On Tue, Apr 11, 2017 at 01:12:24PM +1000, Benjamin Herrenschmidt wrote: > On Tue, 2017-04-11 at 12:08 +0900, Minchan Kim wrote: > > Hello, > > > > When I tested zram in ppc64, I got random corruption. > > With investigation, it seems clear_page corrupted the memory. > > I passed 64K kmalloced(kmalloc(PAGE_SIZE)) address to clear_page > > and turned on slub debug so address is not aligned with PAGE_SIZE. > > Is it a valid usecase that non-PAGE_SIZE aligned address is > > used for clear_page in ppc64? > > > > As well, copy_page have same rule, too? > > > > Anyway, when I changed clear_page to memset, it seems the problem > > is gone. > > Yes, both clear_page and copy_page assume a PAGE_SHIFT alignment and > are highly optimize according to this. > > I wouldn't be surprised of other architectures implementations are the > same. > > I don't think it's ever legit to call these functions for something > that isn't a naturally aligned page.
If it's the common for every architecture, it would have better to have description about that in somewhere or WARN_ON. :( Thanks for the confirm!
