dquot: cleanup space allocation / freeing routines

Get rid of the alloc_space, free_space, reserve_space, claim_space and
release_rsv dquot operations - they are always called from the filesystem
and if a filesystem really needs their own (which none currently does)
it can just call into it's own routine directly.

Move shared logic into the common __dquot_alloc_space,
dquot_claim_space_nodirty and __dquot_free_space low-level methods,
and rationalize the wrappers around it to move as much as possible
code into the common block for CONFIG_QUOTA vs not.  Also rename
all these helpers to be named dquot_* instead of vfs_dq_*.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index f3a2f7e..ab3a95e 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -494,7 +494,7 @@
 		error = ext4_handle_dirty_metadata(handle, inode, bh);
 		if (IS_SYNC(inode))
 			ext4_handle_sync(handle);
-		vfs_dq_free_block(inode, 1);
+		dquot_free_block(inode, 1);
 		ea_bdebug(bh, "refcount now=%d; releasing",
 			  le32_to_cpu(BHDR(bh)->h_refcount));
 		if (ce)
@@ -787,8 +787,8 @@
 			else {
 				/* The old block is released after updating
 				   the inode. */
-				error = -EDQUOT;
-				if (vfs_dq_alloc_block(inode, 1))
+				error = dquot_alloc_block(inode, 1);
+				if (error)
 					goto cleanup;
 				error = ext4_journal_get_write_access(handle,
 								      new_bh);
@@ -876,7 +876,7 @@
 	return error;
 
 cleanup_dquot:
-	vfs_dq_free_block(inode, 1);
+	dquot_free_block(inode, 1);
 	goto cleanup;
 
 bad_block: