/*
 *  file.c
 *
 *  Copyright (C) 1995, 1996, 1997 by Paal-Kr. Engstad and Volker Lendecke
 *  Copyright (C) 1997 by Volker Lendecke
 *
 *  Please add a note about your changes to smbfs in the ChangeLog file.
 */

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>

#include <asm/uaccess.h>
#include <asm/system.h>

#include <linux/smbno.h>
#include <linux/smb_fs.h>

#include "smb_debug.h"
#include "proto.h"

static int
smb_fsync(struct file *file, struct dentry * dentry, int datasync)
{
        struct smb_sb_info *server = server_from_dentry(dentry);
        int result;

        VERBOSE("sync file %s/%s\n", DENTRY_PATH(dentry));

        /*
         * The VFS will writepage() all dirty pages for us, but we
         * should send a SMBflush to the server, letting it know that
         * we want things synchronized with actual storage.
         *
         * Note: this function requires all pages to have been written already
         *       (should be ok with writepage_sync)
         */
        smb_lock_server(server);
        result = smb_proc_flush(server, dentry->d_inode->u.smbfs_i.fileid);
        smb_unlock_server(server);
        return result;
}

/*
 * Read a page synchronously.
 */
static int
smb_readpage_sync(struct dentry *dentry, struct page *page)
{
        char *buffer = kmap(page);
        loff_t offset = (loff_t)page->index << PAGE_CACHE_SHIFT;
        struct smb_sb_info *server = server_from_dentry(dentry);
        unsigned int rsize = smb_get_rsize(server);
        int count = PAGE_SIZE;
        int result;

        VERBOSE("file %s/%s, count=%d@%ld, rsize=%d\n",
                DENTRY_PATH(dentry), count, offset, rsize);

        result = smb_open(dentry, SMB_O_RDONLY);
        if (result < 0) {
                PARANOIA("%s/%s open failed, error=%d\n",
                         DENTRY_PATH(dentry), result);
                goto io_error;
        }

        do {
                if (count < rsize)
                        rsize = count;

                result = server->ops->read(dentry->d_inode,offset,rsize,buffer);
                if (result < 0)
                        goto io_error;

                count -= result;
                offset += result;
                buffer += result;
                dentry->d_inode->i_atime = CURRENT_TIME;
                if (result < rsize)
                        break;
        } while (count);

        memset(buffer, 0, count);
        flush_dcache_page(page);
        SetPageUptodate(page);
        result = 0;

io_error:
        kunmap(page);
        UnlockPage(page);
        return result;
}

/*
 * We are called with the page locked and we unlock it when done.
 */
static int
smb_readpage(struct file *file, struct page *page)
{
        int             error;
        struct dentry  *dentry = file->f_dentry;

        get_page(page);
        error = smb_readpage_sync(dentry, page);
        put_page(page);
        return error;
}

/*
 * Write a page synchronously.
 * Offset is the data offset within the page.
 */
static int
smb_writepage_sync(struct inode *inode, struct page *page,
                   unsigned long pageoffset, unsigned int count)
{
        loff_t offset;
        char *buffer = kmap(page) + pageoffset;
        struct smb_sb_info *server = server_from_inode(inode);
        unsigned int wsize = smb_get_wsize(server);
        int result, written = 0;

        offset = ((loff_t)page->index << PAGE_CACHE_SHIFT) + pageoffset;
        VERBOSE("file ino=%ld, fileid=%d, count=%d@%Ld, wsize=%d\n",
                inode->i_ino, inode->u.smbfs_i.fileid, count, offset, wsize);

        do {
                if (count < wsize)
                        wsize = count;

                result = server->ops->write(inode, offset, wsize, buffer);
                if (result < 0) {
                        PARANOIA("failed write, wsize=%d, result=%d\n",
                                 wsize, result);
                        break;
                }
                /* N.B. what if result < wsize?? */
#ifdef SMBFS_PARANOIA
                if (result < wsize)
                        PARANOIA("short write, wsize=%d, result=%d\n",
                                 wsize, result);
#endif
                buffer += wsize;
                offset += wsize;
                written += wsize;
                count -= wsize;
                /*
                 * Update the inode now rather than waiting for a refresh.
                 */
                inode->i_mtime = inode->i_atime = CURRENT_TIME;
                inode->u.smbfs_i.flags |= SMB_F_LOCALWRITE;
                if (offset > inode->i_size)
                        inode->i_size = offset;
        } while (count);

        kunmap(page);
        return written ? written : result;
}

/*
 * Write a page to the server. This will be used for NFS swapping only
 * (for now), and we currently do this synchronously only.
 *
 * We are called with the page locked and we unlock it when done.
 */
static int
smb_writepage(struct page *page)
{
        struct address_space *mapping = page->mapping;
        struct inode *inode;
        unsigned long end_index;
        unsigned offset = PAGE_CACHE_SIZE;
        int err;

        if (!mapping)
                BUG();
        inode = mapping->host;
        if (!inode)
                BUG();

        end_index = inode->i_size >> PAGE_CACHE_SHIFT;

        /* easy case */
        if (page->index < end_index)
                goto do_it;
        /* things got complicated... */
        offset = inode->i_size & (PAGE_CACHE_SIZE-1);
        /* OK, are we completely out? */
        if (page->index >= end_index+1 || !offset)
                return -EIO;
do_it:
        get_page(page);
        err = smb_writepage_sync(inode, page, 0, offset);
        SetPageUptodate(page);
        UnlockPage(page);
        put_page(page);
        return err;
}

static int
smb_updatepage(struct file *file, struct page *page, unsigned long offset,
               unsigned int count)
{
        struct dentry *dentry = file->f_dentry;

