Regression after commit 19809c2da28a ("mm, vmalloc: use __GFP_HIGHMEM implicitly")

[Kai Heng Feng]

A user with i386 instead of AMD64 machine reports [1] that commit 19809c2da28a ("mm, vmalloc: use __GFP_HIGHMEM implicitlyâ) causes a regression.
BUG_ON(PageHighMem(pg)) in drivers/media/common/saa7146/saa7146_core.c always gets triggered after that commit.

Commit 704b862f9efd ("mm/vmalloc.c: don't unconditonally use __GFP_HIGHMEMâ) adjusts the mask logic, now the __GFP_HIGHMEM only gets applied when there is no GFP_DMA or GFP_DMA32.

So I tried to adjust its malloc to "__vmalloc(nr_pages * sizeof(struct scatterlist), GFP_KERNEL | GFP_DMA | __GFP_ZERO, PAGE_KERNEL)â, but both GFP_DMA or GFP_DMA32 still trigger the BUG_ON(PageHighMem()) macro.

Also there are other BUG_ON(PageHighMem()) in drivers/media, I think they will get hit by same regression in 32bit machine too.

[1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1742316

Kai-Heng