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| author |   Wei Yang <richard.weiyang@gmail.com> | 2018-12-28 00:37:02 -0800 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2018-12-28 12:11:49 -0800 |
| commit | 83af658898cb292a32d8b6cd9b51266d7cfc4b6a (patch) | |
| tree | 7a6c4daecefff22c007fb1326f10737a17920eb2 /include | |
| parent | mm: remove pte_lock_deinit() (diff) | |
| download | linux-dev-83af658898cb292a32d8b6cd9b51266d7cfc4b6a.tar.xz linux-dev-83af658898cb292a32d8b6cd9b51266d7cfc4b6a.zip | |
mm, sparse: drop pgdat_resize_lock in sparse_add/remove_one_section()
pgdat_resize_lock is used to protect pgdat's memory region information
like: node_start_pfn, node_present_pages, etc. While in function
sparse_add/remove_one_section(), pgdat_resize_lock is used to protect
initialization/release of one mem_section. This looks not proper.
These code paths are currently protected by mem_hotplug_lock currently but
should there ever be any reason for locking at the sparse layer a
dedicated lock should be introduced.
Following is the current call trace of sparse_add/remove_one_section()
mem_hotplug_begin()
arch_add_memory()
add_pages()
__add_pages()
__add_section()
sparse_add_one_section()
mem_hotplug_done()
mem_hotplug_begin()
arch_remove_memory()
__remove_pages()
__remove_section()
sparse_remove_one_section()
mem_hotplug_done()
The comment above the pgdat_resize_lock also mentions "Holding this will
also guarantee that any pfn_valid() stays that way.", which is true with
the current implementation and false after this patch. But current
implementation doesn't meet this comment. There isn't any pfn walkers to
take the lock so this looks like a relict from the past. This patch also
removes this comment.
[richard.weiyang@gmail.com: v4]
Link: http://lkml.kernel.org/r/20181204085657.20472-1-richard.weiyang@gmail.com
[mhocko@suse.com: changelog suggestion]
Link: http://lkml.kernel.org/r/20181128091243.19249-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/mmzone.h | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index a6e300732ec7..fc4b5cdb6c2d 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -637,8 +637,7 @@ typedef struct pglist_data { #if defined(CONFIG_MEMORY_HOTPLUG) || defined(CONFIG_DEFERRED_STRUCT_PAGE_INIT) /* * Must be held any time you expect node_start_pfn, node_present_pages - * or node_spanned_pages stay constant. Holding this will also - * guarantee that any pfn_valid() stays that way. + * or node_spanned_pages stay constant. * * pgdat_resize_lock() and pgdat_resize_unlock() are provided to * manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG |