Re: [PATCH v2 1/4] selftests: add tests_sysfs module

On Fri, Jul 02, 2021 at 05:46:29PM -0700, Luis Chamberlain wrote:

This adds a new selftest module which can be used to test sysfs, which would otherwise require using an existing driver. This lets us muck with a template driver to test breaking things without affecting system behaviour or requiring the dependencies of a real device driver.

A series of 28 tests are added. Support for using two device types are supported:

• misc
• block

Contrary to sysctls, sysfs requires a full write to happen at once, and so we reduce the digit tests to single writes. Two main sysfs knobs are provided for testing reading/storing, one which doesn't inclur any delays and another which can incur programmed delays. What locks are held, if any, are configurable, at module load time, or through dynamic configuration at run time.

Since sysfs is a technically filesystem, but a pseudo one, which requires a kernel user, our test_sysfs module and respective test script embraces fstests format for tests in the kernel ring bufffer. Likewise, a scraper for kernel crashes is provided which matches what fstests does as well.

Two tests are kept disabled as they currently cause a deadlock, and so this provides a mechanism to easily show proof and demo how the deadlock can happen:

Demos the deadlock with a device specific lock ./tools/testing/selftests/sysfs/sysfs.sh -t 0027

Demos the deadlock with rtnl_lock() ./tools/testing/selftests/sysfs/sysfs.sh -t 0028

Two separate solutions to the deadlock issue have been proposed, and so now its a matter of either documenting this limitation or eventually adopting a generic fix.

This selftests will shortly be expanded upon with more tests which require further kernel changes in order to provide better test coverage.

Why is this not using kunit? We should not be adding new in-kernel tests that are not using that api anymore.

Signed-off-by: Luis Chamberlain mcgrof@kernel.org

MAINTAINERS | 7 + lib/Kconfig.debug | 10 + lib/Makefile | 1 + lib/test_sysfs.c | 943 +++++++++++++++++++ tools/testing/selftests/sysfs/Makefile | 12 + tools/testing/selftests/sysfs/config | 2 + tools/testing/selftests/sysfs/sysfs.sh | 1202 ++++++++++++++++++++++++ 7 files changed, 2177 insertions(+) create mode 100644 lib/test_sysfs.c create mode 100644 tools/testing/selftests/sysfs/Makefile create mode 100644 tools/testing/selftests/sysfs/config create mode 100755 tools/testing/selftests/sysfs/sysfs.sh

diff --git a/MAINTAINERS b/MAINTAINERS index 66d047dc6880..fd369ed50040 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -17958,6 +17958,13 @@ L: linux-mmc@vger.kernel.org S: Maintained F: drivers/mmc/host/sdhci-pci-dwc-mshc.c +SYSFS TEST DRIVER +M: Luis Chamberlain mcgrof@kernel.org +L: linux-kernel@vger.kernel.org +S: Maintained +F: lib/test_sysfs.c +F: tools/testing/selftests/sysfs/

SYSTEM CONFIGURATION (SYSCON) M: Lee Jones lee.jones@linaro.org M: Arnd Bergmann arnd@arndb.de diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index fb370c7c4756..568838ac1189 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -2360,6 +2360,16 @@ config TEST_SYSCTL If unsure, say N. +config TEST_SYSFS

• tristate "sysfs test driver"
• depends on SYSFS
• help

•  This builds the "test_sysfs" module. This driver enables to test the
  

•  sysfs file system safely without affecting production knobs which
  

•  might alter system functionality.
  

•  If unsure, say N.
  

config BITFIELD_KUNIT tristate "KUnit test bitfield functions at runtime" depends on KUNIT diff --git a/lib/Makefile b/lib/Makefile index 5efd1b435a37..effd1ef806f0 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -61,6 +61,7 @@ obj-$(CONFIG_TEST_FIRMWARE) += test_firmware.o obj-$(CONFIG_TEST_BITOPS) += test_bitops.o CFLAGS_test_bitops.o += -Werror obj-$(CONFIG_TEST_SYSCTL) += test_sysctl.o +obj-$(CONFIG_TEST_SYSFS) += test_sysfs.o obj-$(CONFIG_TEST_HASH) += test_hash.o test_siphash.o obj-$(CONFIG_TEST_IDA) += test_ida.o obj-$(CONFIG_KASAN_KUNIT_TEST) += test_kasan.o diff --git a/lib/test_sysfs.c b/lib/test_sysfs.c new file mode 100644 index 000000000000..bf43016d40b5 --- /dev/null +++ b/lib/test_sysfs.c @@ -0,0 +1,943 @@ +// SPDX-License-Identifier: GPL-2.0-or-later

This does not match your "boiler-plate" text below, sorry.

thanks,

greg k-h