diff options
| author | Will Deacon <will.deacon@arm.com> | 2017-07-10 15:48:28 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-07-10 16:32:31 -0700 |
| commit | 108a7ac448caff8e35e8c3f92f65faad893e5aca (patch) | |
| tree | 5f89dd3053a152be5dedb660a232584ec35b507f /include/linux/page_ref.h | |
| parent | baabda261424517110ea98c6651f632ebf2561e3 (diff) | |
include/linux/page_ref.h: ensure page_ref_unfreeze is ordered against prior accesses
page_ref_freeze and page_ref_unfreeze are designed to be used as a pair,
wrapping a critical section where struct pages can be modified without
having to worry about consistency for a concurrent fast-GUP.
Whilst page_ref_freeze has full barrier semantics due to its use of
atomic_cmpxchg, page_ref_unfreeze is implemented using atomic_set, which
doesn't provide any barrier semantics and allows the operation to be
reordered with respect to page modifications in the critical section.
This patch ensures that page_ref_unfreeze is ordered after any critical
section updates, by invoking smp_mb() prior to the atomic_set.
Link: http://lkml.kernel.org/r/1497349722-6731-3-git-send-email-will.deacon@arm.com
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Steve Capper <steve.capper@arm.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/page_ref.h')
| -rw-r--r-- | include/linux/page_ref.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/page_ref.h b/include/linux/page_ref.h index 610e13271918..1fd71733aa68 100644 --- a/include/linux/page_ref.h +++ b/include/linux/page_ref.h @@ -174,6 +174,7 @@ static inline void page_ref_unfreeze(struct page *page, int count) VM_BUG_ON_PAGE(page_count(page) != 0, page); VM_BUG_ON(count == 0); + smp_mb(); atomic_set(&page->_refcount, count); if (page_ref_tracepoint_active(__tracepoint_page_ref_unfreeze)) __page_ref_unfreeze(page, count); |