1/*
  2 *  linux/drivers/video/fb_defio.c
  3 *
  4 *  Copyright (C) 2006 Jaya Kumar
  5 *
  6 * This file is subject to the terms and conditions of the GNU General Public
  7 * License. See the file COPYING in the main directory of this archive
  8 * for more details.
  9 */
 10
 11#include <linux/module.h>
 12#include <linux/kernel.h>
 13#include <linux/errno.h>
 14#include <linux/string.h>
 15#include <linux/mm.h>
 16#include <linux/vmalloc.h>
 17#include <linux/delay.h>
 18#include <linux/interrupt.h>
 19#include <linux/fb.h>
 20#include <linux/list.h>
 21
 22/* to support deferred IO */
 23#include <linux/rmap.h>
 24#include <linux/pagemap.h>
 25
 26static struct page *fb_deferred_io_page(struct fb_info *info, unsigned long offs)
 27{
 28	void *screen_base = (void __force *) info->screen_base;
 29	struct page *page;
 30
 31	if (is_vmalloc_addr(screen_base + offs))
 32		page = vmalloc_to_page(screen_base + offs);
 33	else
 34		page = pfn_to_page((info->fix.smem_start + offs) >> PAGE_SHIFT);
 35
 36	return page;
 37}
 38
 39/* this is to find and return the vmalloc-ed fb pages */
 40static int fb_deferred_io_fault(struct vm_area_struct *vma,
 41				struct vm_fault *vmf)
 42{
 43	unsigned long offset;
 44	struct page *page;
 45	struct fb_info *info = vma->vm_private_data;
 46
 47	offset = vmf->pgoff << PAGE_SHIFT;
 48	if (offset >= info->fix.smem_len)
 49		return VM_FAULT_SIGBUS;
 50
 51	page = fb_deferred_io_page(info, offset);
 52	if (!page)
 53		return VM_FAULT_SIGBUS;
 54
 55	get_page(page);
 56
 57	if (vma->vm_file)
 58		page->mapping = vma->vm_file->f_mapping;
 59	else
 60		printk(KERN_ERR "no mapping available\n");
 61
 62	BUG_ON(!page->mapping);
 63	page->index = vmf->pgoff;
 64
 65	vmf->page = page;
 66	return 0;
 67}
 68
 69int fb_deferred_io_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 70{
 71	struct fb_info *info = file->private_data;
 72	struct inode *inode = file->f_path.dentry->d_inode;
 73	int err = filemap_write_and_wait_range(inode->i_mapping, start, end);
 74	if (err)
 75		return err;
 76
 77	/* Skip if deferred io is compiled-in but disabled on this fbdev */
 78	if (!info->fbdefio)
 79		return 0;
 80
 81	mutex_lock(&inode->i_mutex);
 82	/* Kill off the delayed work */
 83	cancel_delayed_work_sync(&info->deferred_work);
 84
 85	/* Run it immediately */
 86	err = schedule_delayed_work(&info->deferred_work, 0);
 87	mutex_unlock(&inode->i_mutex);
 88	return err;
 89}
 90EXPORT_SYMBOL_GPL(fb_deferred_io_fsync);
 91
 92/* vm_ops->page_mkwrite handler */
 93static int fb_deferred_io_mkwrite(struct vm_area_struct *vma,
 94				  struct vm_fault *vmf)
 95{
 96	struct page *page = vmf->page;
 97	struct fb_info *info = vma->vm_private_data;
 98	struct fb_deferred_io *fbdefio = info->fbdefio;
 99	struct page *cur;
100
101	/* this is a callback we get when userspace first tries to
102	write to the page. we schedule a workqueue. that workqueue
103	will eventually mkclean the touched pages and execute the
104	deferred framebuffer IO. then if userspace touches a page
105	again, we repeat the same scheme */
106
107	/* protect against the workqueue changing the page list */
108	mutex_lock(&fbdefio->lock);
109
110	/* first write in this cycle, notify the driver */
111	if (fbdefio->first_io && list_empty(&fbdefio->pagelist))
112		fbdefio->first_io(info);
113
114	/*
115	 * We want the page to remain locked from ->page_mkwrite until
116	 * the PTE is marked dirty to avoid page_mkclean() being called
117	 * before the PTE is updated, which would leave the page ignored
118	 * by defio.
119	 * Do this by locking the page here and informing the caller
120	 * about it with VM_FAULT_LOCKED.
