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, int datasync)
  70 {
  71         struct fb_info *info = file->private_data;
  72
  73         /* Skip if deferred io is compiled-in but disabled on this fbdev */
  74         if (!info->fbdefio)
  75                 return 0;
  76
  77         /* Kill off the delayed work */
  78         cancel_rearming_delayed_work(&info->deferred_work);
  79
  80         /* Run it immediately */
  81         return schedule_delayed_work(&info->deferred_work, 0);
  82 }
  83 EXPORT_SYMBOL_GPL(fb_deferred_io_fsync);
  84
  85 /* vm_ops->page_mkwrite handler */
  86 static int fb_deferred_io_mkwrite(struct vm_area_struct *vma,
  87                                   struct vm_fault *vmf)
  88 {
  89         struct page *page = vmf->page;
  90         struct fb_info *info = vma->vm_private_data;
  91         struct fb_deferred_io *fbdefio = info->fbdefio;
  92         struct page *cur;
  93
  94         /* this is a callback we get when userspace first tries to
  95         write to the page. we schedule a workqueue. that workqueue
  96         will eventually mkclean the touched pages and execute the
  97         deferred framebuffer IO. then if userspace touches a page
  98         again, we repeat the same scheme */
  99
 100         /* protect against the workqueue changing the page list */
 101         mutex_lock(&fbdefio->lock);
 102
 103         /* we loop through the pagelist before adding in order
 104         to keep the pagelist sorted */
 105         list_for_each_entry(cur, &fbdefio->pagelist, lru) {
 106                 /* this check is to catch the case where a new
 107                 process could start writing to the same page
 108                 through a new pte. this new access can cause the
 109                 mkwrite even when the original ps's pte is marked
 110                 writable */
 111                 if (unlikely(cur == page))
 112                         goto page_already_added;
 113                 else if (cur->index > page->index)
 114                         break;
 115         }
 116
 117         list_add_tail(&page->lru, &cur->lru);
 118
 119 page_already_added:
 120         mutex_unlock(&fbdefio->lock);
 121
 122         /* come back after delay to process the deferred IO */
 123         schedule_delayed_work(&info->deferred_work, fbdefio->delay);
 124         return 0;
 125 }
 126
 127 static const struct vm_operations_struct fb_deferred_io_vm_ops = {
 128         .fault          = fb_deferred_io_fault,
 129         .page_mkwrite   = fb_deferred_io_mkwrite,
 130 };
 131
 132 static int fb_deferred_io_set_page_dirty(struct page *page)
 133 {
 134         if (!PageDirty(page))
 135                 SetPageDirty(page);
 136         return 0;
 137 }
 138
 139 static const struct address_space_operations fb_deferred_io_aops = {
 140         .set_page_dirty = fb_deferred_io_set_page_dirty,
 141 };
 142
 143 static int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
 144 {
 145         vma->vm_ops = &fb_deferred_io_vm_ops;
 146         vma->vm_flags |= ( VM_RESERVED | VM_DONTEXPAND );
 147         if (!(info->flags & FBINFO_VIRTFB))
 148                 vma->vm_flags |= VM_IO;
 149         vma->vm_private_data = info;
 150         return 0;
 151 }
 152
 153 /* workqueue callback */
 154 static void fb_deferred_io_work(struct work_struct *work)
 155 {
 156         struct fb_info *info = container_of(work, struct fb_info,
 157                                                 deferred_work.work);
 158         struct fb_deferred_io *fbdefio = info->fbdefio;
 159         struct page *page, *tmp_page;
 160         struct list_head *node, *tmp_node;
 161         struct list_head non_dirty;
 162
 163         INIT_LIST_HEAD(&non_dirty);
 164
 165         /* here we mkclean the pages, then do all deferred IO */
 166         mutex_lock(&fbdefio->lock);
 167         list_for_each_entry_safe(page, tmp_page, &fbdefio->pagelist, lru) {
 168                 lock_page(page);
 169                 /*
 170                  * The workqueue callback can be triggered after a
 171                  * ->page_mkwrite() call but before the PTE has been marked
 172                  * dirty. In this case page_mkclean() won't "rearm" the page.
 173                  *
 174                  * To avoid this, remove those "non-dirty" pages from the
 175                  * pagelist before calling the driver's callback, then add
 176                  * them back to get processed on the next work iteration.
 177                  * At that time, their PTEs will hopefully be dirty for real.
 178                  */
 179                 if (!page_mkclean(page))
 180                         list_move_tail(&page->lru, &non_dirty);
 181                 unlock_page(page);
 182         }
 183
 184         /* driver's callback with pagelist */
 185         fbdefio->deferred_io(info, &fbdefio->pagelist);
 186
 187         /* clear the list... */
 188         list_for_each_safe(node, tmp_node, &fbdefio->pagelist) {
 189                 list_del(node);
 190         }
 191         /* ... and add back the "non-dirty" pages to the list */
 192         list_splice_tail(&non_dirty, &fbdefio->pagelist);
 193         mutex_unlock(&fbdefio->lock);
 194 }
 195
 196 void fb_deferred_io_init(struct fb_info *info)
 197 {
 198         struct fb_deferred_io *fbdefio = info->fbdefio;
 199
 200         BUG_ON(!fbdefio);
 201         mutex_init(&fbdefio->lock);
 202         info->fbops->fb_mmap = fb_deferred_io_mmap;
 203         INIT_DELAYED_WORK(&info->deferred_work, fb_deferred_io_work);
 204         INIT_LIST_HEAD(&fbdefio->pagelist);
 205         if (fbdefio->delay == 0) /* set a default of 1 s */
 206                 fbdefio->delay = HZ;
 207 }
 208 EXPORT_SYMBOL_GPL(fb_deferred_io_init);
 209
 210 void fb_deferred_io_open(struct fb_info *info,
 211                          struct inode *inode,
 212                          struct file *file)
 213 {
 214         file->f_mapping->a_ops = &fb_deferred_io_aops;
 215 }
 216 EXPORT_SYMBOL_GPL(fb_deferred_io_open);
 217
 218 void fb_deferred_io_cleanup(struct fb_info *info)
 219 {
 220         struct fb_deferred_io *fbdefio = info->fbdefio;
 221         struct list_head *node, *tmp_node;
 222         struct page *page;
 223         int i;
 224
 225         BUG_ON(!fbdefio);
 226         cancel_delayed_work(&info->deferred_work);
 227         flush_scheduled_work();
 228
 229         /*  the list may have still some non-dirty pages at this point */
 230         mutex_lock(&fbdefio->lock);
 231         list_for_each_safe(node, tmp_node, &fbdefio->pagelist) {
 232                 list_del(node);
 233         }
 234         mutex_unlock(&fbdefio->lock);
 235
 236         /* clear out the mapping that we setup */
 237         for (i = 0 ; i < info->fix.smem_len; i += PAGE_SIZE) {
 238                 page = fb_deferred_io_page(info, i);
 239                 page->mapping = NULL;
 240         }
 241
 242         info->fbops->fb_mmap = NULL;
 243         mutex_destroy(&fbdefio->lock);
 244 }
 245 EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);
 246
 247 MODULE_LICENSE("GPL");