linux.git/kernel/bpf/memalloc.c, branch v6.18.21

bpf: replace use of system_unbound_wq with system_dfl_wq

2025-09-08T17:04:37+00:00

Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.

This lack of consistentcy cannot be addressed without refactoring the API.

system_unbound_wq should be the default workqueue so as not to enforce
locality constraints for random work whenever it's not required.

Adding system_dfl_wq to encourage its use when unbound work should be used.

queue_work() / queue_delayed_work() / mod_delayed_work() will now use the
new unbound wq: whether the user still use the old wq a warn will be
printed along with a wq redirect to the new one.

The old system_unbound_wq will be kept for a few release cycles.

Suggested-by: Tejun Heo 
Signed-off-by: Marco Crivellari 
Link: https://lore.kernel.org/r/20250905085309.94596-3-marco.crivellari@suse.com
Signed-off-by: Alexei Starovoitov

Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf

2024-11-13T20:52:51+00:00

Cross-merge bpf fixes after downstream PR.

In particular to bring the fix in
commit aa30eb3260b2 ("bpf: Force checkpoint when jmp history is too long").
The follow up verifier work depends on it.
And the fix in
commit 6801cf7890f2 ("selftests/bpf: Use -4095 as the bad address for bits iterator").
It's fixing instability of BPF CI on s390 arch.

No conflicts.

Adjacent changes in:
Auto-merging arch/Kconfig
Auto-merging kernel/bpf/helpers.c
Auto-merging kernel/bpf/memalloc.c
Auto-merging kernel/bpf/verifier.c
Auto-merging mm/slab_common.c

Signed-off-by: Alexei Starovoitov

bpf: Add bpf_mem_alloc_check_size() helper

2024-10-30T19:13:46+00:00

Introduce bpf_mem_alloc_check_size() to check whether the allocation
size exceeds the limitation for the kmalloc-equivalent allocator. The
upper limit for percpu allocation is LLIST_NODE_SZ bytes larger than
non-percpu allocation, so a percpu argument is added to the helper.

The helper will be used in the following patch to check whether the size
parameter passed to bpf_mem_alloc() is too big.

Signed-off-by: Hou Tao 
Link: https://lore.kernel.org/r/20241030100516.3633640-3-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov

bpf: Call kfree(obj) only once in free_one()

2024-10-04T00:47:35+00:00

A kfree() call is always used at the end of this function implementation.
Thus specify such a function call only once instead of duplicating it
in a previous if branch.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring 
Signed-off-by: Andrii Nakryiko 
Acked-by: Eduard Zingerman 
Link: https://lore.kernel.org/bpf/08987123-668c-40f3-a8ee-c3038d94f069@web.de
Signed-off-by: Alexei Starovoitov

bpf: Fix percpu address space issues

2024-08-22T15:01:50+00:00

In arraymap.c:

In bpf_array_map_seq_start() and bpf_array_map_seq_next()
cast return values from the __percpu address space to
the generic address space via uintptr_t [1].

Correct the declaration of pptr pointer in __bpf_array_map_seq_show()
to void __percpu * and cast the value from the generic address
space to the __percpu address space via uintptr_t [1].

In hashtab.c:

Assign the return value from bpf_mem_cache_alloc() to void pointer
and cast the value to void __percpu ** (void pointer to percpu void
pointer) before dereferencing.

In memalloc.c:

Explicitly declare __percpu variables.

Cast obj to void __percpu **.

In helpers.c:

Cast ptr in BPF_CALL_1 and BPF_CALL_2 from generic address space
to __percpu address space via const uintptr_t [1].

Found by GCC's named address space checks.

There were no changes in the resulting object files.

