Commit b05fbcc36be1 ("btrfs: disable build on platforms having page size
256K") disabled btrfs for configurations that used a 256kB page size.
However, it did not fully solve the problem because CONFIG_TEST_KMOD
selects CONFIG_BTRFS, which does not account for the dependency. This
results in a Kconfig warning and the failed BUILD_BUG_ON error
returning.

WARNING: unmet direct dependencies detected for BTRFS_FS
  Depends on [n]: BLOCK [=y] && !PPC_256K_PAGES && !PAGE_SIZE_256KB [=y]
  Selected by [m]:
  - TEST_KMOD [=m] && RUNTIME_TESTING_MENU [=y] && m && MODULES [=y] && NETDEVICES [=y] && NET_CORE [=y] && INET [=y] && BLOCK [=y]

To resolve this, add CONFIG_PAGE_SIZE_LESS_THAN_256KB as a dependency of
CONFIG_TEST_KMOD so there is no more invalid configuration or build
errors.

Fixes: b05fbcc36be1 ("btrfs: disable build on platforms having page size 256K")
Reported-by: kernel test robot <redacted>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 lib/Kconfig.debug | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 5c12bde10996..a32f6bb4642c 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug

@@ -2486,6 +2486,7 @@ config TEST_KMOD
 	depends on m
 	depends on NETDEVICES && NET_CORE && INET # for TUN
 	depends on BLOCK
+	depends on PAGE_SIZE_LESS_THAN_256KB # for BTRFS
 	select TEST_LKM
 	select XFS_FS
 	select TUN

-- 
2.34.1