diff --git a/tests/golden/data-prealloc b/tests/golden/data-prealloc
new file mode 100644
index 00000000..93854034
--- /dev/null
+++ b/tests/golden/data-prealloc
@@ -0,0 +1,26 @@
+== initial writes smaller than prealloc grow to prealloc size
+/mnt/test/test/data-prealloc/file-1: 7 extents found
+/mnt/test/test/data-prealloc/file-2: 7 extents found
+== larger files get full prealloc extents
+/mnt/test/test/data-prealloc/file-1: 9 extents found
+/mnt/test/test/data-prealloc/file-2: 9 extents found
+== non-streaming writes with contig have per-block extents
+/mnt/test/test/data-prealloc/file-1: 32 extents found
+/mnt/test/test/data-prealloc/file-2: 32 extents found
+== any writes to region prealloc get full extents
+/mnt/test/test/data-prealloc/file-1: 4 extents found
+/mnt/test/test/data-prealloc/file-2: 4 extents found
+/mnt/test/test/data-prealloc/file-1: 4 extents found
+/mnt/test/test/data-prealloc/file-2: 4 extents found
+== streaming offline writes get full extents either way
+/mnt/test/test/data-prealloc/file-1: 4 extents found
+/mnt/test/test/data-prealloc/file-2: 4 extents found
+/mnt/test/test/data-prealloc/file-1: 4 extents found
+/mnt/test/test/data-prealloc/file-2: 4 extents found
+== goofy preallocation amounts work
+/mnt/test/test/data-prealloc/file-1: 5 extents found
+/mnt/test/test/data-prealloc/file-2: 5 extents found
+/mnt/test/test/data-prealloc/file-1: 5 extents found
+/mnt/test/test/data-prealloc/file-2: 5 extents found
+/mnt/test/test/data-prealloc/file-1: 3 extents found
+/mnt/test/test/data-prealloc/file-2: 3 extents found
diff --git a/tests/sequence b/tests/sequence
index db6e9ba0..43a599b0 100644
--- a/tests/sequence
+++ b/tests/sequence
@@ -6,6 +6,7 @@ simple-inode-index.sh
 simple-staging.sh
 simple-release-extents.sh
 fallocate.sh
+data-prealloc.sh
 setattr_more.sh
 offline-extent-waiting.sh
 move-blocks.sh
diff --git a/tests/tests/data-prealloc.sh b/tests/tests/data-prealloc.sh
new file mode 100644
index 00000000..b0bb81d2
--- /dev/null
+++ b/tests/tests/data-prealloc.sh
@@ -0,0 +1,136 @@
+#
+# test that the data prealloc options behave as expected.  We write to
+# two files a block at a time so that a single file doesn't naturally
+# merge adjacent consecutive allocations.  (we don't have multiple
+# allocation cursors)
+#
+t_require_commands scoutfs stat filefrag dd touch truncate
+
+write_forwards()
+{
+	local prefix="$1"
+	local nr="$2"
+	local blk
+
+	touch "$prefix"-{1,2}
+	truncate -s 0 "$prefix"-{1,2}
+
+	for blk in $(seq 0 1 $((nr - 1))); do
+		dd if=/dev/zero of="$prefix"-1 bs=4096 seek=$blk count=1 conv=notrunc status=none
+		dd if=/dev/zero of="$prefix"-2 bs=4096 seek=$blk count=1 conv=notrunc status=none
+	done
+}
+
+write_backwards()
+{
+	local prefix="$1"
+	local nr="$2"
+	local blk
+
+	touch "$prefix"-{1,2}
+	truncate -s 0 "$prefix"-{1,2}
+
+	for blk in $(seq $((nr - 1)) -1 0); do
+		dd if=/dev/zero of="$prefix"-1 bs=4096 seek=$blk count=1 conv=notrunc status=none
+		dd if=/dev/zero of="$prefix"-2 bs=4096 seek=$blk count=1 conv=notrunc status=none
+	done
+}
+
+release_files() {
+	local prefix="$1"
+	local size=$(($2 * 4096))
+	local vers
+	local f
+
+	for f in "$prefix"*; do
+		size=$(stat -c "%s" "$f")
+		vers=$(scoutfs stat -s data_version "$f")
+		scoutfs release "$f" -V "$vers" -o 0 -l $size
+	done
+}
+
+stage_files() {
+	local prefix="$1"
+	local nr="$2"
+	local vers
+	local f
+
+	for blk in $(seq 0 1 $((nr - 1))); do
+		for f in "$prefix"*; do
+			vers=$(scoutfs stat -s data_version "$f")
+			scoutfs stage /dev/zero "$f" -V "$vers" -o $((blk * 4096)) -l 4096
+		done
+	done
+}
+
+print_extents_found()
+{
+	local prefix="$1"
+
+	filefrag "$prefix"* 2>&1 | grep "extent.*found" | t_filter_fs
+}
+
+t_save_all_sysfs_mount_options data_prealloc_blocks
+t_save_all_sysfs_mount_options data_prealloc_contig_only
+restore_options()
+{
+	t_restore_all_sysfs_mount_options data_prealloc_blocks
+	t_restore_all_sysfs_mount_options data_prealloc_contig_only
+}
+trap restore_options EXIT
+
+prefix="$T_D0/file"
+
+echo "== initial writes smaller than prealloc grow to prealloc size"
+t_set_sysfs_mount_option 0 data_prealloc_blocks 32
+t_set_sysfs_mount_option 0 data_prealloc_contig_only 1
+write_forwards $prefix 64
+print_extents_found $prefix
+
+echo "== larger files get full prealloc extents"
+t_set_sysfs_mount_option 0 data_prealloc_blocks 32
+t_set_sysfs_mount_option 0 data_prealloc_contig_only 1
+write_forwards $prefix 128
+print_extents_found $prefix
+
+echo "== non-streaming writes with contig have per-block extents"
+t_set_sysfs_mount_option 0 data_prealloc_blocks 32
+t_set_sysfs_mount_option 0 data_prealloc_contig_only 1
+write_backwards $prefix 32
+print_extents_found $prefix
+
+echo "== any writes to region prealloc get full extents"
+t_set_sysfs_mount_option 0 data_prealloc_blocks 16
+t_set_sysfs_mount_option 0 data_prealloc_contig_only 0
+write_forwards $prefix 64
+print_extents_found $prefix
+write_backwards $prefix 64
+print_extents_found $prefix
+
+echo "== streaming offline writes get full extents either way"
+t_set_sysfs_mount_option 0 data_prealloc_blocks 16
+t_set_sysfs_mount_option 0 data_prealloc_contig_only 1
+write_forwards $prefix 64
+release_files $prefix 64
+stage_files $prefix 64
+print_extents_found $prefix
+t_set_sysfs_mount_option 0 data_prealloc_contig_only 0
+release_files $prefix 64
+stage_files $prefix 64
+print_extents_found $prefix
+
+echo "== goofy preallocation amounts work"
+t_set_sysfs_mount_option 0 data_prealloc_blocks 7
+t_set_sysfs_mount_option 0 data_prealloc_contig_only 1
+write_forwards $prefix 14
+print_extents_found $prefix
+t_set_sysfs_mount_option 0 data_prealloc_blocks 13
+t_set_sysfs_mount_option 0 data_prealloc_contig_only 0
+write_forwards $prefix 53
+print_extents_found $prefix
+t_set_sysfs_mount_option 0 data_prealloc_blocks 1
+t_set_sysfs_mount_option 0 data_prealloc_contig_only 0
+write_forwards $prefix 3
+print_extents_found $prefix
+
+t_pass