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    SubjectRe: [PATCH 1/6] mm: kfence: simplify kfence pool initialization
    On Tue, 28 Mar 2023 at 11:58, Muchun Song <songmuchun@bytedance.com> wrote:
    >
    > There are three similar loops to initialize kfence pool, we could merge
    > all of them into one loop to simplify the code and make code more
    > efficient.
    >
    > Signed-off-by: Muchun Song <songmuchun@bytedance.com>

    Reviewed-by: Marco Elver <elver@google.com>

    > ---
    > mm/kfence/core.c | 47 ++++++-----------------------------------------
    > 1 file changed, 6 insertions(+), 41 deletions(-)
    >
    > diff --git a/mm/kfence/core.c b/mm/kfence/core.c
    > index 7d01a2c76e80..de62a84d4830 100644
    > --- a/mm/kfence/core.c
    > +++ b/mm/kfence/core.c
    > @@ -539,35 +539,10 @@ static void rcu_guarded_free(struct rcu_head *h)
    > static unsigned long kfence_init_pool(void)
    > {
    > unsigned long addr = (unsigned long)__kfence_pool;
    > - struct page *pages;
    > int i;
    >
    > if (!arch_kfence_init_pool())
    > return addr;
    > -
    > - pages = virt_to_page(__kfence_pool);
    > -
    > - /*
    > - * Set up object pages: they must have PG_slab set, to avoid freeing
    > - * these as real pages.
    > - *
    > - * We also want to avoid inserting kfence_free() in the kfree()
    > - * fast-path in SLUB, and therefore need to ensure kfree() correctly
    > - * enters __slab_free() slow-path.
    > - */
    > - for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
    > - struct slab *slab = page_slab(nth_page(pages, i));
    > -
    > - if (!i || (i % 2))
    > - continue;
    > -
    > - __folio_set_slab(slab_folio(slab));
    > -#ifdef CONFIG_MEMCG
    > - slab->memcg_data = (unsigned long)&kfence_metadata[i / 2 - 1].objcg |
    > - MEMCG_DATA_OBJCGS;
    > -#endif
    > - }
    > -
    > /*
    > * Protect the first 2 pages. The first page is mostly unnecessary, and
    > * merely serves as an extended guard page. However, adding one
    > @@ -581,8 +556,9 @@ static unsigned long kfence_init_pool(void)
    > addr += PAGE_SIZE;
    > }
    >
    > - for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) {
    > + for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++, addr += 2 * PAGE_SIZE) {
    > struct kfence_metadata *meta = &kfence_metadata[i];
    > + struct slab *slab = page_slab(virt_to_page(addr));
    >
    > /* Initialize metadata. */
    > INIT_LIST_HEAD(&meta->list);
    > @@ -593,26 +569,15 @@ static unsigned long kfence_init_pool(void)
    >
    > /* Protect the right redzone. */
    > if (unlikely(!kfence_protect(addr + PAGE_SIZE)))
    > - goto reset_slab;
    > -
    > - addr += 2 * PAGE_SIZE;
    > - }
    > -
    > - return 0;
    > -
    > -reset_slab:
    > - for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
    > - struct slab *slab = page_slab(nth_page(pages, i));
    > + return addr;
    >
    > - if (!i || (i % 2))
    > - continue;
    > + __folio_set_slab(slab_folio(slab));
    > #ifdef CONFIG_MEMCG
    > - slab->memcg_data = 0;
    > + slab->memcg_data = (unsigned long)&meta->objcg | MEMCG_DATA_OBJCGS;
    > #endif
    > - __folio_clear_slab(slab_folio(slab));
    > }
    >
    > - return addr;
    > + return 0;
    > }
    >
    > static bool __init kfence_init_pool_early(void)
    > --
    > 2.11.0
    >

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