/*
   *  linux/drivers/video/fb_defio.c
   *
   *  Copyright (C) 2006 Jaya Kumar
   *
   * This file is subject to the terms and conditions of the GNU General Public
   * License. See the file COPYING in the main directory of this archive
   * for more details.
   */
  
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/errno.h>
  #include <linux/string.h>
  #include <linux/mm.h>
  #include <linux/vmalloc.h>
  #include <linux/delay.h>
  #include <linux/interrupt.h>
  #include <linux/fb.h>
  #include <linux/list.h>
  
  /* to support deferred IO */
  #include <linux/rmap.h>
  #include <linux/pagemap.h>
  
  static struct page *fb_deferred_io_page(struct fb_info *info, unsigned long offs)
  {
  	void *screen_base = (void __force *) info->screen_base;
  	struct page *page;
  
  	if (is_vmalloc_addr(screen_base + offs))
  		page = vmalloc_to_page(screen_base + offs);
  	else
  		page = pfn_to_page((info->fix.smem_start + offs) >> PAGE_SHIFT);
  
  	return page;
  }
  
  /* this is to find and return the vmalloc-ed fb pages */
  static int fb_deferred_io_fault(struct vm_area_struct *vma,
  				struct vm_fault *vmf)
  {
  	unsigned long offset;
  	struct page *page;
  	struct fb_info *info = vma->vm_private_data;
  
  	offset = vmf->pgoff << PAGE_SHIFT;
  	if (offset >= info->fix.smem_len)
  		return VM_FAULT_SIGBUS;
  
  	page = fb_deferred_io_page(info, offset);
  	if (!page)
  		return VM_FAULT_SIGBUS;
  
  	get_page(page);
  
  	if (vma->vm_file)
  		page->mapping = vma->vm_file->f_mapping;
  	else
  		printk(KERN_ERR "no mapping available
  ");
  
  	BUG_ON(!page->mapping);
  	page->index = vmf->pgoff;
  
  	vmf->page = page;
  	return 0;
  }
  
  int fb_deferred_io_fsync(struct file *file, loff_t start, loff_t end, int datasync)
  {
  	struct fb_info *info = file->private_data;
  	struct inode *inode = file_inode(file);
  	int err = filemap_write_and_wait_range(inode->i_mapping, start, end);
  	if (err)
  		return err;
  
  	/* Skip if deferred io is compiled-in but disabled on this fbdev */
  	if (!info->fbdefio)
  		return 0;
  
  	mutex_lock(&inode->i_mutex);
  	/* Kill off the delayed work */
  	cancel_delayed_work_sync(&info->deferred_work);
  
  	/* Run it immediately */
  	err = schedule_delayed_work(&info->deferred_work, 0);
  	mutex_unlock(&inode->i_mutex);
  	return err;
  }
  EXPORT_SYMBOL_GPL(fb_deferred_io_fsync);
  
  /* vm_ops->page_mkwrite handler */
  static int fb_deferred_io_mkwrite(struct vm_area_struct *vma,
  				  struct vm_fault *vmf)
  {
  	struct page *page = vmf->page;
  	struct fb_info *info = vma->vm_private_data;
  	struct fb_deferred_io *fbdefio = info->fbdefio;
  	struct page *cur;
  
  	/* 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(vma->vm_file);
  
  	/* protect against the workqueue changing the page list */
  	mutex_lock(&fbdefio->lock);
  
  	/* first write in this cycle, notify the driver */
  	if (fbdefio->first_io && list_empty(&fbdefio->pagelist))
  		fbdefio->first_io(info);
  
  	/*
  	 * We want the page to remain locked from ->page_mkwrite until
  	 * the PTE is marked dirty to avoid page_mkclean() being called
  	 * before the PTE is updated, which would leave the page ignored
  	 * by defio.
  	 * Do this by locking the page here and informing the caller
  	 * about it with VM_FAULT_LOCKED.
  	 */
  	lock_page(page);
  
  	/* we loop through the pagelist before adding in order
  	to keep the pagelist sorted */
  	list_for_each_entry(cur, &fbdefio->pagelist, lru) {
  		/* this check is to catch the case where a new
  		process could start writing to the same page
  		through a new pte. this new access can cause the
  		mkwrite even when the original ps's pte is marked
  		writable */
  		if (unlikely(cur == page))
  			goto page_already_added;
  		else if (cur->index > page->index)
  			break;
  	}
  
  	list_add_tail(&page->lru, &cur->lru);
  
  page_already_added:
  	mutex_unlock(&fbdefio->lock);
  
  	/* come back after delay to process the deferred IO */
  	schedule_delayed_work(&info->deferred_work, fbdefio->delay);
  	return VM_FAULT_LOCKED;
  }
  
  static const struct vm_operations_struct fb_deferred_io_vm_ops = {
  	.fault		= fb_deferred_io_fault,
  	.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,
  };
  
  static int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
  {
  	vma->vm_ops = &fb_deferred_io_vm_ops;
  	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
  	if (!(info->flags & FBINFO_VIRTFB))
  		vma->vm_flags |= VM_IO;
  	vma->vm_private_data = info;
  	return 0;
  }
  
  /* workqueue callback */
  static void fb_deferred_io_work(struct work_struct *work)
  {
  	struct fb_info *info = container_of(work, struct fb_info,
  						deferred_work.work);
  	struct list_head *node, *next;
  	struct page *cur;
  	struct fb_deferred_io *fbdefio = info->fbdefio;
  
  	/* here we mkclean the pages, then do all deferred IO */
  	mutex_lock(&fbdefio->lock);
  	list_for_each_entry(cur, &fbdefio->pagelist, lru) {
  		lock_page(cur);
  		page_mkclean(cur);
  		unlock_page(cur);
  	}
  
  	/* driver's callback with pagelist */
  	fbdefio->deferred_io(info, &fbdefio->pagelist);
  
  	/* clear the list */
  	list_for_each_safe(node, next, &fbdefio->pagelist) {
  		list_del(node);
  	}
  	mutex_unlock(&fbdefio->lock);
  }
  
  void fb_deferred_io_init(struct fb_info *info)
  {
  	struct fb_deferred_io *fbdefio = info->fbdefio;
  
  	BUG_ON(!fbdefio);
  	mutex_init(&fbdefio->lock);
  	info->fbops->fb_mmap = fb_deferred_io_mmap;
  	INIT_DELAYED_WORK(&info->deferred_work, fb_deferred_io_work);
  	INIT_LIST_HEAD(&fbdefio->pagelist);
  	if (fbdefio->delay == 0) /* set a default of 1 s */
  		fbdefio->delay = HZ;
  }
  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;
  	}
  
  	info->fbops->fb_mmap = NULL;
  	mutex_destroy(&fbdefio->lock);
  }
  EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);
  
  MODULE_LICENSE("GPL");