From: Oscar Salvador <osalvador@suse.de>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Roman Gushchin <guro@fb.com>, Michal Hocko <mhocko@suse.com>,
Shakeel Butt <shakeelb@google.com>,
David Hildenbrand <david@redhat.com>,
Muchun Song <songmuchun@bytedance.com>,
David Rientjes <rientjes@google.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Peter Zijlstra <peterz@infradead.org>,
Matthew Wilcox <willy@infradead.org>,
HORIGUCHI NAOYA <naoya.horiguchi@nec.com>,
"Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
Waiman Long <longman@redhat.com>, Peter Xu <peterx@redhat.com>,
Mina Almasry <almasrymina@google.com>,
Hillf Danton <hdanton@sina.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 1/8] mm: cma: introduce cma_release_nowait()
Date: Thu, 25 Mar 2021 10:39:24 +0100 [thread overview]
Message-ID: <YFxaTO/17EitJ6eI@localhost.localdomain> (raw)
In-Reply-To: <20210325002835.216118-2-mike.kravetz@oracle.com>
On Wed, Mar 24, 2021 at 05:28:28PM -0700, Mike Kravetz wrote:
> +struct cma_clear_bitmap_work {
> + struct work_struct work;
> + struct cma *cma;
> + unsigned long pfn;
> + unsigned int count;
> +};
> +
> struct cma cma_areas[MAX_CMA_AREAS];
> unsigned cma_area_count;
>
> +struct workqueue_struct *cma_release_wq;
should this be static?
> +
> phys_addr_t cma_get_base(const struct cma *cma)
> {
> return PFN_PHYS(cma->base_pfn);
> @@ -146,6 +155,10 @@ static int __init cma_init_reserved_areas(void)
> for (i = 0; i < cma_area_count; i++)
> cma_activate_area(&cma_areas[i]);
>
> + cma_release_wq = create_workqueue("cma_release");
> + if (!cma_release_wq)
> + return -ENOMEM;
> +
I did not check the code that goes through the initcalls and maybe we
cannot really have this scneario, but what happens if we return -ENOMEM?
Because I can see that later in cma_release_nowait() you mess with
cma_release_wq. Can it be that at that stage cma_release_wq == NULL? due
to -ENOMEM, or are we guaranteed to never reach that point?
Also, should the cma_release_wq go before the cma_activate_area?
> +bool cma_release_nowait(struct cma *cma, const struct page *pages,
> + unsigned int count)
> +{
> + struct cma_clear_bitmap_work *work;
> + unsigned long pfn;
> +
> + if (!cma || !pages)
> + return false;
> +
> + pr_debug("%s(page %p)\n", __func__, (void *)pages);
cma_release() seems to have:
pr_debug("%s(page %p, count %u)\n", __func__, (void *)pages, count);
any reason to not have the same here?
> +
> + pfn = page_to_pfn(pages);
> +
> + if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
> + return false;
> +
> + VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
> +
> + /*
> + * Set CMA_DELAYED_RELEASE flag: subsequent cma_alloc()'s
> + * will wait for the async part of cma_release_nowait() to
> + * finish.
> + */
> + if (unlikely(!test_bit(CMA_DELAYED_RELEASE, &cma->flags)))
> + set_bit(CMA_DELAYED_RELEASE, &cma->flags);
It seems this cannot really happen? This is the only place we set the
bit, right?
Why not set the bit unconditionally? Against what this is guarding us?
> +
> + /*
> + * To make cma_release_nowait() non-blocking, cma bitmap is cleared
> + * from a work context (see cma_clear_bitmap_fn()). The first page
> + * in the cma allocation is used to store the work structure,
> + * so it's released after the cma bitmap clearance. Other pages
> + * are released immediately as previously.
> + */
> + if (count > 1)
> + free_contig_range(pfn + 1, count - 1);
> +
> + work = (struct cma_clear_bitmap_work *)page_to_virt(pages);
> + INIT_WORK(&work->work, cma_clear_bitmap_fn);
> + work->cma = cma;
> + work->pfn = pfn;
> + work->count = count;
> + queue_work(cma_release_wq, &work->work);
As I said above, can cma_release_wq be NULL if we had -ENOMEM before?
