/* AFS filesystem file handling
 *
 * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>
#include "internal.h"

static int afs_readpage(struct file *file, struct page *page);
static void afs_invalidatepage(struct page *page, unsigned long offset);
static int afs_releasepage(struct page *page, gfp_t gfp_flags);
static int afs_launder_page(struct page *page);

const struct file_operations afs_file_operations = {
        .open           = afs_open,
        .release        = afs_release,
        .llseek         = generic_file_llseek,
        .read           = do_sync_read,
        .write          = do_sync_write,
        .aio_read       = generic_file_aio_read,
        .aio_write      = afs_file_write,
        .mmap           = generic_file_readonly_mmap,
        .splice_read    = generic_file_splice_read,
        .fsync          = afs_fsync,
        .lock           = afs_lock,
        .flock          = afs_flock,
};

const struct inode_operations afs_file_inode_operations = {
        .getattr        = afs_getattr,
        .setattr        = afs_setattr,
        .permission     = afs_permission,
};

const struct address_space_operations afs_fs_aops = {
        .readpage       = afs_readpage,
        .set_page_dirty = afs_set_page_dirty,
        .launder_page   = afs_launder_page,
        .releasepage    = afs_releasepage,
        .invalidatepage = afs_invalidatepage,
        .prepare_write  = afs_prepare_write,
        .commit_write   = afs_commit_write,
        .writepage      = afs_writepage,
        .writepages     = afs_writepages,
};

/*
 * open an AFS file or directory and attach a key to it
 */
int afs_open(struct inode *inode, struct file *file)
{
        struct afs_vnode *vnode = AFS_FS_I(inode);
        struct key *key;
        int ret;

        _enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode);

        key = afs_request_key(vnode->volume->cell);
        if (IS_ERR(key)) {
                _leave(" = %ld [key]", PTR_ERR(key));
                return PTR_ERR(key);
        }

        ret = afs_validate(vnode, key);
        if (ret < 0) {
                _leave(" = %d [val]", ret);
                return ret;
        }

        file->private_data = key;
        _leave(" = 0");
        return 0;
}

/*
 * release an AFS file or directory and discard its key
 */
int afs_release(struct inode *inode, struct file *file)
{
        struct afs_vnode *vnode = AFS_FS_I(inode);

        _enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode);

        key_put(file->private_data);
        _leave(" = 0");
        return 0;
}

/*
 * deal with notification that a page was read from the cache
 */
#ifdef AFS_CACHING_SUPPORT
static void afs_readpage_read_complete(void *cookie_data,
                                       struct page *page,
                                       void *data,
                                       int error)
{
        _enter("%p,%p,%p,%d", cookie_data, page, data, error);

        if (error)
                SetPageError(page);
        else
                SetPageUptodate(page);
        unlock_page(page);

}
#endif

/*
 * deal with notification that a page was written to the cache
 */
#ifdef AFS_CACHING_SUPPORT
static void afs_readpage_write_complete(void *cookie_data,
                                        struct page *page,
                                        void *data,
                                        int error)
{
        _enter("%p,%p,%p,%d", cookie_data, page, data, error);

        unlock_page(page);
}
#endif

/*
 * AFS read page from file, directory or symlink
 */
static int afs_readpage(struct file *file, struct page *page)
{
        struct afs_vnode *vnode;
        struct inode *inode;
        struct key *key;
        size_t len;
        off_t offset;
        int ret;

        inode = page->mapping->host;

        ASSERT(file != NULL);
        key = file->private_data;
        ASSERT(key != NULL);

        _enter("{%x},{%lu},{%lu}", key_serial(key), inode->i_ino, page->index);

        vnode = AFS_FS_I(inode);

        BUG_ON(!PageLocked(page));

        ret = -ESTALE;
        if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
                goto error;

#ifdef AFS_CACHING_SUPPORT
        /* is it cached? */
        ret = cachefs_read_or_alloc_page(vnode->cache,
                                         page,
                                         afs_file_readpage_read_complete,
                                         NULL,
                                         GFP_KERNEL);
#else
        ret = -ENOBUFS;
#endif

        switch (ret) {
                /* read BIO submitted and wb-journal entry found */
        case 1:
                BUG(); // TODO - handle wb-journal match

                /* read BIO submitted (page in cache) */
        case 0:
                break;

                /* no page available in cache */
        case -ENOBUFS:
        case -ENODATA:
        default:
                offset = page->index << PAGE_CACHE_SHIFT;
                len = min_t(size_t, i_size_read(inode) - offset, PAGE_SIZE);

                /* read the contents of the file from the server into the
                 * page */
                ret = afs_vnode_fetch_data(vnode, key, offset, len, page);
                if (ret < 0) {
                        if (ret == -ENOENT) {
                                _debug("got NOENT from server"
                                       " - marking file deleted and stale");
                                set_bit(AFS_VNODE_DELETED, &vnode->flags);
                                ret = -ESTALE;
                        }
#ifdef AFS_CACHING_SUPPORT
                        cachefs_uncache_page(vnode->cache, page);
#endif
                        goto error;
                }

                SetPageUptodate(page);

#ifdef AFS_CACHING_SUPPORT
                if (cachefs_write_page(vnode->cache,
                                       page,
                                       afs_file_readpage_write_complete,
                                       NULL,
                                       GFP_KERNEL) != 0
                    ) {
                        cachefs_uncache_page(vnode->cache, page);
                        unlock_page(page);
                }
#else
                unlock_page(page);
#endif
        }

        _leave(" = 0");
        return 0;

error:
        SetPageError(page);
        unlock_page(page);
        _leave(" = %d", ret);
        return ret;
}

/*
 * invalidate part or all of a page
 */
static void afs_invalidatepage(struct page *page, unsigned long offset)
{
        int ret = 1;

        _enter("{%lu},%lu", page->index, offset);

        BUG_ON(!PageLocked(page));

        if (PagePrivate(page)) {
                /* We release buffers only if the entire page is being
                 * invalidated.
                 * The get_block cached value has been unconditionally
                 * invalidated, so real IO is not possible anymore.
                 */
                if (offset == 0) {
                        BUG_ON(!PageLocked(page));

                        ret = 0;
                        if (!PageWriteback(page))
                                ret = page->mapping->a_ops->releasepage(page,
                                                                        0);
                        /* possibly should BUG_ON(!ret); - neilb */
                }
        }

        _leave(" = %d", ret);
}

/*
 * write back a dirty page
 */
static int afs_launder_page(struct page *page)
{
        _enter("{%lu}", page->index);

        return 0;
}

/*
 * release a page and cleanup its private data
 */
static int afs_releasepage(struct page *page, gfp_t gfp_flags)
{
        struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
        struct afs_writeback *wb;

        _enter("{{%x:%u}[%lu],%lx},%x",
               vnode->fid.vid, vnode->fid.vnode, page->index, page->flags,
               gfp_flags);

        if (PagePrivate(page)) {
                wb = (struct afs_writeback *) page_private(page);
                ASSERT(wb != NULL);
                set_page_private(page, 0);
                ClearPagePrivate(page);
                afs_put_writeback(wb);
        }

        _leave(" = 0");
        return 0;
}