Linux 2.6.19.7

[linux-2.6/suspend2-2.6.19.git] / fs / ecryptfs / mmap.c

/**
 * eCryptfs: Linux filesystem encryption layer
 * This is where eCryptfs coordinates the symmetric encryption and
 * decryption of the file data as it passes between the lower
 * encrypted file and the upper decrypted file.
 *
 * Copyright (C) 1997-2003 Erez Zadok
 * Copyright (C) 2001-2003 Stony Brook University
 * Copyright (C) 2004-2006 International Business Machines Corp.
 *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.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.
 *
 * 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 the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 */

#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/page-flags.h>
#include <linux/mount.h>
#include <linux/file.h>
#include <linux/crypto.h>
#include <linux/scatterlist.h>
#include "ecryptfs_kernel.h"

struct kmem_cache *ecryptfs_lower_page_cache;

/**
 * ecryptfs_get1page
 *
 * Get one page from cache or lower f/s, return error otherwise.
 *
 * Returns unlocked and up-to-date page (if ok), with increased
 * refcnt.
 */
static struct page *ecryptfs_get1page(struct file *file, int index)
{
        struct page *page;
        struct dentry *dentry;
        struct inode *inode;
        struct address_space *mapping;

        dentry = file->f_dentry;
        inode = dentry->d_inode;
        mapping = inode->i_mapping;
        page = read_cache_page(mapping, index,
                               (filler_t *)mapping->a_ops->readpage,
                               (void *)file);
        if (IS_ERR(page))
                goto out;
        wait_on_page_locked(page);
out:
        return page;
}

static
int write_zeros(struct file *file, pgoff_t index, int start, int num_zeros);

/**
 * ecryptfs_fill_zeros
 * @file: The ecryptfs file
 * @new_length: The new length of the data in the underlying file;
 *              everything between the prior end of the file and the
 *              new end of the file will be filled with zero's.
 *              new_length must be greater than  current length
 *
 * Function for handling lseek-ing past the end of the file.
 *
 * This function does not support shrinking, only growing a file.
 *
 * Returns zero on success; non-zero otherwise.
 */
int ecryptfs_fill_zeros(struct file *file, loff_t new_length)
{
        int rc = 0;
        struct dentry *dentry = file->f_dentry;
        struct inode *inode = dentry->d_inode;
        pgoff_t old_end_page_index = 0;
        pgoff_t index = old_end_page_index;
        int old_end_pos_in_page = -1;
        pgoff_t new_end_page_index;
        int new_end_pos_in_page;
        loff_t cur_length = i_size_read(inode);

        if (cur_length != 0) {
                index = old_end_page_index =
                    ((cur_length - 1) >> PAGE_CACHE_SHIFT);
                old_end_pos_in_page = ((cur_length - 1) & ~PAGE_CACHE_MASK);
        }
        new_end_page_index = ((new_length - 1) >> PAGE_CACHE_SHIFT);
        new_end_pos_in_page = ((new_length - 1) & ~PAGE_CACHE_MASK);
        ecryptfs_printk(KERN_DEBUG, "old_end_page_index = [0x%.16x]; "
                        "old_end_pos_in_page = [%d]; "
                        "new_end_page_index = [0x%.16x]; "
                        "new_end_pos_in_page = [%d]\n",
                        old_end_page_index, old_end_pos_in_page,
                        new_end_page_index, new_end_pos_in_page);
        if (old_end_page_index == new_end_page_index) {
                /* Start and end are in the same page; we just need to
                 * set a portion of the existing page to zero's */
                rc = write_zeros(file, index, (old_end_pos_in_page + 1),
                                 (new_end_pos_in_page - old_end_pos_in_page));
                if (rc)
                        ecryptfs_printk(KERN_ERR, "write_zeros(file=[%p], "
                                        "index=[0x%.16x], "
                                        "old_end_pos_in_page=[d], "
                                        "(PAGE_CACHE_SIZE - new_end_pos_in_page"
                                        "=[%d]"
                                        ")=[d]) returned [%d]\n", file, index,
                                        old_end_pos_in_page,
                                        new_end_pos_in_page,
                                        (PAGE_CACHE_SIZE - new_end_pos_in_page),
                                        rc);
                goto out;
        }
        /* Fill the remainder of the previous last page with zeros */
        rc = write_zeros(file, index, (old_end_pos_in_page + 1),
                         ((PAGE_CACHE_SIZE - 1) - old_end_pos_in_page));
        if (rc) {
                ecryptfs_printk(KERN_ERR, "write_zeros(file=[%p], "
                                "index=[0x%.16x], old_end_pos_in_page=[d], "
                                "(PAGE_CACHE_SIZE - old_end_pos_in_page)=[d]) "
                                "returned [%d]\n", file, index,
                                old_end_pos_in_page,
                                (PAGE_CACHE_SIZE - old_end_pos_in_page), rc);
                goto out;
        }
        index++;
        while (index < new_end_page_index) {
                /* Fill all intermediate pages with zeros */
                rc = write_zeros(file, index, 0, PAGE_CACHE_SIZE);
                if (rc) {
                        ecryptfs_printk(KERN_ERR, "write_zeros(file=[%p], "
                                        "index=[0x%.16x], "
                                        "old_end_pos_in_page=[d], "
                                        "(PAGE_CACHE_SIZE - new_end_pos_in_page"
                                        "=[%d]"
                                        ")=[d]) returned [%d]\n", file, index,
                                        old_end_pos_in_page,
                                        new_end_pos_in_page,
                                        (PAGE_CACHE_SIZE - new_end_pos_in_page),
                                        rc);
                        goto out;
                }
                index++;
        }
        /* Fill the portion at the beginning of the last new page with
         * zero's */
        rc = write_zeros(file, index, 0, (new_end_pos_in_page + 1));
        if (rc) {
                ecryptfs_printk(KERN_ERR, "write_zeros(file="
                                "[%p], index=[0x%.16x], 0, "
                                "new_end_pos_in_page=[%d]"
                                "returned [%d]\n", file, index,
                                new_end_pos_in_page, rc);
                goto out;
        }
out:
        return rc;
}

/**
 * ecryptfs_writepage
 * @page: Page that is locked before this call is made
 *
 * Returns zero on success; non-zero otherwise
 */
static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
{
        struct ecryptfs_page_crypt_context ctx;
        int rc;

        ctx.page = page;
        ctx.mode = ECRYPTFS_WRITEPAGE_MODE;
        ctx.param.wbc = wbc;
        rc = ecryptfs_encrypt_page(&ctx);
        if (rc) {
                ecryptfs_printk(KERN_WARNING, "Error encrypting "
                                "page (upper index [0x%.16x])\n", page->index);
                ClearPageUptodate(page);
                goto out;
        }
        SetPageUptodate(page);
        unlock_page(page);
out:
        return rc;
}

/**
 * Reads the data from the lower file file at index lower_page_index
 * and copies that data into page.
 *
 * @param page  Page to fill
 * @param lower_page_index Index of the page in the lower file to get
 */
int ecryptfs_do_readpage(struct file *file, struct page *page,
                         pgoff_t lower_page_index)
{
        int rc;
        struct dentry *dentry;
        struct file *lower_file;
        struct dentry *lower_dentry;
        struct inode *inode;
        struct inode *lower_inode;
        char *page_data;
        struct page *lower_page = NULL;
        char *lower_page_data;
        const struct address_space_operations *lower_a_ops;

