vfs_addr.c

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/*
 *  linux/fs/9p/vfs_addr.c
 *
 * This file contians vfs address (mmap) ops for 9P2000.
 *
 *  Copyright (C) 2005 by Eric Van Hensbergen <[email protected]>
 *  Copyright (C) 2002 by Ron Minnich <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to:
 *  Free Software Foundation
 *  51 Franklin Street, Fifth Floor
 *  Boston, MA  02111-1301  USA
 *
 */

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/inet.h>
#include <linux/pagemap.h>
#include <linux/idr.h>
#include <linux/sched.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>

#include "v9fs.h"
#include "v9fs_vfs.h"
#include "cache.h"
#include "fid.h"

static int v9fs_fid_readpage(struct p9_fid *fid, struct page *page)
{
    int retval;
    loff_t offset;
    char *buffer;
    struct inode *inode;

    inode = page->mapping->host;
    p9_debug(P9_DEBUG_VFS, "\n");

    BUG_ON(!PageLocked(page));

    retval = v9fs_readpage_from_fscache(inode, page);
    if (retval == 0)
        return retval;

    buffer = kmap(page);
    offset = page_offset(page);

    retval = v9fs_fid_readn(fid, buffer, NULL, PAGE_CACHE_SIZE, offset);
    if (retval < 0) {
        v9fs_uncache_page(inode, page);
        goto done;
    }

    memset(buffer + retval, 0, PAGE_CACHE_SIZE - retval);
    flush_dcache_page(page);
    SetPageUptodate(page);

    v9fs_readpage_to_fscache(inode, page);
    retval = 0;

done:
    kunmap(page);
    unlock_page(page);
    return retval;
}

static int v9fs_vfs_readpage(struct file *filp, struct page *page)
{
    return v9fs_fid_readpage(filp->private_data, page);
}

static int v9fs_vfs_readpages(struct file *filp, struct address_space *mapping,
                 struct list_head *pages, unsigned nr_pages)
{
    int ret = 0;
    struct inode *inode;

    inode = mapping->host;
    p9_debug(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, filp);

    ret = v9fs_readpages_from_fscache(inode, mapping, pages, &nr_pages);
    if (ret == 0)
        return ret;

    ret = read_cache_pages(mapping, pages, (void *)v9fs_vfs_readpage, filp);
    p9_debug(P9_DEBUG_VFS, "  = %d\n", ret);
    return ret;
}

static int v9fs_release_page(struct page *page, gfp_t gfp)
{
    if (PagePrivate(page))
        return 0;
    return v9fs_fscache_release_page(page, gfp);
}

static void v9fs_invalidate_page(struct page *page, unsigned long offset)
{
    /*
     * If called with zero offset, we should release
     * the private state assocated with the page
     */
    if (offset == 0)
        v9fs_fscache_invalidate_page(page);
}

static int v9fs_vfs_writepage_locked(struct page *page)
{
    char *buffer;
    int retval, len;
    loff_t offset, size;
    mm_segment_t old_fs;
    struct v9fs_inode *v9inode;
    struct inode *inode = page->mapping->host;

    v9inode = V9FS_I(inode);
    size = i_size_read(inode);
    if (page->index == size >> PAGE_CACHE_SHIFT)
        len = size & ~PAGE_CACHE_MASK;
    else
        len = PAGE_CACHE_SIZE;

    set_page_writeback(page);

    buffer = kmap(page);
    offset = page_offset(page);

    old_fs = get_fs();
    set_fs(get_ds());
    /* We should have writeback_fid always set */
    BUG_ON(!v9inode->writeback_fid);

    retval = v9fs_file_write_internal(inode,
                      v9inode->writeback_fid,
                      (__force const char __user *)buffer,
                      len, &offset, 0);
    if (retval > 0)
        retval = 0;

    set_fs(old_fs);
    kunmap(page);
    end_page_writeback(page);
    return retval;
}

static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
{
    int retval;

    retval = v9fs_vfs_writepage_locked(page);
    if (retval < 0) {
        if (retval == -EAGAIN) {
            redirty_page_for_writepage(wbc, page);
            retval = 0;
        } else {
            SetPageError(page);
            mapping_set_error(page->mapping, retval);
        }
    } else
        retval = 0;

    unlock_page(page);
    return retval;
}

static int v9fs_launder_page(struct page *page)
{
    int retval;
    struct inode *inode = page->mapping->host;

    v9fs_fscache_wait_on_page_write(inode, page);
    if (clear_page_dirty_for_io(page)) {
        retval = v9fs_vfs_writepage_locked(page);
        if (retval)
            return retval;
    }
    return 0;
}

static ssize_t
v9fs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
           loff_t pos, unsigned long nr_segs)
{
    /*
     * FIXME
     * Now that we do caching with cache mode enabled, We need
     * to support direct IO
     */
    p9_debug(P9_DEBUG_VFS, "v9fs_direct_IO: v9fs_direct_IO (%s) off/no(%lld/%lu) EINVAL\n",
         iocb->ki_filp->f_path.dentry->d_name.name,
         (long long)pos, nr_segs);

    return -EINVAL;
}

static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
                loff_t pos, unsigned len, unsigned flags,
                struct page **pagep, void **fsdata)
{
    int retval = 0;
    struct page *page;
    struct v9fs_inode *v9inode;
    pgoff_t index = pos >> PAGE_CACHE_SHIFT;
    struct inode *inode = mapping->host;

    v9inode = V9FS_I(inode);
start:
    page = grab_cache_page_write_begin(mapping, index, flags);
    if (!page) {
        retval = -ENOMEM;
        goto out;
    }
    BUG_ON(!v9inode->writeback_fid);
    if (PageUptodate(page))
        goto out;

    if (len == PAGE_CACHE_SIZE)
        goto out;

    retval = v9fs_fid_readpage(v9inode->writeback_fid, page);
    page_cache_release(page);
    if (!retval)
        goto start;
out:
    *pagep = page;
    return retval;
}

static int v9fs_write_end(struct file *filp, struct address_space *mapping,
              loff_t pos, unsigned len, unsigned copied,
              struct page *page, void *fsdata)
{
    loff_t last_pos = pos + copied;
    struct inode *inode = page->mapping->host;

    if (unlikely(copied < len)) {
        /*
         * zero out the rest of the area
         */
        unsigned from = pos & (PAGE_CACHE_SIZE - 1);

        zero_user(page, from + copied, len - copied);
        flush_dcache_page(page);
    }

    if (!PageUptodate(page))
        SetPageUptodate(page);
    /*
     * No need to use i_size_read() here, the i_size
     * cannot change under us because we hold the i_mutex.
     */
    if (last_pos > inode->i_size) {
        inode_add_bytes(inode, last_pos - inode->i_size);
        i_size_write(inode, last_pos);
    }
    set_page_dirty(page);
    unlock_page(page);
    page_cache_release(page);

    return copied;
}


const struct address_space_operations v9fs_addr_operations = {
    .readpage = v9fs_vfs_readpage,
    .readpages = v9fs_vfs_readpages,
    .set_page_dirty = __set_page_dirty_nobuffers,
    .writepage = v9fs_vfs_writepage,
    .write_begin = v9fs_write_begin,
    .write_end = v9fs_write_end,
    .releasepage = v9fs_release_page,
    .invalidatepage = v9fs_invalidate_page,
    .launder_page = v9fs_launder_page,
    .direct_IO = v9fs_direct_IO,
};