From 8702048bb8313a21ec9179e9ce7ad3c5cb2ef072 Mon Sep 17 00:00:00 2001 From: Jocelyn Falempe Date: Mon, 7 Apr 2025 15:42:25 +0200 Subject: [PATCH] mm/kmap: Add kmap_local_page_try_from_panic() kmap_local_page() can be unsafe to call from a panic handler, if CONFIG_HIGHMEM is set, and the page is in the highmem zone. So add kmap_local_page_try_from_panic() to handle this case. Suggested-by: Simona Vetter Reviewed-by: Thomas Gleixner Signed-off-by: Jocelyn Falempe Link: https://lore.kernel.org/r/20250407140138.162383-2-jfalempe@redhat.com --- include/linux/highmem-internal.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h index dd100e849f5e..9a7683d79a4b 100644 --- a/include/linux/highmem-internal.h +++ b/include/linux/highmem-internal.h @@ -73,6 +73,14 @@ static inline void *kmap_local_page(struct page *page) return __kmap_local_page_prot(page, kmap_prot); } +static inline void *kmap_local_page_try_from_panic(struct page *page) +{ + if (!PageHighMem(page)) + return page_address(page); + /* If the page is in HighMem, it's not safe to kmap it.*/ + return NULL; +} + static inline void *kmap_local_folio(struct folio *folio, size_t offset) { struct page *page = folio_page(folio, offset / PAGE_SIZE); @@ -180,6 +188,11 @@ static inline void *kmap_local_page(struct page *page) return page_address(page); } +static inline void *kmap_local_page_try_from_panic(struct page *page) +{ + return page_address(page); +} + static inline void *kmap_local_folio(struct folio *folio, size_t offset) { return page_address(&folio->page) + offset; -- 2.50.1