        dentry = file->f_dentry;
        lower_file = ecryptfs_file_to_lower(file);
        lower_dentry = ecryptfs_dentry_to_lower(dentry);
        inode = dentry->d_inode;
        lower_inode = ecryptfs_inode_to_lower(inode);
        lower_a_ops = lower_inode->i_mapping->a_ops;
        lower_page = read_cache_page(lower_inode->i_mapping, lower_page_index,
                                     (filler_t *)lower_a_ops->readpage,
                                     (void *)lower_file);
        if (IS_ERR(lower_page)) {
                rc = PTR_ERR(lower_page);
                lower_page = NULL;
                ecryptfs_printk(KERN_ERR, "Error reading from page cache\n");
                goto out;
        }
        wait_on_page_locked(lower_page);
        page_data = (char *)kmap(page);
        if (!page_data) {
                rc = -ENOMEM;
                ecryptfs_printk(KERN_ERR, "Error mapping page\n");
                goto out;
        }
        lower_page_data = (char *)kmap(lower_page);
        if (!lower_page_data) {
                rc = -ENOMEM;
                ecryptfs_printk(KERN_ERR, "Error mapping page\n");
                kunmap(page);
                goto out;
        }
        memcpy(page_data, lower_page_data, PAGE_CACHE_SIZE);
        kunmap(lower_page);
        kunmap(page);
        rc = 0;
out:
        if (likely(lower_page))
                page_cache_release(lower_page);
        if (rc == 0)
                SetPageUptodate(page);
        else
                ClearPageUptodate(page);
        return rc;
}

/**
 * ecryptfs_readpage
 * @file: This is an ecryptfs file
 * @page: ecryptfs associated page to stick the read data into
 *
 * Read in a page, decrypting if necessary.
 *
 * Returns zero on success; non-zero on error.
 */
static int ecryptfs_readpage(struct file *file, struct page *page)
{
        int rc = 0;
        struct ecryptfs_crypt_stat *crypt_stat;

        BUG_ON(!(file && file->f_dentry && file->f_dentry->d_inode));
        crypt_stat =
                &ecryptfs_inode_to_private(file->f_dentry->d_inode)->crypt_stat;
        if (!crypt_stat
            || !ECRYPTFS_CHECK_FLAG(crypt_stat->flags, ECRYPTFS_ENCRYPTED)
            || ECRYPTFS_CHECK_FLAG(crypt_stat->flags, ECRYPTFS_NEW_FILE)) {
                ecryptfs_printk(KERN_DEBUG,
                                "Passing through unencrypted page\n");
                rc = ecryptfs_do_readpage(file, page, page->index);
                if (rc) {
                        ecryptfs_printk(KERN_ERR, "Error reading page; rc = "
                                        "[%d]\n", rc);
                        goto out;
                }
        } else {
                rc = ecryptfs_decrypt_page(file, page);
                if (rc) {

                        ecryptfs_printk(KERN_ERR, "Error decrypting page; "
                                        "rc = [%d]\n", rc);
                        goto out;
                }
        }
        SetPageUptodate(page);
out:
        if (rc)
                ClearPageUptodate(page);
        ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
                        page->index);
        unlock_page(page);
        return rc;
}

static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
{
        struct inode *inode = page->mapping->host;
        int end_byte_in_page;
        int rc = 0;
        char *page_virt;

        if ((i_size_read(inode) / PAGE_CACHE_SIZE) == page->index) {
                end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
                if (to > end_byte_in_page)
                        end_byte_in_page = to;
                page_virt = kmap(page);
                if (!page_virt) {
                        rc = -ENOMEM;
                        ecryptfs_printk(KERN_WARNING,
                                        "Could not map page\n");
                        goto out;
                }
                memset((page_virt + end_byte_in_page), 0,
                       (PAGE_CACHE_SIZE - end_byte_in_page));
                kunmap(page);
        }
out:
        return rc;
}

static int ecryptfs_prepare_write(struct file *file, struct page *page,
                                  unsigned from, unsigned to)
{
        int rc = 0;

        kmap(page);
        if (from == 0 && to == PAGE_CACHE_SIZE)
                goto out;       /* If we are writing a full page, it will be
                                   up to date. */
        if (!PageUptodate(page))
                rc = ecryptfs_do_readpage(file, page, page->index);
out:
        return rc;
}

int ecryptfs_grab_and_map_lower_page(struct page **lower_page,
                                     char **lower_virt,
                                     struct inode *lower_inode,
                                     unsigned long lower_page_index)
{
        int rc = 0;

