From: Michal Hocko <mhocko@suse.com>
To: Oscar Salvador <osalvador@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
David Hildenbrand <david@redhat.com>,
Muchun Song <songmuchun@bytedance.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/2] mm: Make alloc_contig_range handle free hugetlb pages
Date: Fri, 26 Feb 2021 10:51:24 +0100 [thread overview]
Message-ID: <YDjEnKex9bBmQv7C@dhcp22.suse.cz> (raw)
In-Reply-To: <20210226094507.GA3240@linux>
On Fri 26-02-21 10:45:14, Oscar Salvador wrote:
> On Fri, Feb 26, 2021 at 09:35:09AM +0100, Michal Hocko wrote:
> > I think it would be helpful to call out that specific case explicitly
> > here. I can see only one scenario (are there more?)
> > __free_huge_page() isolate_or_dissolve_huge_page
> > PageHuge() == T
> > alloc_and_dissolve_huge_page
> > alloc_fresh_huge_page()
> > spin_lock(hugetlb_lock)
> > // PageHuge() && !PageHugeFreed &&
> > // !PageCount()
> > spin_unlock(hugetlb_lock)
> > spin_lock(hugetlb_lock)
> > 1) update_and_free_page
> > PageHuge() == F
> > __free_pages()
> > 2) enqueue_huge_page
> > SetPageHugeFreed()
> > spin_unlock(&hugetlb_lock)
>
> I do not think there are more scenarios. The thing is to find a !page_count &&
> !PageHugeFreed.
> AFAICS, this can only happen after:
> put_page->put_page_test_zero->..->_free_huge_page gets called but __free_huge_page
> has not reached enqueue_huge_page yet (as you just described above)
>
> By calling out this case, you meant to describe it in the changelog?
Yes.
[...]
> > struct hstate *h;
> >
> > /*
> > * The page might have been dissloved from under our feet
> > * so make sure to carefully check the state under the lock.
> > * Return success on when racing as if we dissloved the page
> > * ourselves.
> > */
> > spin_lock(&hugetlb_lock);
> > if (PageHuge(page)) {
> > head = compound_head(page);
> > h = page_hstate(head);
> > } else {
> > spin_unlock(&hugetlb_lock);
> > return true;
> > }
> > spin_unlock(&hugetlb_lock);
>
> Yes, I find this less eyesore.
>
> I will fix it up in v4.
Thanks!
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-02-26 9:51 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-22 13:51 [PATCH v3 0/2] Make alloc_contig_range handle Hugetlb pages Oscar Salvador
2021-02-22 13:51 ` [PATCH v3 1/2] mm: Make alloc_contig_range handle free hugetlb pages Oscar Salvador
2021-02-25 20:03 ` Mike Kravetz
2021-02-26 9:48 ` Oscar Salvador
2021-02-26 8:35 ` Michal Hocko
2021-02-26 8:38 ` Michal Hocko
2021-02-26 9:25 ` David Hildenbrand
2021-02-26 9:47 ` Oscar Salvador
2021-02-26 9:45 ` Oscar Salvador
2021-02-26 9:51 ` Michal Hocko [this message]
2021-03-01 14:09 ` David Hildenbrand
2021-03-04 10:19 ` Oscar Salvador
2021-03-04 10:32 ` David Hildenbrand
2021-03-04 10:41 ` Oscar Salvador
2021-02-22 13:51 ` [PATCH v3 2/2] mm: Make alloc_contig_range handle in-use " Oscar Salvador
2021-02-25 23:05 ` Mike Kravetz
2021-02-26 8:46 ` Michal Hocko
2021-02-26 10:24 ` Oscar Salvador
2021-02-26 10:27 ` Oscar Salvador
2021-02-26 12:46 ` Michal Hocko
2021-02-28 13:43 ` Oscar Salvador
2021-03-05 17:30 ` David Hildenbrand
2021-03-01 12:43 ` [PATCH v3 0/2] Make alloc_contig_range handle Hugetlb pages David Hildenbrand
2021-03-01 12:57 ` Oscar Salvador
2021-03-01 12:59 ` David Hildenbrand
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