[PATCH 24/58] mm: fix the TLB range flushed when __tlb_remove_page() runs out of slots

[Kamal Mostafa]

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

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

From: Vineet Gupta <Vineet.Gupta1 at synopsys.com>

commit e6c495a96ce02574e765d5140039a64c8d4e8c9e upstream.

zap_pte_range loops from @addr to @end.  In the middle, if it runs out of
batching slots, TLB entries needs to be flushed for @start to @interim,
NOT @interim to @end.

Since ARC port doesn't use page free batching I can't test it myself but
this seems like the right thing to do.

Observed this when working on a fix for the issue at thread:
http://www.spinics.net/lists/linux-arch/msg21736.html

Signed-off-by: Vineet Gupta <vgupta at synopsys.com>
Cc: Mel Gorman <mgorman at suse.de>
Cc: Hugh Dickins <hughd at google.com>
Cc: Rik van Riel <riel at redhat.com>
Cc: David Rientjes <rientjes at google.com>
Cc: Peter Zijlstra <peterz at infradead.org>
Acked-by: Catalin Marinas <catalin.marinas at arm.com>
Cc: Max Filippov <jcmvbkbc at gmail.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
[ kamal: 3.8.y-stable prereq for:
  2b04725 Fix TLB gather virtual address range invalidation corner cases ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 mm/memory.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 32a495a..b81825a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1106,6 +1106,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
 	spinlock_t *ptl;
 	pte_t *start_pte;
 	pte_t *pte;
+	unsigned long range_start = addr;
 
 again:
 	init_rss_vec(rss);
@@ -1211,12 +1212,14 @@ again:
 		force_flush = 0;
 
 #ifdef HAVE_GENERIC_MMU_GATHER
-		tlb->start = addr;
-		tlb->end = end;
+		tlb->start = range_start;
+		tlb->end = addr;
 #endif
 		tlb_flush_mmu(tlb);
-		if (addr != end)
+		if (addr != end) {
+			range_start = addr;
 			goto again;
+		}
 	}
 
 	return addr;
-- 
1.8.1.2