        (*lower_page) = grab_cache_page(lower_inode->i_mapping,
                                        lower_page_index);
        if (!(*lower_page)) {
                ecryptfs_printk(KERN_ERR, "grab_cache_page for "
                                "lower_page_index = [0x%.16x] failed\n",
                                lower_page_index);
                rc = -EINVAL;
                goto out;
        }
        if (lower_virt)
                (*lower_virt) = kmap((*lower_page));
        else
                kmap((*lower_page));
out:
        return rc;
}

int ecryptfs_writepage_and_release_lower_page(struct page *lower_page,
                                              struct inode *lower_inode,
                                              struct writeback_control *wbc)
{
        int rc = 0;

        rc = lower_inode->i_mapping->a_ops->writepage(lower_page, wbc);
        if (rc) {
                ecryptfs_printk(KERN_ERR, "Error calling lower writepage(); "
                                "rc = [%d]\n", rc);
                goto out;
        }
        lower_inode->i_mtime = lower_inode->i_ctime = CURRENT_TIME;
        page_cache_release(lower_page);
out:
        return rc;
}

static void ecryptfs_unmap_and_release_lower_page(struct page *lower_page)
{
        kunmap(lower_page);
        ecryptfs_printk(KERN_DEBUG, "Unlocking lower page with index = "
                        "[0x%.16x]\n", lower_page->index);
        unlock_page(lower_page);
        page_cache_release(lower_page);
}

/**
 * ecryptfs_write_inode_size_to_header
 *
 * Writes the lower file size to the first 8 bytes of the header.
 *
 * Returns zero on success; non-zero on error.
 */
int
ecryptfs_write_inode_size_to_header(struct file *lower_file,
                                    struct inode *lower_inode,
                                    struct inode *inode)
{
        int rc = 0;
        struct page *header_page;
        char *header_virt;
        const struct address_space_operations *lower_a_ops;
        u64 file_size;

        rc = ecryptfs_grab_and_map_lower_page(&header_page, &header_virt,
                                              lower_inode, 0);
        if (rc) {
                ecryptfs_printk(KERN_ERR, "grab_cache_page for header page "
                                "failed\n");
                goto out;
        }
        lower_a_ops = lower_inode->i_mapping->a_ops;
        rc = lower_a_ops->prepare_write(lower_file, header_page, 0, 8);
        file_size = (u64)i_size_read(inode);
        ecryptfs_printk(KERN_DEBUG, "Writing size: [0x%.16x]\n", file_size);
        file_size = cpu_to_be64(file_size);
        memcpy(header_virt, &file_size, sizeof(u64));
        rc = lower_a_ops->commit_write(lower_file, header_page, 0, 8);
        if (rc < 0)
                ecryptfs_printk(KERN_ERR, "Error commiting header page "
                                "write\n");
        ecryptfs_unmap_and_release_lower_page(header_page);
        lower_inode->i_mtime = lower_inode->i_ctime = CURRENT_TIME;
        mark_inode_dirty_sync(inode);
out:
        return rc;
}

int ecryptfs_get_lower_page(struct page **lower_page, struct inode *lower_inode,
                            struct file *lower_file,
                            unsigned long lower_page_index, int byte_offset,
                            int region_bytes)
{
        int rc = 0;

        rc = ecryptfs_grab_and_map_lower_page(lower_page, NULL, lower_inode,
                                              lower_page_index);
        if (rc) {
                ecryptfs_printk(KERN_ERR, "Error attempting to grab and map "
                                "lower page with index [0x%.16x]\n",
                                lower_page_index);
                goto out;
        }
        rc = lower_inode->i_mapping->a_ops->prepare_write(lower_file,
                                                          (*lower_page),
                                                          byte_offset,
                                                          region_bytes);
        if (rc) {
                ecryptfs_printk(KERN_ERR, "prepare_write for "
                                "lower_page_index = [0x%.16x] failed; rc = "
                                "[%d]\n", lower_page_index, rc);
        }
out:
        if (rc && (*lower_page)) {
                ecryptfs_unmap_and_release_lower_page(*lower_page);
                (*lower_page) = NULL;
        }
        return rc;
}

