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OpenCloudOS-Kernel/fs/ecryptfs/mmap.c

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/**
* 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) 2004-2007 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_path.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_path.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_path.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 = kmap_atomic(page, KM_USER0);
lower_page_data = kmap_atomic(lower_page, KM_USER1);
memcpy(page_data, lower_page_data, PAGE_CACHE_SIZE);
kunmap_atomic(lower_page_data, KM_USER1);
kunmap_atomic(page_data, KM_USER0);
flush_dcache_page(page);
rc = 0;
out:
if (likely(lower_page))
page_cache_release(lower_page);
if (rc == 0)
SetPageUptodate(page);
else
ClearPageUptodate(page);
return rc;
}
/**
* Header Extent:
* Octets 0-7: Unencrypted file size (big-endian)
* Octets 8-15: eCryptfs special marker
* Octets 16-19: Flags
* Octet 16: File format version number (between 0 and 255)
* Octets 17-18: Reserved
* Octet 19: Bit 1 (lsb): Reserved
* Bit 2: Encrypted?
* Bits 3-8: Reserved
* Octets 20-23: Header extent size (big-endian)
* Octets 24-25: Number of header extents at front of file
* (big-endian)
* Octet 26: Begin RFC 2440 authentication token packet set
*/
static void set_header_info(char *page_virt,
struct ecryptfs_crypt_stat *crypt_stat)
{
size_t written;
int save_num_header_extents_at_front =
crypt_stat->num_header_extents_at_front;
crypt_stat->num_header_extents_at_front = 1;
ecryptfs_write_header_metadata(page_virt + 20, crypt_stat, &written);
crypt_stat->num_header_extents_at_front =
save_num_header_extents_at_front;
}
/**
* 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_path.dentry && file->f_path.dentry->d_inode));
crypt_stat = &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)
->crypt_stat;
if (!crypt_stat
|| !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
|| (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 if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
int num_pages_in_header_region =
(crypt_stat->header_extent_size
/ PAGE_CACHE_SIZE);
if (page->index < num_pages_in_header_region) {
char *page_virt;
page_virt = kmap_atomic(page, KM_USER0);
memset(page_virt, 0, PAGE_CACHE_SIZE);
if (page->index == 0) {
rc = ecryptfs_read_xattr_region(
page_virt, file->f_path.dentry);
set_header_info(page_virt, crypt_stat);
}
kunmap_atomic(page_virt, KM_USER0);
flush_dcache_page(page);
if (rc) {
printk(KERN_ERR "Error reading xattr "
"region\n");
goto out;
}
} else {
rc = ecryptfs_do_readpage(
file, page,
(page->index
- num_pages_in_header_region));
if (rc) {
printk(KERN_ERR "Error reading page; "
"rc = [%d]\n", rc);
goto out;
}
}
} else {
rc = ecryptfs_do_readpage(file, page, page->index);
if (rc) {
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;
}
/**
* Called with lower inode mutex held.
*/
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;
char *page_virt;
if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
goto out;
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_atomic(page, KM_USER0);
memset((page_virt + end_byte_in_page), 0,
(PAGE_CACHE_SIZE - end_byte_in_page));
kunmap_atomic(page_virt, KM_USER0);
flush_dcache_page(page);
out:
return 0;
}
static int ecryptfs_prepare_write(struct file *file, struct page *page,
unsigned from, unsigned to)
{
int rc = 0;
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_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_release_lower_page(struct page *lower_page, int page_locked)
{
if (page_locked)
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.
