Btrfs: using rcu lock in the reader side of devices list
fs_devices->devices is only updated on remove and add device paths, so we can
use rcu to protect it in the reader side
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 4e53a4f..deba3d9 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1410,8 +1410,8 @@
struct btrfs_device *device;
struct backing_dev_info *bdi;
- mutex_lock(&info->fs_devices->device_list_mutex);
- list_for_each_entry(device, &info->fs_devices->devices, dev_list) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(device, &info->fs_devices->devices, dev_list) {
if (!device->bdev)
continue;
bdi = blk_get_backing_dev_info(device->bdev);
@@ -1420,7 +1420,7 @@
break;
}
}
- mutex_unlock(&info->fs_devices->device_list_mutex);
+ rcu_read_unlock();
return ret;
}
@@ -2332,9 +2332,9 @@
sb = &root->fs_info->super_for_commit;
dev_item = &sb->dev_item;
- mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
+ rcu_read_lock();
head = &root->fs_info->fs_devices->devices;
- list_for_each_entry(dev, head, dev_list) {
+ list_for_each_entry_rcu(dev, head, dev_list) {
if (!dev->bdev) {
total_errors++;
continue;
@@ -2367,7 +2367,7 @@
}
total_errors = 0;
- list_for_each_entry(dev, head, dev_list) {
+ list_for_each_entry_rcu(dev, head, dev_list) {
if (!dev->bdev)
continue;
if (!dev->in_fs_metadata || !dev->writeable)
@@ -2377,7 +2377,7 @@
if (ret)
total_errors++;
}
- mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
+ rcu_read_unlock();
if (total_errors > max_errors) {
printk(KERN_ERR "btrfs: %d errors while writing supers\n",
total_errors);