fbdev/deferred-io: Always call get_page() for framebuffer pages

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>
Link: https://patchwork.freedesktop.org/patch/msgid/20240419083331.7761-7-tzimmermann@suse.de

diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
index 37910753759cdc4d2c614424648d8ac1b634a8fd..c68c51d0ef70e7773c55fda3e701cadfd6d7e1fb 100644 (file)
--- 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