121	 */
122	lock_page(page);
123
124	/* we loop through the pagelist before adding in order
125	to keep the pagelist sorted */
126	list_for_each_entry(cur, &fbdefio->pagelist, lru) {
127		/* this check is to catch the case where a new
128		process could start writing to the same page
129		through a new pte. this new access can cause the
130		mkwrite even when the original ps's pte is marked
131		writable */
132		if (unlikely(cur == page))
133			goto page_already_added;
134		else if (cur->index > page->index)
135			break;
136	}
137
138	list_add_tail(&page->lru, &cur->lru);
139
140page_already_added:
141	mutex_unlock(&fbdefio->lock);
142
143	/* come back after delay to process the deferred IO */
144	schedule_delayed_work(&info->deferred_work, fbdefio->delay);
145	return VM_FAULT_LOCKED;
146}
147
148static const struct vm_operations_struct fb_deferred_io_vm_ops = {
149	.fault		= fb_deferred_io_fault,
150	.page_mkwrite	= fb_deferred_io_mkwrite,
151};
152
153static int fb_deferred_io_set_page_dirty(struct page *page)
154{
155	if (!PageDirty(page))
156		SetPageDirty(page);
157	return 0;
158}
159
160static const struct address_space_operations fb_deferred_io_aops = {
161	.set_page_dirty = fb_deferred_io_set_page_dirty,
162};
163
164static int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
165{
166	vma->vm_ops = &fb_deferred_io_vm_ops;
167	vma->vm_flags |= ( VM_RESERVED | VM_DONTEXPAND );
168	if (!(info->flags & FBINFO_VIRTFB))
169		vma->vm_flags |= VM_IO;
170	vma->vm_private_data = info;
171	return 0;
172}
173
174/* workqueue callback */
175static void fb_deferred_io_work(struct work_struct *work)
176{
177	struct fb_info *info = container_of(work, struct fb_info,
178						deferred_work.work);
179	struct list_head *node, *next;
180	struct page *cur;
181	struct fb_deferred_io *fbdefio = info->fbdefio;
182
183	/* here we mkclean the pages, then do all deferred IO */
184	mutex_lock(&fbdefio->lock);
185	list_for_each_entry(cur, &fbdefio->pagelist, lru) {
186		lock_page(cur);
187		page_mkclean(cur);
188		unlock_page(cur);
189	}
190
191	/* driver's callback with pagelist */
192	fbdefio->deferred_io(info, &fbdefio->pagelist);
193
194	/* clear the list */
195	list_for_each_safe(node, next, &fbdefio->pagelist) {
196		list_del(node);
197	}
198	mutex_unlock(&fbdefio->lock);
199}
200
201void fb_deferred_io_init(struct fb_info *info)
202{
203	struct fb_deferred_io *fbdefio = info->fbdefio;
204
205	BUG_ON(!fbdefio);
206	mutex_init(&fbdefio->lock);
207	info->fbops->fb_mmap = fb_deferred_io_mmap;
208	INIT_DELAYED_WORK(&info->deferred_work, fb_deferred_io_work);
209	INIT_LIST_HEAD(&fbdefio->pagelist);
210	if (fbdefio->delay == 0) /* set a default of 1 s */
211		fbdefio->delay = HZ;
212}
213EXPORT_SYMBOL_GPL(fb_deferred_io_init);
214
215void fb_deferred_io_open(struct fb_info *info,
216			 struct inode *inode,
217			 struct file *file)
218{
219	file->f_mapping->a_ops = &fb_deferred_io_aops;
220}
221EXPORT_SYMBOL_GPL(fb_deferred_io_open);
222
223void fb_deferred_io_cleanup(struct fb_info *info)
224{
225	struct fb_deferred_io *fbdefio = info->fbdefio;
226	struct page *page;
227	int i;
228
229	BUG_ON(!fbdefio);
230	cancel_delayed_work_sync(&info->deferred_work);
231
232	/* clear out the mapping that we setup */
233	for (i = 0 ; i < info->fix.smem_len; i += PAGE_SIZE) {
234		page = fb_deferred_io_page(info, i);
235		page->mapping = NULL;
236	}
237
238	info->fbops->fb_mmap = NULL;
239	mutex_destroy(&fbdefio->lock);
240}
241EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);
242
243MODULE_LICENSE("GPL");