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Fri, 19 Apr 2024 10:00:29 +0800 Subject: Re: [PATCH 1/2] mm/hugetlb: fix DEBUG_LOCKS_WARN_ON(1) when dissolve_free_hugetlb_folio() To: Oscar Salvador CC: , , , , , , References: <20240418022000.3524229-1-linmiaohe@huawei.com> <20240418022000.3524229-2-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: <32c97464-fcc2-18a2-5b72-8602cffa895a@huawei.com> Date: Fri, 19 Apr 2024 10:00:29 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.173.135.154] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500002.china.huawei.com (7.192.104.244) X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 8945C40005 X-Rspam-User: X-Stat-Signature: c4kcbxjxznqhq5b3mx71yhc7mfek5o41 X-HE-Tag: 1713492036-925904 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2024/4/18 20:41, Oscar Salvador wrote: > On Thu, Apr 18, 2024 at 04:00:42PM +0800, Miaohe Lin wrote: >> On 2024/4/18 12:05, Oscar Salvador wrote: >>> On Thu, Apr 18, 2024 at 10:19:59AM +0800, Miaohe Lin wrote: >>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >>>> index 26ab9dfc7d63..1da9a14a5513 100644 >>>> --- a/mm/hugetlb.c >>>> +++ b/mm/hugetlb.c >>>> @@ -1788,7 +1788,8 @@ static void __update_and_free_hugetlb_folio(struct hstate *h, >>>> destroy_compound_gigantic_folio(folio, huge_page_order(h)); >>>> free_gigantic_folio(folio, huge_page_order(h)); >>>> } else { >>>> - INIT_LIST_HEAD(&folio->_deferred_list); >>>> + if (!folio_test_hugetlb(folio)) >>>> + INIT_LIST_HEAD(&folio->_deferred_list); >>> >>> Ok, it took me a bit to figure this out. >>> >>> So we basically init __deferred_list when we know that >>> folio_put will not end up calling free_huge_folio >>> because a previous call to remove_hugetlb_folio has already cleared the >>> bit. >>> >>> Maybe Matthew thought that any folio ending here would not end up in >>> free_huge_folio (which is the one fiddling subpool). >>> >>> I mean, fix looks good because if hugetlb flag is cleared, >>> destroy_large_folio will go straight to free_the_page, but the >>> whole thing is a bit subtle. >> >> AFAICS, this is the most straightforward way to fix the issue. Do you have any suggestions >> on how to fix this in a more graceful way? > > Not from the top of my head. > Anyway, I have been thinking for a while that this code needs some love, > so I will check how this can be untangled. That would be really nice. Thanks Oscar. . > >