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Thu, 18 Apr 2024 04:05:19 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id U7gVHv+bIGbZSgAAD6G6ig (envelope-from ); Thu, 18 Apr 2024 04:05:19 +0000 Date: Thu, 18 Apr 2024 06:05:18 +0200 From: Oscar Salvador To: Miaohe Lin Cc: akpm@linux-foundation.org, muchun.song@linux.dev, david@redhat.com, vbabka@suse.cz, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm/hugetlb: fix DEBUG_LOCKS_WARN_ON(1) when dissolve_free_hugetlb_folio() Message-ID: References: <20240418022000.3524229-1-linmiaohe@huawei.com> <20240418022000.3524229-2-linmiaohe@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240418022000.3524229-2-linmiaohe@huawei.com> X-Rspamd-Action: no action X-Stat-Signature: nhw8swt96wmqh4u8onzpj8phuu79u6at X-Rspamd-Queue-Id: BF9CBA0002 X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1713413121-717755 X-HE-Meta: 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 4bFxJdB3 W4GUMSMI/0IlZbIQxjgoLbXmyMr7TzbOrEw9ZvXgfeqlc44QSaHV+fFMhNlExnuz6EzDujCNGpwM+xhFDdUqGGuYIl2zoLqO98pRWSAlk1KagHDgVItguXYODmA9MF1ImbdtdhoL+1ODUYC2xl+D7J9zbrmiPwoifRyct+ROuNgmIlLm8EL7skHpS+ymgbjhmP/fIYXN7daHQmsijnheKhZOIUB0LShYFKj0o1x0laiyAc/ct1SDf/M3fc28qjTotfC8s 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 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. And if we decide to go with this, I think we are going to need a comment in there explaining what is going on like "only init _deferred_list if free_huge_folio cannot be call". -- Oscar Salvador SUSE Labs