summaryrefslogtreecommitdiffstats
path: root/drivers/video/fb_defio.c
blob: 1105a591dcc191c3607cac8208b2bfe13eb96e04 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
/*
 *  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>

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\n");

	BUG_ON(!page->mapping);
	page->index = vmf->pgoff;

	vmf->page = page;
	return 0;
}

int fb_deferred_io_fsync(struct file *file, struct dentry *dentry, int datasync)
{
	struct fb_info *info = file->private_data;

	/* Skip if deferred io is compiled-in but disabled on this fbdev */
	if (!info->fbdefio)
		return 0;

	/* Kill off the delayed work */
	cancel_rearming_delayed_work(&info->deferred_work);

	/* Run it immediately */
	return schedule_delayed_work(&info->deferred_work, 0);
}
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 */

	/* protect against the workqueue changing the page list */
	mutex_lock(&fbdefio->lock);

	/* 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 0;
}

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_RESERVED | VM_DONTEXPAND );
	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 fb_deferred_io *fbdefio = info->fbdefio;
	struct page *page, *tmp_page;
	struct list_head *node, *tmp_node;
	struct list_head non_dirty;

	INIT_LIST_HEAD(&non_dirty);

	/* here we mkclean the pages, then do all deferred IO */
	mutex_lock(&fbdefio->lock);
	list_for_each_entry_safe(page, tmp_page, &fbdefio->pagelist, lru) {
		lock_page(page);
		/*
		 * The workqueue callback can be triggered after a
		 * ->page_mkwrite() call but before the PTE has been marked
		 * dirty. In this case page_mkclean() won't "rearm" the page.
		 *
		 * To avoid this, remove those "non-dirty" pages from the
		 * pagelist before calling the driver's callback, then add
		 * them back to get processed on the next work iteration.
		 * At that time, their PTEs will hopefully be dirty for real.
		 */
		if (!page_mkclean(page))
			list_move_tail(&page->lru, &non_dirty);
		unlock_page(page);
	}

	/* driver's callback with pagelist */
	fbdefio->deferred_io(info, &fbdefio->pagelist);

	/* clear the list... */
	list_for_each_safe(node, tmp_node, &fbdefio->pagelist) {
		list_del(node);
	}
	/* ... and add back the "non-dirty" pages to the list */
	list_splice_tail(&non_dirty, &fbdefio->pagelist);
	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 list_head *node, *tmp_node;
	struct page *page;
	int i;

	BUG_ON(!fbdefio);
	cancel_delayed_work(&info->deferred_work);
	flush_scheduled_work();

	/*  the list may have still some non-dirty pages at this point */
	mutex_lock(&fbdefio->lock);
	list_for_each_safe(node, tmp_node, &fbdefio->pagelist) {
		list_del(node);
	}
	mutex_unlock(&fbdefio->lock);

	/* 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");