[PATCH 09/13] gup: Don't allow FOLL_LONGTERM pinning of FS DAX pages

Alistair Popple
2024-06-27T00:55:22Z

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@nvidia.com>
---
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);

--
git-series 0.9.1