fbdev: Refactor implementation of page_mkwrite

Refactor the page-write handler for deferred I/O. Drivers use the
function to let fbdev track written pages of mmap'ed framebuffer
memory.

v3:
	* keep locking within track-pages function for readability (Sam)
v2:
	* don't export the helper until we have an external caller

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220429100834.18898-4-tzimmermann@suse.de

diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
index 1bdef5c..3f9bb47 100644 (file)
--- a/drivers/video/fbdev/core/fb_defio.c
+++ b/drivers/video/fbdev/core/fb_defio.c
@@ -143,26 +143,17 @@ int fb_deferred_io_fsync(struct file *file, loff_t start, loff_t end, int datasy
 }
 EXPORT_SYMBOL_GPL(fb_deferred_io_fsync);
 
-/* vm_ops->page_mkwrite handler */
-static vm_fault_t fb_deferred_io_mkwrite(struct vm_fault *vmf)
+/*
+ * Adds a page to the dirty list. Call this from struct
+ * vm_operations_struct.page_mkwrite.
+ */
+static vm_fault_t fb_deferred_io_track_page(struct fb_info *info, unsigned long offset,
+                                           struct page *page)
 {
-       struct page *page = vmf->page;
-       struct fb_info *info = vmf->vma->vm_private_data;
        struct fb_deferred_io *fbdefio = info->fbdefio;
        struct fb_deferred_io_pageref *pageref;
-       unsigned long offset;
        vm_fault_t ret;
 
-       offset = (vmf->address - vmf->vma->vm_start);
-
-       /* this is a callback we get when userspace first tries to
-       write to the page. we schedule a workqueue. that workqueue
-       will eventually mkclean the touched pages and execute the
-       deferred framebuffer IO. then if userspace touches a page
-       again, we repeat the same scheme */
-
-       file_update_time(vmf->vma->vm_file);
-
        /* protect against the workqueue changing the page list */
        mutex_lock(&fbdefio->lock);
 
@@ -197,6 +188,38 @@ err_mutex_unlock:
        return ret;
 }
 
+/*
+ * fb_deferred_io_page_mkwrite - Mark a page as written for deferred I/O
+ * @fb_info: The fbdev info structure
+ * @vmf: The VM fault
+ *
+ * This is a callback we get when userspace first tries to
+ * write to the page. We schedule a workqueue. That workqueue
+ * will eventually mkclean the touched pages and execute the
+ * deferred framebuffer IO. Then if userspace touches a page
+ * again, we repeat the same scheme.
+ *
+ * Returns:
+ * VM_FAULT_LOCKED on success, or a VM_FAULT error otherwise.
+ */
+static vm_fault_t fb_deferred_io_page_mkwrite(struct fb_info *info, struct vm_fault *vmf)
+{
+       unsigned long offset = vmf->address - vmf->vma->vm_start;
+       struct page *page = vmf->page;
+
+       file_update_time(vmf->vma->vm_file);
+
+       return fb_deferred_io_track_page(info, offset, page);
+}
+
+/* vm_ops->page_mkwrite handler */
+static vm_fault_t fb_deferred_io_mkwrite(struct vm_fault *vmf)
+{
+       struct fb_info *info = vmf->vma->vm_private_data;
+
+       return fb_deferred_io_page_mkwrite(info, vmf);
+}
+
 static const struct vm_operations_struct fb_deferred_io_vm_ops = {
        .fault          = fb_deferred_io_fault,
        .page_mkwrite   = fb_deferred_io_mkwrite,