/**
 * ecryptfs_commit_lower_page
 *
 * Returns zero on success; non-zero on error
 */
int
ecryptfs_commit_lower_page(struct page *lower_page, struct inode *lower_inode,
                           struct file *lower_file, int byte_offset,
                           int region_size)
{
        int rc = 0;

        rc = lower_inode->i_mapping->a_ops->commit_write(
                lower_file, lower_page, byte_offset, region_size);
        if (rc < 0) {
                ecryptfs_printk(KERN_ERR,
                                "Error committing write; rc = [%d]\n", rc);
        } else
                rc = 0;
        ecryptfs_unmap_and_release_lower_page(lower_page);
        return rc;
}

/**
 * ecryptfs_copy_page_to_lower
 *
 * Used for plaintext pass-through; no page index interpolation
 * required.
 */
int ecryptfs_copy_page_to_lower(struct page *page, struct inode *lower_inode,
                                struct file *lower_file)
{
        int rc = 0;
        struct page *lower_page;

        rc = ecryptfs_get_lower_page(&lower_page, lower_inode, lower_file,
                                     page->index, 0, PAGE_CACHE_SIZE);
        if (rc) {
                ecryptfs_printk(KERN_ERR, "Error attempting to get page "
                                "at index [0x%.16x]\n", page->index);
                goto out;
        }
        /* TODO: aops */
        memcpy((char *)page_address(lower_page), page_address(page),
               PAGE_CACHE_SIZE);
        rc = ecryptfs_commit_lower_page(lower_page, lower_inode, lower_file,
                                        0, PAGE_CACHE_SIZE);
        if (rc)
                ecryptfs_printk(KERN_ERR, "Error attempting to commit page "
                                "at index [0x%.16x]\n", page->index);
out:
        return rc;
}

static int
process_new_file(struct ecryptfs_crypt_stat *crypt_stat,
                 struct file *file, struct inode *inode)
{
        struct page *header_page;
        const struct address_space_operations *lower_a_ops;
        struct inode *lower_inode;
        struct file *lower_file;
        char *header_virt;
        int rc = 0;
        int current_header_page = 0;
        int header_pages;
        int more_header_data_to_be_written = 1;

