[PATCH v3 11/27] x86, irq: Add realloc_irq_and_cfg_at()

[Yinghai Lu]

For ioapic hot-add support, it would be easy if we put all irqs
for that ioapic controller together.

We can reserve irq range at first, then reallocate those
pre-reserved one when it is needed.

Add realloc_irq_and_cfg_at() to really allocate irq_desc and cfg,
because pre-reserved only mark bits in allocate_irqs bit maps.

The reasons for not allocating them during reserving:
1. only several pins in ioapic are used, allocate for all pins, will
   waste memory for not used pins.
2. relocate later could make sure irq_desc is allocated on local node ram.
   as dev->node is set at that point.

-v2: update changelog by adding reasons, requested by Konrad.

Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <sebastian@xxxxxxxxxxxxx>
---
 arch/x86/kernel/apic/io_apic.c | 32 +++++++++++++++++++++++++++++++-
 include/linux/irq.h            |  5 +++++
 kernel/irq/irqdesc.c           | 26 ++++++++++++++++++++++++++
 3 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 670c538..a157a56 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -301,6 +301,36 @@ static void free_irq_at(unsigned int at, struct irq_cfg *cfg)
 	irq_free_desc(at);
 }
 
+static struct irq_cfg *realloc_irq_and_cfg_at(unsigned int at, int node)
+{
+	struct irq_desc *desc = irq_to_desc(at);
+	struct irq_cfg *cfg;
+	int res;
+
+	if (desc) {
+		if (irq_desc_get_irq_data(desc)->node == node)
+			return alloc_irq_and_cfg_at(at, node);
+
+		cfg = irq_desc_get_chip_data(desc);
+		if (cfg) {
+			/* shared irq */
+			if (!list_empty(&cfg->irq_2_pin))
+				return cfg;
+			free_irq_cfg(at, cfg);
+		}
+	}
+
+	res = irq_realloc_desc_at(at, node);
+	if (res >= 0) {
+		cfg = alloc_irq_cfg(at, node);
+		if (cfg) {
+			irq_set_chip_data(at, cfg);
+			return cfg;
+		}
+	}
+
+	return alloc_irq_and_cfg_at(at, node);
+}
 
 struct io_apic {
 	unsigned int index;
@@ -3352,7 +3382,7 @@ int arch_setup_ht_irq(unsigned int irq, struct pci_dev *dev)
 static int
 io_apic_setup_irq_pin(unsigned int irq, int node, struct io_apic_irq_attr *attr)
 {
-	struct irq_cfg *cfg = alloc_irq_and_cfg_at(irq, node);
+	struct irq_cfg *cfg = realloc_irq_and_cfg_at(irq, node);
 	int ret;
 
 	if (!cfg)
diff --git a/include/linux/irq.h b/include/linux/irq.h
index 4e0fcbb..9c6c047 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -602,6 +602,11 @@ void irq_free_descs(unsigned int irq, unsigned int cnt);
 int irq_reserve_irqs(unsigned int from, unsigned int cnt);
 int __irq_reserve_irqs(int irq, unsigned int from, unsigned int cnt);
 
+int __irq_realloc_desc(int at, int node, struct module *owner);
+/* use macros to avoid needing export.h for THIS_MODULE */
+#define irq_realloc_desc_at(at, node)	\
+	__irq_realloc_desc(at, node, THIS_MODULE)
+
 static inline void irq_free_desc(unsigned int irq)
 {
 	irq_free_descs(irq, 1);
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 3b9fb92..b48f65b 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -99,6 +99,11 @@ EXPORT_SYMBOL_GPL(nr_irqs);
 static DEFINE_MUTEX(sparse_irq_lock);
 static DECLARE_BITMAP(allocated_irqs, IRQ_BITMAP_BITS);
 
+static bool __irq_is_reserved(int irq)
+{
+	return !!test_bit(irq, allocated_irqs);
+}
+
 #ifdef CONFIG_SPARSE_IRQ
 
 static RADIX_TREE(irq_desc_tree, GFP_KERNEL);
@@ -410,6 +415,27 @@ __irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node,
 EXPORT_SYMBOL_GPL(__irq_alloc_descs);
 
 /**
+ * irq_realloc_desc - allocate irq descriptor for irq that is already reserved
+ * @irq:	Allocate for specific irq number if irq >= 0
+ * @node:	Preferred node on which the irq descriptor should be allocated
+ * @owner:	Owning module (can be NULL)
+ *
+ * Returns the irq number or error code
+ */
+int __ref
+__irq_realloc_desc(int irq, int node, struct module *owner)
+{
+	if (!__irq_is_reserved(irq))
+		return -EINVAL;
+
+	if (irq_to_desc(irq))
+		free_desc(irq);
+
+	return alloc_descs(irq, 1, node, owner);
+}
+EXPORT_SYMBOL_GPL(__irq_realloc_desc);
+
+/**
  * irq_reserve_irqs - mark irqs allocated
  * @from:	mark from irq number
  * @cnt:	number of irqs to mark
-- 
1.8.1.4

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