From: Vlastimil Babka <vbabka@xxxxxxx> Subject: mm, slub: make reclaim_account attribute read-only The attribute reflects the SLAB_RECLAIM_ACCOUNT cache flag. It's not clear why this attribute was writable in the first place, as it's tied to how the cache is used by its creator, it's not a user tunable. Furthermore: - it affects slab merging, but that's not being checked while toggled - if affects whether __GFP_RECLAIMABLE flag is used to allocate page, but the runtime toggle doesn't update allocflags - it affects cache_vmstat_idx() so runtime toggling might lead to incosistency of NR_SLAB_RECLAIMABLE and NR_SLAB_UNRECLAIMABLE Thus make it read-only. Link: http://lkml.kernel.org/r/20200610163135.17364-6-vbabka@xxxxxxx Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Acked-by: Roman Gushchin <guro@xxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Jann Horn <jannh@xxxxxxxxxx> Cc: Vijayanand Jitta <vjitta@xxxxxxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/slub.c | 11 +---------- 1 file changed, 1 insertion(+), 10 deletions(-) --- a/mm/slub.c~mm-slub-make-reclaim_account-attribute-read-only +++ a/mm/slub.c @@ -5207,16 +5207,7 @@ static ssize_t reclaim_account_show(stru { return sprintf(buf, "%d\n", !!(s->flags & SLAB_RECLAIM_ACCOUNT)); } - -static ssize_t reclaim_account_store(struct kmem_cache *s, - const char *buf, size_t length) -{ - s->flags &= ~SLAB_RECLAIM_ACCOUNT; - if (buf[0] == '1') - s->flags |= SLAB_RECLAIM_ACCOUNT; - return length; -} -SLAB_ATTR(reclaim_account); +SLAB_ATTR_RO(reclaim_account); static ssize_t hwcache_align_show(struct kmem_cache *s, char *buf) { _
