dquot: cleanup dquot transfer routine

Get rid of the transfer dquot operation - it is now always called from
the filesystem and if a filesystem really needs it's own (which none
currently does) it can just call into it's own routine directly.

Rename the now static low-level dquot_transfer helper to __dquot_transfer
and vfs_dq_transfer to dquot_transfer to have a consistent namespace,
and make the new dquot_transfer return a normal negative errno value
which all callers expect.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 9f607ea..6a002a6 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5263,7 +5263,7 @@
 			error = PTR_ERR(handle);
 			goto err_out;
 		}
-		error = vfs_dq_transfer(inode, attr) ? -EDQUOT : 0;
+		error = dquot_transfer(inode, attr);
 		if (error) {
 			ext4_journal_stop(handle);
 			return error;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index d231da8..b4253fb 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1017,7 +1017,6 @@
 #ifdef CONFIG_QUOTA
 	.get_reserved_space = ext4_get_reserved_space,
 #endif
-	.transfer	= dquot_transfer,
 	.write_dquot	= ext4_write_dquot,
 	.acquire_dquot	= ext4_acquire_dquot,
 	.release_dquot	= ext4_release_dquot,