kernel/git/next/linux-next.git/tools/testing/selftests/cgroup, branch master

selftests/cgroup: test_zswap: fix implicit unsigned promotion bug in test_no_kmem_bypass

2026-09-14T04:31:19+00:00

In test_no_kmem_bypass(), delta (stored_pages * page_size - zswapped) is checked against stored_pages * page_size / 4 to verify that the pages pushed to zswap belong to the test memory cgroup. Due to slight stat update timing differences, delta can evaluate to a small negative number (e.g. -5MB out of 1GB). Because delta is declared as a signed int and stored_pages is an unsigned size_t, C's usual arithmetic conversions implicitly promote a negative delta to a large unsigned 64-bit integer, causing `delta < stored_pages * page_size / 4` to falsely evaluate to 0 and fail the test. Fix this by declaring zswapped and delta as signed long long and comparing against a signed threshold, ensuring negative deltas correctly evaluate to true. Link: https://lore.kernel.org/20260828033741.2184560-3-wfelipe@google.com Fixes: a549f9f31561a ("selftests: cgroup: add test_zswap with no kmem bypass test") Signed-off-by: Wilson Felipe Pereira Signed-off-by: Andrew Morton Acked-by: Michal Koutný Cc: Chengming Zhou Cc: Johannes Weiner Cc: Nhat Pham Cc: Shuah Khan Cc: Tejun Heo

selftests/cgroup: test_zswap: wait for cgroup to unpopulate in test_zswap_writeback

2026-09-14T04:31:19+00:00

Patch series "selftests/cgroup: fixes for test_zswap on single core VM", v4. This series fixes two test failures in test_zswap observed when running on a single-core VM (-smp 1) with 4GB of RAM. Patch 1 addresses a race condition in test_zswap_writeback() where waitpid() returns before the exiting child process is switched away by the kernel, causing an immediate write of "+memory" to cgroup.subtree_control to fail with -EBUSY. We fix this by waiting for cgroup.events to report "populated 0". Patch 2 fixes an implicit unsigned conversion bug in test_no_kmem_bypass() where small negative timing differences between debugfs stored_pages and cgroup zswapped bytes caused the comparison to falsely fail due to unsigned promotion. This patch (of 2): When running test_zswap on a single-core VM (-smp 1) with 4GB of RAM, test_zswap_writeback intermittently fails on the initial run after boot. In test_zswap_writeback(), after waitpid() reaps the child process created by test_zswap_writeback_one(), writing "+memory" to cgroup.subtree_control can fail with -EBUSY. Under cgroup v2, enabling domain subtree controllers is forbidden while any tasks remain in cgroup.procs. When a child process exits, exit_notify() wakes the parent process, allowing waitpid() to return immediately. However, the cgroup populated task count (nr_populated_csets) is only decremented when the exiting task is switched away via finish_task_switch() -> cgroup_task_dead(). On single-core systems, the parent runs before the dead child has been switched out, causing "+memory" to fail with -EBUSY if written immediately after waitpid() returns. Fix this by waiting for cgroup.events to report "populated 0\n" via cg_read_strcmp_wait() before enabling subtree control. Link: https://lore.kernel.org/20260828033741.2184560-1-wfelipe@google.com Link: https://lore.kernel.org/20260828033741.2184560-2-wfelipe@google.com Signed-off-by: Wilson Felipe Pereira Signed-off-by: Andrew Morton Acked-by: Michal Koutný Cc: Chengming Zhou Cc: Johannes Weiner Cc: Nhat Pham Cc: Shuah Khan Cc: Tejun Heo

