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/ocfs2/aops.c b/fs/ocfs2/aops.c
index 7e9df11..7d04c17 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -1763,10 +1763,11 @@
 
 	wc->w_handle = handle;
 
-	if (clusters_to_alloc && vfs_dq_alloc_space_nodirty(inode,
-			ocfs2_clusters_to_bytes(osb->sb, clusters_to_alloc))) {
-		ret = -EDQUOT;
-		goto out_commit;
+	if (clusters_to_alloc) {
+		ret = dquot_alloc_space_nodirty(inode,
+			ocfs2_clusters_to_bytes(osb->sb, clusters_to_alloc));
+		if (ret)
+			goto out_commit;
 	}
 	/*
 	 * We don't want this to fail in ocfs2_write_end(), so do it
@@ -1809,7 +1810,7 @@
 	return 0;
 out_quota:
 	if (clusters_to_alloc)
-		vfs_dq_free_space(inode,
+		dquot_free_space(inode,
 			  ocfs2_clusters_to_bytes(osb->sb, clusters_to_alloc));
 out_commit:
 	ocfs2_commit_trans(osb, handle);