[PATCH v11 04/16] mm/gup: drop secretmem optimization from gup_fast_folio_allowed

Kalyazin, Nikita
2026-03-17T14:11:28Z

From: Patrick Roy <patrick.roy@linux.dev>

This drops an optimization in gup_fast_folio_allowed() where
secretmem_mapping() was only called if CONFIG_SECRETMEM=y. secretmem is
enabled by default since commit b758fe6df50d ("mm/secretmem: make it on
by default"), so the secretmem check did not actually end up elided in
most cases anymore anyway.

This is in preparation of the generalization of handling mappings where
direct map entries of folios are set to not present. Currently,
mappings that match this description are secretmem mappings
(memfd_secret()). Later, some guest_memfd configurations will also fall
into this category.

Signed-off-by: Patrick Roy <patrick.roy@linux.dev>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Signed-off-by: Nikita Kalyazin <kalyazin@amazon.com>
---
mm/gup.c | 11 +----------
1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 8e7dc2c6ee73..5856d35be385 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2739,7 +2739,6 @@ static bool gup_fast_folio_allowed(struct folio *folio, unsigned int flags)
{
bool reject_file_backed = false;
struct address_space *mapping;
- bool check_secretmem = false;
unsigned long mapping_flags;

/*
@@ -2751,14 +2750,6 @@ static bool gup_fast_folio_allowed(struct folio *folio, unsigned int flags)
reject_file_backed = true;

/* We hold a folio reference, so we can safely access folio fields. */
-
- /* secretmem folios are always order-0 folios. */
- if (IS_ENABLED(CONFIG_SECRETMEM) && !folio_test_large(folio))
- check_secretmem = true;
-
- if (!reject_file_backed && !check_secretmem)
- return true;
-
if (WARN_ON_ONCE(folio_test_slab(folio)))
return false;

@@ -2800,7 +2791,7 @@ static bool gup_fast_folio_allowed(struct folio *folio, unsigned int flags)
* At this point, we know the mapping is non-null and points to an
* address_space object.
*/
- if (check_secretmem && secretmem_mapping(mapping))
+ if (secretmem_mapping(mapping))
return false;
/* The only remaining allowed file system is shmem. */
return !reject_file_backed || shmem_mapping(mapping);
--
2.50.1