selftests/cgroup: account for zswap shrinker writeback

2026-09-14T04:30:08+00:00

The test_no_invasive_cgroup_shrink selftest checks that when a cgroup has zswapped out more memory than memory.zswap.max, it does not trigger writeback for other cgroups. To do this, it compares the writeback count in a control cgroup and makes sure that it is 0, and then checks the writeback count in an aggressor cgroup who does expect to see writeback. However, when the zswap shrinker is enabled, the victim cgroup can see legitimate writebacks not triggered by the aggressor. In some Meta CI tests, we have seen this failure mode happen. Instead of checking that the victim cgroup has 0 writeback, compare the writeback values before and after the aggressor runs and check that the victim cgroup did not perform any additional writeback. Note that this can still lead to probabilistic failures if writebacks take longer than 5 seconds, but this should fix the systematic failure case and make "not ok test_no_invasive_cgroup_shrink" less likely. Link: https://lore.kernel.org/20260902194521.3652178-1-joshua.hahnjy@gmail.com Fixes: b5ba474f3f51 ("zswap: shrink zswap pool based on memory pressure") Signed-off-by: Joshua Hahn Signed-off-by: Andrew Morton Reported-by: Krush Chavan Suggested-by: Nhat Pham Cc:

Merge tag 'cgroup-for-7.3-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2026-08-31T21:20:32+00:00

Pull cgroup fixes from Tejun Heo: - After cgroup.kill was written to a cgroup, every child cloned into it with CLONE_INTO_CGROUP was spuriously killed because the fork path snapshotted the kill counter before resolving the target cgroup - Releasing an isolated cpuset partition dropped the isolation of CPUs isolated on the kernel command line - Selftest and documentation fixes * tag 'cgroup-for-7.3-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: selftests/cgroup: test clone3() into a previously killed cgroup cgroup: fix spurious SIGKILL of CLONE_INTO_CGROUP children selftests/cgroup: Add test for preserving boot-isolated CPUs cgroup/cpuset: Preserve boot-isolated CPUs on partition release selftests/cgroup: Drop invalid boot isolation comparison docs: cgroup-v2: fix misc.events key format description selftests/cgroup: Fix cg_run_in_subcgroups ignoring arg parameter selftests/cgroup: set the test plan after the setup checks

selftests/cgroup: test clone3() into a previously killed cgroup

2026-08-31T16:19:53+00:00

Once cgroup.kill had been written to a cgroup, a stale kill_seq snapshot (taken in cgroup_css_set_fork() before the target cgroup was resolved) caused every child subsequently cloned into that cgroup with clone3(CLONE_INTO_CGROUP) to be SIGKILLed on the spot. Add a regression test: create a cgroup, kill it while it is empty, then clone a child into it and check that the child runs and exits cleanly. On a kernel without the fix, the test fails: not ok 4 test_cgkill_clone_into_killed The test is skipped on kernels without clone3() or without CLONE_INTO_CGROUP. Cc: Shakeel Butt Assisted-by: LLM Signed-off-by: Etienne Perot Signed-off-by: Tejun Heo

Merge tag 'mm-stable-2026-08-26-15-22' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2026-08-27T16:17:06+00:00

