btrfs-progs: tests: mkfs: don't overwrite first 1M for single

Add test case to check if the first device extent is occupying reserved
0~1M range.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/tests/mkfs-tests/013-reserved-1M-for-single/test.sh b/tests/mkfs-tests/013-reserved-1M-for-single/test.sh
new file mode 100755 (executable)
index 0000000..775573e
--- /dev/null
+++ b/tests/mkfs-tests/013-reserved-1M-for-single/test.sh
@@ -0,0 +1,38 @@
+#!/bin/bash
+# Test if "-m single" or "--mixed" can cause dev extent to use the reserved 1M
+# range
+#
+# Other profiles will cause mkfs.btrfs to allocate new meta/sys chunks
+# using btrfs_alloc_chunk() which won't use the 0~1M range, so other profiles
+# are safe.
+
+source "$TOP/tests/common"
+
+check_prereq mkfs.btrfs
+check_prereq btrfs
+
+prepare_test_dev
+
+do_one_test ()
+{
+       run_check "$TOP/mkfs.btrfs" -f "$@" "$TEST_DEV"
+
+       # Use dev-extent tree to find first device extent
+       first_dev_extent=$(run_check_stdout "$TOP/btrfs" inspect-internal \
+               dump-tree -t device "$TEST_DEV" | \
+               grep -oP '(?<=DEV_EXTENT )[[:digit:]]*' | head -n1)
+
+       if [ -z $first_dev_extent ]; then
+               _fail "failed to get first device extent"
+       fi
+
+       echo "first dev extent starts at $first_dev_extent" >> "$RESULTS"
+       echo "reserved range is [0, $(( 1024 * 1024)))" >> "$RESULTS"
+       # First device extent should not start below 1M
+       if [ $first_dev_extent -lt $(( 1024 * 1024 )) ]; then
+               _fail "first device extent occupies reserved 0~1M range"
+       fi
+}
+
+do_one_test --mixed
+do_one_test -m single