On Fri, Dec 11, 2015 at 01:54:25AM +0000, Al Viro wrote: > BTW, why are we passing unsigned long to free_page()? We have > a bit under 700 callers; excluding the ones that have an explicit cast > to unsigned long right in the argument of call leaves ~150, and the rest > tend to contain a lot of pointer casts of unsigned long thing they are feeding > to free_page() (IOW, they would be just as happy if they kept it as a pointer > all along). Sure, that would mean __get_free_page() et.al. returning void *, > but I don't see any problems with that either... Is that just for historical > reasons, or is there anything more subtle I'm missing here? The situation with free_pages() is even funnier - we have 313 call sites, and after converting it to void(void *, unsigned) 31 of them need casts to void *. Right now the mainline has 249 of those call sites with cast to unsigned long (or ulong, in several places). Then there's a bunch of places where we do __get_free_pages(), then use it a lot (all with casts to pointers), then pass to free_pages() - those would be just fine with storing it as void *, but even leaving those aside... The current signature is contrary to actual use - nearly 80% of call sites are forced to cast a pointer to unsigned long, only to have it cast back to void * in free_pages() itself, we would obviously be better off if we'd switched to just passing the damn thing as a pointer. Especially since that 80% turn into 90% once you add the callers that could easily switch to storing the value eventually passed to free_pages() as a pointer. And free_page() is basically the same story, only with twice as many call sites... While we are at it: __get_free_pages() has 238 call sites. 193 of them immediately cast to pointer. And there's a bunch of places like this: static inline void __tlb_alloc_page(struct mmu_gather *tlb) { unsigned long addr = __get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0); if (addr) { tlb->pages = (void *)addr; tlb->max = PAGE_SIZE / sizeof(struct page *); } } where the cast is not immediate, but might as well had been. And conversion of free_pages() whittles it down even more. For __get_free_page() the situation is about the same, ditto for get_zeroed_page(). I realize that get_free_page() has been returning unsigned long since 0.01, but looking at 0.01... it might as well had been returning void * - wouldn't be more inconvenient. The kludge you had in get_pipe_inode() would've been a bit more obviously wrong, but that's about it ;-) Seriously, though - what do you think about a flagday commit right after 4.5-rc1 switching all those guys to void *? For __get_user_pages(), __get_user_page(), get_zeroed_page() - return values, for free_pages(), free_page() - argument. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html