/*
 *  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>

static 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 vm_fault_t fb_deferred_io_fault(struct vm_fault *vmf)
{
        unsigned long offset;
        struct page *page;
        struct fb_info *info = vmf->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 (vmf->vma->vm_file)
                page->mapping = vmf->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, loff_t start, loff_t end, int datasync)
{
        struct fb_info *info = file->private_data;
        struct inode *inode = file_inode(file);
        int err = file_write_and_wait_range(file, start, end);
        if (err)
                return err;

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

        inode_lock(inode);
        /* Kill off the delayed work */
        cancel_delayed_work_sync(&info->deferred_work);

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

        return 0;
}
EXPORT_SYMBOL_GPL(fb_deferred_io_fsync);

/* vm_ops->page_mkwrite handler */
static vm_fault_t fb_deferred_io_mkwrite(struct vm_fault *vmf)
{
        struct page *page = vmf->page;
        struct fb_info *info = vmf->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 */

        file_update_time(vmf->vma->vm_file);

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

        /* first write in this cycle, notify the driver */
        if (fbdefio->first_io && list_empty(&fbdefio->pagelist))
                fbdefio->first_io(info);

        /*
         * We want the page to remain locked from ->page_mkwrite until
         * the PTE is marked dirty to avoid page_mkclean() being called
         * before the PTE is updated, which would leave the page ignored
         * by defio.
         * Do this by locking the page here and informing the caller
         * about it with VM_FAULT_LOCKED.
         */
        lock_page(page);

        /* 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 VM_FAULT_LOCKED;
}

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,
};

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_DONTEXPAND | VM_DONTDUMP;
        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 list_head *node, *next;
        struct page *cur;
        struct fb_deferred_io *fbdefio = info->fbdefio;

        /* here we mkclean the pages, then do all deferred IO */
        mutex_lock(&fbdefio->lock);
        list_for_each_entry(cur, &fbdefio->pagelist, lru) {
                lock_page(cur);
                page_mkclean(cur);
                unlock_page(cur);
        }

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

        /* clear the list */
        list_for_each_safe(node, next, &fbdefio->pagelist) {
                list_del(node);
        }
        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);
        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 page *page;
        int i;

        BUG_ON(!fbdefio);
        cancel_delayed_work_sync(&info->deferred_work);

        /* 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;
        }

        mutex_destroy(&fbdefio->lock);
}
EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);