On 2021/8/30 22:24, Matthew Wilcox wrote: > On Mon, Aug 30, 2021 at 10:10:51PM +0800, Miaohe Lin wrote: >> Don't use with __GFP_HIGHMEM because page_address() cannot represent >> highmem pages without kmap(). Newly allocated pages would leak as >> page_address() will return NULL for highmem pages here. But It works >> now because the only caller does not specify __GFP_HIGHMEM now. > > This is a misunderstanding of how alloc_pages_exact() / > alloc_pages_exact_nid() work. You simply can't call them with > GFP_HIGHMEM. > Yep, they can't work with GFP_HIGHMEM. So IMO it might be better to get rid of GFP_HIGHMEM explicitly or add a comment to clarify this situation to avoid future misbehavior. But this may be a unnecessary worry... Do you prefer to not change anything here? Many thanks. > If you really must change anything here, > s/__GFP_COMP/(__GFP_COMP|__GFP_HIGHMEM)/g throughout both > alloc_pages_exact() and alloc_pages_exact_nid(). > . >
