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Revert "mm: numa: defer TLB flush for THP migration as long as possible"

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While deferring TLB flushes is a good practice, the reverted patch
caused pending TLB flushes to be checked while the page-table lock is
not taken.  As a result, in architectures with weak memory model (PPC),
Linux may miss a memory-barrier, miss the fact TLB flushes are pending,
and cause (in theory) a memory corruption.

Since the alternative of using smp_mb__after_unlock_lock() was
considered a bit open-coded, and the performance impact is expected to
be small, the previous patch is reverted.

This reverts b0943d61b8 ("mm: numa: defer TLB flush for THP migration
as long as possible").

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Nadav Amit <[email protected]>
Suggested-by: Mel Gorman <[email protected]>
Acked-by: Mel Gorman <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jeff Dike <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Nadav Amit <[email protected]>
Cc: Russell King <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Yoshinori Sato <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Nadav Amit 2017-08-10 15:24:02 -07:00 • committed by Linus Torvalds
commit a9b802500e
2 changed files with 7 additions and 6 deletions
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6
mm/migrate.c
View file

@ -1937,12 +1937,6 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
put_page(new_page);
goto out_fail;
}
/*
* We are not sure a pending tlb flush here is for a huge page
* mapping or not. Hence use the tlb range variant
*/
if (mm_tlb_flush_pending(mm))
flush_tlb_range(vma, mmun_start, mmun_end);
/* Prepare a page as a migration target */
__SetPageLocked(new_page);