Btrfs: Integrate metadata reservation with start_transaction

Besides simplify the code, this change makes sure all metadata
reservation for normal metadata operations are released after
committing transaction.

Changes since V1:

Add code that check if unlink and rmdir will free space.

Add ENOSPC handling for clone ioctl.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/fs/btrfs/inode-item.c b/fs/btrfs/inode-item.c
index 72ce3c173d6a..64f1150bb48d 100644
--- a/fs/btrfs/inode-item.c
+++ b/fs/btrfs/inode-item.c
@@ -49,6 +49,33 @@ static int find_name_in_backref(struct btrfs_path *path, const char *name,
         return 0;
 }
 
+struct btrfs_inode_ref *
+btrfs_lookup_inode_ref(struct btrfs_trans_handle *trans,
+                        struct btrfs_root *root,
+                        struct btrfs_path *path,
+                        const char *name, int name_len,
+                        u64 inode_objectid, u64 ref_objectid, int mod)
+{
+        struct btrfs_key key;
+        struct btrfs_inode_ref *ref;
+        int ins_len = mod < 0 ? -1 : 0;
+        int cow = mod != 0;
+        int ret;
+
+        key.objectid = inode_objectid;
+        key.type = BTRFS_INODE_REF_KEY;
+        key.offset = ref_objectid;
+
+        ret = btrfs_search_slot(trans, root, &key, path, ins_len, cow);
+        if (ret < 0)
+                return ERR_PTR(ret);
+        if (ret > 0)
+                return NULL;
+        if (!find_name_in_backref(path, name, name_len, &ref))
+                return NULL;
+        return ref;
+}
+
 int btrfs_del_inode_ref(struct btrfs_trans_handle *trans,
                            struct btrfs_root *root,
                            const char *name, int name_len,