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/ext3/balloc.c b/fs/ext3/balloc.c
index 27967f9..161da2d 100644
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -676,7 +676,7 @@
 	}
 	ext3_free_blocks_sb(handle, sb, block, count, &dquot_freed_blocks);
 	if (dquot_freed_blocks)
-		vfs_dq_free_block(inode, dquot_freed_blocks);
+		dquot_free_block(inode, dquot_freed_blocks);
 	return;
 }
 
@@ -1502,8 +1502,9 @@
 	/*
 	 * Check quota for allocation of this block.
 	 */
-	if (vfs_dq_alloc_block(inode, num)) {
-		*errp = -EDQUOT;
+	err = dquot_alloc_block(inode, num);
+	if (err) {
+		*errp = err;
 		return 0;
 	}
 
@@ -1713,7 +1714,7 @@
 
 	*errp = 0;
 	brelse(bitmap_bh);
-	vfs_dq_free_block(inode, *count-num);
+	dquot_free_block(inode, *count-num);
 	*count = num;
 	return ret_block;
 
@@ -1728,7 +1729,7 @@
 	 * Undo the block allocation
 	 */
 	if (!performed_allocation)
-		vfs_dq_free_block(inode, *count);
+		dquot_free_block(inode, *count);
 	brelse(bitmap_bh);
 	return 0;
 }