drivers/video/fb_defio.c

   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
  26 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 */
  40 static 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
  69 int 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 }
  90 EXPORT_SYMBOL_GPL(fb_deferred_io_fsync);
  91
  92 /* vm_ops->page_mkwrite handler */
  93 static 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         /*
 111          * We want the page to remain locked from ->page_mkwrite until
 112          * the PTE is marked dirty to avoid page_mkclean() being called
 113          * before the PTE is updated, which would leave the page ignored
 114          * by defio.
 115          * Do this by locking the page here and informing the caller
 116          * about it with VM_FAULT_LOCKED.
 117          */
 118         lock_page(page);
 119
 120         /* we loop through the pagelist before adding in order
 121         to keep the pagelist sorted */
 122         list_for_each_entry(cur, &fbdefio->pagelist, lru) {
 123                 /* this check is to catch the case where a new
 124                 process could start writing to the same page
 125                 through a new pte. this new access can cause the
 126                 mkwrite even when the original ps's pte is marked
 127                 writable */
 128                 if (unlikely(cur == page))
 129                         goto page_already_added;
 130                 else if (cur->index > page->index)
 131                         break;
 132         }
 133
 134         list_add_tail(&page->lru, &cur->lru);
 135
 136 page_already_added:
 137         mutex_unlock(&fbdefio->lock);
 138
 139         /* come back after delay to process the deferred IO */
 140         schedule_delayed_work(&info->deferred_work, fbdefio->delay);
 141         return VM_FAULT_LOCKED;
 142 }
 143
 144 static const struct vm_operations_struct fb_deferred_io_vm_ops = {
 145         .fault          = fb_deferred_io_fault,
 146         .page_mkwrite   = fb_deferred_io_mkwrite,
 147 };
 148
 149 static int fb_deferred_io_set_page_dirty(struct page *page)
 150 {
 151         if (!PageDirty(page))
 152                 SetPageDirty(page);
 153         return 0;
 154 }
 155
 156 static const struct address_space_operations fb_deferred_io_aops = {
 157         .set_page_dirty = fb_deferred_io_set_page_dirty,
 158 };
 159
 160 static int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
 161 {
 162         vma->vm_ops = &fb_deferred_io_vm_ops;
 163         vma->vm_flags |= ( VM_RESERVED | VM_DONTEXPAND );
 164         if (!(info->flags & FBINFO_VIRTFB))
 165                 vma->vm_flags |= VM_IO;
 166         vma->vm_private_data = info;
 167         return 0;
 168 }
 169
 170 /* workqueue callback */
 171 static void fb_deferred_io_work(struct work_struct *work)
 172 {
 173         struct fb_info *info = container_of(work, struct fb_info,
 174                                                 deferred_work.work);
 175         struct list_head *node, *next;
 176         struct page *cur;
 177         struct fb_deferred_io *fbdefio = info->fbdefio;
 178
 179         /* here we mkclean the pages, then do all deferred IO */
 180         mutex_lock(&fbdefio->lock);
 181         list_for_each_entry(cur, &fbdefio->pagelist, lru) {
 182                 lock_page(cur);
 183                 page_mkclean(cur);
 184                 unlock_page(cur);
 185         }
 186
 187         /* driver's callback with pagelist */
 188         fbdefio->deferred_io(info, &fbdefio->pagelist);
 189
 190         /* clear the list */
 191         list_for_each_safe(node, next, &fbdefio->pagelist) {
 192                 list_del(node);
 193         }
 194         mutex_unlock(&fbdefio->lock);
 195 }
 196
 197 void fb_deferred_io_init(struct fb_info *info)
 198 {
 199         struct fb_deferred_io *fbdefio = info->fbdefio;
 200
 201         BUG_ON(!fbdefio);
 202         mutex_init(&fbdefio->lock);
 203         info->fbops->fb_mmap = fb_deferred_io_mmap;
 204         INIT_DELAYED_WORK(&info->deferred_work, fb_deferred_io_work);
 205         INIT_LIST_HEAD(&fbdefio->pagelist);
 206         if (fbdefio->delay == 0) /* set a default of 1 s */
 207                 fbdefio->delay = HZ;
 208 }
 209 EXPORT_SYMBOL_GPL(fb_deferred_io_init);
 210
 211 void fb_deferred_io_open(struct fb_info *info,
 212                          struct inode *inode,
 213                          struct file *file)
 214 {
 215         file->f_mapping->a_ops = &fb_deferred_io_aops;
 216 }
 217 EXPORT_SYMBOL_GPL(fb_deferred_io_open);
 218
 219 void fb_deferred_io_cleanup(struct fb_info *info)
 220 {
 221         struct fb_deferred_io *fbdefio = info->fbdefio;
 222         struct page *page;
 223         int i;
 224
 225         BUG_ON(!fbdefio);
 226         cancel_delayed_work_sync(&info->deferred_work);
 227
 228         /* clear out the mapping that we setup */
 229         for (i = 0 ; i < info->fix.smem_len; i += PAGE_SIZE) {
 230                 page = fb_deferred_io_page(info, i);
 231                 page->mapping = NULL;
 232         }
 233
 234         info->fbops->fb_mmap = NULL;
 235         mutex_destroy(&fbdefio->lock);
 236 }
 237 EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);
 238
 239 MODULE_LICENSE("GPL");