@@ -21,6 +21,7 @@
#include <linux/mm.h>
#include <linux/stat.h>
#include <linux/slab.h>
+#include <linux/xarray.h>
#include <linux/atomic.h>
#include <linux/uaccess.h>
@@ -74,6 +75,13 @@ static struct bus_type memory_subsys = {
.offline = memory_subsys_offline,
};
+/*
+ * Memory blocks are cached in a local radix tree to avoid
+ * a costly linear search for the corresponding device on
+ * the subsystem bus.
+ */
+static DEFINE_XARRAY(memory_blocks);
+
static BLOCKING_NOTIFIER_HEAD(memory_chain);
int register_memory_notifier(struct notifier_block *nb)
@@ -489,22 +497,23 @@ int __weak arch_get_memory_phys_device(u
return 0;
}
-/* A reference for the returned memory block device is acquired. */
+/*
+ * A reference for the returned memory block device is acquired.
+ *
+ * Called under device_hotplug_lock.
+ */
static struct memory_block *find_memory_block_by_id(unsigned long block_id)
{
- struct device *dev;
+ struct memory_block *mem;
- dev = subsys_find_device_by_id(&memory_subsys, block_id, NULL);
- return dev ? to_memory_block(dev) : NULL;
+ mem = xa_load(&memory_blocks, block_id);
+ if (mem)
+ get_device(&mem->dev);
+ return mem;
}
/*
- * For now, we have a linear search to go find the appropriate
- * memory_block corresponding to a particular phys_index. If
- * this gets to be a real problem, we can always use a radix
- * tree or something here.
- *
- * This could be made generic for all device subsystems.
+ * Called under device_hotplug_lock.
*/
struct memory_block *find_memory_block(struct mem_section *section)
{
@@ -548,9 +557,16 @@ int register_memory(struct memory_block
memory->dev.offline = memory->state == MEM_OFFLINE;
ret = device_register(&memory->dev);
- if (ret)
+ if (ret) {
put_device(&memory->dev);
-
+ return ret;
+ }
+ ret = xa_err(xa_store(&memory_blocks, memory->dev.id, memory,
+ GFP_KERNEL));
+ if (ret) {
+ put_device(&memory->dev);
+ device_unregister(&memory->dev);
+ }
return ret;
}
@@ -604,6 +620,8 @@ static void unregister_memory(struct mem
if (WARN_ON_ONCE(memory->dev.bus != &memory_subsys))
return;
+ WARN_ON(xa_erase(&memory_blocks, memory->dev.id) == NULL);
+
/* drop the ref. we got via find_memory_block() */
put_device(&memory->dev);
device_unregister(&memory->dev);
@@ -750,6 +768,8 @@ void __init memory_dev_init(void)
*
* In case func() returns an error, walking is aborted and the error is
* returned.
+ *
+ * Called under device_hotplug_lock.
*/
int walk_memory_blocks(unsigned long start, unsigned long size,
void *arg, walk_memory_blocks_func_t func)