On Fri, Jan 16, 2026 at 11:22:15AM +0000, Pratyush Yadav wrote: > When restoring a page (from kho_restore_pages()) or folio (from > kho_restore_folio()), KHO must initialize the struct page. The > initialization differs slightly depending on if a folio is requested or > a set of 0-order pages is requested. > > Conceptually, it is quite simple to understand. When restoring 0-order > pages, each page gets a refcount of 1 and that's it. When restoring a > folio, head page gets a refcount of 1 and tail pages get 0. > > kho_restore_page() tries to combine the two separate initialization flow > into one piece of code. While it works fine, it is more complicated to > read than it needs to be. Make the code simpler by splitting the two > initalization paths into two separate functions. This improves > readability by clearly showing how each type must be initialized. > > Signed-off-by: Pratyush Yadav <[email protected]>
Reviewed-by: Mike Rapoport (Microsoft) <[email protected]> > --- > > Changes in v2: > - Use unsigned long for nr_pages. > > kernel/liveupdate/kexec_handover.c | 40 +++++++++++++++++++----------- > 1 file changed, 26 insertions(+), 14 deletions(-) > > diff --git a/kernel/liveupdate/kexec_handover.c > b/kernel/liveupdate/kexec_handover.c > index 709484fbf9fd..92da76977684 100644 > --- a/kernel/liveupdate/kexec_handover.c > +++ b/kernel/liveupdate/kexec_handover.c > @@ -219,11 +219,32 @@ static int __kho_preserve_order(struct kho_mem_track > *track, unsigned long pfn, > return 0; > } > > +/* For physically contiguous 0-order pages. */ > +static void kho_init_pages(struct page *page, unsigned long nr_pages) > +{ > + for (unsigned long i = 0; i < nr_pages; i++) > + set_page_count(page + i, 1); > +} > + > +static void kho_init_folio(struct page *page, unsigned int order) > +{ > + unsigned long nr_pages = (1 << order); > + > + /* Head page gets refcount of 1. */ > + set_page_count(page, 1); > + > + /* For higher order folios, tail pages get a page count of zero. */ > + for (unsigned long i = 1; i < nr_pages; i++) > + set_page_count(page + i, 0); > + > + if (order > 0) > + prep_compound_page(page, order); > +} > + > static struct page *kho_restore_page(phys_addr_t phys, bool is_folio) > { > struct page *page = pfn_to_online_page(PHYS_PFN(phys)); > unsigned long nr_pages; > - unsigned int ref_cnt; > union kho_page_info info; > > if (!page) > @@ -241,20 +262,11 @@ static struct page *kho_restore_page(phys_addr_t phys, > bool is_folio) > > /* Clear private to make sure later restores on this page error out. */ > page->private = 0; > - /* Head page gets refcount of 1. */ > - set_page_count(page, 1); > - > - /* > - * 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 long i = 1; i < nr_pages; i++) > - set_page_count(page + i, ref_cnt); > > - if (is_folio && info.order) > - prep_compound_page(page, info.order); > + if (is_folio) > + kho_init_folio(page, info.order); > + else > + kho_init_pages(page, nr_pages); > > adjust_managed_page_count(page, nr_pages); > return page; > -- > 2.52.0.457.g6b5491de43-goog > -- Sincerely yours, Mike.
