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slab: separate struct freelist_tid from kmem_cache_cpu

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In kmem_cache_cpu we currently have a union of the freelist+tid pair
with freelist_aba_t, relying implicitly on the type compatibility with the
freelist+counters pair used in freelist_aba_t.

To allow further changes to freelist_aba_t, we can instead define a
separate struct freelist_tid (instead of a typedef, per the coding
style) for kmem_cache_cpu, as that affects only a single helper
__update_cpu_freelist_fast().

We can add the resulting struct freelist_tid to kmem_cache_cpu as
unnamed field thanks to -fms-extensions, so that freelist and tid fields
can still be accessed directly.

Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
This commit is contained in:
Vlastimil Babka 2025-11-07 14:51:23 +01:00
parent c99f969d9a
commit b244358e9a
1 changed files with 15 additions and 11 deletions
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26
mm/slub.c
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@ -411,18 +411,22 @@ enum stat_item {
};
#ifndef CONFIG_SLUB_TINY
struct freelist_tid {
union {
struct {
void *freelist; /* Pointer to next available object */
unsigned long tid; /* Globally unique transaction id */
};
freelist_full_t freelist_tid;
};
};
/*
* When changing the layout, make sure freelist and tid are still compatible
* with this_cpu_cmpxchg_double() alignment requirements.
*/
struct kmem_cache_cpu {
union {
struct {
void **freelist; /* Pointer to next available object */
unsigned long tid; /* Globally unique transaction id */
};
freelist_aba_t freelist_tid;
};
struct freelist_tid;
struct slab *slab; /* The slab from which we are allocating */
#ifdef CONFIG_SLUB_CPU_PARTIAL
struct slab *partial; /* Partially allocated slabs */
@ -4367,11 +4371,11 @@ __update_cpu_freelist_fast(struct kmem_cache *s,
void *freelist_old, void *freelist_new,
unsigned long tid)
{
freelist_aba_t old = { .freelist = freelist_old, .counter = tid };
freelist_aba_t new = { .freelist = freelist_new, .counter = next_tid(tid) };
struct freelist_tid old = { .freelist = freelist_old, .tid = tid };
struct freelist_tid new = { .freelist = freelist_new, .tid = next_tid(tid) };
return this_cpu_try_cmpxchg_freelist(s->cpu_slab->freelist_tid.full,
&old.full, new.full);
return this_cpu_try_cmpxchg_freelist(s->cpu_slab->freelist_tid,
&old.freelist_tid, new.freelist_tid);
}
/*