diff --git a/common/reflink b/common/reflink
index 22adc4449b..1082642e4e 100644
--- a/common/reflink
+++ b/common/reflink
@@ -521,3 +521,30 @@ _sweave_reflink_rainbow_delalloc() {
 		_pwrite_byte 0x62 $((blksz * i)) $blksz $dfile.chk
 	done
 }
+
+# Require that the COW extent size hint can actually be used to combat
+# fragmentation on the scratch filesystem.  This is (so far) true for any
+# filesystem except for the ones where the realtime extent size is larger
+# than one fs block, for it is assumed that setting a rt extent size is the
+# preferred fragmentation avoidance strategy.
+_require_scratch_cowextsize_useful() {
+	local testfile=$SCRATCH_MNT/hascowextsize
+	local param="${1:-1m}"
+
+	rm -f $testfile
+	touch $testfile
+	local before="$($XFS_IO_PROG -c 'cowextsize' $testfile)"
+
+	$XFS_IO_PROG -c "cowextsize $param" $testfile
+	local after="$($XFS_IO_PROG -c 'cowextsize' $testfile)"
+	rm -f $testfile
+
+	test "$before" != "$after" || \
+		_notrun "setting cowextsize to $param had no effect"
+
+	local fileblocksize=$(_get_file_block_size $SCRATCH_MNT)
+	local fsblocksize=$(_get_block_size $SCRATCH_MNT)
+
+	test $fsblocksize -eq $fileblocksize || \
+		_notrun "XFS does not support cowextsize when rt extsize ($fileblocksize) > 1FSB ($fsblocksize)"
+}
diff --git a/tests/xfs/180 b/tests/xfs/180
index cfea2020ce..06b4b69d52 100755
--- a/tests/xfs/180
+++ b/tests/xfs/180
@@ -37,6 +37,7 @@ nr=128
 filesize=$((blksz * nr))
 bufnr=16
 bufsize=$((blksz * bufnr))
+_require_scratch_cowextsize_useful $bufsize
 
 _require_fs_space $SCRATCH_MNT $((filesize / 1024 * 3 * 5 / 4))
 real_blksz=$(_get_block_size $testdir)
diff --git a/tests/xfs/182 b/tests/xfs/182
index 511aca6f2d..7c0713b248 100755
--- a/tests/xfs/182
+++ b/tests/xfs/182
@@ -39,6 +39,7 @@ nr=128
 filesize=$((blksz * nr))
 bufnr=16
 bufsize=$((blksz * bufnr))
+_require_scratch_cowextsize_useful $bufsize
 
 _require_fs_space $SCRATCH_MNT $((filesize / 1024 * 3 * 5 / 4))
 real_blksz=$(_get_block_size $testdir)
diff --git a/tests/xfs/184 b/tests/xfs/184
index 3bdd86addf..a0dc2741f5 100755
--- a/tests/xfs/184
+++ b/tests/xfs/184
@@ -39,6 +39,7 @@ nr=128
 filesize=$((blksz * nr))
 bufnr=16
 bufsize=$((blksz * bufnr))
+_require_scratch_cowextsize_useful $bufsize
 
 _require_fs_space $SCRATCH_MNT $((filesize / 1024 * 3 * 5 / 4))
 real_blksz=$(_get_block_size $testdir)
diff --git a/tests/xfs/192 b/tests/xfs/192
index eb577f15fc..daa4fcb1e0 100755
--- a/tests/xfs/192
+++ b/tests/xfs/192
@@ -41,6 +41,7 @@ nr=128
 filesize=$((blksz * nr))
 bufnr=16
 bufsize=$((blksz * bufnr))
+_require_scratch_cowextsize_useful $bufsize
 
 _require_fs_space $SCRATCH_MNT $((filesize / 1024 * 3 * 5 / 4))
 real_blksz=$(_get_block_size $testdir)
diff --git a/tests/xfs/200 b/tests/xfs/200
index b51b9a54f5..8eb54b5755 100755
--- a/tests/xfs/200
+++ b/tests/xfs/200
@@ -41,6 +41,7 @@ nr=128
 filesize=$((blksz * nr))
 bufnr=16
 bufsize=$((blksz * bufnr))
+_require_scratch_cowextsize_useful $bufsize
 
 _require_fs_space $SCRATCH_MNT $((filesize / 1024 * 3 * 5 / 4))
 real_blksz=$(_get_block_size $testdir)
diff --git a/tests/xfs/204 b/tests/xfs/204
index 7d6b79a86d..85b7ed7cd9 100755
--- a/tests/xfs/204
+++ b/tests/xfs/204
@@ -43,6 +43,7 @@ nr=128
 filesize=$((blksz * nr))
 bufnr=16
 bufsize=$((blksz * bufnr))
+_require_scratch_cowextsize_useful $bufsize
 
 _require_fs_space $SCRATCH_MNT $((filesize / 1024 * 3 * 5 / 4))
 real_blksz=$(_get_block_size $testdir)
diff --git a/tests/xfs/208 b/tests/xfs/208
index 9a71b74f6f..3a4a3e4df1 100755
--- a/tests/xfs/208
+++ b/tests/xfs/208
@@ -40,6 +40,7 @@ nr=128
 filesize=$((blksz * nr))
 bufnr=16
 bufsize=$((blksz * bufnr))
+_require_scratch_cowextsize_useful $bufsize
 
 _require_fs_space $SCRATCH_MNT $((filesize / 1024 * 3 * 5 / 4))
 real_blksz=$(_get_file_block_size $testdir)
diff --git a/tests/xfs/315 b/tests/xfs/315
index 9f6b39c8cc..3a618a3680 100755
--- a/tests/xfs/315
+++ b/tests/xfs/315
@@ -38,6 +38,7 @@ echo "Format filesystem"
 _scratch_mkfs >/dev/null 2>&1
 _scratch_mount >> $seqres.full
 _require_congruent_file_oplen $SCRATCH_MNT $blksz
+_require_scratch_cowextsize_useful $sz
 
 $XFS_IO_PROG -c "cowextsize $sz" $SCRATCH_MNT
 
diff --git a/tests/xfs/326 b/tests/xfs/326
index ac620fc433..a3fed8b6ac 100755
--- a/tests/xfs/326
+++ b/tests/xfs/326
@@ -55,6 +55,12 @@ $XFS_IO_PROG -c "cowextsize $sz" $SCRATCH_MNT
 # staging extent for an unshared extent and trips over the injected error.
 _require_no_xfs_always_cow
 
+# This test uses a very large cowextszhint to manipulate the COW fork to
+# contain a large unwritten extent before injecting the error.  XFS ignores
+# cowextsize when the realtime extent size is greater than 1FSB, so this test
+# cannot set up the preconditions for the test.
+_require_scratch_cowextsize_useful $sz
+
 echo "Create files"
 _pwrite_byte 0x66 0 $sz $SCRATCH_MNT/file1 >> $seqres.full
 _cp_reflink $SCRATCH_MNT/file1 $SCRATCH_MNT/file2
