/*
 *  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/export.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_get_page(struct fb_info *info, unsigned long offs)
{
        struct fb_deferred_io *fbdefio = info->fbdefio;
        const void *screen_buffer = info->screen_buffer;
        struct page *page = NULL;

        if (fbdefio->get_page)
                return fbdefio->get_page(info, offs);

        if (is_vmalloc_addr(screen_buffer + offs))
                page = vmalloc_to_page(screen_buffer + offs);
        else if (info->fix.smem_start)
                page = pfn_to_page((info->fix.smem_start + offs) >> PAGE_SHIFT);

        if (page)
                get_page(page);

        return page;
}

static struct fb_deferred_io_pageref *fb_deferred_io_pageref_lookup(struct fb_info *info,
                                                                    unsigned long offset,
                                                                    struct page *page)
{
        unsigned long pgoff = offset >> PAGE_SHIFT;
        struct fb_deferred_io_pageref *pageref;

        if (fb_WARN_ON_ONCE(info, pgoff >= info->npagerefs))
                return NULL; /* incorrect allocation size */

        /* 1:1 mapping between pageref and page offset */
        pageref = &info->pagerefs[pgoff];

        if (pageref->page)
                goto out;

        pageref->page = page;
        pageref->offset = pgoff << PAGE_SHIFT;
        INIT_LIST_HEAD(&pageref->list);

out:
        if (fb_WARN_ON_ONCE(info, pageref->page != page))
                return NULL; /* inconsistent state */
        return pageref;
}

static struct fb_deferred_io_pageref *fb_deferred_io_pageref_get(struct fb_info *info,
                                                                 unsigned long offset,
                                                                 struct page *page)
{
        struct fb_deferred_io *fbdefio = info->fbdefio;
        struct list_head *pos = &fbdefio->pagereflist;
        struct fb_deferred_io_pageref *pageref, *cur;

        pageref = fb_deferred_io_pageref_lookup(info, offset, page);
        if (!pageref)
                return NULL;

        /*
         * 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 a call to .page_mkwrite even if the original process'
         * PTE is marked writable.
         */
        if (!list_empty(&pageref->list))
                goto pageref_already_added;

        if (unlikely(fbdefio->sort_pagereflist)) {
                /*
                 * We loop through the list of pagerefs before adding in
                 * order to keep the pagerefs sorted. This has significant
                 * overhead of O(n^2) with n being the number of written
                 * pages. If possible, drivers should try to work with
                 * unsorted page lists instead.
                 */
                list_for_each_entry(cur, &fbdefio->pagereflist, list) {
                        if (cur->offset > pageref->offset)
                                break;
                }
                pos = &cur->list;
        }

        list_add_tail(&pageref->list, pos);

pageref_already_added:
        return pageref;
}

static void fb_deferred_io_pageref_put(struct fb_deferred_io_pageref *pageref,
                                       struct fb_info *info)
{
        list_del_init(&pageref->list);
}

/* 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_get_page(info, offset);
        if (!page)
                return VM_FAULT_SIGBUS;

        if (!vmf->vma->vm_file)
                fb_err(info, "no mapping available\n");

        BUG_ON(!info->fbdefio->mapping);

        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);
        flush_delayed_work(&info->deferred_work);
        inode_unlock(inode);

        return 0;
}
EXPORT_SYMBOL_GPL(fb_deferred_io_fsync);

/*
 * Adds a page to the dirty list. Call this from struct
 * vm_operations_struct.page_mkwrite.
 */
static vm_fault_t fb_deferred_io_track_page(struct fb_info *info, unsigned long offset,
                                            struct page *page)
{
        struct fb_deferred_io *fbdefio = info->fbdefio;
        struct fb_deferred_io_pageref *pageref;
        vm_fault_t ret;

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

        pageref = fb_deferred_io_pageref_get(info, offset, page);
        if (WARN_ON_ONCE(!pageref)) {
                ret = VM_FAULT_OOM;
                goto err_mutex_unlock;
        }

        /*
         * We want the page to remain locked from ->page_mkwrite until
         * the PTE is marked dirty to avoid mapping_wrprotect_range()
         * 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(pageref->page);

