[linux-block.git] / 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 zero on success; non-zero on error
 */
int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
			 loff_t offset, size_t size)
{
	struct ecryptfs_inode_info *inode_info;
	ssize_t octets_written;
	mm_segment_t fs_save;
	int rc = 0;

	inode_info = ecryptfs_inode_to_private(ecryptfs_inode);
	mutex_lock(&inode_info->lower_file_mutex);
	BUG_ON(!inode_info->lower_file);
	inode_info->lower_file->f_pos = offset;
	fs_save = get_fs();
	set_fs(get_ds());
	octets_written = vfs_write(inode_info->lower_file, data, size,
				   &inode_info->lower_file->f_pos);
	set_fs(fs_save);
	if (octets_written < 0) {
		printk(KERN_ERR "%s: octets_written = [%td]; "
		       "expected [%td]\n", __func__, octets_written, size);
		rc = -EINVAL;
	}
	mutex_unlock(&inode_info->lower_file_mutex);
	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);
	kunmap(page_for_lower);
	return rc;
}

/**
 * ecryptfs_write
 * @ecryptfs_file: 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 file *ecryptfs_file, char *data, loff_t offset,
		   size_t size)
{
	struct page *ecryptfs_page;
	char *ecryptfs_page_virt;
	loff_t ecryptfs_file_size =
		i_size_read(ecryptfs_file->f_dentry->d_inode);
	loff_t data_offset = 0;
	loff_t pos;
	int rc = 0;

	/*
	 * 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);
		size_t total_remaining_bytes = ((offset + size) - pos);

		if (num_bytes > total_remaining_bytes)
			num_bytes = total_remaining_bytes;
		if (pos < offset) {
			/* remaining zeros to write, up to destination offset */
			size_t total_remaining_zeros = (offset - pos);

			if (num_bytes > total_remaining_zeros)
				num_bytes = total_remaining_zeros;
		}
		ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file,
							 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, KM_USER0);

		/*
		 * 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, KM_USER0);
		flush_dcache_page(ecryptfs_page);
		SetPageUptodate(ecryptfs_page);
		unlock_page(ecryptfs_page);
		rc = ecryptfs_encrypt_page(ecryptfs_page);
		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 ((offset + size) > ecryptfs_file_size) {
		i_size_write(ecryptfs_file->f_dentry->d_inode, (offset + size));
		rc = ecryptfs_write_inode_size_to_metadata(
			ecryptfs_file->f_dentry->d_inode);
		if (rc) {
			printk(KERN_ERR	"Problem with "
			       "ecryptfs_write_inode_size_to_metadata; "
			       "rc = [%d]\n", rc);
			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 zero on success; non-zero on error
 */
int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
			struct inode *ecryptfs_inode)
{
	struct ecryptfs_inode_info *inode_info =
		ecryptfs_inode_to_private(ecryptfs_inode);
	ssize_t octets_read;
	mm_segment_t fs_save;
	int rc = 0;

	mutex_lock(&inode_info->lower_file_mutex);
	BUG_ON(!inode_info->lower_file);
	inode_info->lower_file->f_pos = offset;
	fs_save = get_fs();
	set_fs(get_ds());
	octets_read = vfs_read(inode_info->lower_file, data, size,
			       &inode_info->lower_file->f_pos);
	set_fs(fs_save);
	if (octets_read < 0) {
		printk(KERN_ERR "%s: octets_read = [%td]; "
		       "expected [%td]\n", __func__, octets_read, size);
		rc = -EINVAL;
	}
	mutex_unlock(&inode_info->lower_file_mutex);
	return rc;
}

/**
 * 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);
	kunmap(page_for_ecryptfs);
	flush_dcache_page(page_for_ecryptfs);
	return rc;
}