--
Oscar Salvador
SUSE L3
next prev parent reply other threads:[~2021-03-25 9:39 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-25 0:28 [PATCH 0/8] make hugetlb put_page safe for all calling contexts Mike Kravetz
2021-03-25 0:28 ` [PATCH 1/8] mm: cma: introduce cma_release_nowait() Mike Kravetz
2021-03-25 9:39 ` Oscar Salvador [this message]
2021-03-25 9:45 ` Michal Hocko
2021-03-25 9:54 ` Oscar Salvador
2021-03-25 10:10 ` Michal Hocko
2021-03-25 10:11 ` Michal Hocko
2021-03-25 10:13 ` David Hildenbrand
2021-03-25 10:17 ` Oscar Salvador
2021-03-25 10:24 ` Michal Hocko
2021-03-25 9:56 ` David Hildenbrand
2021-03-25 10:22 ` Michal Hocko
2021-03-25 16:56 ` Mike Kravetz
2021-03-25 17:15 ` David Hildenbrand
2021-03-25 20:12 ` Minchan Kim
2021-03-25 23:19 ` Roman Gushchin
2021-03-25 23:49 ` Mike Kravetz
2021-03-26 21:32 ` Mike Kravetz
2021-03-29 7:46 ` Michal Hocko
2021-03-29 22:27 ` Mike Kravetz
2021-03-25 0:28 ` [PATCH 2/8] mm: hugetlb: don't drop hugetlb_lock around cma_release() call Mike Kravetz
2021-03-25 0:28 ` [PATCH 3/8] hugetlb: add per-hstate mutex to synchronize user adjustments Mike Kravetz
2021-03-25 10:47 ` Michal Hocko
2021-03-25 12:29 ` Oscar Salvador
2021-03-26 1:52 ` Miaohe Lin
2021-03-25 0:28 ` [PATCH 4/8] hugetlb: create remove_hugetlb_page() to separate functionality Mike Kravetz
2021-03-25 10:49 ` Michal Hocko
2021-03-26 2:10 ` Miaohe Lin
2021-03-26 19:57 ` Mike Kravetz
2021-03-27 1:40 ` Miaohe Lin
2021-03-27 6:36 ` [External] " Muchun Song
2021-03-25 0:28 ` [PATCH 5/8] hugetlb: call update_and_free_page without hugetlb_lock Mike Kravetz
2021-03-25 10:55 ` Michal Hocko
2021-03-25 17:12 ` Mike Kravetz
2021-03-25 19:39 ` Michal Hocko
2021-03-25 20:33 ` Mike Kravetz
2021-03-27 6:54 ` [External] " Muchun Song
2021-03-28 21:40 ` Mike Kravetz
2021-03-25 0:28 ` [PATCH 6/8] hugetlb: change free_pool_huge_page to remove_pool_huge_page Mike Kravetz
2021-03-25 11:06 ` Michal Hocko
2021-03-25 17:29 ` Mike Kravetz
2021-03-25 0:28 ` [PATCH 7/8] hugetlb: make free_huge_page irq safe Mike Kravetz
2021-03-25 11:21 ` Michal Hocko
2021-03-25 17:32 ` Mike Kravetz
2021-03-27 7:06 ` [External] " Muchun Song
2021-03-29 7:49 ` Michal Hocko
2021-03-29 22:44 ` Mike Kravetz
2021-03-25 0:28 ` [PATCH 8/8] hugetlb: add lockdep_assert_held() calls for hugetlb_lock Mike Kravetz
2021-03-25 11:22 ` Michal Hocko
2021-03-26 2:12 ` Miaohe Lin
2021-03-27 8:14 ` [External] " Muchun Song
2021-03-26 1:42 ` [PATCH 0/8] make hugetlb put_page safe for all calling contexts Miaohe Lin
2021-03-26 20:00 ` Mike Kravetz
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