On Wed, 12 Nov 2014 10:22:45 +0900 Joonsoo Kim iamjoonsoo.kim@lge.com wrote:
On Tue, Nov 11, 2014 at 05:02:43PM -0800, Andrew Morton wrote:
On Wed, 12 Nov 2014 00:54:01 +0000 Luke Dashjr luke@dashjr.org wrote:
On Wednesday, November 12, 2014 12:49:13 AM Andrew Morton wrote:
But anyway - Luke, please attach your .config to https://bugzilla.kernel.org/show_bug.cgi?id=87891?
OK, thanks. No CONFIG_HIGHMEM of course. I'm stumped.
Hello, Andrew.
I think that the cause is GFP_HIGHMEM. GFP_HIGHMEM is always defined regardless CONFIG_HIGHMEM. Please look at the do_huge_pmd_anonymous_page(). It calls alloc_hugepage_vma() and then alloc_pages_vma() is called with alloc_hugepage_gfpmask(). This gfpmask includes GFP_TRANSHUGE and then GFP_HIGHUSER_MOVABLE.
OK.
So where's the bug? I'm inclined to say that it's in ttm. It's taking a gfp_mask which means "this is the allocation attempt which we are attempting to satisfy" and uses that for its own allocation.
But ttm has no business using that gfp_mask for its own allocation attempt. If anything it should use something like, err,
GFP_KERNEL & ~__GFP_IO & ~__GFP_FS | __GFP_HIGH
although as I mentioned earlier, it would be better to avoid allocation altogether.
Poor ttm guys - this is a bit of a trap we set for them.