#if 0
/**
 * ecryptfs_read
 * @data: The virtual address into which to write the data read (and
 *        possibly decrypted) from the lower file
 * @offset: The offset in the decrypted view of the file from which to
 *          read into @data
 * @size: The number of bytes to read into @data
 * @ecryptfs_file: The eCryptfs file from which to read
 *
 * Read an arbitrary amount of data from an arbitrary location in the
 * eCryptfs page cache. This is done on an extent-by-extent basis;
 * individual extents are decrypted and read from the lower page
 * cache (via VFS reads). This function takes care of all the
 * address translation to locations in the lower filesystem.
 *
 * Returns zero on success; non-zero otherwise
 */
int ecryptfs_read(char *data, loff_t offset, size_t size,
		  struct file *ecryptfs_file)
{
	struct page *ecryptfs_page;
	char *ecryptfs_page_virt;
	loff_t ecryptfs_file_size =
		i_size_read(ecryptfs_file->f_dentry->d_inode);
	loff_t data_offset = 0;
	loff_t pos;
	int rc = 0;

	if ((offset + size) > ecryptfs_file_size) {
		rc = -EINVAL;
		printk(KERN_ERR "%s: Attempt to read data past the end of the "
			"file; offset = [%lld]; size = [%td]; "
		       "ecryptfs_file_size = [%lld]\n",
		       __func__, offset, size, ecryptfs_file_size);
		goto out;
	}
	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);
		size_t total_remaining_bytes = ((offset + size) - pos);

