transparent hugepages
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 186ad235bf32..bab6a8b01202 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4904,14 +4904,6 @@
last alloc / free. For more information see
- slub_memcg_sysfs= [MM, SLUB]
- Determines whether to enable sysfs directories for
- memory cgroup sub-caches. 1 to enable, 0 to disable.
- The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
- Enabling this can lead to a very high number of debug
- directories and files being created under
- /sys/kernel/slub.
slub_max_order= [MM, SLUB]
Determines the maximum allowed order for slabs.
A high setting may cause OOMs due to memory
diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst
index e35a3f2fb006..586cd4b86428 100644
--- a/Documentation/admin-guide/sysctl/vm.rst
+++ b/Documentation/admin-guide/sysctl/vm.rst
@@ -983,11 +983,11 @@ that benefit from having their data cached, zone_reclaim_mode should be
left disabled as the caching effect is likely to be more important than
data locality.
-zone_reclaim may be enabled if it's known that the workload is partitioned
-such that each partition fits within a NUMA node and that accessing remote
-memory would cause a measurable performance reduction. The page allocator
-will then reclaim easily reusable pages (those page cache pages that are
-currently not used) before allocating off node pages.
+Consider enabling one or more zone_reclaim mode bits if it's known that the
+workload is partitioned such that each partition fits within a NUMA node
+and that accessing remote memory would cause a measurable performance
+reduction. The page allocator will take additional actions before
+allocating off node pages.
Allowing zone reclaim to write out pages stops processes that are
writing large amounts of data from dirtying pages on other nodes. Zone
diff --git a/Documentation/core-api/mm-api.rst b/Documentation/core-api/mm-api.rst
index 2adffb3f7914..201b5423303b 100644
--- a/Documentation/core-api/mm-api.rst
+++ b/Documentation/core-api/mm-api.rst
@@ -19,11 +19,8 @@ User Space Memory Access
Memory Allocation Controls
-Functions which need to allocate memory often use GFP flags to express
-how that memory should be allocated. The GFP acronym stands for "get
-free pages", the underlying memory allocation function. Not every GFP
-flag is allowed to every function which may allocate memory. Most
-users will want to use a plain ``GFP_KERNEL``.
+.. kernel-doc:: include/linux/gfp.h
+ :internal:
.. kernel-doc:: include/linux/gfp.h
:doc: Page mobility and placement hints
diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
index a248ac3941be..cde14aeefca7 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -147,15 +147,14 @@ negative values to distinguish between different kinds of inaccessible memory
like redzones or freed memory (see mm/kasan/kasan.h).
In the report above the arrows point to the shadow byte 03, which means that
-the accessed address is partially accessible.
-For tag-based KASAN this last report section shows the memory tags around the
-accessed address (see `Implementation details`_ section).
+the accessed address is partially accessible. For tag-based KASAN modes this
+last report section shows the memory tags around the accessed address
+(see the `Implementation details`_ section).
Boot parameters
-Hardware tag-based KASAN mode (see the section about different mode below) is
+Hardware tag-based KASAN mode (see the section about various modes below) is
intended for use in production as a security mitigation. Therefore it supports
boot parameters that allow to disable KASAN competely or otherwise control
particular KASAN features.
@@ -289,6 +288,13 @@ reserved to tag freed memory regions.
Hardware tag-based KASAN currently only supports tagging of
kmem_cache_alloc/kmalloc and page_alloc memory.
+If the hardware doesn't support MTE (pre ARMv8.5), hardware tag-based KASAN
+won't be enabled. In this case all boot parameters are ignored.
+Note, that enabling CONFIG_KASAN_HW_TAGS always results in in-kernel TBI being
+enabled. Even when kasan.mode=off is provided, or when the hardware doesn't
+support MTE (but supports TBI).
What memory accesses are sanitised by KASAN?
@@ -352,17 +358,17 @@ unmapped. This will require changes in arch-specific code.
This allows ``VMAP_STACK`` support on x86, and can simplify support of
architectures that do not have a fixed module region.
-KASAN tests consist on two parts:
+KASAN tests consist of two parts:
1. Tests that are integrated with the KUnit Test Framework. Enabled with
``CONFIG_KASAN_KUNIT_TEST``. These tests can be run and partially verified
automatically in a few different ways, see the instructions below.
2. Tests that are currently incompatible with KUnit. Enabled with
-``CONFIG_TEST_KASAN_MODULE`` and can only be run as a module. These tests can
+``CONFIG_KASAN_MODULE_TEST`` and can only be run as a module. These tests can
only be verified manually, by loading the kernel module and inspecting the
kernel log for KASAN reports.
diff --git a/Documentation/vm/arch_pgtable_helpers.rst b/Documentation/vm/arch_pgtable_helpers.rst
index f3591ee3aaa8..552567d863b8 100644
--- a/Documentation/vm/arch_pgtable_helpers.rst
+++ b/Documentation/vm/arch_pgtable_helpers.rst
@@ -50,7 +50,7 @@ PTE Page Table Helpers
| pte_mkwrite | Creates a writable PTE |
-| pte_mkwrprotect | Creates a write protected PTE |
+| pte_wrprotect | Creates a write protected PTE |
| pte_mkspecial | Creates a special PTE |
@@ -120,7 +120,7 @@ PMD Page Table Helpers
| pmd_mkwrite | Creates a writable PMD |
-| pmd_mkwrprotect | Creates a write protected PMD |
+| pmd_wrprotect | Creates a write protected PMD |
| pmd_mkspecial | Creates a special PMD |
@@ -186,7 +186,7 @@ PUD Page Table Helpers
| pud_mkwrite | Creates a writable PUD |
-| pud_mkwrprotect | Creates a write protected PUD |
+| pud_wrprotect | Creates a write protected PUD |
| pud_mkdevmap | Creates a ZONE_DEVICE mapped PUD |
@@ -224,7 +224,7 @@ HugeTLB Page Table Helpers
| huge_pte_mkwrite | Creates a writable HugeTLB |
-| huge_pte_mkwrprotect | Creates a write protected HugeTLB |
+| huge_pte_wrprotect | Creates a write protected HugeTLB |
| huge_ptep_get_and_clear | Clears a HugeTLB |