diff mbox series

[50/67] asm-generic/tlb: avoid potential double flush

Message ID 20200204013653.4NMd_OKtw%akpm@linux-foundation.org (mailing list archive)
State New, archived
Headers show
Series [01/67] ocfs2: fix oops when writing cloned file | expand

Commit Message

Andrew Morton Feb. 4, 2020, 1:36 a.m. UTC 
From: Peter Zijlstra <peterz@infradead.org>
Subject: asm-generic/tlb: avoid potential double flush

Aneesh reported that:

	tlb_flush_mmu()
	  tlb_flush_mmu_tlbonly()
	    tlb_flush()			<-- #1
	  tlb_flush_mmu_free()
	    tlb_table_flush()
	      tlb_table_invalidate()
		tlb_flush_mmu_tlbonly()
		  tlb_flush()		<-- #2

does two TLBIs when tlb->fullmm, because __tlb_reset_range() will not
clear tlb->end in that case.

Observe that any caller to __tlb_adjust_range() also sets at least one of
the tlb->freed_tables || tlb->cleared_p* bits, and those are
unconditionally cleared by __tlb_reset_range().

Change the condition for actually issuing TLBI to having one of those bits
set, as opposed to having tlb->end != 0.

Link: http://lkml.kernel.org/r/20200116064531.483522-4-aneesh.kumar@linux.ibm.com
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reported-by: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/asm-generic/tlb.h |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
diff mbox series

Patch

--- a/include/asm-generic/tlb.h~asm-generic-tlb-avoid-potential-double-flush
+++ a/include/asm-generic/tlb.h
@@ -402,7 +402,12 @@  tlb_update_vma_flags(struct mmu_gather *
 
 static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
 {
-	if (!tlb->end)
+	/*
+	 * Anything calling __tlb_adjust_range() also sets at least one of
+	 * these bits.
+	 */
+	if (!(tlb->freed_tables || tlb->cleared_ptes || tlb->cleared_pmds ||
+	      tlb->cleared_puds || tlb->cleared_p4ds))
 		return;
 
 	tlb_flush(tlb);