The function default will traverse the all orphan items on the tree root,
and recover the all intact subvolumes. If subvol_id is specified, then only
the corresponding subvolume will be recovered.

Signed-off-by: Lu Fengqi <lufq.f...@cn.fujitsu.com>
---
v2: add subvol_id argumenta to specify subvol_id instead of recovering
all subvolumes.

 undelete-subvol.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 undelete-subvol.h |  2 ++
 2 files changed, 72 insertions(+)

diff --git a/undelete-subvol.c b/undelete-subvol.c
index 9243e35545c5..5b494ca086ab 100644
--- a/undelete-subvol.c
+++ b/undelete-subvol.c
@@ -15,6 +15,7 @@
 #include "transaction.h"
 #include "disk-io.h"
 #include "messages.h"
+#include "undelete-subvol.h"
 
 /*
  * Determines whether the subvolume is intact, according to the drop_progress
@@ -182,3 +183,72 @@ static int link_subvol_to_lostfound(struct btrfs_root 
*root, u64 subvol_id)
 out:
        return ret;
 }
+
+/*
+ * Traverse all orphan items on the root tree, restore them to the lost+found
+ * directory if the corresponding subvolumes are still intact left on the disk.
+ *
+ * @root       the root of the root tree.
+ * @subvol_id  if not set to 0, skip other subvolumes and only recover the
+ *             subvolume specified by @subvol_id.
+ *
+ * Return 0 if no error occurred even if no subvolume was recovered.
+ */
+int btrfs_undelete_intact_subvols(struct btrfs_root *root, u64 subvol_id)
+{
+       struct btrfs_key key;
+       struct btrfs_path path;
+       u64 found_count = 0;
+       u64 recovered_count = 0;
+       int ret = 0;
+
+       key.objectid = BTRFS_ORPHAN_OBJECTID;
+       key.type = BTRFS_ORPHAN_ITEM_KEY;
+       key.offset = subvol_id ? subvol_id + 1 : (u64)-1;
+
+       btrfs_init_path(&path);
+       while (subvol_id != key.offset) {
+               ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
+               if (ret < 0) {
+                       error("search ORPHAN_ITEM for %llu failed.\n",
+                             key.offset);
+                       break;
+               }
+
+               path.slots[0]--;
+               btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+
+               btrfs_release_path(&path);
+
+               /* No more BTRFS_ORPHAN_ITEM, so we don't need to continue. */
+               if (key.type != BTRFS_ORPHAN_ITEM_KEY) {
+                       ret = 0;
+                       break;
+               }
+
+               /* If subvol_id is non-zero, skip other deleted subvolume. */
+               if (subvol_id && subvol_id != key.offset) {
+                       ret = -ENOENT;
+                       break;
+               }
+
+               if (!is_subvol_intact(root, key.offset))
+                       continue;
+
+               /* Here we can confirm there is an intact subvolume. */
+               found_count++;
+               ret = link_subvol_to_lostfound(root, key.offset);
+               if (ret == 0) {
+                       recovered_count++;
+                       printf(
+               "Recovered subvolume %llu to lost+found successfully.\n",
+                               key.offset);
+               }
+
+       }
+
+       printf("Found %llu subvols left intact\n", found_count);
+       printf("Recovered %llu subvols\n", found_count);
+
+       return ret;
+}
diff --git a/undelete-subvol.h b/undelete-subvol.h
index 7cfd100cce37..f773210c46fe 100644
--- a/undelete-subvol.h
+++ b/undelete-subvol.h
@@ -14,4 +14,6 @@
 #ifndef __BTRFS_UNDELETE_SUBVOLUME_H__
 #define __BTRFS_UNDELETE_SUBVOLUME_H__
 
+int btrfs_undelete_intact_subvols(struct btrfs_root *root, u64 subvol_id);
+
 #endif
-- 
2.16.2



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