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SubjectRe: [RESEND v4 6/7] mm, slab_common: Initialize the same size of kmalloc_caches[]
On Mon, 16 Sep 2019, Pengfei Li wrote:

> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 2aed30deb071..e7903bd28b1f 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -1165,12 +1165,9 @@ void __init setup_kmalloc_cache_index_table(void)
> size_index[size_index_elem(i)] = 0;
> }
>
> -static void __init
> +static __always_inline void __init
> new_kmalloc_cache(int idx, enum kmalloc_cache_type type, slab_flags_t flags)
> {
> - if (type == KMALLOC_RECLAIM)
> - flags |= SLAB_RECLAIM_ACCOUNT;
> -
> kmalloc_caches[type][idx] = create_kmalloc_cache(
> kmalloc_info[idx].name[type],
> kmalloc_info[idx].size, flags, 0,
> @@ -1185,30 +1182,22 @@ new_kmalloc_cache(int idx, enum kmalloc_cache_type type, slab_flags_t flags)
> void __init create_kmalloc_caches(slab_flags_t flags)
> {
> int i;
> - enum kmalloc_cache_type type;
>
> - for (type = KMALLOC_NORMAL; type <= KMALLOC_RECLAIM; type++) {
> - for (i = 0; i < KMALLOC_CACHE_NUM; i++) {
> - if (!kmalloc_caches[type][i])
> - new_kmalloc_cache(i, type, flags);
> - }
> - }
> + for (i = 0; i < KMALLOC_CACHE_NUM; i++) {
> + if (!kmalloc_caches[KMALLOC_NORMAL][i])
> + new_kmalloc_cache(i, KMALLOC_NORMAL, flags);
>
> - /* Kmalloc array is now usable */
> - slab_state = UP;
> + new_kmalloc_cache(i, KMALLOC_RECLAIM,
> + flags | SLAB_RECLAIM_ACCOUNT);

This seems less robust, no? Previously we verified that the cache doesn't
exist before creating a new cache over top of it (for NORMAL and RECLAIM).
Now we presume that the RECLAIM cache never exists.

Can we just move a check to new_kmalloc_cache() to see if
kmalloc_caches[type][idx] already exists and, if so, just return? This
should be more robust and simplify create_kmalloc_caches() slightly more.

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