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-rw-r--r--fs/btrfs/super.c15
1 files changed, 10 insertions, 5 deletions
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index d41d5960ef4a..170baef49fae 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2304,11 +2304,18 @@ static int btrfs_show_devname(struct seq_file *m, struct dentry *root)
struct list_head *head;
struct rcu_string *name;
- mutex_lock(&fs_info->fs_devices->device_list_mutex);
+ /*
+ * Lightweight locking of the devices. We should not need
+ * device_list_mutex here as we only read the device data and the list
+ * is protected by RCU. Even if a device is deleted during the list
+ * traversals, we'll get valid data, the freeing callback will wait at
+ * least until until the rcu_read_unlock.
+ */
+ rcu_read_lock();
cur_devices = fs_info->fs_devices;
while (cur_devices) {
head = &cur_devices->devices;
- list_for_each_entry(dev, head, dev_list) {
+ list_for_each_entry_rcu(dev, head, dev_list) {
if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state))
continue;
if (!dev->name)
@@ -2320,14 +2327,12 @@ static int btrfs_show_devname(struct seq_file *m, struct dentry *root)
}
if (first_dev) {
- rcu_read_lock();
name = rcu_dereference(first_dev->name);
seq_escape(m, name->str, " \t\n\\");
- rcu_read_unlock();
} else {
WARN_ON(1);
}
- mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+ rcu_read_unlock();
return 0;
}