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>

fs/ext2/xattr.c

@@ -644,8 +644,8 @@ ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 				   the inode.  */
 				ea_bdebug(new_bh, "reusing block");
 
-				error = -EDQUOT;
-				if (vfs_dq_alloc_block(inode, 1)) {
+				error = dquot_alloc_block(inode, 1);
+				if (error) {
 					unlock_buffer(new_bh);
 					goto cleanup;
 				}
@@ -702,7 +702,7 @@ ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 		 * as if nothing happened and cleanup the unused block */
 		if (error && error != -ENOSPC) {
 			if (new_bh && new_bh != old_bh)
-				vfs_dq_free_block(inode, 1);
+				dquot_free_block(inode, 1);
 			goto cleanup;
 		}
 	} else
@@ -734,7 +734,7 @@ ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 			le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
 			if (ce)
 				mb_cache_entry_release(ce);
-			vfs_dq_free_block(inode, 1);
+			dquot_free_block(inode, 1);
 			mark_buffer_dirty(old_bh);
 			ea_bdebug(old_bh, "refcount now=%d",
 				le32_to_cpu(HDR(old_bh)->h_refcount));
@@ -797,7 +797,7 @@ ext2_xattr_delete_inode(struct inode *inode)
 		mark_buffer_dirty(bh);
 		if (IS_SYNC(inode))
 			sync_dirty_buffer(bh);
-		vfs_dq_free_block(inode, 1);
+		dquot_free_block(inode, 1);
 	}
 	EXT2_I(inode)->i_file_acl = 0;