diff options
| author | Mike Rapoport (Microsoft) <rppt@kernel.org> | 2025-11-25 13:09:17 +0200 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2025-11-27 14:24:44 -0800 |
| commit | 7b71205ae1120e90c7f6d41d282e26c00e9ee6a7 (patch) | |
| tree | f569a3fa0e7cc2ed6d4aa7cf76826a8669a1f0b9 | |
| parent | 4bc84cd539dff1a6346ffeb5f174bb79e238fa78 (diff) | |
kho: fix restoring of contiguous ranges of order-0 pages
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.
Link: https://lkml.kernel.org/r/20251125110917.843744-3-rppt@kernel.org
Fixes: a667300bd53f ("kho: add support for preserving vmalloc allocations")
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reported-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | kernel/liveupdate/kexec_handover.c | 20 |
1 files changed, 12 insertions, 8 deletions
diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c index 096b7db28baf..9dc51fab604f 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; } |