        DEBUG1("(%s/%s %d@%ld)\n", DENTRY_PATH(dentry), 
               count, (page->index << PAGE_CACHE_SHIFT)+offset);

        return smb_writepage_sync(dentry->d_inode, page, offset, count);
}

static ssize_t
smb_file_read(struct file * file, char * buf, size_t count, loff_t *ppos)
{
        struct dentry * dentry = file->f_dentry;
        ssize_t status;

        VERBOSE("file %s/%s, count=%lu@%lu\n", DENTRY_PATH(dentry),
                (unsigned long) count, (unsigned long) *ppos);

        status = smb_revalidate_inode(dentry);
        if (status) {
                PARANOIA("%s/%s validation failed, error=%Zd\n",
                         DENTRY_PATH(dentry), status);
                goto out;
        }

        VERBOSE("before read, size=%ld, flags=%x, atime=%ld\n",
                (long)dentry->d_inode->i_size,
                dentry->d_inode->i_flags, dentry->d_inode->i_atime);

        status = generic_file_read(file, buf, count, ppos);
out:
        return status;
}

static int
smb_file_mmap(struct file * file, struct vm_area_struct * vma)
{
        struct dentry * dentry = file->f_dentry;
        int     status;

        VERBOSE("file %s/%s, address %lu - %lu\n",
                DENTRY_PATH(dentry), vma->vm_start, vma->vm_end);

        status = smb_revalidate_inode(dentry);
        if (status) {
                PARANOIA("%s/%s validation failed, error=%d\n",
                         DENTRY_PATH(dentry), status);
                goto out;
        }
        status = generic_file_mmap(file, vma);
out:
        return status;
}

/*
 * This does the "real" work of the write. The generic routine has
 * allocated the page, locked it, done all the page alignment stuff
 * calculations etc. Now we should just copy the data from user
 * space and write it back to the real medium..
 *
 * If the writer ends up delaying the write, the writer needs to
 * increment the page use counts until he is done with the page.
 */
static int smb_prepare_write(struct file *file, struct page *page, 
                             unsigned offset, unsigned to)
{
        return 0;
}

static int smb_commit_write(struct file *file, struct page *page,
                            unsigned offset, unsigned to)
{
        int status;

        status = -EFAULT;
        lock_kernel();
        status = smb_updatepage(file, page, offset, to-offset);
        unlock_kernel();
        return status;
}

struct address_space_operations smb_file_aops = {
        readpage: smb_readpage,
        writepage: smb_writepage,
        prepare_write: smb_prepare_write,
        commit_write: smb_commit_write
};

/* 
 * Write to a file (through the page cache).
 */
static ssize_t
smb_file_write(struct file *file, const char *buf, size_t count, loff_t *ppos)
{
        struct dentry * dentry = file->f_dentry;
        ssize_t result;

        VERBOSE("file %s/%s, count=%lu@%lu\n",
                DENTRY_PATH(dentry),
                (unsigned long) count, (unsigned long) *ppos);

        result = smb_revalidate_inode(dentry);
        if (result) {
                PARANOIA("%s/%s validation failed, error=%Zd\n",
                         DENTRY_PATH(dentry), result);
                goto out;
        }

        result = smb_open(dentry, SMB_O_WRONLY);
        if (result)
                goto out;

        if (count > 0) {
                result = generic_file_write(file, buf, count, ppos);
                VERBOSE("pos=%ld, size=%ld, mtime=%ld, atime=%ld\n",
                        (long) file->f_pos, (long) dentry->d_inode->i_size,
                        dentry->d_inode->i_mtime, dentry->d_inode->i_atime);
        }
out:
        return result;
}

static int
smb_file_open(struct inode *inode, struct file * file)
{
        int result;
        struct dentry *dentry = file->f_dentry;
        int smb_mode = (file->f_mode & O_ACCMODE) - 1;

        lock_kernel();
        result = smb_open(dentry, smb_mode);
        if (result)
                goto out;
        inode->u.smbfs_i.openers++;
out:
        unlock_kernel();
        return 0;
}

static int
smb_file_release(struct inode *inode, struct file * file)
{
        lock_kernel();
        if (!--inode->u.smbfs_i.openers) {
                /* We must flush any dirty pages now as we won't be able to
                   write anything after close. mmap can trigger this.
                   "openers" should perhaps include mmap'ers ... */
                filemap_fdatasync(inode->i_mapping);
                filemap_fdatawait(inode->i_mapping);
                smb_close(inode);
        }
        unlock_kernel();
        return 0;
}

/*
 * Check whether the required access is compatible with
 * an inode's permission. SMB doesn't recognize superuser
 * privileges, so we need our own check for this.
 */
static int
smb_file_permission(struct inode *inode, int mask)
{
        int mode = inode->i_mode;
        int error = 0;

        VERBOSE("mode=%x, mask=%x\n", mode, mask);

        /* Look at user permissions */
        mode >>= 6;
        if ((mode & 7 & mask) != mask)
                error = -EACCES;
        return error;
}

struct file_operations smb_file_operations =
{
        llseek:         generic_file_llseek,
        read:           smb_file_read,
        write:          smb_file_write,
        ioctl:          smb_ioctl,
        mmap:           smb_file_mmap,
        open:           smb_file_open,
        release:        smb_file_release,
        fsync:          smb_fsync,
};

struct inode_operations smb_file_inode_operations =
{
        permission:     smb_file_permission,
        revalidate:     smb_revalidate_inode,
        setattr:        smb_notify_change,
};