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bh=Jk6Zy4/AUwBU7wb2nBxfNQOQXPbgWFB6fRcPP6ab5vU=; b=wMTYom4AnX077uvX3q64GYuD5atZcOXWMh8igLbRr/7omMTB5hFdxHQyWhJuuOs19bvC6f pDzrTlcTfq7UnNCg== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id C7E6113927; Tue, 15 Apr 2025 05:47:15 +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 kc+5LePy/We2EwAAD6G6ig (envelope-from ); Tue, 15 Apr 2025 05:47:15 +0000 From: Oscar Salvador To: Andrew Morton Cc: Muchun Song , David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vlastimil Babka , Matthew Wilcox , Oscar Salvador Subject: [PATCH] mm, hugetlb: Reset mapping to TAIL_MAPPING before restoring vmemmap Date: Tue, 15 Apr 2025 07:47:05 +0200 Message-ID: <20250415054705.370412-1-osalvador@suse.de> X-Mailer: git-send-email 2.49.0 MIME-Version: 1.0 X-Rspamd-Queue-Id: 2704140004 X-Rspamd-Server: rspam05 X-Rspam-User: X-Stat-Signature: 7obgfwj9n3rmnih6qcxxbhgcsyw4bsix X-HE-Tag: 1744696037-381378 X-HE-Meta: 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 EJa1cakn 9FfJDCLHfKnapF4EJdwbttJRKRT98ycEOWviVBLK7JaqjN3g3iV6qeOunv/ai8xkT0kEDNL8cP3V1e0ZXpvFx2s2A7nBuSCwzGmFIwHPK2+Y1RdF+Bllfs5+6VB5V+TU9HOIRrWRYCuU8pfi3FYR7dkkiWvIQePYhx2KiMvZxoEAp6UGyqObUSkVSwL4ke88IQia8lBlG81j+sY7xD6hFSVRiuPuPsEdI+ujrAWWy0H1XfJRYjBrE2U3rK1S3DQWR1qhBRArvSM6++MmbZycte49O0Q5wWqmLtlmKfjIG5Zw4rFwkqVte9249dg== 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: commit 4eeec8c89a0c ("mm: move hugetlb specific things in folio to page[3]") shifted hugetlb specific stuff, and now mapping overlaps _hugetlb_cgroup field. _hugetlb_cgroup is set to NULL when preparing the hugetlb page in init_new_hugetlb_folio(). For a better picture, this is page->mapping before and after the comming for the first three tail pages: before: page: fffff51a44358040 0000000000000000 page: fffff51a44358080 0000000000000000 page: fffff51a443580c0 dead000000000400 after: page: fffff1f0042b0040 0000000000000000 page: fffff1f0042b0080 fffff1f0042b0090 page: fffff1f0042b00c0 0000000000000000 Tail#2 has fffff1f0042b0090 because of the _deferred_list initialization, which was also shifted, but that is not a problem. For HVO, upon restoring that gets copied in some tail pages (reset_struct_pages) and so those tail pages will not have TAIL_MAPPING set and the check in free_tail_page_prepare() will fail: kernel: BUG: Bad page state in process kworker/0:3 pfn:10ac40 kernel: page does not match folio kernel: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10ac40 kernel: flags: 0x17ffffc0000000(node=0|zone=2|lastcpupid=0x1fffff) kernel: raw: 0017ffffc0000000 fffff1f0042b0000 0000000000000000 0000000000000000 kernel: raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 kernel: page dumped because: corrupted mapping in tail page Reset _hugetlb_cgroup to TAIL_MAPPING before restoring so tail pages have the right value. Signed-off-by: Oscar Salvador --- Hi guys, Although I can no longer reproduce the issue with this patch, I'm not entirely sure this is the right way to fix the problem, so I'm open to suggestions. --- mm/hugetlb_vmemmap.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c index 9a99dfa3c495..3d763182c834 100644 --- a/mm/hugetlb_vmemmap.c +++ b/mm/hugetlb_vmemmap.c @@ -498,6 +498,12 @@ static int __hugetlb_vmemmap_restore_folio(const struct hstate *h, */ int hugetlb_vmemmap_restore_folio(const struct hstate *h, struct folio *folio) { + /* + * Before restoring vmemmap, make sure to reset mapping to TAIL_MAPPING, + * so tail pages that were reset will have the right thing after being + * restored, and the checks in free_tail_page_prepare() will pass. + */ + set_hugetlb_cgroup(folio, TAIL_MAPPING); return __hugetlb_vmemmap_restore_folio(h, folio, VMEMMAP_SYNCHRONIZE_RCU); }