        lower_inode = ecryptfs_inode_to_lower(inode);
        lower_file = ecryptfs_file_to_lower(file);
        lower_a_ops = lower_inode->i_mapping->a_ops;
        header_pages = ((crypt_stat->header_extent_size
                         * crypt_stat->num_header_extents_at_front)
                        / PAGE_CACHE_SIZE);
        BUG_ON(header_pages < 1);
        while (current_header_page < header_pages) {
                rc = ecryptfs_grab_and_map_lower_page(&header_page,
                                                      &header_virt,
                                                      lower_inode,
                                                      current_header_page);
                if (rc) {
                        ecryptfs_printk(KERN_ERR, "grab_cache_page for "
                                        "header page [%d] failed; rc = [%d]\n",
                                        current_header_page, rc);
                        goto out;
                }
                rc = lower_a_ops->prepare_write(lower_file, header_page, 0,
                                                PAGE_CACHE_SIZE);
                if (rc) {
                        ecryptfs_printk(KERN_ERR, "Error preparing to write "
                                        "header page out; rc = [%d]\n", rc);
                        goto out;
                }
                memset(header_virt, 0, PAGE_CACHE_SIZE);
                if (more_header_data_to_be_written) {
                        rc = ecryptfs_write_headers_virt(header_virt,
                                                         crypt_stat,
                                                         file->f_dentry);
                        if (rc) {
                                ecryptfs_printk(KERN_WARNING, "Error "
                                                "generating header; rc = "
                                                "[%d]\n", rc);
                                rc = -EIO;
                                memset(header_virt, 0, PAGE_CACHE_SIZE);
                                ecryptfs_unmap_and_release_lower_page(
                                        header_page);
                                goto out;
                        }
                        if (current_header_page == 0)
                                memset(header_virt, 0, 8);
                        more_header_data_to_be_written = 0;
                }
                rc = lower_a_ops->commit_write(lower_file, header_page, 0,
                                               PAGE_CACHE_SIZE);
                ecryptfs_unmap_and_release_lower_page(header_page);
                if (rc < 0) {
                        ecryptfs_printk(KERN_ERR,
                                        "Error commiting header page write; "
                                        "rc = [%d]\n", rc);
                        break;
                }
                current_header_page++;
        }
        if (rc >= 0) {
                rc = 0;
                ecryptfs_printk(KERN_DEBUG, "lower_inode->i_blocks = "
                                "[0x%.16x]\n", lower_inode->i_blocks);
                i_size_write(inode, 0);
                lower_inode->i_mtime = lower_inode->i_ctime = CURRENT_TIME;
                mark_inode_dirty_sync(inode);
        }
        ecryptfs_printk(KERN_DEBUG, "Clearing ECRYPTFS_NEW_FILE flag in "
                        "crypt_stat at memory location [%p]\n", crypt_stat);
        ECRYPTFS_CLEAR_FLAG(crypt_stat->flags, ECRYPTFS_NEW_FILE);
out:
        return rc;
}

/**
 * ecryptfs_commit_write
 * @file: The eCryptfs file object
 * @page: The eCryptfs page
 * @from: Ignored (we rotate the page IV on each write)
 * @to: Ignored
 *
 * This is where we encrypt the data and pass the encrypted data to
 * the lower filesystem.  In OpenPGP-compatible mode, we operate on
 * entire underlying packets.
 */
static int ecryptfs_commit_write(struct file *file, struct page *page,
                                 unsigned from, unsigned to)
{
        struct ecryptfs_page_crypt_context ctx;
        loff_t pos;
        struct inode *inode;
        struct inode *lower_inode;
        struct file *lower_file;
        struct ecryptfs_crypt_stat *crypt_stat;
        int rc;

        inode = page->mapping->host;
        lower_inode = ecryptfs_inode_to_lower(inode);
        lower_file = ecryptfs_file_to_lower(file);
        mutex_lock(&lower_inode->i_mutex);
        crypt_stat =
                &ecryptfs_inode_to_private(file->f_dentry->d_inode)->crypt_stat;
        if (ECRYPTFS_CHECK_FLAG(crypt_stat->flags, ECRYPTFS_NEW_FILE)) {
                ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in "
                        "crypt_stat at memory location [%p]\n", crypt_stat);
                rc = process_new_file(crypt_stat, file, inode);
                if (rc) {
                        ecryptfs_printk(KERN_ERR, "Error processing new "
                                        "file; rc = [%d]\n", rc);
                        goto out;
                }
        } else
                ecryptfs_printk(KERN_DEBUG, "Not a new file\n");
        ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
                        "(page w/ index = [0x%.16x], to = [%d])\n", page->index,
                        to);
        rc = fill_zeros_to_end_of_page(page, to);
        if (rc) {
                ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
                                "zeros in page with index = [0x%.16x]\n",
                                page->index);
                goto out;
        }
        ctx.page = page;
        ctx.mode = ECRYPTFS_PREPARE_COMMIT_MODE;
        ctx.param.lower_file = lower_file;
        rc = ecryptfs_encrypt_page(&ctx);
        if (rc) {
                ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
                                "index [0x%.16x])\n", page->index);
                goto out;
        }
        rc = 0;
        inode->i_blocks = lower_inode->i_blocks;
        pos = (page->index << PAGE_CACHE_SHIFT) + to;
        if (pos > i_size_read(inode)) {
                i_size_write(inode, pos);
                ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
                                "[0x%.16x]\n", i_size_read(inode));
        }
        ecryptfs_write_inode_size_to_header(lower_file, lower_inode, inode);
        lower_inode->i_mtime = lower_inode->i_ctime = CURRENT_TIME;
        mark_inode_dirty_sync(inode);
out:
        kunmap(page); /* mapped in prior call (prepare_write) */
        if (rc < 0)
                ClearPageUptodate(page);
        else
                SetPageUptodate(page);
        mutex_unlock(&lower_inode->i_mutex);
        return rc;
}

