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Btrfs: using rcu lock in the reader side of devices list

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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>
This commit is contained in:
Xiao Guangrong
2011-04-20 10:09:16 +00:00
committed by Chris Mason
parent 4622470565
commit 1f78160ce1
4 changed files with 72 additions and 36 deletions
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14
fs/btrfs/disk-io.c
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@@ -1410,8 +1410,8 @@ static int btrfs_congested_fn(void *congested_data, int bdi_bits)
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 @@ static int btrfs_congested_fn(void *congested_data, int bdi_bits)
break;
}
}
mutex_unlock(&info->fs_devices->device_list_mutex);
rcu_read_unlock();
return ret;
}
@@ -2332,9 +2332,9 @@ int write_all_supers(struct btrfs_root *root, int max_mirrors)
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 @@ int write_all_supers(struct btrfs_root *root, int max_mirrors)
}
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 @@ int write_all_supers(struct btrfs_root *root, int max_mirrors)
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);