• Nadav Amit's avatar
    Revert "mm: numa: defer TLB flush for THP migration as long as possible" · a9b80250
    Nadav Amit authored
    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 b0943d61 ("mm: numa: defer TLB flush for THP migration
    as long as possible").
    
    Link: http://lkml.kernel.org/r/20170802000818.4760-4-namit@vmware.comSigned-off-by: default avatarNadav Amit <namit@vmware.com>
    Suggested-by: default avatarMel Gorman <mgorman@suse.de>
    Acked-by: default avatarMel Gorman <mgorman@suse.de>
    Acked-by: default avatarRik van Riel <riel@redhat.com>
    Cc: Minchan Kim <minchan@kernel.org>
    Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: "David S. Miller" <davem@davemloft.net>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: Hugh Dickins <hughd@google.com>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Jeff Dike <jdike@addtoit.com>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Mel Gorman <mgorman@techsingularity.net>
    Cc: Nadav Amit <nadav.amit@gmail.com>
    Cc: Russell King <linux@armlinux.org.uk>
    Cc: Tony Luck <tony.luck@intel.com>
    Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    a9b80250
migrate.c 51.8 KB