On 05/03/2026 19:07, David Hildenbrand (Arm) wrote:
On 1/26/26 17:47, Kalyazin, Nikita wrote:
From: Nikita Kalyazin <[email protected]>
Move the check for pinning closer to where the result is used.
No functional changes.
Signed-off-by: Nikita Kalyazin <[email protected]>
---
mm/gup.c | 19 ++++++++-----------
1 file changed, 8 insertions(+), 11 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index 9cad53acbc99..e72dacce3e34 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2737,18 +2737,9 @@ EXPORT_SYMBOL(get_user_pages_unlocked);
*/
static bool gup_fast_folio_allowed(struct folio *folio, unsigned int flags)
{
- bool reject_file_backed = false;
struct address_space *mapping;
unsigned long mapping_flags;
- /*
- * If we aren't pinning then no problematic write can occur. A long term
- * pin is the most egregious case so this is the one we disallow.
- */
- if ((flags & (FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE)) ==
- (FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE))
- reject_file_backed = true;
-
/* We hold a folio reference, so we can safely access folio fields. */
if (WARN_ON_ONCE(folio_test_slab(folio)))
return false;
@@ -2793,8 +2784,14 @@ static bool gup_fast_folio_allowed(struct folio *folio,
unsigned int flags)
*/
if (secretmem_mapping(mapping))
return false;
- /* The only remaining allowed file system is shmem. */
- return !reject_file_backed || shmem_mapping(mapping);
+
+ /*
+ * If we aren't pinning then no problematic write can occur. A long term
+ * pin is the most egregious case so this is the one we disallow.
+ * Also check the only remaining allowed file system - shmem.
+ */
+ return (flags & (FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE)) !=
+ (FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE) || shmem_mapping(mapping);
Best to keep this split and a bit more readable.
/*
* If we aren't pinning then no problematic write can occur. A writable
* long term pin is the most egregious case, so this is the one we
* allow only for ...
*/
if ((flags & (FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE)) !=
(FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE)
return true;
/* ... hugetlb (which we allowed above already) and shared memory. */
return shmem_mapping(mapping);
Makes sense, thank you!
}
static void __maybe_unused gup_fast_undo_dev_pagemap(int *nr, int nr_start,
--
Cheers,
David
