- 根目录:
- fs
- ecryptfs
- read_write.c
/**
* eCryptfs: Linux filesystem encryption layer
*
* Copyright (C) 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/fs.h>
#include <linux/pagemap.h>
#include "ecryptfs_kernel.h"
/**
* ecryptfs_write_lower
* @ecryptfs_inode: The eCryptfs inode
* @data: Data to write
* @offset: Byte offset in the lower file to which to write the data
* @size: Number of bytes from @data to write at @offset in the lower
* file
*
* Write data to the lower file.
*
* Returns bytes written on success; less than zero on error
*/
int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
loff_t offset, size_t size)
{
struct file *lower_file;
ssize_t rc;
lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
if (!lower_file)
return -EIO;
rc = kernel_write(lower_file, data, size, offset);
mark_inode_dirty_sync(ecryptfs_inode);
return rc;
}
/**
* ecryptfs_write_lower_page_segment
* @ecryptfs_inode: The eCryptfs inode
* @page_for_lower: The page containing the data to be written to the
* lower file
* @offset_in_page: The offset in the @page_for_lower from which to
* start writing the data
* @size: The amount of data from @page_for_lower to write to the
* lower file
*
* Determines the byte offset in the file for the given page and
* offset within the page, maps the page, and makes the call to write
* the contents of @page_for_lower to the lower inode.
*
* Returns zero on success; non-zero otherwise
*/
int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
struct page *page_for_lower,
size_t offset_in_page, size_t size)
{
char *virt;
loff_t offset;
int rc;
offset = ((((loff_t)page_for_lower->index) << PAGE_CACHE_SHIFT)
+ offset_in_page);
virt = kmap(page_for_lower);
rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
if (rc > 0)
rc = 0;
kunmap(page_for_lower);
return rc;
}
/**
* ecryptfs_write
* @ecryptfs_inode: The eCryptfs file into which to write
* @data: Virtual address where data to write is located
* @offset: Offset in the eCryptfs file at which to begin writing the
* data from @data
* @size: The number of bytes to write from @data
*
* Write an arbitrary amount of data to an arbitrary location in the
* eCryptfs inode page cache. This is done on a page-by-page, and then
* by an extent-by-extent, basis; individual extents are encrypted and
* written to the lower page cache (via VFS writes). This function
* takes care of all the address translation to locations in the lower
* filesystem; it also handles truncate events, writing out zeros
* where necessary.
*
* Returns zero on success; non-zero otherwise
*/
int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
size_t size)
{
struct page *ecryptfs_page;
struct ecryptfs_crypt_stat *crypt_stat;
char *ecryptfs_page_virt;
loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
loff_t data_offset = 0;
loff_t pos;
int rc = 0;
crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
/*
* if we are writing beyond current size, then start pos
* at the current size - we'll fill in zeros from there.
*/
if (offset > ecryptfs_file_size)
pos = ecryptfs_file_size;
else
pos = offset;
while (pos < (offset + size)) {
pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
loff_t total_remaining_bytes = ((offset + size) - pos);
if (fatal_signal_pending(current)) {
rc = -EINTR;
break;
}
if (num_bytes > total_remaining_bytes)
num_bytes = total_remaining_bytes;
if (pos < offset) {
/* remaining zeros to write, up to destination offset */
loff_t total_remaining_zeros = (offset - pos);
if (num_bytes > total_remaining_zeros)
num_bytes = total_remaining_zeros;
}
ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode,
ecryptfs_page_idx);
if (IS_ERR(ecryptfs_page)) {
rc = PTR_ERR(ecryptfs_page);
printk(KERN_ERR "%s: Error getting page at "
"index [%ld] from eCryptfs inode "
"mapping; rc = [%d]\n", __func__,
ecryptfs_page_idx, rc);
goto out;
}
ecryptfs_page_virt = kmap_atomic(ecryptfs_page);
/*
* pos: where we're now writing, offset: where the request was
* If current pos is before request, we are filling zeros
* If we are at or beyond request, we are writing the *data*
* If we're in a fresh page beyond eof, zero it in either case
*/
if (pos < offset || !start_offset_in_page) {
/* We are extending past the previous end of the file.
* Fill in zero values to the end of the page */
memset(((char *)ecryptfs_page_virt
+ start_offset_in_page), 0,
PAGE_CACHE_SIZE - start_offset_in_page);
}
/* pos >= offset, we are now writing the data request */
if (pos >= offset) {
memcpy(((char *)ecryptfs_page_virt
+ start_offset_in_page),
(data + data_offset), num_bytes);
data_offset += num_bytes;
}
kunmap_atomic(ecryptfs_page_virt);
flush_dcache_page(ecryptfs_page);
SetPageUptodate(ecryptfs_page);
unlock_page(ecryptfs_page);
if (crypt_stat->flags & ECRYPTFS_ENCRYPTED)
rc = ecryptfs_encrypt_page(ecryptfs_page);
else
rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
ecryptfs_page,
start_offset_in_page,
data_offset);
page_cache_release(ecryptfs_page);
if (rc) {
printk(KERN_ERR "%s: Error encrypting "
"page; rc = [%d]\n", __func__, rc);
goto out;
}
pos += num_bytes;
}
if (pos > ecryptfs_file_size) {
i_size_write(ecryptfs_inode, pos);
if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
int rc2;
rc2 = ecryptfs_write_inode_size_to_metadata(
ecryptfs_inode);
if (rc2) {
printk(KERN_ERR "Problem with "
"ecryptfs_write_inode_size_to_metadata; "
"rc = [%d]\n", rc2);
if (!rc)
rc = rc2;
goto out;
}
}
}
out:
return rc;
}
/**
* ecryptfs_read_lower
* @data: The read data is stored here by this function
* @offset: Byte offset in the lower file from which to read the data
* @size: Number of bytes to read from @offset of the lower file and
* store into @data
* @ecryptfs_inode: The eCryptfs inode
*
* Read @size bytes of data at byte offset @offset from the lower
* inode into memory location @data.
*
* Returns bytes read on success; 0 on EOF; less than zero on error
*/
int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
struct inode *ecryptfs_inode)
{
struct file *lower_file;
lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
if (!lower_file)
return -EIO;
return kernel_read(lower_file, offset, data, size);
}
/**
* ecryptfs_read_lower_page_segment
* @page_for_ecryptfs: The page into which data for eCryptfs will be
* written
* @offset_in_page: Offset in @page_for_ecryptfs from which to start
* writing
* @size: The number of bytes to write into @page_for_ecryptfs
* @ecryptfs_inode: The eCryptfs inode
*
* Determines the byte offset in the file for the given page and
* offset within the page, maps the page, and makes the call to read
* the contents of @page_for_ecryptfs from the lower inode.
*
* Returns zero on success; non-zero otherwise
*/
int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
pgoff_t page_index,
size_t offset_in_page, size_t size,
struct inode *ecryptfs_inode)
{
char *virt;
loff_t offset;
int rc;
offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page);
virt = kmap(page_for_ecryptfs);
rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
if (rc > 0)
rc = 0;
kunmap(page_for_ecryptfs);
flush_dcache_page(page_for_ecryptfs);
return rc;
}