On Fri, Jan 22, 2021 at 11:52:29AM -0800, Mike Kravetz wrote: > The HP_Migratable flag indicates a page is a candidate for migration. > Only set the flag if the page's hstate supports migration. This allows > the migration paths to detect non-migratable pages earlier. If migration > is not supported for the hstate, HP_Migratable will not be set, the page > will not be isolated and no attempt will be made to migrate. We should > never get to unmap_and_move_huge_page for a page where migration is not > supported, so throw a warning if we do. > > Signed-off-by: Mike Kravetz <[email protected]>
I wish there was a better way to do this like opencode it at fault path, but as you mentioned that is troublesome. I am not a big fan of the name either, too long for my taste but I cannot come up with anything better so: Reviewed-by: Oscar Salvador <[email protected]> > --- > fs/hugetlbfs/inode.c | 2 +- > include/linux/hugetlb.h | 9 +++++++++ > mm/hugetlb.c | 8 ++++---- > mm/migrate.c | 9 ++++----- > 4 files changed, 18 insertions(+), 10 deletions(-) > > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > index e1d7ed2a53a9..93f7b8d3c5fd 100644 > --- a/fs/hugetlbfs/inode.c > +++ b/fs/hugetlbfs/inode.c > @@ -735,7 +735,7 @@ static long hugetlbfs_fallocate(struct file *file, int > mode, loff_t offset, > > mutex_unlock(&hugetlb_fault_mutex_table[hash]); > > - SetHPageMigratable(page); > + SetHPageMigratableIfSupported(page); > /* > * unlock_page because locked by add_to_page_cache() > * put_page() due to reference from alloc_huge_page() > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index 58be44a915d1..cd1960541f2a 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -740,6 +740,15 @@ static inline bool hugepage_migration_supported(struct > hstate *h) > return arch_hugetlb_migration_supported(h); > } > > +/* > + * Only set HPageMigratable if migration supported for page > + */ > +static inline void SetHPageMigratableIfSupported(struct page *page) > +{ > + if (hugepage_migration_supported(page_hstate(page))) > + SetHPageMigratable(page); > +} > + > /* > * Movability check is different as compared to migration check. > * It determines whether or not a huge page should be placed on > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index f1a3c8230dbf..4da1a29ac5e2 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -4194,7 +4194,7 @@ static vm_fault_t hugetlb_cow(struct mm_struct *mm, > struct vm_area_struct *vma, > make_huge_pte(vma, new_page, 1)); > page_remove_rmap(old_page, true); > hugepage_add_new_anon_rmap(new_page, vma, haddr); > - SetHPageMigratable(new_page); > + SetHPageMigratableIfSupported(new_page); > /* Make the old page be freed below */ > new_page = old_page; > } > @@ -4436,7 +4436,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, > * been isolated for migration. > */ > if (new_page) > - SetHPageMigratable(page); > + SetHPageMigratableIfSupported(page); > > unlock_page(page); > out: > @@ -4747,7 +4747,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, > update_mmu_cache(dst_vma, dst_addr, dst_pte); > > spin_unlock(ptl); > - SetHPageMigratable(page); > + SetHPageMigratableIfSupported(page); > if (vm_shared) > unlock_page(page); > ret = 0; > @@ -5589,7 +5589,7 @@ void putback_active_hugepage(struct page *page) > { > VM_BUG_ON_PAGE(!PageHead(page), page); > spin_lock(&hugetlb_lock); > - SetHPageMigratable(page); > + SetHPageMigratableIfSupported(page); > list_move_tail(&page->lru, &(page_hstate(page))->hugepage_activelist); > spin_unlock(&hugetlb_lock); > put_page(page); > diff --git a/mm/migrate.c b/mm/migrate.c > index a3e1acc72ad7..c8d19e83f372 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1275,13 +1275,12 @@ static int unmap_and_move_huge_page(new_page_t > get_new_page, > struct address_space *mapping = NULL; > > /* > - * Migratability of hugepages depends on architectures and their size. > - * This check is necessary because some callers of hugepage migration > - * like soft offline and memory hotremove don't walk through page > - * tables or check whether the hugepage is pmd-based or not before > - * kicking migration. > + * Support for migration should be checked at isolation time. > + * Therefore, we should never get here if migration is not supported > + * for the page. > */ > if (!hugepage_migration_supported(page_hstate(hpage))) { > + VM_WARN_ON(1); > list_move_tail(&hpage->lru, ret); > return -ENOSYS; > } > -- > 2.29.2 > > -- Oscar Salvador SUSE L3
