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Fri, 28 Mar 2025 13:23:21 +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 pV8RO8mi5meeYQAAD6G6ig (envelope-from ); Fri, 28 Mar 2025 13:23:21 +0000 Date: Fri, 28 Mar 2025 14:23:20 +0100 From: Oscar Salvador To: Jinjiang Tu Cc: david@redhat.com, akpm@linux-foundation.org, nao.horiguchi@gmail.com, zi.yan@cs.rutgers.edu, linux-mm@kvack.org, wangkefeng.wang@huawei.com, sunnanyong@huawei.com Subject: Re: [PATCH] mm/memory_hotplug: fix call folio_test_large with tail page in do_migrate_range Message-ID: References: <20250324131750.1551884-1-tujinjiang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250324131750.1551884-1-tujinjiang@huawei.com> X-Rspamd-Action: no action X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 1B54D20018 X-Stat-Signature: du8i9cui5e83obhysitryrsq3ajh8ts1 X-Rspam-User: X-HE-Tag: 1743168203-408615 X-HE-Meta: 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 aXSZQL7Z YmZSVxzXJNMzRslEmFtMADEZXYIs4UmDRN3wuIHVrJCwq1bMru1TIqFtYv36+jA+Fd0QjGPgYKJDF5uSrZtrR5Tos/mVZToypSTPYmPDF2gsqPOwzKaO9WMuOp57gYdIHM616YRbUhss8jsMqPKWeRzaiZSV+Vdm/CsjzkQFcsSnW79c0ovY5kjfs1QNXDAiP+L6cm+B5neyUlXlDAWTzGMkGqixTVyXmGF5x82nNSzN3Hq7Vr3h6XVY6pOetX0jfCuVC83lb/I9amM0OqzjW4glKFNH3szsUbUNKE+Eeg5XoeshpqKvNjUzEVmjYaEEBSnHs4DTA7GsoaW6GqE76TiEOGgg5XYcYCuWLScEEfaR+EIoO6COaa9I9WHCfheNeEjtwTOCJPipmhpmqLQggHVhTAg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000701, 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 Mon, Mar 24, 2025 at 09:17:50PM +0800, Jinjiang Tu wrote: > We triggered the below BUG: > ... > When allocating a hugetlb folio, between the folio is taken from buddy > and prep_compound_page() is called, start_isolate_page_range() and > do_migrate_range() is called. When do_migrate_range() scans the head page > of the hugetlb folio, the compound_head field isn't set, so scans the > tail page next. And at this time, the compound_head field of tail page is > set, folio_test_large() is called by tail page, thus triggers VM_BUG_ON(). > > To fix it, get folio refcount before calling folio_test_large(). > > Fixes: 8135d8926c08 ("mm: memory_hotplug: memory hotremove supports thp migration") > Signed-off-by: Jinjiang Tu Acked-by: Oscar Salvador As David mentions, I think too that this was introduced in commit: b62b51d2d1593e65 ("mm: memory_hotplug: remove head variable in do_migrate_range()") -- Oscar Salvador SUSE Labs