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Thu, 18 Apr 2024 12:41:24 +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 iKYuIvQUIWYyfQAAD6G6ig (envelope-from ); Thu, 18 Apr 2024 12:41:24 +0000 Date: Thu, 18 Apr 2024 14:41:23 +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: X-Rspamd-Action: no action X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: CF4E44000A X-Rspam-User: X-Stat-Signature: u65dkhwtreuztba1o8eykj8b41a38nfw X-HE-Tag: 1713444086-608047 X-HE-Meta: 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 +NKiPo5v 4VLRLxTeeR7nx6KD1+tgJOJHqeqLo73Tj4F4A061/KDZCGkrEFHDfwKRLbcODe1zbTgd9PUTGMB+y6wWCdOzAWmZomeycUkYtIHenQkPdmk/iFKHJY57gEfWulqetmT8MahMnv8J0pBX8nA5ofYsQfKuORQQNM1G61/250ccbkh+48HfMUm6sLXfZ4aiG0tTmdeGmwqwg3k17CMd5crQ8K2fpX+xSteub6bbVokBX5rLCzhXYwbeYpDO2yPMjxBpFH+oV 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 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. -- Oscar Salvador SUSE Labs