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b=IL+MewD2vccgFyCl83IBplNj7nZAp3OmlK7ap4lcO9Suh408qb8kBRDwhD5hR77RJ +lJioiWjhFZV9M3k2xrBWD+cNXir5DaHSn8KUwDQI59e1wlH4qjQ8fWgHTPemittIP D2OILvVd+b33cfmj6H9JM+GrqAHFwbwb1brsJvFD3FtCexu+X6CneRzKUu4lNqGbzf gzQd7SF319Io0kg6PDxH01y/r/LU5PcgGarQC5XC2XMP0izIOex/YiQbIzBPDr+o+f fkCvr7RRA9+2uTEs3gcNgqi1tgO9VkXfDc3G7ePKncGs7Tfd7ynmcuFGu/Igw95F3R qSzXObEyFSLKQ== From: Mike Rapoport To: Andrew Morton Cc: Alexander Graf , Mike Rapoport , Pasha Tatashin , Pratyush Yadav , kexec@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 2/2] kho: fix restoring of contiguous ranges of order-0 pages Date: Tue, 25 Nov 2025 13:09:17 +0200 Message-ID: <20251125110917.843744-3-rppt@kernel.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20251125110917.843744-1-rppt@kernel.org> References: <20251125110917.843744-1-rppt@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspam-User: X-Rspamd-Queue-Id: 32EC6A0003 X-Stat-Signature: 5nreseh7wz7x3x6pydqz5tfk9i7pkfuc X-HE-Tag: 1764068969-541136 X-HE-Meta: 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 pDdA74k+ Ef1vLkWRv6ghb8223CT8JSlyIr35cIZRj/PoFhzcC3TwiCEaEhZSIFLoim9w6GEILNhB2x2649wp/oJXBftuCdXQd2gpp2eTNX/V4GFcNMMvTWD5/Bg5QRRl5/0KgMK+Ej6dBFazpPX6TiqvUf2yTNXf9KKjpyqzeLQAzR9eBF+gIMgttwUOTHsCNeQPExRXJgRgSuVO+VVDgL4frjV3CxvOnpTPWdf2z2w5cp9H/IK6Cyk8= 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: From: "Mike Rapoport (Microsoft)" When contiguous ranges of order-0 pages are restored, kho_restore_page() calls prep_compound_page() with the first page in the range and order as parameters and then kho_restore_pages() calls split_page() to make sure all pages in the range are order-0. However, since split_page() is not intended to split compound pages and with VM_DEBUG enabled it will trigger a VM_BUG_ON_PAGE(). Update kho_restore_page() so that it will use prep_compound_page() when it restores a folio and make sure it properly sets page count for both large folios and ranges of order-0 pages. Reported-by: Pratyush Yadav Fixes: a667300bd53f ("kho: add support for preserving vmalloc allocations") Signed-off-by: Mike Rapoport (Microsoft) --- kernel/liveupdate/kexec_handover.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c index e64ee87fa62a..61d17ed1f423 100644 --- a/kernel/liveupdate/kexec_handover.c +++ b/kernel/liveupdate/kexec_handover.c @@ -219,11 +219,11 @@ static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn, return 0; } -static struct page *kho_restore_page(phys_addr_t phys) +static struct page *kho_restore_page(phys_addr_t phys, bool is_folio) { struct page *page = pfn_to_online_page(PHYS_PFN(phys)); + unsigned int nr_pages, ref_cnt; union kho_page_info info; - unsigned int nr_pages; if (!page) return NULL; @@ -243,11 +243,16 @@ static struct page *kho_restore_page(phys_addr_t phys) /* Head page gets refcount of 1. */ set_page_count(page, 1); - /* For higher order folios, tail pages get a page count of zero. */ + /* + * For higher order folios, tail pages get a page count of zero. + * For physically contiguous order-0 pages every pages gets a page + * count of 1 + */ + ref_cnt = is_folio ? 0 : 1; for (unsigned int i = 1; i < nr_pages; i++) - set_page_count(page + i, 0); + set_page_count(page + i, ref_cnt); - if (info.order > 0) + if (is_folio && info.order) prep_compound_page(page, info.order); adjust_managed_page_count(page, nr_pages); @@ -262,7 +267,7 @@ static struct page *kho_restore_page(phys_addr_t phys) */ struct folio *kho_restore_folio(phys_addr_t phys) { - struct page *page = kho_restore_page(phys); + struct page *page = kho_restore_page(phys, true); return page ? page_folio(page) : NULL; } @@ -287,11 +292,10 @@ struct page *kho_restore_pages(phys_addr_t phys, unsigned int nr_pages) while (pfn < end_pfn) { const unsigned int order = min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn)); - struct page *page = kho_restore_page(PFN_PHYS(pfn)); + struct page *page = kho_restore_page(PFN_PHYS(pfn), false); if (!page) return NULL; - split_page(page, order); pfn += 1 << order; } -- 2.50.1