[PATCH v2 06/43] fbdev/deferred-io: Always call get_page() for framebuffer pages

Thomas Zimmermann
2024-04-10T13:06:02Z

Unconditionally call get_page() after looking up a page from the
framebuffer memory. Guarantees that we always hold a reference.

This change also refactors the code such that it can support a
driver-supplied get_page helper. This will be useful for DRM's
fbdev emulation.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
---
drivers/video/fbdev/core/fb_defio.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
index fe84218ded457..6e0bbcfdb01b5 100644
--- a/drivers/video/fbdev/core/fb_defio.c
+++ b/drivers/video/fbdev/core/fb_defio.c
@@ -23,7 +23,7 @@
#include <linux/rmap.h>
#include <linux/pagemap.h>

-static struct page *fb_deferred_io_page(struct fb_info *info, unsigned long offs)
+static struct page *fb_deferred_io_get_page(struct fb_info *info, unsigned long offs)
{
const void *screen_buffer = info->screen_buffer;
struct page *page = NULL;
@@ -33,6 +33,9 @@ static struct page *fb_deferred_io_page(struct fb_info *info, unsigned long offs
else if (info->fix.smem_start)
page = pfn_to_page((info->fix.smem_start + offs) >> PAGE_SHIFT);

+ if (page)
+ get_page(page);
+
return page;
}

@@ -129,12 +132,10 @@ static vm_fault_t fb_deferred_io_fault(struct vm_fault *vmf)
if (offset >= info->fix.smem_len)
return VM_FAULT_SIGBUS;

- page = fb_deferred_io_page(info, offset);
+ page = fb_deferred_io_get_page(info, offset);
if (!page)
return VM_FAULT_SIGBUS;

- get_page(page);
-
if (vmf->vma->vm_file)
page->mapping = vmf->vma->vm_file->f_mapping;
else
--
2.44.0