/**
 * write_zeros
 * @file: The ecryptfs file
 * @index: The index in which we are writing
 * @start: The position after the last block of data
 * @num_zeros: The number of zeros to write
 *
 * Write a specified number of zero's to a page.
 *
 * (start + num_zeros) must be less than or equal to PAGE_CACHE_SIZE
 */
static
int write_zeros(struct file *file, pgoff_t index, int start, int num_zeros)
{
        int rc = 0;
        struct page *tmp_page;

        tmp_page = ecryptfs_get1page(file, index);
        if (IS_ERR(tmp_page)) {
                ecryptfs_printk(KERN_ERR, "Error getting page at index "
                                "[0x%.16x]\n", index);
                rc = PTR_ERR(tmp_page);
                goto out;
        }
        kmap(tmp_page);
        rc = ecryptfs_prepare_write(file, tmp_page, start, start + num_zeros);
        if (rc) {
                ecryptfs_printk(KERN_ERR, "Error preparing to write zero's "
                                "to remainder of page at index [0x%.16x]\n",
                                index);
                kunmap(tmp_page);
                page_cache_release(tmp_page);
                goto out;
        }
        memset(((char *)page_address(tmp_page) + start), 0, num_zeros);
        rc = ecryptfs_commit_write(file, tmp_page, start, start + num_zeros);
        if (rc < 0) {
                ecryptfs_printk(KERN_ERR, "Error attempting to write zero's "
                                "to remainder of page at index [0x%.16x]\n",
                                index);
                kunmap(tmp_page);
                page_cache_release(tmp_page);
                goto out;
        }
        rc = 0;
        kunmap(tmp_page);
        page_cache_release(tmp_page);
out:
        return rc;
}

static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
{
        int rc = 0;
        struct inode *inode;
        struct inode *lower_inode;

        inode = (struct inode *)mapping->host;
        lower_inode = ecryptfs_inode_to_lower(inode);
        if (lower_inode->i_mapping->a_ops->bmap)
                rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
                                                         block);
        return rc;
}

static void ecryptfs_sync_page(struct page *page)
{
        struct inode *inode;
        struct inode *lower_inode;
        struct page *lower_page;

        inode = page->mapping->host;
        lower_inode = ecryptfs_inode_to_lower(inode);
        /* NOTE: Recently swapped with grab_cache_page(), since
         * sync_page() just makes sure that pending I/O gets done. */
        lower_page = find_lock_page(lower_inode->i_mapping, page->index);
        if (!lower_page) {
                ecryptfs_printk(KERN_DEBUG, "find_lock_page failed\n");
                return;
        }
        lower_page->mapping->a_ops->sync_page(lower_page);
        ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
                        lower_page->index);
        unlock_page(lower_page);
        page_cache_release(lower_page);
}

struct address_space_operations ecryptfs_aops = {
        .writepage = ecryptfs_writepage,
        .readpage = ecryptfs_readpage,
        .prepare_write = ecryptfs_prepare_write,
        .commit_write = ecryptfs_commit_write,
        .bmap = ecryptfs_bmap,
        .sync_page = ecryptfs_sync_page,
};