From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A0E1F372064; Wed, 1 Jul 2026 17:59:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782928756; cv=none; b=ZVwBm42MQ8pKTZmEyviUVrMN5gHZuwNPHxv8Sb1VqgH/ifcwGSdYoCrkjtzA5eAhPAFwIPkRZFVykCV6y8bSWCrwQB15fWPry/ZubX9Zg8iqGndAIN7AP4KwUO68ON5Tv/j1FsI0Wc/5+gcGCEuaixwxXzAh1gSfcoMYYNSg1P0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782928756; c=relaxed/simple; bh=wC6VbQ2fn5i1xjrwkl7o5SV+oivH8PPpQHIk/wSRVNo=; h=Date:To:From:Subject:Message-Id; b=MFdY61OVk3yfTO8nzm4TT3co1sXVg4ycvIEq2Nzad+Ri5u0ywfWsBuMyUQv4UoddCQc4tP+Qks5fDSn/59orP0c23TXY+ITjaapBfE8OiSe5vAj7EnV5s0edu+gKgyyvjbuPUis0ftO5oyXTcL63CCIB4Ke/wWCwXH+rt+MtHZ4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=tm6bJ6qE; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="tm6bJ6qE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1FAF41F000E9; Wed, 1 Jul 2026 17:59:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1782928755; bh=xHj/blAs7xxBqGS0oB3FC/vAwyh9Mivo3cKwhMDuLyw=; h=Date:To:From:Subject; b=tm6bJ6qEEBkbO2VP6LHZrLDft1fSI1MeZMpgSkwaiEQLipYmEoe9FHPYsDKc9DRmn LR8awQoJCqbxFYT0aVzCetI765fElbV41LclTHXj2s7RxNsVtysqUP2Oq8Q49jJqkE aZbtXELG3TKSurGZYMP3ifh1mkP8JGW/pH2gUSQU= Date: Wed, 01 Jul 2026 10:59:14 -0700 To: mm-commits@vger.kernel.org,ziy@nvidia.com,yang@os.amperecomputing.com,stable@vger.kernel.org,ryan.roberts@arm.com,npache@redhat.com,ljs@kernel.org,liam@infradead.org,lance.yang@linux.dev,dev.jain@arm.com,david@kernel.org,baolin.wang@linux.alibaba.com,baohua@kernel.org,riel@surriel.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-huge_memory-set-pg_has_hwpoisoned-only-after-new-folio-head-is-established.patch added to mm-hotfixes-unstable branch Message-Id: <20260701175915.1FAF41F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/huge_memory: set PG_has_hwpoisoned only after new folio head is established has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-huge_memory-set-pg_has_hwpoisoned-only-after-new-folio-head-is-established.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-huge_memory-set-pg_has_hwpoisoned-only-after-new-folio-head-is-established.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Rik van Riel Subject: mm/huge_memory: set PG_has_hwpoisoned only after new folio head is established Date: Wed, 1 Jul 2026 13:42:34 -0400 __split_folio_to_order() copies the hwpoison state onto each new sub-folio while splitting a folio to a non-zero order. It does so via if (handle_hwpoison && page_range_has_hwpoisoned(new_head, new_nr_pages)) folio_set_has_hwpoisoned(new_folio); *before* clear_compound_head(new_head)/prep_compound_page(new_head, ...) turns @new_head from a tail page into a proper folio head. PG_has_hwpoisoned is a FOLIO_SECOND_PAGE flag, so folio_set_has_hwpoisoned() resolves to folio_flags(folio, 1). With the new compound_info-based page-flags layout, folio_flags() asserts the page is not a tail: VM_BUG_ON_PGFLAGS(page->compound_info & 1, page); VM_BUG_ON_PGFLAGS(n > 0 && !test_bit(PG_head, &page->flags.f), page); At the current call site @new_head still has the tail marker (compound_info bit 0 set, PG_head clear), so on CONFIG_DEBUG_VM kernels this hits: kernel BUG at include/linux/page-flags.h:354 folio_flags+0x82 folio_set_has_hwpoisoned __split_folio_to_order __split_unmapped_folio __folio_split truncate_inode_partial_folio (shmem hole-punch / MADV_REMOVE) Reproduced by syzkaller: hwpoison-inject a few subpages of a large shmem folio, then MADV_REMOVE (fallocate punch hole) on the same range, which splits the partial folio to a non-zero order. memory_failure() tries to split the poisoned folio to order 0 first, but that split is best-effort; when it fails the folio is left large with PG_has_hwpoisoned set, the case fa5a06170036 added this hwpoison copying for. Move the folio_set_has_hwpoisoned() call to after clear_compound_head()/prep_compound_page(), where @new_folio is a real order-new_order head folio (handle_hwpoison implies new_order != 0, so a second page always exists). The flag still lands on the same struct page (page[1] of the new folio); only the ordering relative to compound-head setup changes, satisfying the FOLIO_SECOND_PAGE precondition. Link: https://lore.kernel.org/20260701174235.3173401-1-riel@surriel.com Fixes: fa5a06170036 ("mm/huge_memory: preserve PG_has_hwpoisoned if a folio is split to >0 order") Signed-off-by: Rik van Riel Assisted-by: Claude:claude-opus-4-8 Reviewed-by: Zi Yan Acked-by: David Hildenbrand (Arm) Tested-by: Lance Yang Cc: Baolin Wang Cc: Barry Song Cc: Dev Jain Cc: Lance Yang Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Nico Pache Cc: Ryan Roberts Cc: Yang Shi Cc: Signed-off-by: Andrew Morton --- mm/huge_memory.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) --- a/mm/huge_memory.c~mm-huge_memory-set-pg_has_hwpoisoned-only-after-new-folio-head-is-established +++ a/mm/huge_memory.c @@ -3587,10 +3587,6 @@ static void __split_folio_to_order(struc (1L << PG_dropbehind) | LRU_GEN_MASK | LRU_REFS_MASK)); - if (handle_hwpoison && - page_range_has_hwpoisoned(new_head, new_nr_pages)) - folio_set_has_hwpoisoned(new_folio); - new_folio->mapping = folio->mapping; new_folio->index = folio->index + i; @@ -3612,6 +3608,14 @@ static void __split_folio_to_order(struc folio_set_large_rmappable(new_folio); } + /* + * PG_has_hwpoisoned is on the 2nd page, so set it after + * the compound head is prepped. + */ + if (handle_hwpoison && + page_range_has_hwpoisoned(new_head, new_nr_pages)) + folio_set_has_hwpoisoned(new_folio); + if (folio_test_young(folio)) folio_set_young(new_folio); if (folio_test_idle(folio)) _ Patches currently in -mm which might be from riel@surriel.com are mm-huge_memory-set-pg_has_hwpoisoned-only-after-new-folio-head-is-established.patch