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b=sQEqNcn0RVU/IcZMKtRGuPfTEkCa0ftTy/KsYvzMc3vySV8NIyQSfoyOOB2AZ0qf7 uvKDbh8G2D1egXCoXYyAkAROQqrV/L6uYZ7WwgHjGV6vU8XN/U2gdNN/81/ykgz74x BKM5zcBdLMGa9+WaH5hvAylH3sHfMjkc4ahHvOAvCLfYgVwBPOFIVTbNicQsvWEIor nkYqUQw2pr2C/CaUkc+/SWb3ZjvoyWXxJZ8jQhUlkTcGlL0mShtgbI6PzxxuQVbuiO duNhZzx8ephb7lWkr8DQmTnrYbA5pTXGmjtpRlB4u3M1eBQqoK/0aWk+CWHFSahNCV GweR5D4v6nbEA== Date: Wed, 17 Sep 2025 17:31:43 +0300 From: Mike Rapoport To: Pratyush Yadav Cc: Alexander Graf , Changyuan Lyu , Andrew Morton , Baoquan He , Pasha Tatashin , Jason Gunthorpe , Chris Li , Jason Miu , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org Subject: Re: [PATCH v2 1/2] kho: move sanity checks to kho_restore_page() Message-ID: References: <20250917125725.665-1-pratyush@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250917125725.665-1-pratyush@kernel.org> X-Rspamd-Queue-Id: 5835B16000A X-Stat-Signature: owdqdxt95w5d958jwy888h9m3b1g9f5k X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1758119512-485226 X-HE-Meta: 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 9LxsJmml 14BFC 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: On Wed, Sep 17, 2025 at 02:56:53PM +0200, Pratyush Yadav wrote: > While KHO exposes folio as the primitive externally, internally its > restoration machinery operates on pages. This can be seen with > kho_restore_folio() for example. It performs some sanity checks and > hands it over to kho_restore_page() to do the heavy lifting of page > restoration. After the work done by kho_restore_page(), > kho_restore_folio() only converts the head page to folio and returns it. > Similarly, deserialize_bitmap() operates on the head page directly to > store the order. > > Move the sanity checks for valid phys and order from the public-facing > kho_restore_folio() to the private-facing kho_restore_page(). This makes > the boundary between page and folio clearer from KHO's perspective. > > While at it, drop the comment above kho_restore_page(). The comment is > misleading now. The function stopped looking like free_reserved_page() > since 12b9a2c05d1b4 ("kho: initialize tail pages for higher order folios > properly"), and now looks even more different. > > Signed-off-by: Pratyush Yadav Reviewed-by: Mike Rapoport (Microsoft) > --- > > Notes: > Changes in v2: > > - New in v2. > > kernel/kexec_handover.c | 28 ++++++++++++++-------------- > 1 file changed, 14 insertions(+), 14 deletions(-) > > diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c > index ecd1ac210dbd7..69cab82abaaef 100644 > --- a/kernel/kexec_handover.c > +++ b/kernel/kexec_handover.c > @@ -183,10 +183,18 @@ static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn, > return 0; > } > > -/* almost as free_reserved_page(), just don't free the page */ > -static void kho_restore_page(struct page *page, unsigned int order) > +static struct page *kho_restore_page(phys_addr_t phys) > { > - unsigned int nr_pages = (1 << order); > + struct page *page = pfn_to_online_page(PHYS_PFN(phys)); > + unsigned int nr_pages, order; > + > + if (!page) > + return NULL; > + > + order = page->private; > + if (order > MAX_PAGE_ORDER) > + return NULL; > + nr_pages = (1 << order); > > /* Head page gets refcount of 1. */ > set_page_count(page, 1); > @@ -199,6 +207,7 @@ static void kho_restore_page(struct page *page, unsigned int order) > prep_compound_page(page, order); > > adjust_managed_page_count(page, nr_pages); > + return page; > } > > /** > @@ -209,18 +218,9 @@ static void kho_restore_page(struct page *page, unsigned int order) > */ > struct folio *kho_restore_folio(phys_addr_t phys) > { > - struct page *page = pfn_to_online_page(PHYS_PFN(phys)); > - unsigned long order; > - > - if (!page) > - return NULL; > - > - order = page->private; > - if (order > MAX_PAGE_ORDER) > - return NULL; > + struct page *page = kho_restore_page(phys); > > - kho_restore_page(page, order); > - return page_folio(page); > + return page ? page_folio(page) : NULL; > } > EXPORT_SYMBOL_GPL(kho_restore_folio); > > -- > 2.47.3 > -- Sincerely yours, Mike.