linux-kernel - [PATCH 4.4 07/78] mm/rmap: batched invalidations should use existing api

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Date:   Fri, 22 Dec 2017 09:45:48 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nadav Amit <namit@...are.com>,
        Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.4 07/78] mm/rmap: batched invalidations should use existing api

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nadav Amit <namit@...are.com>

commit 858eaaa711700ce4595e039441e239e56d7b9514 upstream.

The recently introduced batched invalidations mechanism uses its own
mechanism for shootdown.  However, it does wrong accounting of
interrupts (e.g., inc_irq_stat is called for local invalidations),
trace-points (e.g., TLB_REMOTE_SHOOTDOWN for local invalidations) and
may break some platforms as it bypasses the invalidation mechanisms of
Xen and SGI UV.

This patch reuses the existing TLB flushing mechnaisms instead.  We use
NULL as mm to indicate a global invalidation is required.

Fixes 72b252aed506b8 ("mm: send one IPI per CPU to TLB flush all entries after unmapping pages")
Signed-off-by: Nadav Amit <namit@...are.com>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Rik van Riel <riel@...hat.com>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/include/asm/tlbflush.h |    6 ------
 arch/x86/mm/tlb.c               |    2 +-
 mm/rmap.c                       |   28 +++++++---------------------
 3 files changed, 8 insertions(+), 28 deletions(-)

--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -325,12 +325,6 @@ static inline void reset_lazy_tlbstate(v
 
 #endif	/* SMP */
 
-/* Not inlined due to inc_irq_stat not being defined yet */
-#define flush_tlb_local() {		\
-	inc_irq_stat(irq_tlb_count);	\
-	local_flush_tlb();		\
-}
-
 #ifndef CONFIG_PARAVIRT
 #define flush_tlb_others(mask, mm, start, end)	\
 	native_flush_tlb_others(mask, mm, start, end)
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -104,7 +104,7 @@ static void flush_tlb_func(void *info)
 
 	inc_irq_stat(irq_tlb_count);
 
-	if (f->flush_mm != this_cpu_read(cpu_tlbstate.active_mm))
+	if (f->flush_mm && f->flush_mm != this_cpu_read(cpu_tlbstate.active_mm))
 		return;
 
 	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -587,19 +587,6 @@ vma_address(struct page *page, struct vm
 }
 
 #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
-static void percpu_flush_tlb_batch_pages(void *data)
-{
-	/*
-	 * All TLB entries are flushed on the assumption that it is
-	 * cheaper to flush all TLBs and let them be refilled than
-	 * flushing individual PFNs. Note that we do not track mm's
-	 * to flush as that might simply be multiple full TLB flushes
-	 * for no gain.
-	 */
-	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
-	flush_tlb_local();
-}
-
 /*
  * Flush TLB entries for recently unmapped pages from remote CPUs. It is
  * important if a PTE was dirty when it was unmapped that it's flushed
@@ -616,15 +603,14 @@ void try_to_unmap_flush(void)
 
 	cpu = get_cpu();
 
-	trace_tlb_flush(TLB_REMOTE_SHOOTDOWN, -1UL);
-
-	if (cpumask_test_cpu(cpu, &tlb_ubc->cpumask))
-		percpu_flush_tlb_batch_pages(&tlb_ubc->cpumask);
-
-	if (cpumask_any_but(&tlb_ubc->cpumask, cpu) < nr_cpu_ids) {
-		smp_call_function_many(&tlb_ubc->cpumask,
-			percpu_flush_tlb_batch_pages, (void *)tlb_ubc, true);
+	if (cpumask_test_cpu(cpu, &tlb_ubc->cpumask)) {
+		count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
+		local_flush_tlb();
+		trace_tlb_flush(TLB_LOCAL_SHOOTDOWN, TLB_FLUSH_ALL);
 	}
+
+	if (cpumask_any_but(&tlb_ubc->cpumask, cpu) < nr_cpu_ids)
+		flush_tlb_others(&tlb_ubc->cpumask, NULL, 0, TLB_FLUSH_ALL);
 	cpumask_clear(&tlb_ubc->cpumask);
 	tlb_ubc->flush_required = false;
 	tlb_ubc->writable = false;