xfs: create a helper to count per-device inode block usage

Create a helper to compute the number of blocks that a file has
allocated from the data realtime volumes.  This patch was
split out to reduce the size of the upcoming quotacheck patch.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/xfs_inode.c

@@ -3755,3 +3755,19 @@ xfs_ifork_zapped(
 		return false;
 	}
 }
+
+/* Compute the number of data and realtime blocks used by a file. */
+void
+xfs_inode_count_blocks(
+	struct xfs_trans	*tp,
+	struct xfs_inode	*ip,
+	xfs_filblks_t		*dblocks,
+	xfs_filblks_t		*rblocks)
+{
+	struct xfs_ifork	*ifp = xfs_ifork_ptr(ip, XFS_DATA_FORK);
+
+	*rblocks = 0;
+	if (XFS_IS_REALTIME_INODE(ip))
+		xfs_bmap_count_leaves(ifp, rblocks);
+	*dblocks = ip->i_nblocks - *rblocks;
+}

fs/xfs/xfs_inode.h

@@ -623,5 +623,7 @@ int xfs_inode_reload_unlinked_bucket(struct xfs_trans *tp, struct xfs_inode *ip)
 int xfs_inode_reload_unlinked(struct xfs_inode *ip);
 
 bool xfs_ifork_zapped(const struct xfs_inode *ip, int whichfork);
+void xfs_inode_count_blocks(struct xfs_trans *tp, struct xfs_inode *ip,
+		xfs_filblks_t *dblocks, xfs_filblks_t *rblocks);
 
 #endif	/* __XFS_INODE_H__ */