1 files changed, 56 insertions, 0 deletions

diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index 22124122728c..47733fb55df7 100644
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -9,6 +9,8 @@
 #include "transaction.h"
 #include "disk-io.h"
 #include "print-tree.h"
+#include "qgroup.h"
+#include "space-info.h"
 
 /*
  * Read a root item from the tree. In case we detect a root item smaller then
@@ -497,3 +499,57 @@ void btrfs_update_root_times(struct btrfs_trans_handle *trans,
         btrfs_set_stack_timespec_nsec(&item->ctime, ct.tv_nsec);
         spin_unlock(&root->root_item_lock);
 }
+
+/*
+ * btrfs_subvolume_reserve_metadata() - reserve space for subvolume operation
+ * root: the root of the parent directory
+ * rsv: block reservation
+ * items: the number of items that we need do reservation
+ * use_global_rsv: allow fallback to the global block reservation
+ *
+ * This function is used to reserve the space for snapshot/subvolume
+ * creation and deletion. Those operations are different with the
+ * common file/directory operations, they change two fs/file trees
+ * and root tree, the number of items that the qgroup reserves is
+ * different with the free space reservation. So we can not use
+ * the space reservation mechanism in start_transaction().
+ */
+int btrfs_subvolume_reserve_metadata(struct btrfs_root *root,
+                                     struct btrfs_block_rsv *rsv, int items,
+                                     bool use_global_rsv)
+{
+        u64 qgroup_num_bytes = 0;
+        u64 num_bytes;
+        int ret;
+        struct btrfs_fs_info *fs_info = root->fs_info;
+        struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
+
+        if (test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags)) {
+                /* One for parent inode, two for dir entries */
+                qgroup_num_bytes = 3 * fs_info->nodesize;
+                ret = btrfs_qgroup_reserve_meta_prealloc(root,
+                                qgroup_num_bytes, true);
+                if (ret)
+                        return ret;
+        }
+
+        num_bytes = btrfs_calc_trans_metadata_size(fs_info, items);
+        rsv->space_info = btrfs_find_space_info(fs_info,
+                                            BTRFS_BLOCK_GROUP_METADATA);
+        ret = btrfs_block_rsv_add(root, rsv, num_bytes,
+                                  BTRFS_RESERVE_FLUSH_ALL);
+
+        if (ret == -ENOSPC && use_global_rsv)
+                ret = btrfs_block_rsv_migrate(global_rsv, rsv, num_bytes, true);
+
+        if (ret && qgroup_num_bytes)
+                btrfs_qgroup_free_meta_prealloc(root, qgroup_num_bytes);
+
+        return ret;
+}
+
+void btrfs_subvolume_release_metadata(struct btrfs_fs_info *fs_info,
+                                      struct btrfs_block_rsv *rsv)
+{
+        btrfs_block_rsv_release(fs_info, rsv, (u64)-1);
+}