*/
static 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;
retry:
header_page = grab_cache_page(lower_inode->i_mapping, 0);
if (!header_page) {
ecryptfs_printk(KERN_ERR, "grab_cache_page for "
"lower_page_index 0 failed\n");
rc = -EINVAL;
goto out;
}
lower_a_ops = lower_inode->i_mapping->a_ops;
rc = lower_a_ops->prepare_write(lower_file, header_page, 0, 8);
if (rc) {
if (rc == AOP_TRUNCATED_PAGE) {
ecryptfs_release_lower_page(header_page, 0);
goto retry;
} else
ecryptfs_release_lower_page(header_page, 1);
goto out;
}
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);
header_virt = kmap_atomic(header_page, KM_USER0);
memcpy(header_virt, &file_size, sizeof(u64));
kunmap_atomic(header_virt, KM_USER0);
flush_dcache_page(header_page);
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");
if (rc == AOP_TRUNCATED_PAGE) {
ecryptfs_release_lower_page(header_page, 0);
goto retry;
} else
ecryptfs_release_lower_page(header_page, 1);
lower_inode->i_mtime = lower_inode->i_ctime = CURRENT_TIME;
mark_inode_dirty_sync(inode);
out:
return rc;
}
static int ecryptfs_write_inode_size_to_xattr(struct inode *lower_inode,
struct inode *inode,
struct dentry *ecryptfs_dentry,
int lower_i_mutex_held)
{
ssize_t size;
void *xattr_virt;
struct dentry *lower_dentry;
u64 file_size;
int rc;
xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
if (!xattr_virt) {
printk(KERN_ERR "Out of memory whilst attempting to write "
"inode size to xattr\n");
rc = -ENOMEM;
goto out;
}
lower_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry);
if (!lower_dentry->d_inode->i_op->getxattr ||
!lower_dentry->d_inode->i_op->setxattr) {
printk(KERN_WARNING
"No support for setting xattr in lower filesystem\n");
rc = -ENOSYS;
kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
goto out;
}
if (!lower_i_mutex_held)
mutex_lock(&lower_dentry->d_inode->i_mutex);
size = lower_dentry->d_inode->i_op->getxattr(lower_dentry,
ECRYPTFS_XATTR_NAME,
xattr_virt,
PAGE_CACHE_SIZE);
if (!lower_i_mutex_held)
mutex_unlock(&lower_dentry->d_inode->i_mutex);
if (size < 0)
size = 8;
file_size = (u64)i_size_read(inode);
file_size = cpu_to_be64(file_size);
memcpy(xattr_virt, &file_size, sizeof(u64));
if (!lower_i_mutex_held)
mutex_lock(&lower_dentry->d_inode->i_mutex);
rc = lower_dentry->d_inode->i_op->setxattr(lower_dentry,
ECRYPTFS_XATTR_NAME,
xattr_virt, size, 0);
if (!lower_i_mutex_held)
mutex_unlock(&lower_dentry->d_inode->i_mutex);
if (rc)
printk(KERN_ERR "Error whilst attempting to write inode size "
"to lower file xattr; rc = [%d]\n", rc);
kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
out:
return rc;
}
int
ecryptfs_write_inode_size_to_metadata(struct file *lower_file,
struct inode *lower_inode,
struct inode *inode,
struct dentry *ecryptfs_dentry,
int lower_i_mutex_held)
{
struct ecryptfs_crypt_stat *crypt_stat;
crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
return ecryptfs_write_inode_size_to_xattr(lower_inode, inode,
ecryptfs_dentry,
lower_i_mutex_held);
else
return ecryptfs_write_inode_size_to_header(lower_file,
lower_inode,
inode);
}
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;
retry:
*lower_page = grab_cache_page(lower_inode->i_mapping, lower_page_index);
if (!(*lower_page)) {
rc = -EINVAL;
ecryptfs_printk(KERN_ERR, "Error attempting to grab "
"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) {
if (rc == AOP_TRUNCATED_PAGE) {
ecryptfs_release_lower_page(*lower_page, 0);
goto retry;
} else {
ecryptfs_printk(KERN_ERR, "prepare_write for "
"lower_page_index = [0x%.16x] failed; rc = "
"[%d]\n", lower_page_index, rc);
ecryptfs_release_lower_page(*lower_page, 1);
(*lower_page) = NULL;
}
}
out:
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 page_locked = 1;
int rc = 0;
rc = lower_inode->i_mapping->a_ops->commit_write(
lower_file, lower_page, byte_offset, region_size);
if (rc == AOP_TRUNCATED_PAGE)
page_locked = 0;
if (rc < 0) {
ecryptfs_printk(KERN_ERR,
"Error committing write; rc = [%d]\n", rc);
} else
rc = 0;
ecryptfs_release_lower_page(lower_page, page_locked);
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;
}
struct kmem_cache *ecryptfs_xattr_cache;
/**
* 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_path.dentry->d_inode)
->crypt_stat;
if (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);
crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE);
} 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;
}
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));
}
rc = ecryptfs_write_inode_size_to_metadata(lower_file, lower_inode,
inode, file->f_dentry,
ECRYPTFS_LOWER_I_MUTEX_HELD);
if (rc)
printk(KERN_ERR "Error writing inode size to metadata; "
"rc = [%d]\n", rc);
lower_inode->i_mtime = lower_inode->i_ctime = CURRENT_TIME;
mark_inode_dirty_sync(inode);
out:
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;
char *tmp_page_virt;
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;
}
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);
page_cache_release(tmp_page);
goto out;
}
tmp_page_virt = kmap_atomic(tmp_page, KM_USER0);
memset(((char *)tmp_page_virt + start), 0, num_zeros);
kunmap_atomic(tmp_page_virt, KM_USER0);
flush_dcache_page(tmp_page);
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);
page_cache_release(tmp_page);
goto out;
}
rc = 0;
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,
};
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