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fallback versions of clear_pages(), clear_user_pages(). >>>> In absence of architectural primitives, we just clear pages >>>> sequentially. >>>> Signed-off-by: Ankur Arora >>>> --- >>>> include/linux/mm.h | 38 ++++++++++++++++++++++++++++++++++++++ >>>> 1 file changed, 38 insertions(+) >>>> diff --git a/include/linux/mm.h b/include/linux/mm.h >>>> index 1ae97a0b8ec7..0cde9b01da5e 100644 >>>> --- a/include/linux/mm.h >>>> +++ b/include/linux/mm.h >>>> @@ -3768,6 +3768,44 @@ static inline void clear_page_guard(struct zone *zone, struct page *page, >>>> unsigned int order) {} >>>> #endif /* CONFIG_DEBUG_PAGEALLOC */ >>>> +#ifndef clear_pages >>>> +/** >>>> + * clear_pages() - clear a page range using a kernel virtual address. >>> >>> I'd just call this "clear a page range for kernel-internal use" >>> >>>> + * @addr: start address >>>> + * @npages: number of pages >>>> + * >>>> + * Assumes that (@addr, +@npages) references a kernel region. >>> >>> And say here simply that "Use clear_user_pages() instead for clearing a page >>> range to be mapped to user space". >> So, comments that actually speak to the use instead of technically >> correct but unhelpful generalities :). Thanks, good lesson. >> >>>> + * Does absolutely no exception handling. >>>> + */ >>>> +static inline void clear_pages(void *addr, unsigned int npages) >>>> +{ >>>> + do { >>>> + clear_page(addr); >>>> + addr += PAGE_SIZE; >>>> + } while (--npages); >>>> +} >>>> +#endif >>>> + >>>> +#ifndef clear_user_pages >>>> +/** >>>> + * clear_user_pages() - clear a page range mapped by the user. >>> >>> I'd call this then "clear a page range to be mapped to user space" >>> >>> Because it's usually called before we actually map it and it will properly flush >>> the dcache if required. >> Makes sense. >> >>>> + * @addr: kernel mapped address >>> >>> "start address" >>> >>>> + * @vaddr: user mapped address >>> >>> "start address of the user mapping" ? >>> >>>> + * @pg: start page >>> >>> Please just call it "page". I know, clear_user_page() has this weird page vs. pg >>> thingy, but let's do it better here. >>> >>>> + * @npages: number of pages >>>> + * >>>> + * Assumes that the region (@addr, +@npages) has been validated >>>> + * already so this does no exception handling. >>>> + */ >>>> +#define clear_user_pages(addr, vaddr, pg, npages) \ >>>> +do { \ >>>> + clear_user_page(addr, vaddr, pg); \ >>>> + addr += PAGE_SIZE; \ >>>> + vaddr += PAGE_SIZE; \ >>>> + pg++; \ >>>> +} while (--npages) >>>> +#endif >>> >>> Should indent with one tab. >> Will do. Also acking to the ones above. >> >>> Any reason this is not a static inline function? >> Alas yes. Most architecture code defines clear_user_page() as a macro >> where, if they need a to flush the dcache or otherwise do something >> special, they need access to some external primitive. And this primitive >> which might not be visible in contexts that we include this header. >> For instance this one on sparc: >> https://lore.kernel.org/lkml/202509030338.DlQJTxIk-lkp@intel.com/ >> Defining as a macro to get around that. But maybe there's a better >> way? > > Can we just move it to mm/utils.c and not have it be an inline function? Thanks. Yeah, that's a good place for it. -- ankur