David Hildenbrand <david@xxxxxxxxxx> writes: > On 27.06.24 02:54, Alistair Popple wrote: >> Longterm pinning of FS DAX pages should already be disallowed by >> various pXX_devmap checks. However a future change will cause these >> checks to be invalid for FS DAX pages so make >> folio_is_longterm_pinnable() return false for FS DAX pages. >> Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx> >> --- >> include/linux/memremap.h | 11 +++++++++++ >> include/linux/mm.h | 4 ++++ >> 2 files changed, 15 insertions(+) >> diff --git a/include/linux/memremap.h b/include/linux/memremap.h >> index 6505713..19a448e 100644 >> --- a/include/linux/memremap.h >> +++ b/include/linux/memremap.h >> @@ -193,6 +193,17 @@ static inline bool folio_is_device_coherent(const struct folio *folio) >> return is_device_coherent_page(&folio->page); >> } >> +static inline bool is_device_dax_page(const struct page *page) >> +{ >> + return is_zone_device_page(page) && >> + page_dev_pagemap(page)->type == MEMORY_DEVICE_FS_DAX; >> +} >> + >> +static inline bool folio_is_device_dax(const struct folio *folio) >> +{ >> + return is_device_dax_page(&folio->page); >> +} >> + >> #ifdef CONFIG_ZONE_DEVICE >> void zone_device_page_init(struct page *page); >> void *memremap_pages(struct dev_pagemap *pgmap, int nid); >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index b84368b..4d1cdea 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -2032,6 +2032,10 @@ static inline bool folio_is_longterm_pinnable(struct folio *folio) >> if (folio_is_device_coherent(folio)) >> return false; >> + /* DAX must also always allow eviction. */ >> + if (folio_is_device_dax(folio)) >> + return false; >> + >> /* Otherwise, non-movable zone folios can be pinned. */ >> return !folio_is_zone_movable(folio); >> > > Why is the check in check_vma_flags() insufficient? GUP-fast maybe? Right. This came up when I was changing the code for GUP-fast, but also they shouldn't be longterm pinnable and adding the case to folio_is_longterm_pinnable() is an excellent way of documenting that.