/*
 * fs/logfs/file.c      - prepare_write, commit_write and friends
 *
 * As should be obvious for Linux kernel code, license is GPLv2
 *
 * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
 */
#include "logfs.h"
#include <linux/sched.h>
#include <linux/writeback.h>

static int logfs_write_begin(struct file *file, struct address_space *mapping,
                loff_t pos, unsigned len, unsigned flags,
                struct page **pagep, void **fsdata)
{
        struct inode *inode = mapping->host;
        struct page *page;
        pgoff_t index = pos >> PAGE_SHIFT;

        page = grab_cache_page_write_begin(mapping, index, flags);
        if (!page)
                return -ENOMEM;
        *pagep = page;

        if ((len == PAGE_SIZE) || PageUptodate(page))
                return 0;
        if ((pos & PAGE_MASK) >= i_size_read(inode)) {
                unsigned start = pos & (PAGE_SIZE - 1);
                unsigned end = start + len;

                /* Reading beyond i_size is simple: memset to zero */
                zero_user_segments(page, 0, start, end, PAGE_SIZE);
                return 0;
        }
        return logfs_readpage_nolock(page);
}

static int logfs_write_end(struct file *file, struct address_space *mapping,
                loff_t pos, unsigned len, unsigned copied, struct page *page,
                void *fsdata)
{
        struct inode *inode = mapping->host;
        pgoff_t index = page->index;
        unsigned start = pos & (PAGE_SIZE - 1);
        unsigned end = start + copied;
        int ret = 0;

        BUG_ON(PAGE_SIZE != inode->i_sb->s_blocksize);
        BUG_ON(page->index > I3_BLOCKS);

        if (copied < len) {
                /*
                 * Short write of a non-initialized paged.  Just tell userspace
                 * to retry the entire page.
                 */
                if (!PageUptodate(page)) {
                        copied = 0;
                        goto out;
                }
        }
        if (copied == 0)
                goto out; /* FIXME: do we need to update inode? */

        if (i_size_read(inode) < (index << PAGE_SHIFT) + end) {
                i_size_write(inode, (index << PAGE_SHIFT) + end);
                mark_inode_dirty_sync(inode);
        }

        SetPageUptodate(page);
        if (!PageDirty(page)) {
                if (!get_page_reserve(inode, page))
                        __set_page_dirty_nobuffers(page);
                else
                        ret = logfs_write_buf(inode, page, WF_LOCK);
        }
out:
        unlock_page(page);
        put_page(page);
        return ret ? ret : copied;
}

int logfs_readpage(struct file *file, struct page *page)
{
        int ret;

        ret = logfs_readpage_nolock(page);
        unlock_page(page);
        return ret;
}

/* Clear the page's dirty flag in the radix tree. */
/* TODO: mucking with PageWriteback is silly.  Add a generic function to clear
 * the dirty bit from the radix tree for filesystems that don't have to wait
 * for page writeback to finish (i.e. any compressing filesystem).
 */
static void clear_radix_tree_dirty(struct page *page)
{
        BUG_ON(PagePrivate(page) || page->private);
        set_page_writeback(page);
        end_page_writeback(page);
}

static int __logfs_writepage(struct page *page)
{
        struct inode *inode = page->mapping->host;
        int err;

        err = logfs_write_buf(inode, page, WF_LOCK);
        if (err)
                set_page_dirty(page);
        else
                clear_radix_tree_dirty(page);
        unlock_page(page);
        return err;
}

static int logfs_writepage(struct page *page, struct writeback_control *wbc)
{
        struct inode *inode = page->mapping->host;
        loff_t i_size = i_size_read(inode);
        pgoff_t end_index = i_size >> PAGE_SHIFT;
        unsigned offset;
        u64 bix;
        level_t level;

        log_file("logfs_writepage(%lx, %lx, %p)\n", inode->i_ino, page->index,
                        page);

        logfs_unpack_index(page->index, &bix, &level);

        /* Indirect blocks are never truncated */
        if (level != 0)
                return __logfs_writepage(page);

        /*
         * TODO: everything below is a near-verbatim copy of nobh_writepage().
         * The relevant bits should be factored out after logfs is merged.
         */

        /* Is the page fully inside i_size? */
        if (bix < end_index)
                return __logfs_writepage(page);

