3 files changed, 49 insertions, 8 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 3002e5d4da0b..6bb34fc1ff22 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2353,6 +2353,9 @@ void btrfs_free_block_rsv(struct btrfs_root *root,
 int btrfs_block_rsv_add(struct btrfs_root *root,
                         struct btrfs_block_rsv *block_rsv,
                         u64 num_bytes);
+int btrfs_block_rsv_add_noflush(struct btrfs_root *root,
+                                struct btrfs_block_rsv *block_rsv,
+                                u64 num_bytes);
 int btrfs_block_rsv_check(struct btrfs_root *root,
                           struct btrfs_block_rsv *block_rsv, int min_factor);
 int btrfs_block_rsv_refill(struct btrfs_root *root,
diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
index fc4026af7290..bbe8496d5339 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -624,13 +624,36 @@ static int btrfs_delayed_inode_reserve_metadata(
         u64 num_bytes;
         int ret;
 
-        if (!trans->bytes_reserved)
-                return 0;
-
         src_rsv = trans->block_rsv;
         dst_rsv = &root->fs_info->delayed_block_rsv;
 
         num_bytes = btrfs_calc_trans_metadata_size(root, 1);
+
+        /*
+         * btrfs_dirty_inode will update the inode under btrfs_join_transaction
+         * which doesn't reserve space for speed.  This is a problem since we
+         * still need to reserve space for this update, so try to reserve the
+         * space.
+         *
+         * Now if src_rsv == delalloc_block_rsv we'll let it just steal since
+         * we're accounted for.
+         */
+        if (!trans->bytes_reserved &&
+            src_rsv != &root->fs_info->delalloc_block_rsv) {
+                ret = btrfs_block_rsv_add_noflush(root, dst_rsv, num_bytes);
+                /*
+                 * Since we're under a transaction reserve_metadata_bytes could
+                 * try to commit the transaction which will make it return
+                 * EAGAIN to make us stop the transaction we have, so return
+                 * ENOSPC instead so that btrfs_dirty_inode knows what to do.
+                 */
+                if (ret == -EAGAIN)
+                        ret = -ENOSPC;
+                if (!ret)
+                        node->bytes_reserved = num_bytes;
+                return ret;
+        }
+
         ret = btrfs_block_rsv_migrate(src_rsv, dst_rsv, num_bytes);
         if (!ret)
                 node->bytes_reserved = num_bytes;
@@ -1686,11 +1709,8 @@ int btrfs_delayed_update_inode(struct btrfs_trans_handle *trans,
         }
 
         ret = btrfs_delayed_inode_reserve_metadata(trans, root, delayed_node);
-        /*
-         * we must reserve enough space when we start a new transaction,
-         * so reserving metadata failure is impossible
-         */
-        BUG_ON(ret);
+        if (ret)
+                goto release_node;
 
         fill_stack_inode_item(trans, &delayed_node->inode_item, inode);
         delayed_node->inode_dirty = 1;
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 5b84205e7685..23e936c3de76 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3814,6 +3814,24 @@ int btrfs_block_rsv_add(struct btrfs_root *root,
         return ret;
 }
 
+int btrfs_block_rsv_add_noflush(struct btrfs_root *root,
+                                struct btrfs_block_rsv *block_rsv,
+                                u64 num_bytes)
+{
+        int ret;
+
+        if (num_bytes == 0)
+                return 0;
+
+        ret = reserve_metadata_bytes(root, block_rsv, num_bytes, 0);
+        if (!ret) {
+                block_rsv_add_bytes(block_rsv, num_bytes, 1);
+                return 0;
+        }
+
+        return ret;
+}
+
 int btrfs_block_rsv_check(struct btrfs_root *root,
                           struct btrfs_block_rsv *block_rsv, int min_factor)
 {