1 files changed, 83 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 4066803fe765..75bdea6bf188 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3559,10 +3559,76 @@ out:
         btrfs_free_path(path);
         if (ret)
                 pr_warn("btrfs: btrfs_uuid_scan_kthread failed %d\n", ret);
+        else
+                fs_info->update_uuid_tree_gen = 1;
         up(&fs_info->uuid_tree_rescan_sem);
         return 0;
 }
 
+/*
+ * Callback for btrfs_uuid_tree_iterate().
+ * returns:
+ * 0    check succeeded, the entry is not outdated.
+ * < 0  if an error occured.
+ * > 0  if the check failed, which means the caller shall remove the entry.
+ */
+static int btrfs_check_uuid_tree_entry(struct btrfs_fs_info *fs_info,
+                                       u8 *uuid, u8 type, u64 subid)
+{
+        struct btrfs_key key;
+        int ret = 0;
+        struct btrfs_root *subvol_root;
+
+        if (type != BTRFS_UUID_KEY_SUBVOL &&
+            type != BTRFS_UUID_KEY_RECEIVED_SUBVOL)
+                goto out;
+
+        key.objectid = subid;
+        key.type = BTRFS_ROOT_ITEM_KEY;
+        key.offset = (u64)-1;
+        subvol_root = btrfs_read_fs_root_no_name(fs_info, &key);
+        if (IS_ERR(subvol_root)) {
+                ret = PTR_ERR(subvol_root);
+                if (ret == -ENOENT)
+                        ret = 1;
+                goto out;
+        }
+
+        switch (type) {
+        case BTRFS_UUID_KEY_SUBVOL:
+                if (memcmp(uuid, subvol_root->root_item.uuid, BTRFS_UUID_SIZE))
+                        ret = 1;
+                break;
+        case BTRFS_UUID_KEY_RECEIVED_SUBVOL:
+                if (memcmp(uuid, subvol_root->root_item.received_uuid,
+                           BTRFS_UUID_SIZE))
+                        ret = 1;
+                break;
+        }
+
+out:
+        return ret;
+}
+
+static int btrfs_uuid_rescan_kthread(void *data)
+{
+        struct btrfs_fs_info *fs_info = (struct btrfs_fs_info *)data;
+        int ret;
+
+        /*
+         * 1st step is to iterate through the existing UUID tree and
+         * to delete all entries that contain outdated data.
+         * 2nd step is to add all missing entries to the UUID tree.
+         */
+        ret = btrfs_uuid_tree_iterate(fs_info, btrfs_check_uuid_tree_entry);
+        if (ret < 0) {
+                pr_warn("btrfs: iterating uuid_tree failed %d\n", ret);
+                up(&fs_info->uuid_tree_rescan_sem);
+                return ret;
+        }
+        return btrfs_uuid_scan_kthread(data);
+}
+
 int btrfs_create_uuid_tree(struct btrfs_fs_info *fs_info)
 {
         struct btrfs_trans_handle *trans;
@@ -3596,6 +3662,7 @@ int btrfs_create_uuid_tree(struct btrfs_fs_info *fs_info)
         down(&fs_info->uuid_tree_rescan_sem);
         task = kthread_run(btrfs_uuid_scan_kthread, fs_info, "btrfs-uuid");
         if (IS_ERR(task)) {
+                /* fs_info->update_uuid_tree_gen remains 0 in all error case */
                 pr_warn("btrfs: failed to start uuid_scan task\n");
                 up(&fs_info->uuid_tree_rescan_sem);
                 return PTR_ERR(task);
@@ -3604,6 +3671,22 @@ int btrfs_create_uuid_tree(struct btrfs_fs_info *fs_info)
         return 0;
 }
 
+int btrfs_check_uuid_tree(struct btrfs_fs_info *fs_info)
+{
+        struct task_struct *task;
+
+        down(&fs_info->uuid_tree_rescan_sem);
+        task = kthread_run(btrfs_uuid_rescan_kthread, fs_info, "btrfs-uuid");
+        if (IS_ERR(task)) {
+                /* fs_info->update_uuid_tree_gen remains 0 in all error case */
+                pr_warn("btrfs: failed to start uuid_rescan task\n");
+                up(&fs_info->uuid_tree_rescan_sem);
+                return PTR_ERR(task);
+        }
+
+        return 0;
+}
+
 /*
  * shrinking a device means finding all of the device extents past
  * the new size, and then following the back refs to the chunks.