[PATCH v9 10/14] x86/mm: Factor out flush_tlb_info initialization

[Chuyi Zhou]

get_flush_tlb_info() has two responsibilities: it reserves the per-CPU
flush_tlb_info storage and it initializes the fields that describe the
flush operation. The per-CPU storage also carries the DEBUG_VM
reentrancy check and the matching put_flush_tlb_info() lifetime rules.

Moving flush_tlb_info back to caller-provided storage requires the same
field initialization without tying the caller to the per-CPU object.
Leaving the field setup embedded in get_flush_tlb_info() would either
keep those callers tied to the per-CPU object or duplicate the
initialization logic.

Split the field setup into init_flush_tlb_info(). Keep the per-CPU
storage selection, DEBUG_VM reentrancy check and put_flush_tlb_info()
lifetime rules in get_flush_tlb_info().

No functional change intended.

Signed-off-by: Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
 arch/x86/mm/tlb.c | 42 +++++++++++++++++++++++++++---------------
 1 file changed, 27 insertions(+), 15 deletions(-)

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index af43d177087e..f76f576d3899 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -1379,22 +1379,12 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(struct flush_tlb_info, flush_tlb_info);
 static DEFINE_PER_CPU(unsigned int, flush_tlb_info_idx);
 #endif
 
-static struct flush_tlb_info *get_flush_tlb_info(struct mm_struct *mm,
-			unsigned long start, unsigned long end,
-			unsigned int stride_shift, bool freed_tables,
-			u64 new_tlb_gen)
+static void init_flush_tlb_info(struct flush_tlb_info *info,
+				struct mm_struct *mm,
+				unsigned long start, unsigned long end,
+				unsigned int stride_shift, bool freed_tables,
+				u64 new_tlb_gen)
 {
-	struct flush_tlb_info *info = this_cpu_ptr(&flush_tlb_info);
-
-#ifdef CONFIG_DEBUG_VM
-	/*
-	 * Ensure that the following code is non-reentrant and flush_tlb_info
-	 * is not overwritten. This means no TLB flushing is initiated by
-	 * interrupt handlers and machine-check exception handlers.
-	 */
-	BUG_ON(this_cpu_inc_return(flush_tlb_info_idx) != 1);
-#endif
-
 	/*
 	 * If the number of flushes is so large that a full flush
 	 * would be faster, do a full flush.
@@ -1412,6 +1402,28 @@ static struct flush_tlb_info *get_flush_tlb_info(struct mm_struct *mm,
 	info->new_tlb_gen	= new_tlb_gen;
 	info->initiating_cpu	= smp_processor_id();
 	info->trim_cpumask	= 0;
+}
+
+static struct flush_tlb_info *get_flush_tlb_info(struct mm_struct *mm,
+						 unsigned long start,
+						 unsigned long end,
+						 unsigned int stride_shift,
+						 bool freed_tables,
+						 u64 new_tlb_gen)
+{
+	struct flush_tlb_info *info = this_cpu_ptr(&flush_tlb_info);
+
+#ifdef CONFIG_DEBUG_VM
+	/*
+	 * Ensure that the following code is non-reentrant and flush_tlb_info
+	 * is not overwritten. This means no TLB flushing is initiated by
+	 * interrupt handlers and machine-check exception handlers.
+	 */
+	BUG_ON(this_cpu_inc_return(flush_tlb_info_idx) != 1);
+#endif
+
+	init_flush_tlb_info(info, mm, start, end, stride_shift, freed_tables,
+			    new_tlb_gen);
 
 	return info;
 }
-- 
2.20.1