slab: turn freelist_aba_t to a struct and fully define counters there

In struct slab we currently have freelist and counters pair, where
counters itself is a union of unsigned long with a sub-struct of
several smaller fields. Then for the usage with double cmpxchg we have
freelist_aba_t that duplicates the definition of the freelist+counters
with implicitly the same layout as the full definition in struct slab.

Thanks to -fms-extension we can now move the full counters definition to
freelist_aba_t (while changing it to struct freelist_counters as a
typedef is unnecessary and discouraged) and replace the relevant part in
struct slab to an unnamed reference to it.

The immediate benefit is the removal of duplication and no longer
relying on the same layout implicitly. It also allows further cleanups
thanks to having the full definition of counters in struct
freelist_counters.

Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

1 files changed, 5 insertions, 3 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 5f6408c9e0fd..8330e4f8b3b2 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -764,10 +764,12 @@ __update_freelist_fast(struct slab *slab,
 		      void *freelist_new, unsigned long counters_new)
 {
 #ifdef system_has_freelist_aba
-	freelist_aba_t old = { .freelist = freelist_old, .counter = counters_old };
-	freelist_aba_t new = { .freelist = freelist_new, .counter = counters_new };
+	struct freelist_counters old = { .freelist = freelist_old, .counters = counters_old };
+	struct freelist_counters new = { .freelist = freelist_new, .counters = counters_new };
 
-	return try_cmpxchg_freelist(&slab->freelist_counter.full, &old.full, new.full);
+	return try_cmpxchg_freelist(&slab->freelist_counters,
+				    &old.freelist_counters,
+				    new.freelist_counters);
 #else
 	return false;
 #endif