[1] https://sparse.docs.kernel.org/en/latest/annotations.html#address-space-name

Signed-off-by: Uros Bizjak 
Cc: Alexei Starovoitov 
Cc: Daniel Borkmann 
Cc: Andrii Nakryiko 
Cc: Martin KaFai Lau 
Cc: Eduard Zingerman 
Cc: Song Liu 
Cc: Yonghong Song 
Cc: John Fastabend 
Cc: KP Singh 
Cc: Stanislav Fomichev 
Cc: Hao Luo 
Cc: Jiri Olsa 
Acked-by: Eduard Zingerman 
Link: https://lore.kernel.org/r/20240811161414.56744-1-ubizjak@gmail.com
Signed-off-by: Alexei Starovoitov

mm: remove CONFIG_MEMCG_KMEM

2024-07-10T19:14:54+00:00

CONFIG_MEMCG_KMEM used to be a user-visible option for whether slab
tracking is enabled.  It has been default-enabled and equivalent to
CONFIG_MEMCG for almost a decade.  We've only grown more kernel memory
accounting sites since, and there is no imaginable cgroup usecase going
forward that wants to track user pages but not the multitude of
user-drivable kernel allocations.

Link: https://lkml.kernel.org/r/20240701153148.452230-1-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner 
Acked-by: Roman Gushchin 
Acked-by: Michal Hocko 
Acked-by: Shakeel Butt 
Acked-by: David Hildenbrand 
Cc: Muchun Song 
Signed-off-by: Andrew Morton

mm: memcg: add NULL check to obj_cgroup_put()

2024-04-26T03:55:43+00:00

9 out of 16 callers perform a NULL check before calling obj_cgroup_put(). 
Move the NULL check in the function, similar to mem_cgroup_put().  The
unlikely() NULL check in current_objcg_update() was left alone to avoid
dropping the unlikey() annotation as this a fast path.

Link: https://lkml.kernel.org/r/20240316015803.2777252-1-yosryahmed@google.com
Signed-off-by: Yosry Ahmed 
Acked-by: Johannes Weiner 
Acked-by: Roman Gushchin 
Cc: Michal Hocko 
Cc: Muchun Song 
Cc: Shakeel Butt 
Signed-off-by: Andrew Morton

bpf: Remove unnecessary cpu == 0 check in memalloc

2024-01-04T18:18:14+00:00

After merging the patch set [1] to reduce memory usage
for bpf_global_percpu_ma, Alexei found a redundant check (cpu == 0)
in function bpf_mem_alloc_percpu_unit_init() ([2]).
Indeed, the check is unnecessary since c->unit_size will
be all NULL or all non-NULL for all cpus before
for_each_possible_cpu() loop.
Removing the check makes code less confusing.

  [1] https://lore.kernel.org/all/20231222031729.1287957-1-yonghong.song@linux.dev/
  [2] https://lore.kernel.org/all/20231222031745.1289082-1-yonghong.song@linux.dev/

Signed-off-by: Yonghong Song 
Link: https://lore.kernel.org/r/20240104165744.702239-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov

bpf: Use smaller low/high marks for percpu allocation

2024-01-04T05:08:25+00:00

Currently, refill low/high marks are set with the assumption
of normal non-percpu memory allocation. For example, for
an allocation size 256, for non-percpu memory allocation,
low mark is 32 and high mark is 96, resulting in the
batch allocation of 48 elements and the allocated memory
will be 48 * 256 = 12KB for this particular cpu.
Assuming an 128-cpu system, the total memory consumption
across all cpus will be 12K * 128 = 1.5MB memory.

This might be okay for non-percpu allocation, but may not be
good for percpu allocation, which will consume 1.5MB * 128 = 192MB
memory in the worst case if every cpu has a chance of memory
allocation.

In practice, percpu allocation is very rare compared to
non-percpu allocation. So let us have smaller low/high marks
which can avoid unnecessary memory consumption.

Signed-off-by: Yonghong Song 
Acked-by: Hou Tao 
Link: https://lore.kernel.org/r/20231222031755.1289671-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov

bpf: Refill only one percpu element in memalloc

2024-01-04T05:08:25+00:00

Typically for percpu map element or data structure, once allocated,
most operations are lookup or in-place update. Deletion are really
rare. Currently, for percpu data strcture, 4 elements will be
refilled if the size is <= 256. Let us just do with one element
for percpu data. For example, for size 256 and 128 cpus, the
potential saving will be 3 * 256 * 128 * 128 = 12MB.

Acked-by: Hou Tao 
Signed-off-by: Yonghong Song 
Link: https://lore.kernel.org/r/20231222031750.1289290-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov