Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> writes: > This patch is motivated by the discussion with Aneesh about "extend > hugepage migration" patchset. > http://thread.gmane.org/gmane.linux.kernel.mm/103933/focus=104391 > I'll append this to the patchset in the next post, but before that > I want this patch to be reviewed (I don't want to repeat posting the > whole set for just minor changes.) > > Any comments? > > Thanks, > Naoya Horiguchi > --- > From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > Date: Mon, 5 Aug 2013 13:33:02 -0400 > Subject: [PATCH] hugetlb: add pmd_huge_support() to migrate only pmd-based > hugepage > > Currently hugepage migration works well only for pmd-based hugepages, > because core routines of hugepage migration use pmd specific internal > functions like huge_pte_offset(). So we should not enable the migration > of other levels of hugepages until we are ready for it. I guess huge_pte_offset may not be the right reason because archs do implement huge_pte_offsets even if they are not pmd-based hugepages pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr) { /* Only called for hugetlbfs pages, hence can ignore THP */ return find_linux_pte_or_hugepte(mm->pgd, addr, NULL); } > > Some users of hugepage migration (mbind, move_pages, and migrate_pages) > do page table walk and check pud/pmd_huge() there, so they are safe. > But the other users (softoffline and memory hotremove) don't do this, > so they can try to migrate unexpected types of hugepages. > > To prevent this, we introduce an architecture dependent check of whether > hugepage are implemented on a pmd basis or not. It returns 0 if pmd_huge() > returns always 0, and 1 otherwise. > so why not #define pmd_huge_support pmd_huge or use pmd_huge directly ? > Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > --- > arch/arm/mm/hugetlbpage.c | 5 +++++ > arch/arm64/mm/hugetlbpage.c | 5 +++++ > arch/ia64/mm/hugetlbpage.c | 5 +++++ > arch/metag/mm/hugetlbpage.c | 5 +++++ > arch/mips/mm/hugetlbpage.c | 5 +++++ > arch/powerpc/mm/hugetlbpage.c | 10 ++++++++++ > arch/s390/mm/hugetlbpage.c | 5 +++++ > arch/sh/mm/hugetlbpage.c | 5 +++++ > arch/sparc/mm/hugetlbpage.c | 5 +++++ > arch/tile/mm/hugetlbpage.c | 5 +++++ > arch/x86/mm/hugetlbpage.c | 8 ++++++++ > include/linux/hugetlb.h | 2 ++ > mm/migrate.c | 11 +++++++++++ > 13 files changed, 76 insertions(+) > > diff --git a/arch/arm/mm/hugetlbpage.c b/arch/arm/mm/hugetlbpage.c > index 3d1e4a2..3f3b6a7 100644 > --- a/arch/arm/mm/hugetlbpage.c > +++ b/arch/arm/mm/hugetlbpage.c > @@ -99,3 +99,8 @@ int pmd_huge(pmd_t pmd) > { > return pmd_val(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT); > } > + > +int pmd_huge_support(void) > +{ > + return 1; > +} -aneesh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>