On Mon, Sep 21, 2026 at 12:58:17AM -0700, Kees Cook wrote: > A bucket set holds one row of caches, cloned from KMALLOC_NORMAL, and an > allocation of any other kmalloc type falls back to the general caches. > Extend this to handle __GFP_ACCOUNT, so that a single bucket user can > isolate either GFP_KERNEL or GFP_KERNEL_ACCOUNT allocations, as is > needed for skb data, where AF_UNIX uses: > > sk->sk_allocation = GFP_KERNEL_ACCOUNT; > > The coverage is selected at bucket creation time: > > b = kmem_buckets_create_types(name, flags, 0, INT_MAX, NULL, > BIT(KMEM_BUCKET_NORMAL) | > BIT(KMEM_BUCKET_CGROUP)); > > The prior kmem_buckets_create() function keeps its name and defaults > to only KMEM_BUCKET_NORMAL, leaving existing users as-is. > > Only the accounted type is offered. Nothing wants a reclaimable or > no-obj-ext row, and of the twelve places passing GFP_DMA to an skb > allocator, all rare hardware: b44, b43legacy, prestera and s390 ctcm. > > The choice is made at creation rather than every set getting every type > because the rows, when populated, are not free. Each holds 13 caches, and > a cache is a 1208 byte struct plus an unconditional per-cpu allocation, > a node struct, and an entry in /proc/slabinfo and under /sys/kernel/slab. > > KMEM_BUCKET_CGROUP collapses to KMEM_BUCKET_NORMAL without CONFIG_MEMCG, > exactly as KMALLOC_CGROUP does, so NR_KMEM_BUCKET_TYPES is 1 there and a > bucket set is the same single row it is today. Where the type is asked for > but the system is not creating caches of it (under "cgroup.memory=nokmem") > the row is aliased to the normal one, as new_kmalloc_cache() does for the > general caches, so those allocations stay isolated rather than falling > back to the general caches. > > Built and tests pass (and skip as expected) on ARCH=x86_64 defconfig > with GCC 16.2.0 in all combinations of CONFIG_SLAB_BUCKETS=y/n and > CONFIG_MEMCG=y/n/y+"cgroup.memory=nokmem". > > Assisted-by: LLM > Signed-off-by: Kees Cook <[email protected]> > --- > Cc: Vlastimil Babka <[email protected]> > Cc: Harry Yoo <[email protected]> > Cc: Andrew Morton <[email protected]> > Cc: Hao Li <[email protected]> > Cc: Christoph Lameter <[email protected]> > Cc: David Rientjes <[email protected]> > Cc: Roman Gushchin <[email protected]> > Cc: <[email protected]> > Cc: Pedro Falcato <[email protected]> > Cc: Kuniyuki Iwashima <[email protected]> > Cc: <[email protected]> > --- > include/linux/slab.h | 45 ++++++++++++- > mm/slab.h | 23 ++++++- > lib/tests/slub_kunit.c | 65 +++++++++++++++--- > mm/slab_common.c | 145 ++++++++++++++++++++++++++++++++--------- > 4 files changed, 235 insertions(+), 43 deletions(-) > > diff --git a/lib/tests/slub_kunit.c b/lib/tests/slub_kunit.c > index 823607e06248..58f800582170 100644 > --- a/lib/tests/slub_kunit.c > +++ b/lib/tests/slub_kunit.c > @@ -723,15 +723,63 @@ static void test_kmem_buckets_type_fallback(struct > kunit *test) > "expected a DMA cache, got %s", c->name); > } > > - /* Nor can one that has to be accounted. */ > - if (IS_ENABLED(CONFIG_MEMCG) && !mem_cgroup_kmem_disabled()) {
Didn't take a deeper look at this yet but this is causing an error: MODPOST Module.symvers ERROR: modpost: lib/tests/slub_kunit.ko: symbol 'mem_cgroup_kmem_disabled' undefined! make[3]: *** [../scripts/Makefile.modpost:147: Module.symvers] Error 1 make[2]: *** [/var/lib/jenkins/agent/workspace/harry-linux/ARCH/x86_64/COMPILER/clang/DEBUG/light/PREEMPT/lazy/src/Makefile:2179: modpost] Error 2 make[1]: *** [/var/lib/jenkins/agent/workspace/harry-linux/ARCH/x86_64/COMPILER/clang/DEBUG/light/PREEMPT/lazy/src/Makefile:248: __sub-make] Error 2 make[1]: Leaving directory '/var/lib/jenkins/agent/workspace/harry-linux/ARCH/x86_64/COMPILER/clang/DEBUG/light/PREEMPT/lazy/src/build' make: *** [Makefile:248: __sub-make] Error 2 Build step 'Execute shell' marked build as failure -- Cheers, Harry / Hyeonggon