Pull more MM updates from Andrew Morton: - "mm/rmap: index MAP_PRIVATE file-backed folios by anonymous pgoff" (Lorenzo Stoakes) Index MAP_PRIVATE file-backed folios by their anonymous page offset to resolve confusion around reverse mapping for zeroed and CoW'd file-backed memory. Use this new VMA anonymous page offset tracking to eliminate index conflicts and lay the foundation for scalable CoW performance improvements. - "promote mapped executable folios after first usage for MGLRU" (Baolin Wang) Make MGLRU's protection of mapped executable file folios more reliable. Follow the classical LRU's logic, promoting mapped executable file folios after their first usage to give executable code a better chance to stay in memory and improve workload performance. - "mm: vmscan: fix node reclaim ignoring swappiness parameter" (Ridong Chen) Fix per-node proactive reclaim interface's ignoring the swappiness parameter when CONFIG_MEMCG is disabled by consolidating sc_swappiness() into a single function that checks proactive_swappiness regardless of kernel configuration. - "mm/vmscan: reduce lru_lock contention via vmstat-derived scan-balance cost" (Usama Arif) Reduce lru_lock contention in the reclaim path by deriving scan-balance costs from vmstat counters rather than lock-acquired producer updates. Read and decay these cost signals on the reclaim side under a dedicated per-lruvec lock, reducing total LRU lock wait time by over 60% without impacting scan throughput. - "zram: fix zram issues reported by sashiko" (Sergey Senozhatsky) Fix two low-risk zram bugs which Sashiko spotted in drive-by review. - "Honor XA_FLAGS_ACCOUNT in xas_split_alloc() and charge to folio's memcg" (Zi Yan) Fix xas_split_alloc() by enabling target folio memcg charging during splits and adding the missing __GFP_ACCOUNT flag for proper XArray node memory accounting. - "selftests/mm: use pattern matching in .gitignore" (Pratyush Mallick) Replace hardcoded binary names in selftests/mm/.gitignore with a generic pattern-matching rule to automatically ignore generated test files and avoid manual updates when adding new tests. - "mm/page_ext: remove pgdat_page_ext_init()" (Sang-Heon Jeon) Make the incompatibility between FLATMEM and NUMA explicit in mm/Kconfig and remove the unused pgdat_page_ext_init() function. - "zram: fix zstd error paths and add parameter validation" (Haoqin Huang) Clean up zram compression backends by removing redundant error cleanup, adding parameter and dictionary validation, auto-prefixing algorithm error logs, and resetting parameters prior to reinitialization. - "zram: fix stale scan bounds after reinitialization" (Longlong Xia) Prevent out-of-bounds slot accesses during concurrent zram resets by moving table scan bound calculations under dev_lock in writeback_store() and read_block_state(). - "add anon mTHP collapse test cases" (Baolin Wang) Extend selftests helper functions to support arbitrary page orders and add new test cases and options for mTHP collapse in khugepaged. - "selftests/mm: Handle unsupported and transient test conditions" (Muhammad Usama Anjum) Update MM selftests to report a SKIP status instead of a failure when required kernel or filesystem features are unsupported, while adding retry logic for transient page migration errors. - "mm/zswap: Fixes and improves the zswap shrink" (Hao Jia) Fix the missing zswap global shrinker when CONFIG_MEMCG is disabled and extend shrink_memcg() to support batch writeback for improved writeback efficiency. - "alloc_tag: introduce IOCTL-based filtering for MAP" (Suren Baghdasaryan) Introduce an IOCTL-based binary interface for memory allocation profiling that enables kernel-side filtering before per-CPU counter aggregation. This eliminates the text-parsing overhead of /proc/allocinfo and provides up to a 20x speedup by transferring only filtered allocation data to userspace. - "better block swap batching and a different take on swap_ops v5" (Christoph Hellwig) Refactor block swap I/O to use swap_iocb for batching instead of single-bio requests and rebase the swap_ops interface, achieving faster swap throughput during kernel builds. - "mm: kmemleak: reduce transient false positives by confirming leaks" (Catalin Marinas) Reduce false-positive kmemleak reports by combining two kmemleak enhancements that add a second confirmation scan and a configurable minimum unreferenced scan count module parameter. - "mm: kmemleak: default min_unref_scans to 2 for verbose kernels" (Breno Leitao) Auto-scanning kernels can generate false-positive memory leak reports on single scans, so this patch defaults min_unref_scans to 2 when CONFIG_DEBUG_KMEMLEAK_VERBOSE is enabled to require a second confirming scan. - "swap_ops updates" (Christoph Hellwig) Batching I/O for synchronous swap devices causes performance regressions and filesystem-based swap suffers from double-indirection overhead. This series resolves both issues by reintroducing per-folio writes for synchronous swap and allowing filesystems to directly export their own swap_ops. - "mm/khugepaged: several cleanups" (Nico Pache) khugepaged accumulated redundant state-checking patterns and outdated comments following mTHP integration. Introduce dedicated helpers for PTE validation and event counting while refreshing the internal documentation. - "maple_tree: lock checking and clean ups" (Liam Howlett) Syzbot reports incorrectly blame memory management exit paths for locking bugs, maple tree erase operations risk allocation failures without gfp flags and internal documentation lacks clarity. Improve lock error detection, update docs, fix race and allocation edge cases and optimize erase allocations using a fallback to GFP_KERNEL | GFP_NOFAIL. * tag 'mm-stable-2026-08-26-15-22' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (172 commits) selftests/proc: make proc-maps-race work with READ_IMPLIES_EXEC memcg: move LRU size accounting on reparenting instead of copying it mm/vmscan: fix comment logic in balance_pgdat maple_tree: add helper mas_make_walkable() maple_tree: avoid extra gap calculation maple_tree: fix argument name in header maple_tree: change two GFP flags in tests maple_tree: document erase and allocations better maple_tree: avoid mas_erase() and mtree_erase() failures maple_tree: document that erase may use GFP_KERNEL for allocations maple_tree: catch race in mas_alloc_cyclic() maple_tree: add bulk parent set helper maple_tree: micro optimisation of mas_wr_store_type() maple_tree: optimise mas_wr_node_store() when not in rcu mode maple_tree: use prefetched value in mas_wr_store_type() maple_tree: clarify comments on mas_nomem() maple_tree: drop MAPLE_ALLOC_SLOTS maple_tree: drop dead code from mas_extend_spanning_null() maple_tree: documentation fix maple_tree: add write lock checking with lockdep sequence numbers ...

selftests/cgroup: test_zswap: skip test_no_kmem_bypass if debugfs is unavailable

2026-08-25T01:43:21+00:00

test_no_kmem_bypass() needs to read /sys/kernel/debug/zswap/stored_pages via get_zswap_stored_pages() to verify that compressed pages are charged to the memcg. When running in an environment where debugfs is not mounted or CONFIG_DEBUG_FS is disabled, get_zswap_stored_pages() fails, causing the loop to terminate early and report a false negative (KSFT_FAIL). Selftests should not fail if debugfs is unavailable, and it should print a message when it is skipped. While I'm here, also add a warning message if the test is being skipped due to totalram size and make the check for totalram more readable. [akpm@linux-foundation.org: clarify debugfs-unavailable error message] Link: https://lore.kernel.org/20260812050848.848882-1-wfelipe@google.com Link: https://lore.kernel.org/20260811051434.3805648-1-wfelipe@google.com Signed-off-by: Wilson Felipe Pereira Reviewed-by: Anshuman Khandual Reviewed-by: SJ Park Cc: Chengming Zhou Cc: Johannes Weiner Cc: Michal Koutný Cc: Nhat Pham Cc: Shuah Khan Cc: Tejun Heo Signed-off-by: Andrew Morton

selftests/cgroup: Add test for preserving boot-isolated CPUs

2026-08-24T17:01:44+00:00

Put a CPU isolated at boot into an isolated partition, change the partition back to member and check that the CPU remains isolated. Signed-off-by: Guopeng Zhang Reviewed-by: Waiman Long Signed-off-by: Tejun Heo

selftests/cgroup: Drop invalid boot isolation comparison

2026-08-24T17:01:15+00:00

check_isolcpus() clears ISOLCPUS before rebuilding it from sched domain data. Comparing that empty value with /sys/devices/system/cpu/isolated makes the test fail whenever isolcpus=domain is present. That sysfs file is generated from HK_TYPE_DOMAIN_BOOT and does not change when cpuset updates HK_TYPE_DOMAIN. Re-reading it cannot validate dynamic housekeeping updates. The cpuset.cpus.isolated and sched domain checks already cover the two dynamic interfaces, so remove the invalid comparison. This can be reproduced on a kernel booted with isolcpus=domain,15: # tools/testing/selftests/cgroup/test_cpuset_prs.sh The test fails its first state-matrix isolation check before the change and continues past that check afterward. Fixes: 6df415aa46ec ("cgroup/cpuset: Defer housekeeping_update() calls from CPU hotplug to workqueue") Signed-off-by: Guopeng Zhang Reviewed-by: Waiman Long Signed-off-by: Tejun Heo

selftests/cgroup: Fix cg_run_in_subcgroups ignoring arg parameter

2026-08-20T17:48:01+00:00

cg_run_in_subcgroups() discards its arg and always passes NULL to cg_run(), turning the (void *)100 from test_kmem_dead_cgroups() into NULL so no allocation occurs. This makes test_kmem_dead_cgroups() falsely pass without exercising the "dying cgroup with charged slab" scenario it intends to test. Pass the arg through to cg_run() to fix this. Fixes: 933dc80ec262 ("kselftests: cgroup: add kernel memory accounting tests") Signed-off-by: Hongfu Li Reviewed-by: Michal Koutný Signed-off-by: Tejun Heo