/*
 *  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/time.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 <linux/net.h>
#include <linux/aio.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)
         */
        result = smb_proc_flush(server, SMB_I(dentry->d_inode)->fileid);
        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)
                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_fs_time(dentry->d_inode->i_sb);
                if (result < rsize)
                        break;
        } while (count);

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

io_error:
        kunmap(page);
        unlock_page(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_path.dentry;

        page_cache_get(page);
        error = smb_readpage_sync(dentry, page);
        page_cache_release(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 ret = 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, SMB_I(inode)->fileid, count, offset, wsize);

        do {
                int write_ret;

                if (count < wsize)
                        wsize = count;

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

        kunmap(page);
        return ret;
}

/*
 * 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 writeback_control *wbc)
{
        struct address_space *mapping = page->mapping;
        struct inode *inode;
        unsigned long end_index;
        unsigned offset = PAGE_CACHE_SIZE;
        int err;

        BUG_ON(!mapping);
        inode = mapping->host;
        BUG_ON(!inode);

        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 0; /* truncated - don't care */
do_it:
        page_cache_get(page);
        err = smb_writepage_sync(inode, page, 0, offset);
        SetPageUptodate(page);
        unlock_page(page);
        page_cache_release(page);
        return err;
}

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

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

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

static ssize_t
smb_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
                        unsigned long nr_segs, loff_t pos)
{
        struct file * file = iocb->ki_filp;
        struct dentry * dentry = file->f_path.dentry;
        ssize_t status;

        VERBOSE("file %s/%s, count=%lu@%lu\n", DENTRY_PATH(dentry),
                (unsigned long) iocb->ki_left, (unsigned long) pos);

        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.tv_sec);

        status = generic_file_aio_read(iocb, iov, nr_segs, pos);
out:
        return status;
}

static int
smb_file_mmap(struct file * file, struct vm_area_struct * vma)
{
        struct dentry * dentry = file->f_path.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;
}

static ssize_t
smb_file_splice_read(struct file *file, loff_t *ppos,
                     struct pipe_inode_info *pipe, size_t count,
                     unsigned int flags)
{
        struct dentry *dentry = file->f_path.dentry;
        ssize_t status;

        VERBOSE("file %s/%s, pos=%Ld, count=%lu\n",
                DENTRY_PATH(dentry), *ppos, count);

        status = smb_revalidate_inode(dentry);
        if (status) {
                PARANOIA("%s/%s validation failed, error=%Zd\n",
                         DENTRY_PATH(dentry), status);
                goto out;
        }
        status = generic_file_splice_read(file, ppos, pipe, count, flags);
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_write_begin(struct file *file, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned flags,
                        struct page **pagep, void **fsdata)
{
        pgoff_t index = pos >> PAGE_CACHE_SHIFT;
        *pagep = grab_cache_page_write_begin(mapping, index, flags);
        if (!*pagep)
                return -ENOMEM;
        return 0;
}

static int smb_write_end(struct file *file, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned copied,
                        struct page *page, void *fsdata)
{
        int status;
        unsigned offset = pos & (PAGE_CACHE_SIZE - 1);

        lock_kernel();
        status = smb_updatepage(file, page, offset, copied);
        unlock_kernel();

        if (!status) {
                if (!PageUptodate(page) && copied == PAGE_CACHE_SIZE)
                        SetPageUptodate(page);
                status = copied;
        }

        unlock_page(page);
        page_cache_release(page);

        return status;
}

const struct address_space_operations smb_file_aops = {
        .readpage = smb_readpage,
        .writepage = smb_writepage,
        .write_begin = smb_write_begin,
        .write_end = smb_write_end,
};

/* 
 * Write to a file (through the page cache).
 */
static ssize_t
smb_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
                               unsigned long nr_segs, loff_t pos)
{
        struct file * file = iocb->ki_filp;
        struct dentry * dentry = file->f_path.dentry;
        ssize_t result;

        VERBOSE("file %s/%s, count=%lu@%lu\n",
                DENTRY_PATH(dentry),
                (unsigned long) iocb->ki_left, (unsigned long) pos);

        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 (iocb->ki_left > 0) {
                result = generic_file_aio_write(iocb, iov, nr_segs, pos);
                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.tv_sec,
                        dentry->d_inode->i_atime.tv_sec);
        }
out:
        return result;
}

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

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

static int
smb_file_release(struct inode *inode, struct file * file)
{
        lock_kernel();
        if (!--SMB_I(inode)->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_write_and_wait(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 (mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC))
                error = -EACCES;
        return error;
}

static loff_t smb_remote_llseek(struct file *file, loff_t offset, int origin)
{
        loff_t ret;
        lock_kernel();
        ret = generic_file_llseek_unlocked(file, offset, origin);
        unlock_kernel();
        return ret;
}

const struct file_operations smb_file_operations =
{
        .llseek         = smb_remote_llseek,
        .read           = do_sync_read,
        .aio_read       = smb_file_aio_read,
        .write          = do_sync_write,
        .aio_write      = smb_file_aio_write,
        .ioctl          = smb_ioctl,
        .mmap           = smb_file_mmap,
        .open           = smb_file_open,
        .release        = smb_file_release,
        .fsync          = smb_fsync,
        .splice_read    = smb_file_splice_read,
};

const struct inode_operations smb_file_inode_operations =
{
        .permission     = smb_file_permission,
        .getattr        = smb_getattr,
        .setattr        = smb_notify_change,
};