[PATCH 3/4] btrfs-progs: tests/misc/046: fix false alerts on write detection

[Qu Wenruo <wqu@suse.com>]

[BUG]
Test case misc/046-seed-multi-mount would always fail with the following
error:

    [TEST]   misc-tests.sh
    [TEST/misc]   046-seed-multi-mount
unexpected success: writable file despite read-only mount
test failed for case 046-seed-multi-mount

[CAUSE]
Although mounting seed device is indeed read-only, sprouting it with a
new device would always make it read-write by itself.

The behavior is already there for a long time, thus expecting a new
behavior (not changing the read-only flag) is a little weird.

[FIX]
Instead of doing the write check after the sprout, do it before the
sprout.

This looks more correct, and would not rely on the kernel behavior
change (if we determine to go that path).

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 tests/misc-tests/046-seed-multi-mount/test.sh | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tests/misc-tests/046-seed-multi-mount/test.sh b/tests/misc-tests/046-seed-multi-mount/test.sh
index 83f7a91effdd..95654fd904ff 100755
--- a/tests/misc-tests/046-seed-multi-mount/test.sh
+++ b/tests/misc-tests/046-seed-multi-mount/test.sh
@@ -42,9 +42,11 @@ nextdevice() {
 	run_check mkdir -p "$mnt"
 	TEST_MNT="$mnt"
 	run_check_mount_test_dev
-	run_check $SUDO_HELPER "$TOP/btrfs" device add ${loopdevs[$nextdev]} "$TEST_MNT"
 	run_mustfail "writable file despite read-only mount" \
 		$SUDO_HELPER dd if=/dev/zero of="$TEST_MNT/file$nextdevice" bs=1M count=1 status=none
+	run_check $SUDO_HELPER "$TOP/btrfs" device add ${loopdevs[$nextdev]} "$TEST_MNT"
+	# Although seed sprout would make the fs RW, explicitly remount it RW
+	# just in case of future behavior change.
 	run_check $SUDO_HELPER mount -o remount,rw "$TEST_MNT"
 	# Rewrite the file
 	md5sum=$(run_check_stdout md5sum "$TEST_MNT/file$nextdev" | awk '{print $1}')
-- 
2.41.0