arch, mm: Remove tlb_fast_mode()

Since the introduction of preemptible mmu_gather TLB fast mode has been
broken. TLB fast mode relies on there being absolutely no concurrency;
it frees pages first and invalidates TLBs later.

However now we can get concurrency and stuff goes *bang*.

This patch removes all tlb_fast_mode() code; it was found the better
option vs trying to patch the hole by entangling tlb invalidation with
the scheduler.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Tony Luck <tony.luck@intel.com>
Reported-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 16 deletions

diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index b1b1fa6ffffe..13821c339a41 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -97,11 +97,9 @@ struct mmu_gather {
         unsigned long           start;
         unsigned long           end;
         unsigned int            need_flush : 1, /* Did free PTEs */
-                                fast_mode  : 1; /* No batching   */
-
         /* we are in the middle of an operation to clear
          * a full mm and can make some optimizations */
-        unsigned int            fullmm : 1,
+                                fullmm : 1,
         /* we have performed an operation which
          * requires a complete flush of the tlb */
                                 need_flush_all : 1;
@@ -114,19 +112,6 @@ struct mmu_gather {
 
 #define HAVE_GENERIC_MMU_GATHER
 
-static inline int tlb_fast_mode(struct mmu_gather *tlb)
-{
-#ifdef CONFIG_SMP
-        return tlb->fast_mode;
-#else
-        /*
-         * For UP we don't need to worry about TLB flush
-         * and page free order so much..
-         */
-        return 1;
-#endif
-}
-
 void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm);
 void tlb_flush_mmu(struct mmu_gather *tlb);
 void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start,