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drm: use size_t variables to iterate through pages

PATCH In review Jordan Crouse 2 participants 2 messages Oct 3, 2017 – Oct 4, 2017

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Jordan Crouse

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#0 lore raw

PATCH 1/1 drm: use size_t variables to iterate through pages

drm_gem_get_pages() and drm_gem_put_pages() calculate the number of pages to operate on from obj->size which is a size_t. Use similarly sized variables to calculate and iterate through the pages to avoid possibly losing bits from the page calculation.

Signed-off-by Jordan Crouse <[email protected]>
---
 drivers/gpu/drm/drm_gem.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
drivers/gpu/drm/drm_gem.c +2 -2
index af62017..a8c146d 100644
@@ -550,7 +550,7 @@ struct page **drm_gem_get_pages(struct drm_gem_object *obj)
 {
 	struct address_space *mapping;
 	struct page *p, **pages;
-	int i, npages;
+	size_t i, npages;
 
 	/* This is the shared memory object that backs the GEM resource */
 	mapping = obj->filp->f_mapping;

@@ -603,7 +603,7 @@ struct page **drm_gem_get_pages(struct drm_gem_object *obj)
 void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
 		bool dirty, bool accessed)
 {
-	int i, npages;
+	size_t i, npages;
 
 	/* We already BUG_ON() for non-page-aligned sizes in
 	 * drm_gem_object_init(), so we should never hit this unless
Signature · 1 line
1.9.1
#1 lore raw
Quoted 6 lines · Jordan Crouse

drm_gem_get_pages() and drm_gem_put_pages() calculate the number of pages to operate on from obj->size which is a size_t. Use similarly sized variables to calculate and iterate through the pages to avoid possibly losing bits from the page calculation.

Signed-off-by Jordan Crouse <[email protected]>

Not sure it wouldn't be better to move over to u64? In theory you could have a gpu with huge amounts of vram on a 32bit kernel, like PAE.

There's also rough consensus that size_t is just an all-around evil type for anything :-)

Still an issue of course, just probably with a differen (and likely more invasive) fix.
-Daniel

Quoted 33 lines
---
 drivers/gpu/drm/drm_gem.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
drivers/gpu/drm/drm_gem.c +2 -2
index af62017..a8c146d 100644
@@ -550,7 +550,7 @@ struct page **drm_gem_get_pages(struct drm_gem_object *obj)
 {
 	struct address_space *mapping;
 	struct page *p, **pages;
-	int i, npages;
+	size_t i, npages;
 
 	/* This is the shared memory object that backs the GEM resource */
 	mapping = obj->filp->f_mapping;

@@ -603,7 +603,7 @@ struct page **drm_gem_get_pages(struct drm_gem_object *obj)
 void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
 		bool dirty, bool accessed)
 {
-	int i, npages;
+	size_t i, npages;
 
 	/* We already BUG_ON() for non-page-aligned sizes in
 	 * drm_gem_object_init(), so we should never hit this unless
Signature · 6 lines
1.9.1

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Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch