linux/drivers/video/fb_defio.c
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   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        file_update_time(vma->vm_file);
 108
 109        /* protect against the workqueue changing the page list */
 110        mutex_lock(&fbdefio->lock);
 111
 112        /* first write in this cycle, notify the driver */
 113        if (fbdefio->first_io && list_empty(&fbdefio->pagelist))
 114                fbdefio->first_io(info);
 115
 116        /*
 117         * We want the page to remain locked from ->page_mkwrite until
 118         * the PTE is marked dirty to avoid page_mkclean() being called
 119         * before the PTE is updated, which would leave the page ignored
 120         * by defio.
 121         * Do this by locking the page here and informing the caller
 122         * about it with VM_FAULT_LOCKED.
 123         */
 124        lock_page(page);
 125
 126        /* we loop through the pagelist before adding in order
 127        to keep the pagelist sorted */
 128        list_for_each_entry(cur, &fbdefio->pagelist, lru) {
 129                /* this check is to catch the case where a new
 130                process could start writing to the same page
 131                through a new pte. this new access can cause the
 132                mkwrite even when the original ps's pte is marked
 133                writable */
 134                if (unlikely(cur == page))
 135                        goto page_already_added;
 136                else if (cur->index > page->index)
 137                        break;
 138        }
 139
 140        list_add_tail(&page->lru, &cur->lru);
 141
 142page_already_added:
 143        mutex_unlock(&fbdefio->lock);
 144
 145        /* come back after delay to process the deferred IO */
 146        schedule_delayed_work(&info->deferred_work, fbdefio->delay);
 147        return VM_FAULT_LOCKED;
 148}
 149
 150static const struct vm_operations_struct fb_deferred_io_vm_ops = {
 151        .fault          = fb_deferred_io_fault,
 152        .page_mkwrite   = fb_deferred_io_mkwrite,
 153};
 154
 155static int fb_deferred_io_set_page_dirty(struct page *page)
 156{
 157        if (!PageDirty(page))
 158                SetPageDirty(page);
 159        return 0;
 160}
 161
 162static const struct address_space_operations fb_deferred_io_aops = {
 163        .set_page_dirty = fb_deferred_io_set_page_dirty,
 164};
 165
 166static int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
 167{
 168        vma->vm_ops = &fb_deferred_io_vm_ops;
 169        vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
 170        if (!(info->flags & FBINFO_VIRTFB))
 171                vma->vm_flags |= VM_IO;
 172        vma->vm_private_data = info;
 173        return 0;
 174}
 175
 176/* workqueue callback */
 177static void fb_deferred_io_work(struct work_struct *work)
 178{
 179        struct fb_info *info = container_of(work, struct fb_info,
 180                                                deferred_work.work);
 181        struct list_head *node, *next;
 182        struct page *cur;
 183        struct fb_deferred_io *fbdefio = info->fbdefio;
 184
 185        /* here we mkclean the pages, then do all deferred IO */
 186        mutex_lock(&fbdefio->lock);
 187        list_for_each_entry(cur, &fbdefio->pagelist, lru) {
 188                lock_page(cur);
 189                page_mkclean(cur);
 190                unlock_page(cur);
 191        }
 192
 193        /* driver's callback with pagelist */
 194        fbdefio->deferred_io(info, &fbdefio->pagelist);
 195
 196        /* clear the list */
 197        list_for_each_safe(node, next, &fbdefio->pagelist) {
 198                list_del(node);
 199        }
 200        mutex_unlock(&fbdefio->lock);
 201}
 202
 203void fb_deferred_io_init(struct fb_info *info)
 204{
 205        struct fb_deferred_io *fbdefio = info->fbdefio;
 206
 207        BUG_ON(!fbdefio);
 208        mutex_init(&fbdefio->lock);
 209        info->fbops->fb_mmap = fb_deferred_io_mmap;
 210        INIT_DELAYED_WORK(&info->deferred_work, fb_deferred_io_work);
 211        INIT_LIST_HEAD(&fbdefio->pagelist);
 212        if (fbdefio->delay == 0) /* set a default of 1 s */
 213                fbdefio->delay = HZ;
 214}
 215EXPORT_SYMBOL_GPL(fb_deferred_io_init);
 216
 217void fb_deferred_io_open(struct fb_info *info,
 218                         struct inode *inode,
 219                         struct file *file)
 220{
 221        file->f_mapping->a_ops = &fb_deferred_io_aops;
 222}
 223EXPORT_SYMBOL_GPL(fb_deferred_io_open);
 224
 225void fb_deferred_io_cleanup(struct fb_info *info)
 226{
 227        struct fb_deferred_io *fbdefio = info->fbdefio;
 228        struct page *page;
 229        int i;
 230
 231        BUG_ON(!fbdefio);
 232        cancel_delayed_work_sync(&info->deferred_work);
 233
 234        /* clear out the mapping that we setup */
 235        for (i = 0 ; i < info->fix.smem_len; i += PAGE_SIZE) {
 236                page = fb_deferred_io_page(info, i);
 237                page->mapping = NULL;
 238        }
 239
 240        info->fbops->fb_mmap = NULL;
 241        mutex_destroy(&fbdefio->lock);
 242}
 243EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);
 244
 245MODULE_LICENSE("GPL");
 246
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