xfs: support error injection when freeing rt extents

A handful of fstests expect to be able to test what happens when extent
free intents fail to actually free the extent.  Now that we're
supporting EFIs for realtime extents, add to xfs_rtfree_extent the same
injection point that exists in the regular extent freeing code.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

Author: Darrick J. Wong

fs/xfs/libxfs/xfs_rtbitmap.c

@@ -21,6 +21,7 @@
 #include "xfs_rtbitmap.h"
 #include "xfs_health.h"
 #include "xfs_sb.h"
+#include "xfs_errortag.h"
 #include "xfs_log.h"
 #include "xfs_buf_item.h"
 
@@ -1065,6 +1066,9 @@ xfs_rtfree_extent(
 	ASSERT(rbmip->i_itemp != NULL);
 	xfs_assert_ilocked(rbmip, XFS_ILOCK_EXCL);
 
+	if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_FREE_EXTENT))
+		return -EIO;
+
 	error = xfs_rtcheck_alloc_range(&args, start, len);
 	if (error)
 		return error;