PCI/AER: Avoid memory allocation in interrupt handling path

When handling AER events, we previously allocated a struct aer_err_info,
processed the error, and freed the struct.  But aer_isr_one_error() is
serialized by rpc_mutex, so we never need more than one copy of the struct,
and the struct is only about 70 bytes, so we're not saving much by
allocating it dynamically.

Embed a struct aer_err_info directly in struct aer_rpc, which is allocated
at probe-time by aer_probe().

[bhelgaas: changelog]
Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pcie/aer/aerdrv.h

@@ -60,6 +60,7 @@ struct aer_rpc {
 	struct pcie_device *rpd;	/* Root Port device */
 	struct work_struct dpc_handler;
 	struct aer_err_source e_sources[AER_ERROR_SOURCES_MAX];
+	struct aer_err_info e_info;
 	unsigned short prod_idx;	/* Error Producer Index */
 	unsigned short cons_idx;	/* Error Consumer Index */
 	int isr;

drivers/pci/pcie/aer/aerdrv_core.c

@@ -711,15 +711,8 @@ static inline void aer_process_err_devices(struct pcie_device *p_device,
 static void aer_isr_one_error(struct pcie_device *p_device,
 		struct aer_err_source *e_src)
 {
-	struct aer_err_info *e_info;
-
-	/* struct aer_err_info might be big, so we allocate it with slab */
-	e_info = kmalloc(sizeof(struct aer_err_info), GFP_KERNEL);
-	if (!e_info) {
-		dev_printk(KERN_DEBUG, &p_device->port->dev,
-			"Can't allocate mem when processing AER errors\n");
-		return;
-	}
+	struct aer_rpc *rpc = get_service_data(p_device);
+	struct aer_err_info *e_info = &rpc->e_info;
 
 	/*
 	 * There is a possibility that both correctable error and
@@ -758,8 +751,6 @@ static void aer_isr_one_error(struct pcie_device *p_device,
 		if (find_source_device(p_device->port, e_info))
 			aer_process_err_devices(p_device, e_info);
 	}
-
-	kfree(e_info);
 }
 
 /**