Btrfs: fix wrong reserved space in qgroup during snap/subv creation

There are two problems in the space reservation of the snapshot/
subvolume creation.
- don't reserve the space for the root item insertion
- the space which is reserved in the qgroup is different with
  the free space reservation. we need reserve free space for
  7 items, but in qgroup reservation, we need reserve space only
  for 3 items.

So we implement new metadata reservation functions for the
snapshot/subvolume creation.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

5 files changed, 105 insertions, 36 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index ae8dcc406805..0d82922179db 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3106,8 +3106,13 @@ void btrfs_trans_release_metadata(struct btrfs_trans_handle *trans,
 int btrfs_orphan_reserve_metadata(struct btrfs_trans_handle *trans,
                                   struct inode *inode);
 void btrfs_orphan_release_metadata(struct inode *inode);
-int btrfs_snap_reserve_metadata(struct btrfs_trans_handle *trans,
-                                struct btrfs_pending_snapshot *pending);
+int btrfs_subvolume_reserve_metadata(struct btrfs_root *root,
+                                     struct btrfs_block_rsv *rsv,
+                                     int nitems,
+                                     u64 *qgroup_reserved);
+void btrfs_subvolume_release_metadata(struct btrfs_root *root,
+                                      struct btrfs_block_rsv *rsv,
+                                      u64 qgroup_reserved);
 int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes);
 void btrfs_delalloc_release_metadata(struct inode *inode, u64 num_bytes);
 int btrfs_delalloc_reserve_space(struct inode *inode, u64 num_bytes);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 5681a91ed400..7cb9d734f6e5 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4560,19 +4560,60 @@ void btrfs_orphan_release_metadata(struct inode *inode)
         btrfs_block_rsv_release(root, root->orphan_block_rsv, num_bytes);
 }
 
-int btrfs_snap_reserve_metadata(struct btrfs_trans_handle *trans,
-                                struct btrfs_pending_snapshot *pending)
+/*
+ * 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
+ * qgroup_reserved: used to return the reserved size in qgroup
+ *
+ * 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 reseravtion mechanism in start_transaction().
+ */
+int btrfs_subvolume_reserve_metadata(struct btrfs_root *root,
+                                     struct btrfs_block_rsv *rsv,
+                                     int items,
+                                     u64 *qgroup_reserved)
 {
-        struct btrfs_root *root = pending->root;
-        struct btrfs_block_rsv *src_rsv = get_block_rsv(trans, root);
-        struct btrfs_block_rsv *dst_rsv = &pending->block_rsv;
-        /*
-         * two for root back/forward refs, two for directory entries,
-         * one for root of the snapshot and one for parent inode.
-         */
-        u64 num_bytes = btrfs_calc_trans_metadata_size(root, 6);
-        dst_rsv->space_info = src_rsv->space_info;
-        return block_rsv_migrate_bytes(src_rsv, dst_rsv, num_bytes);
+        u64 num_bytes;
+        int ret;
+
+        if (root->fs_info->quota_enabled) {
+                /* One for parent inode, two for dir entries */
+                num_bytes = 3 * root->leafsize;
+                ret = btrfs_qgroup_reserve(root, num_bytes);
+                if (ret)
+                        return ret;
+        } else {
+                num_bytes = 0;
+        }
+
+        *qgroup_reserved = num_bytes;
+
+        num_bytes = btrfs_calc_trans_metadata_size(root, items);
+        rsv->space_info = __find_space_info(root->fs_info,
+                                            BTRFS_BLOCK_GROUP_METADATA);
+        ret = btrfs_block_rsv_add(root, rsv, num_bytes,
+                                  BTRFS_RESERVE_FLUSH_ALL);
+        if (ret) {
+                if (*qgroup_reserved)
+                        btrfs_qgroup_free(root, *qgroup_reserved);
+        }
+
+        return ret;
+}
+
+void btrfs_subvolume_release_metadata(struct btrfs_root *root,
+                                      struct btrfs_block_rsv *rsv,
+                                      u64 qgroup_reserved)
+{
+        btrfs_block_rsv_release(root, rsv, (u64)-1);
+        if (qgroup_reserved)
+                btrfs_qgroup_free(root, qgroup_reserved);
 }
 
 /**
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 8dcd4ff0c3a5..56d92549389c 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -363,7 +363,7 @@ static noinline int btrfs_ioctl_fitrim(struct file *file, void __user *arg)
         return 0;
 }
 
-static noinline int create_subvol(struct btrfs_root *root,
+static noinline int create_subvol(struct inode *dir,
                                   struct dentry *dentry,
                                   char *name, int namelen,
                                   u64 *async_transid,
@@ -374,32 +374,39 @@ static noinline int create_subvol(struct btrfs_root *root,
         struct btrfs_root_item root_item;
         struct btrfs_inode_item *inode_item;
         struct extent_buffer *leaf;
+        struct btrfs_root *root = BTRFS_I(dir)->root;
         struct btrfs_root *new_root;
-        struct dentry *parent = dentry->d_parent;
-        struct inode *dir;
+        struct btrfs_block_rsv block_rsv;
         struct timespec cur_time = CURRENT_TIME;
         int ret;
         int err;
         u64 objectid;
         u64 new_dirid = BTRFS_FIRST_FREE_OBJECTID;
         u64 index = 0;
+        u64 qgroup_reserved;
         uuid_le new_uuid;
 
         ret = btrfs_find_free_objectid(root->fs_info->tree_root, &objectid);
         if (ret)
                 return ret;
 
