This unintended LRU eviction issue was observed while developing the
selftest for
"[PATCH bpf-next v10 0/8] bpf: Introduce BPF_F_CPU and BPF_F_ALL_CPUS flags for percpu maps" [1].
When updating an existing element in lru_hash or lru_percpu_hash maps,
the current implementation calls prealloc_lru_pop() to get a new node
before checking if the key already exists. If the map is full, this
triggers LRU eviction and removes an existing element, even though the
update operation only needs to modify the value in-place.
In the selftest of the aforementioned patch, this was to be worked around by
reserving an extra entry to
void triggering eviction in __htab_lru_percpu_map_update_elem(). However, the
underlying issue remains problematic because:
1. Users may unexpectedly lose entries when updating existing keys in a
full map.
2. The eviction overhead is unnecessary for existing key updates.
This patchset fixes the issue by first checking if the key exists before
allocating a new node. If the key is found, update the value using the extra
LRU node without triggering any eviction. Only proceed with node allocation
if the key does not exist.
Links:
[1] https://lore.kernel.org/bpf/20251117162033.6296-1-leon.hwang@linux.dev/
Changes:
v2 -> v3:
* Rebase onto the latest tree to fix CI build failures.
* Free special fields of 'l_old' on the non-error path (per bot).
v1 -> v2:
* Tidy hash handling in LRU code.
* Factor out bpf_lru_node_reset_state helper.
* Factor out bpf_lru_move_next_inactive_rotation helper.
* Update element using preallocated extra elements in order to avoid
breaking the update atomicity (per Alexei).
* Check values on other CPUs in tests (per bot).
* v1: https://lore.kernel.org/bpf/20251202153032.10118-1-leon.hwang@linux.dev/
Leon Hwang (5):
bpf: lru: Tidy hash handling in LRU code
bpf: lru: Factor out bpf_lru_node_reset_state helper
bpf: lru: Factor out bpf_lru_move_next_inactive_rotation helper
bpf: lru: Fix unintended eviction when updating lru hash maps
selftests/bpf: Add tests to verify no unintended eviction when
updating lru_[percpu_,]hash maps
kernel/bpf/bpf_lru_list.c | 228 ++++++++++++++----
kernel/bpf/bpf_lru_list.h | 10 +-
kernel/bpf/hashtab.c | 96 +++++++-
.../selftests/bpf/prog_tests/htab_update.c | 129 ++++++++++
4 files changed, 408 insertions(+), 55 deletions(-)
--
2.52.0
Nicely enough MS defines a button type for a pressurepad touchpad [2]
and it looks like most touchpad vendors fill this in.
The selftests require a bit of prep work (and a hack for the test
itself) - hidtools 0.12 requires python-libevdev 0.13 which in turn
provides constructors for unknown properties.
[2] https://learn.microsoft.com/en-us/windows-hardware/design/component-guideli…
Signed-off-by: Peter Hutterer <peter.hutterer(a)who-t.net>
---
Changes in v2:
- rebased on top of 6.18
- hid-multitouch changes split out into a separate patch
- Patches reordered for slightly nicer history, tests changes are
grouped together
- Link to v1: https://lore.kernel.org/r/20251121-wip-hid-pressurepad-v1-0-e32e5565a527@wh…
---
Peter Hutterer (4):
HID: multitouch: set INPUT_PROP_PRESSUREPAD based on Digitizer/Button Type
selftests/hid: require hidtools 0.12
selftests/hid: use a enum class for the different button types
selftests/hid: add a test for the Digitizer/Button Type pressurepad
drivers/hid/hid-multitouch.c | 12 ++++-
tools/testing/selftests/hid/tests/conftest.py | 14 +++++
.../testing/selftests/hid/tests/test_multitouch.py | 61 +++++++++++++++++-----
3 files changed, 73 insertions(+), 14 deletions(-)
---
base-commit: 7d0a66e4bb9081d75c82ec4957c50034cb0ea449
change-id: 20251111-wip-hid-pressurepad-8a800cdf1813
Best regards,
--
Peter Hutterer <peter.hutterer(a)who-t.net>
Since the merge with v6.19-rc my CI is broken because of the newly
enabled -fms-extensions.
Add the missing flags when generating the CFLAGS for bpf.o to solve this
and continue running the tests while applying the patches.
Cheers,
Benjamin
Signed-off-by: Benjamin Tissoires <bentiss(a)kernel.org>
---
Benjamin Tissoires (2):
HID: bpf: fix bpf compilation with -fms-extensions
selftests/hid: fix bpf compilations due to -fms-extensions
drivers/hid/bpf/progs/Makefile | 6 ++++--
tools/testing/selftests/hid/Makefile | 2 ++
2 files changed, 6 insertions(+), 2 deletions(-)
---
base-commit: fde4ce068d1bccacf1e2d6a28697a3847f28e0a6
change-id: 20260106-wip-fix-bpf-compilation-4707e0faacb1
Best regards,
--
Benjamin Tissoires <bentiss(a)kernel.org>
pytest can run unittest-based testsuites, like kunit_tool_test.py.
It has a more features than the standard runner.
Unfortunately a few minor issues currently break this.
Adapt the testsuite to work with pytest.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh(a)linutronix.de>
---
Changes in v2:
- Rebase onto current kselftest/kunit branch
- Pick up review tags from LKML
- Link to v1: https://lore.kernel.org/r/20251230-kunit-pytest-v1-0-e2dae0dae200@linutroni…
---
Thomas Weißschuh (2):
kunit: tool: test: Rename test_data_path() to _test_data_path()
kunit: tool: test: Don't rely on implicit working directory change
tools/testing/kunit/kunit_tool_test.py | 61 +++++++++++++++++-----------------
1 file changed, 31 insertions(+), 30 deletions(-)
---
base-commit: ab150c2bbafe9425759eca1e45e08d4ad1456818
change-id: 20251230-kunit-pytest-259a1eb36a42
Best regards,
--
Thomas Weißschuh <thomas.weissschuh(a)linutronix.de>
These two patches improve PSP self tests when there are no PSP devs
found (test failures instead of Python exception) and when there are
multiple PSP devices present (use the first one instead of failing).
Cosmin Ratiu (2):
selftests: drv-net: psp: Use first device when multiple are present
selftests: drv-net: psp: Don't fail psp_responder when no PSP devs
found
.../selftests/drivers/net/psp_responder.c | 21 ++++++++++---------
1 file changed, 11 insertions(+), 10 deletions(-)
--
2.45.0