On 2021/9/1 0:37, Vlastimil Babka wrote: > On 8/31/21 03:56, Miaohe Lin wrote: >> 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? > > I agree with the suggestion below... > >> 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(). > > ... which means __GFP_HIGHMEM would be stripped and additionally there would > be a warning. > Looks good for me. Will do. Many thanks! > . >
