diff options
| author | Vlastimil Babka <vbabka@suse.cz> | 2022-08-26 11:09:11 +0200 |
|---|---|---|
| committer | Vlastimil Babka <vbabka@suse.cz> | 2022-10-24 16:49:55 +0200 |
| commit | bc29d5bd2ba977716e57572030290d6547ff3f6d (patch) | |
| tree | 45ddfd8c7def630b94a8c880c1970babe657395d /mm/slub.c | |
| parent | 247f34f7b80357943234f93f247a1ae6b6c3a740 (diff) | |
mm/slub: perform free consistency checks before call_rcu
For SLAB_TYPESAFE_BY_RCU caches we use call_rcu to perform empty slab
freeing. The rcu callback rcu_free_slab() calls __free_slab() that
currently includes checking the slab consistency for caches with
SLAB_CONSISTENCY_CHECKS flags. This check needs the slab->objects field
to be intact.
Because in the next patch we want to allow rcu_head in struct slab to
become larger in debug configurations and thus potentially overwrite
more fields through a union than slab_list, we want to limit the fields
used in rcu_free_slab(). Thus move the consistency checks to
free_slab() before call_rcu(). This can be done safely even for
SLAB_TYPESAFE_BY_RCU caches where accesses to the objects can still
occur after freeing them.
As a result, only the slab->slab_cache field has to be physically
separate from rcu_head for the freeing callback to work. We also save
some cycles in the rcu callback for caches with consistency checks
enabled.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Diffstat (limited to 'mm/slub.c')
| -rw-r--r-- | mm/slub.c | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/mm/slub.c b/mm/slub.c index 157527d7101b..99ba865afc4a 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1999,14 +1999,6 @@ static void __free_slab(struct kmem_cache *s, struct slab *slab) int order = folio_order(folio); int pages = 1 << order; - if (kmem_cache_debug_flags(s, SLAB_CONSISTENCY_CHECKS)) { - void *p; - - slab_pad_check(s, slab); - for_each_object(p, s, slab_address(slab), slab->objects) - check_object(s, slab, p, SLUB_RED_INACTIVE); - } - __slab_clear_pfmemalloc(slab); __folio_clear_slab(folio); folio->mapping = NULL; @@ -2025,9 +2017,17 @@ static void rcu_free_slab(struct rcu_head *h) static void free_slab(struct kmem_cache *s, struct slab *slab) { - if (unlikely(s->flags & SLAB_TYPESAFE_BY_RCU)) { + if (kmem_cache_debug_flags(s, SLAB_CONSISTENCY_CHECKS)) { + void *p; + + slab_pad_check(s, slab); + for_each_object(p, s, slab_address(slab), slab->objects) + check_object(s, slab, p, SLUB_RED_INACTIVE); + } + + if (unlikely(s->flags & SLAB_TYPESAFE_BY_RCU)) call_rcu(&slab->rcu_head, rcu_free_slab); - } else + else __free_slab(s, slab); } |