The patch titled
Subject: mm, doc: cleanup and clarify munmap behavior for hugetlb memory
has been added to the -mm tree. Its filename is
mm-doc-cleanup-and-clarify-munmap-behavior-for-hugetlb-memory.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-doc-cleanup-and-clarify-munmap-behavior-for-hugetlb-memory.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-doc-cleanup-and-clarify-munmap-behavior-for-hugetlb-memory.patch
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------------------------------------------------------
From: David Rientjes <rientjes@xxxxxxxxxx>
Subject: mm, doc: cleanup and clarify munmap behavior for hugetlb memory
munmap(2) of hugetlb memory requires a length that is hugepage aligned,
otherwise it may fail. Add this to the documentation.
This also cleans up the documentation and separates it into logical units:
one part refers to MAP_HUGETLB and another part refers to requirements for
shared memory segments.
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Davide Libenzi <davidel@xxxxxxxxxxxxxxx>
Cc: Luiz Capitulino <lcapitulino@xxxxxxxxxx>
Cc: Shuah Khan <shuahkh@xxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Joern Engel <joern@xxxxxxxxx>
Cc: Jianguo Wu <wujianguo@xxxxxxxxxx>
Cc: Eric B Munson <emunson@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/vm/hugetlbpage.txt | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)
diff -puN Documentation/vm/hugetlbpage.txt~mm-doc-cleanup-and-clarify-munmap-behavior-for-hugetlb-memory Documentation/vm/hugetlbpage.txt
--- a/Documentation/vm/hugetlbpage.txt~mm-doc-cleanup-and-clarify-munmap-behavior-for-hugetlb-memory
+++ a/Documentation/vm/hugetlbpage.txt
@@ -302,15 +302,20 @@ file systems, write system calls are not
Regular chown, chgrp, and chmod commands (with right permissions) could be
used to change the file attributes on hugetlbfs.
-Also, it is important to note that no such mount command is required if the
+Also, it is important to note that no such mount command is required if
applications are going to use only shmat/shmget system calls or mmap with
-MAP_HUGETLB. Users who wish to use hugetlb page via shared memory segment
-should be a member of a supplementary group and system admin needs to
-configure that gid into /proc/sys/vm/hugetlb_shm_group. It is possible for
-same or different applications to use any combination of mmaps and shm*
-calls, though the mount of filesystem will be required for using mmap calls
-without MAP_HUGETLB. For an example of how to use mmap with MAP_HUGETLB see
-map_hugetlb.c.
+MAP_HUGETLB. For an example of how to use mmap with MAP_HUGETLB see map_hugetlb
+below.
+
+Users who wish to use hugetlb memory via shared memory segment should be a
+member of a supplementary group and system admin needs to configure that gid
+into /proc/sys/vm/hugetlb_shm_group. It is possible for same or different
+applications to use any combination of mmaps and shm* calls, though the mount of
+filesystem will be required for using mmap calls without MAP_HUGETLB.
+
+When using munmap(2) to unmap hugetlb memory, the length specified must be
+hugepage aligned, otherwise it will fail with errno set to EINVAL.
+
Examples
========
_
Patches currently in -mm which might be from rientjes@xxxxxxxxxx are
origin.patch
cxgb4-drop-__gfp_nofail-allocation.patch
sh-dwarf-destroy-mempools-on-cleanup.patch
sh-dwarf-use-mempool_create_slab_pool.patch
jbd2-revert-must-not-fail-allocation-loops-back-to-gfp_nofail.patch
mm-slub-parse-slub_debug-o-option-in-switch-statement.patch
mm-slab-correct-config-option-in-comment.patch
mm-rename-foll_mlock-to-foll_populate.patch
mm-rename-__mlock_vma_pages_range-to-populate_vma_page_range.patch
mm-move-gup-posix-mlock-error-conversion-out-of-__mm_populate.patch
mm-move-mm_populate-related-code-to-mm-gupc.patch
mm-hotplug-fix-concurrent-memory-hot-add-deadlock.patch
mm-cma-change-fallback-behaviour-for-cma-freepage.patch
mm-page_alloc-factor-out-fallback-freepage-checking.patch
mm-compaction-enhance-compaction-finish-condition.patch
mm-compaction-enhance-compaction-finish-condition-fix.patch
mm-incorporate-zero-pages-into-transparent-huge-pages.patch
mm-incorporate-zero-pages-into-transparent-huge-pages-fix.patch
mm-completely-remove-dumping-per-cpu-lists-from-show_mem.patch
mm-mempolicy-migrate_to_node-should-only-migrate-to-node.patch
mm-remove-gfp_thisnode.patch
mm-thp-really-limit-transparent-hugepage-allocation-to-local-node.patch
kernel-cpuset-remove-exception-for-__gfp_thisnode.patch
mm-clarify-__gfp_nofail-deprecation-status.patch
mm-clarify-__gfp_nofail-deprecation-status-checkpatch-fixes.patch
sparc-clarify-__gfp_nofail-allocation.patch
mm-mempool-do-not-allow-atomic-resizing.patch
mm-mempool-do-not-allow-atomic-resizing-checkpatch-fixes.patch
mm-hugetlb-abort-__get_user_pages-if-current-has-been-oom-killed.patch
mm-refactor-zone_movable_is_highmem.patch
mm-memory-failurec-define-page-types-for-action_result-in-one-place.patch
page-flags-define-behavior-slb-related-flags-on-compound-pages.patch
allow-compaction-of-unevictable-pages.patch
mm-compaction-reset-compaction-scanner-positions.patch
hugetlbfs-add-minimum-size-tracking-fields-to-subpool-structure.patch
hugetlbfs-add-minimum-size-accounting-to-subpools.patch
hugetlbfs-accept-subpool-min_size-mount-option-and-setup-accordingly.patch
hugetlbfs-document-min_size-mount-option-and-cleanup.patch
mm-vmalloc-fix-possible-exhaustion-of-vmalloc-space-caused-by-vm_map_ram-allocator.patch
mm-vmalloc-occupy-newly-allocated-vmap-block-just-after-allocation.patch
mm-vmalloc-get-rid-of-dirty-bitmap-inside-vmap_block-structure.patch
mremap-should-return-enomem-when-__vm_enough_memory-fail.patch
clean-up-goto-just-return-err_ptr.patch
fs-jfs-remove-slab-object-constructor.patch
mm-mempool-disallow-mempools-based-on-slab-caches-with-constructors.patch
mm-mempool-poison-elements-backed-by-slab-allocator.patch
mm-mempool-poison-elements-backed-by-page-allocator.patch
thp-handle-errors-in-hugepage_init-properly.patch
thp-do-not-adjust-zone-water-marks-if-khugepaged-is-not-started.patch
mm-doc-cleanup-and-clarify-munmap-behavior-for-hugetlb-memory.patch
mm-selftests-test-return-value-of-munmap-for-map_hugetlb-memory.patch
hung_task-change-hung_taskc-to-use-for_each_process_thread.patch
mm-utilc-add-kstrimdup.patch
linux-next.patch
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