linux-kernel - [RFC][PATCH 1/6] x86: mm: clean up tlb flushing code

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Message-Id: <20140218193009.14C1765F@viggo.jf.intel.com>
Date:	Tue, 18 Feb 2014 11:30:09 -0800
From:	Dave Hansen <dave@...1.net>
To:	linux-kernel@...r.kernel.org
Cc:	linux-mm@...ck.org, ak@...ux.intel.com, alex.shi@...aro.org,
	kirill.shutemov@...ux.intel.com, mgorman@...e.de,
	tim.c.chen@...ux.intel.com, x86@...nel.org, peterz@...radead.org,
	Dave Hansen <dave@...1.net>
Subject: [RFC][PATCH 1/6] x86: mm: clean up tlb flushing code


From: Dave Hansen <dave.hansen@...ux.intel.com>

The

	if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)

line of code is not exactly the easiest to audit, especially when
it ends up at two different indentation levels.  This eliminates
one of the the copy-n-paste versions.  It also gives us a unified
exit point for each path through this function.  We need this in
a minute for our tracepoint.


Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
---

 b/arch/x86/mm/tlb.c |   23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff -puN arch/x86/mm/tlb.c~simplify-tlb-code arch/x86/mm/tlb.c
--- a/arch/x86/mm/tlb.c~simplify-tlb-code	2014-02-18 10:59:35.521325070 -0800
+++ b/arch/x86/mm/tlb.c	2014-02-18 10:59:35.529325436 -0800
@@ -161,23 +161,24 @@ void flush_tlb_current_task(void)
 void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
 				unsigned long end, unsigned long vmflag)
 {
+	int need_flush_others_all = 1;
 	unsigned long addr;
 	unsigned act_entries, tlb_entries = 0;
 	unsigned long nr_base_pages;
 
 	preempt_disable();
 	if (current->active_mm != mm)
-		goto flush_all;
+		goto out;
 
 	if (!current->mm) {
 		leave_mm(smp_processor_id());
-		goto flush_all;
+		goto out;
 	}
 
 	if (end == TLB_FLUSH_ALL || tlb_flushall_shift == -1
 					|| vmflag & VM_HUGETLB) {
 		local_flush_tlb();
-		goto flush_all;
+		goto out;
 	}
 
 	/* In modern CPU, last level tlb used for both data/ins */
@@ -196,22 +197,20 @@ void flush_tlb_mm_range(struct mm_struct
 		count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
 		local_flush_tlb();
 	} else {
+		need_flush_others_all = 0;
 		/* flush range by one by one 'invlpg' */
 		for (addr = start; addr < end;	addr += PAGE_SIZE) {
 			count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ONE);
 			__flush_tlb_single(addr);
 		}
-
-		if (cpumask_any_but(mm_cpumask(mm),
-				smp_processor_id()) < nr_cpu_ids)
-			flush_tlb_others(mm_cpumask(mm), mm, start, end);
-		preempt_enable();
-		return;
 	}
-
-flush_all:
+out:
+	if (need_flush_others_all) {
+		start = 0UL;
+		end = TLB_FLUSH_ALL;
+	}
 	if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
-		flush_tlb_others(mm_cpumask(mm), mm, 0UL, TLB_FLUSH_ALL);
+		flush_tlb_others(mm_cpumask(mm), mm, start, end);
 	preempt_enable();
 }
 
_
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