        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;

err_mutex_unlock:
        mutex_unlock(&fbdefio->lock);
        return ret;
}

/*
 * fb_deferred_io_page_mkwrite - Mark a page as written for deferred I/O
 * @fb_info: The fbdev info structure
 * @vmf: The VM fault
 *
 * 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.
 *
 * Returns:
 * VM_FAULT_LOCKED on success, or a VM_FAULT error otherwise.
 */
static vm_fault_t fb_deferred_io_page_mkwrite(struct fb_info *info, struct vm_fault *vmf)
{
        unsigned long offset = vmf->pgoff << PAGE_SHIFT;
        struct page *page = vmf->page;

        file_update_time(vmf->vma->vm_file);

        return fb_deferred_io_track_page(info, offset, page);
}

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

        return fb_deferred_io_page_mkwrite(info, vmf);
}

static const struct vm_operations_struct fb_deferred_io_vm_ops = {
        .fault          = fb_deferred_io_fault,
        .page_mkwrite   = fb_deferred_io_mkwrite,
};

static const struct address_space_operations fb_deferred_io_aops = {
        .dirty_folio    = noop_dirty_folio,
};

int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
{
        vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);

        vma->vm_ops = &fb_deferred_io_vm_ops;
        vm_flags_set(vma, VM_DONTEXPAND | VM_DONTDUMP);
        if (!(info->flags & FBINFO_VIRTFB))
                vm_flags_set(vma, VM_IO);
        vma->vm_private_data = info;
        return 0;
}
EXPORT_SYMBOL_GPL(fb_deferred_io_mmap);

/* 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_pageref *pageref, *next;
        struct fb_deferred_io *fbdefio = info->fbdefio;

        /* here we wrprotect the page's mappings, then do all deferred IO. */
        mutex_lock(&fbdefio->lock);
#ifdef CONFIG_MMU
        list_for_each_entry(pageref, &fbdefio->pagereflist, list) {
                struct page *page = pageref->page;
                pgoff_t pgoff = pageref->offset >> PAGE_SHIFT;

                mapping_wrprotect_range(fbdefio->mapping, pgoff,
                                        page_to_pfn(page), 1);
        }
#endif

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

        /* clear the list */
        list_for_each_entry_safe(pageref, next, &fbdefio->pagereflist, list)
                fb_deferred_io_pageref_put(pageref, info);

        mutex_unlock(&fbdefio->lock);
}

int fb_deferred_io_init(struct fb_info *info)
{
        struct fb_deferred_io *fbdefio = info->fbdefio;
        struct fb_deferred_io_pageref *pagerefs;
        unsigned long npagerefs;
        int ret;

        BUG_ON(!fbdefio);

        if (WARN_ON(!info->fix.smem_len))
                return -EINVAL;

        mutex_init(&fbdefio->lock);
        INIT_DELAYED_WORK(&info->deferred_work, fb_deferred_io_work);
        INIT_LIST_HEAD(&fbdefio->pagereflist);
        if (fbdefio->delay == 0) /* set a default of 1 s */
                fbdefio->delay = HZ;

        npagerefs = DIV_ROUND_UP(info->fix.smem_len, PAGE_SIZE);

        /* alloc a page ref for each page of the display memory */
        pagerefs = kvzalloc_objs(*pagerefs, npagerefs);
        if (!pagerefs) {
                ret = -ENOMEM;
                goto err;
        }
        info->npagerefs = npagerefs;
        info->pagerefs = pagerefs;

        return 0;

err:
        mutex_destroy(&fbdefio->lock);
        return ret;
}
EXPORT_SYMBOL_GPL(fb_deferred_io_init);

void fb_deferred_io_open(struct fb_info *info,
                         struct inode *inode,
                         struct file *file)
{
        struct fb_deferred_io *fbdefio = info->fbdefio;

        fbdefio->mapping = file->f_mapping;
        file->f_mapping->a_ops = &fb_deferred_io_aops;
        fbdefio->open_count++;
}
EXPORT_SYMBOL_GPL(fb_deferred_io_open);

static void fb_deferred_io_lastclose(struct fb_info *info)
{
        flush_delayed_work(&info->deferred_work);
}

void fb_deferred_io_release(struct fb_info *info)
{
        struct fb_deferred_io *fbdefio = info->fbdefio;

        if (!--fbdefio->open_count)
                fb_deferred_io_lastclose(info);
}
EXPORT_SYMBOL_GPL(fb_deferred_io_release);

void fb_deferred_io_cleanup(struct fb_info *info)
{
        struct fb_deferred_io *fbdefio = info->fbdefio;

        fb_deferred_io_lastclose(info);

        kvfree(info->pagerefs);
        mutex_destroy(&fbdefio->lock);
        fbdefio->mapping = NULL;
}
EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);