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mm: make folio page count functions return unsigned 

As raised by Andrew [1], a folio/compound page never spans a negative
number of pages.  Consequently, let's use "unsigned long" instead of
"long" consistently for folio_nr_pages(), folio_large_nr_pages() and
compound_nr().

Using "unsigned long" as return value is fine, because even
"(long)-folio_nr_pages()" will keep on working as expected.  Using
"unsigned int" instead would actually break these use cases.

This patch takes the first step changing these to return unsigned long
(and making drm_gem_get_pages() use the new types instead of replacing
min()).

In the future, we might want to make more callers of these functions to
consistently use "unsigned long".


Link: https://lore.kernel.org/linux-mm/20250503182858.5a02729fcffd6d4723afcfc2@linux-foundation.org/
Link: https://lkml.kernel.org/r/20250826153721.GA23292@cathedrallabs.org
Link: https://lore.kernel.org/linux-mm/20250503182858.5a02729fcffd6d4723afcfc2@linux-foundation.org/ [1]
Signed-off-by: Aristeu Rozanski <aris@ruivo.org>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: David Hildenbrand <david@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@gmail.com>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Aristeu Rozanski 2025-08-26 11:37:21 -04:00 committed by Andrew Morton
parent 9b375adb39
commit fa17bcd5f6
2 changed files with 6 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/gpu/drm/drm_gem.c
View File

@ -621,7 +621,7 @@ struct page **drm_gem_get_pages(struct drm_gem_object *obj)
struct page **pages;
struct folio *folio;
struct folio_batch fbatch;
long i, j, npages;
unsigned long i, j, npages;
if (WARN_ON(!obj->filp))
return ERR_PTR(-EINVAL);
@ -645,7 +645,7 @@ struct page **drm_gem_get_pages(struct drm_gem_object *obj)
i = 0;
while (i < npages) {
long nr;
unsigned long nr;
folio = shmem_read_folio_gfp(mapping, i,
mapping_gfp_mask(mapping));
if (IS_ERR(folio))

8
include/linux/mm.h
View File

@ -1018,12 +1018,12 @@ static inline unsigned int folio_large_order(const struct folio *folio)
}
#ifdef NR_PAGES_IN_LARGE_FOLIO
static inline long folio_large_nr_pages(const struct folio *folio)
static inline unsigned long folio_large_nr_pages(const struct folio *folio)
{
return folio->_nr_pages;
}
#else
static inline long folio_large_nr_pages(const struct folio *folio)
static inline unsigned long folio_large_nr_pages(const struct folio *folio)
{
return 1L << folio_large_order(folio);
}
@ -2062,7 +2062,7 @@ static inline void set_page_links(struct page *page, enum zone_type zone,
*
* Return: A positive power of two.
*/
static inline long folio_nr_pages(const struct folio *folio)
static inline unsigned long folio_nr_pages(const struct folio *folio)
{
if (!folio_test_large(folio))
return 1;
@ -2097,7 +2097,7 @@ static inline long folio_nr_pages(const struct folio *folio)
* page. compound_nr() can be called on a tail page, and is defined to
* return 1 in that case.
*/
static inline long compound_nr(const struct page *page)
static inline unsigned long compound_nr(const struct page *page)
{
const struct folio *folio = (struct folio *)page;