         /* Is the page fully outside i_size? (truncate in progress) */
        offset = i_size & (PAGE_SIZE-1);
        if (bix > end_index || offset == 0) {
                unlock_page(page);
                return 0; /* don't care */
        }

        /*
         * The page straddles i_size.  It must be zeroed out on each and every
         * writepage invokation because it may be mmapped.  "A file is mapped
         * in multiples of the page size.  For a file that is not a multiple of
         * the  page size, the remaining memory is zeroed when mapped, and
         * writes to that region are not written out to the file."
         */
        zero_user_segment(page, offset, PAGE_SIZE);
        return __logfs_writepage(page);
}

static void logfs_invalidatepage(struct page *page, unsigned int offset,
                                 unsigned int length)
{
        struct logfs_block *block = logfs_block(page);

        if (block->reserved_bytes) {
                struct super_block *sb = page->mapping->host->i_sb;
                struct logfs_super *super = logfs_super(sb);

                super->s_dirty_pages -= block->reserved_bytes;
                block->ops->free_block(sb, block);
                BUG_ON(bitmap_weight(block->alias_map, LOGFS_BLOCK_FACTOR));
        } else
                move_page_to_btree(page);
        BUG_ON(PagePrivate(page) || page->private);
}

static int logfs_releasepage(struct page *page, gfp_t only_xfs_uses_this)
{
        return 0; /* None of these are easy to release */
}


long logfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        struct inode *inode = file_inode(file);
        struct logfs_inode *li = logfs_inode(inode);
        unsigned int oldflags, flags;
        int err;

        switch (cmd) {
        case FS_IOC_GETFLAGS:
                flags = li->li_flags & LOGFS_FL_USER_VISIBLE;
                return put_user(flags, (int __user *)arg);
        case FS_IOC_SETFLAGS:
                if (IS_RDONLY(inode))
                        return -EROFS;

                if (!inode_owner_or_capable(inode))
                        return -EACCES;

                err = get_user(flags, (int __user *)arg);
                if (err)
                        return err;

                inode_lock(inode);
                oldflags = li->li_flags;
                flags &= LOGFS_FL_USER_MODIFIABLE;
                flags |= oldflags & ~LOGFS_FL_USER_MODIFIABLE;
                li->li_flags = flags;
                inode_unlock(inode);

                inode->i_ctime = CURRENT_TIME;
                mark_inode_dirty_sync(inode);
                return 0;

        default:
                return -ENOTTY;
        }
}

int logfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{
        struct super_block *sb = file->f_mapping->host->i_sb;
        struct inode *inode = file->f_mapping->host;
        int ret;

        ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
        if (ret)
                return ret;

        inode_lock(inode);
        logfs_get_wblocks(sb, NULL, WF_LOCK);
        logfs_write_anchor(sb);
        logfs_put_wblocks(sb, NULL, WF_LOCK);
        inode_unlock(inode);

        return 0;
}

static int logfs_setattr(struct dentry *dentry, struct iattr *attr)
{
        struct inode *inode = d_inode(dentry);
        int err = 0;

        err = inode_change_ok(inode, attr);
        if (err)
                return err;

        if (attr->ia_valid & ATTR_SIZE) {
                err = logfs_truncate(inode, attr->ia_size);
                if (err)
                        return err;
        }

        setattr_copy(inode, attr);
        mark_inode_dirty(inode);
        return 0;
}

const struct inode_operations logfs_reg_iops = {
        .setattr        = logfs_setattr,
};

const struct file_operations logfs_reg_fops = {
        .read_iter      = generic_file_read_iter,
        .write_iter     = generic_file_write_iter,
        .fsync          = logfs_fsync,
        .unlocked_ioctl = logfs_ioctl,
        .llseek         = generic_file_llseek,
        .mmap           = generic_file_readonly_mmap,
        .open           = generic_file_open,
};

const struct address_space_operations logfs_reg_aops = {
        .invalidatepage = logfs_invalidatepage,
        .readpage       = logfs_readpage,
        .releasepage    = logfs_releasepage,
        .set_page_dirty = __set_page_dirty_nobuffers,
        .writepage      = logfs_writepage,
        .writepages     = generic_writepages,
        .write_begin    = logfs_write_begin,
        .write_end      = logfs_write_end,
};