-        dir = parent->d_inode;
-
+        btrfs_init_block_rsv(&block_rsv, BTRFS_BLOCK_RSV_TEMP);
         /*
-         * 1 - inode item
-         * 2 - refs
-         * 1 - root item
-         * 2 - dir items
+         * The same as the snapshot creation, please see the comment
+         * of create_snapshot().
          */
-        trans = btrfs_start_transaction(root, 6);
-        if (IS_ERR(trans))
-                return PTR_ERR(trans);
+        ret = btrfs_subvolume_reserve_metadata(root, &block_rsv,
+                                               7, &qgroup_reserved);
+        if (ret)
+                return ret;
+
+        trans = btrfs_start_transaction(root, 0);
+        if (IS_ERR(trans)) {
+                ret = PTR_ERR(trans);
+                goto out;
+        }
+        trans->block_rsv = &block_rsv;
+        trans->bytes_reserved = block_rsv.size;
 
         ret = btrfs_qgroup_inherit(trans, root->fs_info, 0, objectid, inherit);
         if (ret)
@@ -515,6 +522,8 @@ static noinline int create_subvol(struct btrfs_root *root,
         BUG_ON(ret);
 
 fail:
+        trans->block_rsv = NULL;
+        trans->bytes_reserved = 0;
         if (async_transid) {
                 *async_transid = trans->transid;
                 err = btrfs_commit_transaction_async(trans, root, 1);
@@ -526,7 +535,8 @@ fail:
 
         if (!ret)
                 d_instantiate(dentry, btrfs_lookup_dentry(dir, dentry));
-
+out:
+        btrfs_subvolume_release_metadata(root, &block_rsv, qgroup_reserved);
         return ret;
 }
 
@@ -549,21 +559,31 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
 
         btrfs_init_block_rsv(&pending_snapshot->block_rsv,
                              BTRFS_BLOCK_RSV_TEMP);
+        /*
+         * 1 - parent dir inode
+         * 2 - dir entries
+         * 1 - root item
+         * 2 - root ref/backref
+         * 1 - root of snapshot
+         */
+        ret = btrfs_subvolume_reserve_metadata(BTRFS_I(dir)->root,
+                                        &pending_snapshot->block_rsv, 7,
+                                        &pending_snapshot->qgroup_reserved);
+        if (ret)
+                goto out;
+
         pending_snapshot->dentry = dentry;
         pending_snapshot->root = root;
         pending_snapshot->readonly = readonly;
         pending_snapshot->dir = dir;
         pending_snapshot->inherit = inherit;
 
-        trans = btrfs_start_transaction(root->fs_info->extent_root, 6);
+        trans = btrfs_start_transaction(root, 0);
         if (IS_ERR(trans)) {
                 ret = PTR_ERR(trans);
                 goto fail;
         }
 
-        ret = btrfs_snap_reserve_metadata(trans, pending_snapshot);
-        BUG_ON(ret);
-
         spin_lock(&root->fs_info->trans_lock);
         list_add(&pending_snapshot->list,
                  &trans->transaction->pending_snapshots);
@@ -600,6 +620,10 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
         d_instantiate(dentry, inode);
         ret = 0;
 fail:
+        btrfs_subvolume_release_metadata(BTRFS_I(dir)->root,
+                                         &pending_snapshot->block_rsv,
+                                         pending_snapshot->qgroup_reserved);
+out:
         kfree(pending_snapshot);
         return ret;
 }
@@ -733,8 +757,8 @@ static noinline int btrfs_mksubvol(struct path *parent,
                 error = create_snapshot(snap_src, dir, dentry, name, namelen,
                                         async_transid, readonly, inherit);
         } else {
-                error = create_subvol(BTRFS_I(dir)->root, dentry,
-                                      name, namelen, async_transid, inherit);
+                error = create_subvol(dir, dentry, name, namelen,
+                                      async_transid, inherit);
         }
         if (!error)
                 fsnotify_mkdir(dir, dentry);
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 71de435a291e..f11c2e0a3746 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1082,7 +1082,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
         path = btrfs_alloc_path();
         if (!path) {
                 ret = pending->error = -ENOMEM;
-                goto path_alloc_fail;
+                return ret;
         }
 
         new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
@@ -1279,8 +1279,6 @@ no_free_objectid:
         kfree(new_root_item);
 root_item_alloc_fail:
         btrfs_free_path(path);
-path_alloc_fail:
-        btrfs_block_rsv_release(root, &pending->block_rsv, (u64)-1);
         return ret;
 }
 
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 5f67fba07ab4..3c8e0d25c8e4 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -90,6 +90,7 @@ struct btrfs_pending_snapshot {
         struct btrfs_qgroup_inherit *inherit;
         /* block reservation for the operation */
         struct btrfs_block_rsv block_rsv;
+        u64 qgroup_reserved;
         /* extra metadata reseration for relocation */
         int error;
         bool readonly;