btrfs: don't create or leak aliased root while cleaning up orphans

commit 909c3a22da3 (Btrfs: fix loading of orphan roots leading to BUG_ON)
avoids the BUG_ON but can add an aliased root to the dead_roots list or
leak the root.

Since we've already been loading roots into the radix tree, we should
use it before looking the root up on disk.

Cc: <stable@vger.kernel.org> # 4.5
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

3 files changed, 22 insertions, 11 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 17062223fac3..edda47162752 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1624,8 +1624,8 @@ fail:
         return ret;
 }
 
-static struct btrfs_root *btrfs_lookup_fs_root(struct btrfs_fs_info *fs_info,
-                                               u64 root_id)
+struct btrfs_root *btrfs_lookup_fs_root(struct btrfs_fs_info *fs_info,
+                                        u64 root_id)
 {
         struct btrfs_root *root;
 
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index c9d42c92da2b..e0efe45e5282 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -68,6 +68,8 @@ struct extent_buffer *btrfs_find_tree_block(struct btrfs_fs_info *fs_info,
 struct btrfs_root *btrfs_read_fs_root(struct btrfs_root *tree_root,
                                       struct btrfs_key *location);
 int btrfs_init_fs_root(struct btrfs_root *root);
+struct btrfs_root *btrfs_lookup_fs_root(struct btrfs_fs_info *fs_info,
+                                        u64 root_id);
 int btrfs_insert_fs_root(struct btrfs_fs_info *fs_info,
                          struct btrfs_root *root);
 void btrfs_free_fs_roots(struct btrfs_fs_info *fs_info);
diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index 7fd7e1830cfe..091296062456 100644
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -272,6 +272,23 @@ int btrfs_find_orphan_roots(struct btrfs_root *tree_root)
                 root_key.objectid = key.offset;
                 key.offset++;
 
+                /*
+                 * The root might have been inserted already, as before we look
+                 * for orphan roots, log replay might have happened, which
+                 * triggers a transaction commit and qgroup accounting, which
+                 * in turn reads and inserts fs roots while doing backref
+                 * walking.
+                 */
+                root = btrfs_lookup_fs_root(tree_root->fs_info,
+                                            root_key.objectid);
+                if (root) {
+                        WARN_ON(!test_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED,
+                                          &root->state));
+                        if (btrfs_root_refs(&root->root_item) == 0)
+                                btrfs_add_dead_root(root);
+                        continue;
+                }
+
                 root = btrfs_read_fs_root(tree_root, &root_key);
                 err = PTR_ERR_OR_ZERO(root);
                 if (err && err != -ENOENT) {
@@ -310,16 +327,8 @@ int btrfs_find_orphan_roots(struct btrfs_root *tree_root)
                 set_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state);
 
                 err = btrfs_insert_fs_root(root->fs_info, root);
-                /*
-                 * The root might have been inserted already, as before we look
-                 * for orphan roots, log replay might have happened, which
-                 * triggers a transaction commit and qgroup accounting, which
-                 * in turn reads and inserts fs roots while doing backref
-                 * walking.
-                 */
-                if (err == -EEXIST)
-                        err = 0;
                 if (err) {
+                        BUG_ON(err == -EEXIST);
                         btrfs_free_fs_root(root);
                         break;
                 }