[PATCH] Revert "fb_defio: Remove custom address_space_operations"

[Matthew Wilcox (Oracle)]

Commit ccf953d8f3d6 makes framebuffers which use deferred I/O stop
displaying updates after the first one.  This is because the pages
handled by fb_defio no longer have a page_mapping().  That prevents
page_mkclean() from marking the PTEs as clean, and so writes are only
noticed the first time.

Reported-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 drivers/video/fbdev/core/fb_defio.c | 35 +++++++++++++++++++++++++++++
 drivers/video/fbdev/core/fbmem.c    |  4 ++++
 include/linux/fb.h                  |  3 +++
 3 files changed, 42 insertions(+)

diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
index b292887a2481..a591d291b231 100644
--- a/drivers/video/fbdev/core/fb_defio.c
+++ b/drivers/video/fbdev/core/fb_defio.c
@@ -52,6 +52,13 @@ static vm_fault_t fb_deferred_io_fault(struct vm_fault *vmf)
 		return VM_FAULT_SIGBUS;
 
 	get_page(page);
+
+	if (vmf->vma->vm_file)
+		page->mapping = vmf->vma->vm_file->f_mapping;
+	else
+		printk(KERN_ERR "no mapping available\n");
+
+	BUG_ON(!page->mapping);
 	page->index = vmf->pgoff;
 
 	vmf->page = page;
@@ -144,6 +151,17 @@ static const struct vm_operations_struct fb_deferred_io_vm_ops = {
 	.page_mkwrite	= fb_deferred_io_mkwrite,
 };
 
+static int fb_deferred_io_set_page_dirty(struct page *page)
+{
+	if (!PageDirty(page))
+		SetPageDirty(page);
+	return 0;
+}
+
+static const struct address_space_operations fb_deferred_io_aops = {
+	.set_page_dirty = fb_deferred_io_set_page_dirty,
+};
+
 int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
 {
 	vma->vm_ops = &fb_deferred_io_vm_ops;
@@ -194,12 +212,29 @@ void fb_deferred_io_init(struct fb_info *info)
 }
 EXPORT_SYMBOL_GPL(fb_deferred_io_init);
 
+void fb_deferred_io_open(struct fb_info *info,
+			 struct inode *inode,
+			 struct file *file)
+{
+	file->f_mapping->a_ops = &fb_deferred_io_aops;
+}
+EXPORT_SYMBOL_GPL(fb_deferred_io_open);
+
 void fb_deferred_io_cleanup(struct fb_info *info)
 {
 	struct fb_deferred_io *fbdefio = info->fbdefio;
+	struct page *page;
+	int i;
 
 	BUG_ON(!fbdefio);
 	cancel_delayed_work_sync(&info->deferred_work);
+
+	/* clear out the mapping that we setup */
+	for (i = 0 ; i < info->fix.smem_len; i += PAGE_SIZE) {
+		page = fb_deferred_io_page(info, i);
+		page->mapping = NULL;
+	}
+
 	mutex_destroy(&fbdefio->lock);
 }
 EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 072780b0e570..98f193078c05 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1415,6 +1415,10 @@ __releases(&info->lock)
 		if (res)
 			module_put(info->fbops->owner);
 	}
+#ifdef CONFIG_FB_DEFERRED_IO
+	if (info->fbdefio)
+		fb_deferred_io_open(info, inode, file);
+#endif
 out:
 	unlock_fb_info(info);
 	if (res)
diff --git a/include/linux/fb.h b/include/linux/fb.h
index a8dccd23c249..ecfbcc0553a5 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -659,6 +659,9 @@ static inline void __fb_pad_aligned_buffer(u8 *dst, u32 d_pitch,
 /* drivers/video/fb_defio.c */
 int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma);
 extern void fb_deferred_io_init(struct fb_info *info);
+extern void fb_deferred_io_open(struct fb_info *info,
+				struct inode *inode,
+				struct file *file);
 extern void fb_deferred_io_cleanup(struct fb_info *info);
 extern int fb_deferred_io_fsync(struct file *file, loff_t start,
 				loff_t end, int datasync);
-- 
2.30.2


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