[PATCH 1/3] btrfs-progs: tests: fix the wrong kernel version check

[Qu Wenruo <wqu@suse.com>]

[BUG]
After upgrading to kernel v6.0-rc, btrfs-progs selftest mkfs/001 no
longer checks single device RAID0 and other new features introduced in
v5.13:

  # make TEST=001\* test-mkfs
    [TEST]   mkfs-tests.sh
    [TEST/mkfs]   001-basic-profiles
  $ grep -IR "RAID0\/1" tests/mkfs-tests-results.txt
  ^^^ No output

[CAUSE]
The existing check_min_kernel_version() is doing an incorrect check.

The old check looks like this:

	[ "$unamemajor" -lt "$argmajor" ] || return 1
	[ "$unameminor" -lt "$argminor" ] || return 1
	return 0

For 6.0-rc kernels, we have the following values for mkfs/001

 $unamemajor = 6
 $unameminor = 0
 $argmajor   = 5
 $argminor   = 12

The first check doesn't exit immediately, as 6 > 5.
Then we check the minor, which is already incorrect.

If our major is larger than target major, we should exit immediate with
0.

[FIX]
Fix the check and add extra comment.

Personally speaking I'm not a fan or short compare and return, thus all
the checks will explicit "if []; then fi" checks.

Now mkfs/001 works as expected:

  # make TEST=001\* test-mkfs
    [TEST]   mkfs-tests.sh
    [TEST/mkfs]   001-basic-profiles
  $ grep -IR "RAID0\/1" tests/mkfs-tests-results.txt
   Data,RAID0/1:          204.75MiB
   Metadata,RAID0/1:      204.75MiB
   System,RAID0/1:          8.00MiB

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 tests/common | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/tests/common b/tests/common
index 3ee42a80dcda..d985ef72a4f1 100644
--- a/tests/common
+++ b/tests/common
@@ -659,6 +659,9 @@ check_kernel_support()
 # compare running kernel version to the given parameter, return success
 # if running is newer than requested (let caller decide if to fail or skip)
 # $1: minimum version of running kernel in major.minor format (eg. 4.19)
+#
+# Return 0 if we meet the minimal version requirement.
+# Return 1 if not.
 check_min_kernel_version()
 {
 	local unamemajor
@@ -672,10 +675,22 @@ check_min_kernel_version()
 	uname=${uname%%-*}
 	IFS=. read unamemajor unameminor tmp <<< "$uname"
 	IFS=. read argmajor argminor tmp <<< "$1"
-	# "compare versions: ${unamemajor}.${unameminor} ? ${argmajor}.${argminor}"
-	[ "$unamemajor" -lt "$argmajor" ] || return 1
-	[ "$unameminor" -lt "$argminor" ] || return 1
-	return 0
+	# If our major > target major, we definitely meet the requirement.
+	# If our major < target major, we definitely don't meet the requirement.
+	if [ "$unamemajor" -gt "$argmajor" ]; then
+		return 0
+	fi
+	if [ "$unamemajor" -lt "$argmajor" ]; then
+		return 1
+	fi
+
+	# Only when our major is the same as the target, we need to compare
+	# the minor number.
+	# In this case, if our minor >= target minor, we meet the requirement.
+	if [ "$unameminor" -ge "$argminor" ]; then
+		return 0;
+	fi
+	return 1
 }
 
 # Get subvolume id for specified path
-- 
2.37.3