[PATCH 1/2] fstests: btrfs/131: add explicit v1 space cache requirement

[Qu Wenruo <wqu@suse.com>]

The test case is utilizing v1 space cache, meanwhile v1 space cache
is already marked deprecated for a while since kernel commit
1e7bec1f7d65 ("btrfs: emit a warning about space cache v1 being
deprecated").

Furthermore quite some features are not compatible with v1 cache,
including the soon-to-be-default block-group-tree, and hardware
dependent zoned features.

Currently we reject those features for btrfs/131, but what we really
want is to only run the test case for supported features/kernels.
The current way to reject will not handle future kernels that completely
rejects v1 space cache.

Add a new helper, _require_btrfs_v1_cache() to do the check, which
checks the following criteria:

- "space_cache=v1" mount option is supported
  And to handle default v2 cache behavior, also add "clear_cache".
  If the kernel has completely dropped v1 cache support, such mount
  should fail.

- Check if FREE_SPACE_TREE feature exists after above mount
  For bs != ps cases, v2 cache is enforced to replace v1 cache, thus
  we need to double check to make sure above mount didn't result v2
  cache.

- Check if cache generation is correct
  If v1 cache is working, the cache_generation should be some valid
  value other than 0 nor (u64)-1.

And replace the existing checks on zoned and block-group-tree with the
new one.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 common/btrfs    | 25 +++++++++++++++++++++++++
 tests/btrfs/131 |  7 +------
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/common/btrfs b/common/btrfs
index 6a1095ff..c2d616aa 100644
--- a/common/btrfs
+++ b/common/btrfs
@@ -630,6 +630,31 @@ _btrfs_no_v1_cache_opt()
 	echo -n "-onospace_cache"
 }
 
+# v1 space cache is already deprecated and will be removed soon. Furthermore
+# the soon-to-be-default block-group-tree has dependency on v2 space cache, and
+# will reject v1 cache mount option.
+# Make sure v1 space cache is still supported for test cases still utilizing
+# v1 space cache.
+_require_btrfs_v1_cache()
+{
+	_scratch_mkfs &> /dev/null
+	_try_scratch_mount -o clear_cache,space_cache=v1 || _notrun "v1 space cache is not supported"
+	_scratch_unmount
+
+	# Make sure no FREE_SPACE_TREE enabled.
+	if $BTRFS_UTIL_PROG inspect-internal dump-super $SCRATCH_DEV |\
+	   grep -q "FREE_SPACE_TREE"; then
+		_notrun "v1 space cache is not supported"
+	fi
+
+	# Make sure the cache generation is not 0 nor -1.
+	local cache_gen=$($BTRFS_UTIL_PROG inspect-internal dump-super $SCRATCH_DEV |\
+			  grep "cache_generation" | $AWK_PROG '{ print $2 }' )
+	if [ "$cache_gen" -eq 0 -o $(( $test_num + 1 )) -eq 0 ]; then
+		_notrun "v1 space cache is not supported"
+	fi
+}
+
 # Require certain sectorsize support
 _require_btrfs_support_sectorsize()
 {
diff --git a/tests/btrfs/131 b/tests/btrfs/131
index b4756a5f..026d11e6 100755
--- a/tests/btrfs/131
+++ b/tests/btrfs/131
@@ -14,14 +14,9 @@ _begin_fstest auto quick
 _require_scratch
 _require_btrfs_command inspect-internal dump-super
 _require_btrfs_fs_feature free_space_tree
-# Zoned btrfs does not support space_cache(v1)
-_require_non_zoned_device "${SCRATCH_DEV}"
-# Block group tree does not support space_cache(v1)
-_require_btrfs_no_block_group_tree
+_require_btrfs_v1_cache
 
 _scratch_mkfs >/dev/null 2>&1
-[ "$(_get_page_size)" -gt "$(_scratch_btrfs_sectorsize)" ] && \
-	_notrun "cannot run with subpage sectorsize"
 
 mkfs_v1()
 {
-- 
2.51.2