		if (num_bytes > total_remaining_bytes)
			num_bytes = total_remaining_bytes;
		ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file,
							 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, KM_USER0);
		memcpy((data + data_offset),
		       ((char *)ecryptfs_page_virt + start_offset_in_page),
		       num_bytes);
		kunmap_atomic(ecryptfs_page_virt, KM_USER0);
		flush_dcache_page(ecryptfs_page);
		SetPageUptodate(ecryptfs_page);
		unlock_page(ecryptfs_page);
		page_cache_release(ecryptfs_page);
		pos += num_bytes;
		data_offset += num_bytes;
	}
out:
	return rc;
}
#endif  /*  0  */
Commit	Line	Data
da0102a1 MH	1	/**
	2	* eCryptfs: Linux filesystem encryption layer
	3	*
	4	* Copyright (C) 2007 International Business Machines Corp.
	5	* Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
	6	*
	7	* This program is free software; you can redistribute it and/or
	8	* modify it under the terms of the GNU General Public License as
	9	* published by the Free Software Foundation; either version 2 of the
	10	* License, or (at your option) any later version.
	11	*
	12	* This program is distributed in the hope that it will be useful, but
	13	* WITHOUT ANY WARRANTY; without even the implied warranty of
	14	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	15	* General Public License for more details.
	16	*
	17	* You should have received a copy of the GNU General Public License
	18	* along with this program; if not, write to the Free Software
	19	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
	20	* 02111-1307, USA.
	21	*/
	22
	23	#include <linux/fs.h>
	24	#include <linux/pagemap.h>
	25	#include "ecryptfs_kernel.h"
	26
	27	/**
	28	* ecryptfs_write_lower
	29	* @ecryptfs_inode: The eCryptfs inode
	30	* @data: Data to write
	31	* @offset: Byte offset in the lower file to which to write the data
	32	* @size: Number of bytes from @data to write at @offset in the lower
	33	* file
	34	*
	35	* Write data to the lower file.
	36	*
	37	* Returns zero on success; non-zero on error
	38	*/
	39	int ecryptfs_write_lower(struct inode ecryptfs_inode, char data,
	40	loff_t offset, size_t size)
	41	{
	42	struct ecryptfs_inode_info *inode_info;
	43	ssize_t octets_written;
	44	mm_segment_t fs_save;
	45	int rc = 0;
	46
	47	inode_info = ecryptfs_inode_to_private(ecryptfs_inode);
	48	mutex_lock(&inode_info->lower_file_mutex);
	49	BUG_ON(!inode_info->lower_file);
	50	inode_info->lower_file->f_pos = offset;
	51	fs_save = get_fs();
	52	set_fs(get_ds());
	53	octets_written = vfs_write(inode_info->lower_file, data, size,
	54	&inode_info->lower_file->f_pos);
	55	set_fs(fs_save);
	56	if (octets_written < 0) {
	57	printk(KERN_ERR "%s: octets_written = [%td]; "
18d1dbf1	58	"expected [%td]\n", __func__, octets_written, size);
da0102a1 MH	59	rc = -EINVAL;
	60	}
	61	mutex_unlock(&inode_info->lower_file_mutex);
	62	mark_inode_dirty_sync(ecryptfs_inode);
	63	return rc;
	64	}
	65
	66	/**
	67	* ecryptfs_write_lower_page_segment
	68	* @ecryptfs_inode: The eCryptfs inode
	69	* @page_for_lower: The page containing the data to be written to the
	70	* lower file
	71	* @offset_in_page: The offset in the @page_for_lower from which to
	72	* start writing the data
	73	* @size: The amount of data from @page_for_lower to write to the
	74	* lower file
	75	*
	76	* Determines the byte offset in the file for the given page and
	77	* offset within the page, maps the page, and makes the call to write
	78	* the contents of @page_for_lower to the lower inode.
	79	*
	80	* Returns zero on success; non-zero otherwise
	81	*/
	82	int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
	83	struct page *page_for_lower,
	84	size_t offset_in_page, size_t size)
	85	{
	86	char *virt;
	87	loff_t offset;
	88	int rc;
	89
8a146a2b	90	offset = ((((loff_t)page_for_lower->index) << PAGE_CACHE_SHIFT)
d6a13c17	91	+ offset_in_page);
da0102a1 MH	92	virt = kmap(page_for_lower);
	93	rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
	94	kunmap(page_for_lower);
	95	return rc;
	96	}
	97
	98	/**
	99	* ecryptfs_write
	100	* @ecryptfs_file: The eCryptfs file into which to write
	101	* @data: Virtual address where data to write is located
	102	* @offset: Offset in the eCryptfs file at which to begin writing the
	103	* data from @data
	104	* @size: The number of bytes to write from @data
	105	*
	106	* Write an arbitrary amount of data to an arbitrary location in the
	107	* eCryptfs inode page cache. This is done on a page-by-page, and then
	108	* by an extent-by-extent, basis; individual extents are encrypted and
	109	* written to the lower page cache (via VFS writes). This function
	110	* takes care of all the address translation to locations in the lower
	111	* filesystem; it also handles truncate events, writing out zeros
	112	* where necessary.
	113	*
	114	* Returns zero on success; non-zero otherwise
	115	*/
	116	int ecryptfs_write(struct file ecryptfs_file, char data, loff_t offset,
	117	size_t size)
	118	{
	119	struct page *ecryptfs_page;
	120	char *ecryptfs_page_virt;
d6a13c17 MH	121	loff_t ecryptfs_file_size =
d6a13c17 MH	122	i_size_read(ecryptfs_file->f_dentry->d_inode);
da0102a1 MH	123	loff_t data_offset = 0;
	124	loff_t pos;
	125	int rc = 0;
	126
7a3f595c ES	127	/*
	128	* if we are writing beyond current size, then start pos
	129	* at the current size - we'll fill in zeros from there.
	130	*/
da0102a1 MH	131	if (offset > ecryptfs_file_size)
	132	pos = ecryptfs_file_size;
	133	else
	134	pos = offset;
	135	while (pos < (offset + size)) {
	136	pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
	137	size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
	138	size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
	139	size_t total_remaining_bytes = ((offset + size) - pos);
	140
	141	if (num_bytes > total_remaining_bytes)
	142	num_bytes = total_remaining_bytes;
	143	if (pos < offset) {
7a3f595c	144	/* remaining zeros to write, up to destination offset */
da0102a1 MH	145	size_t total_remaining_zeros = (offset - pos);
	146
	147	if (num_bytes > total_remaining_zeros)
	148	num_bytes = total_remaining_zeros;
	149	}
16a72c45 MH	150	ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file,
16a72c45 MH	151	ecryptfs_page_idx);
da0102a1 MH	152	if (IS_ERR(ecryptfs_page)) {
	153	rc = PTR_ERR(ecryptfs_page);
	154	printk(KERN_ERR "%s: Error getting page at "
	155	"index [%ld] from eCryptfs inode "
18d1dbf1	156	"mapping; rc = [%d]\n", __func__,
da0102a1 MH	157	ecryptfs_page_idx, rc);
	158	goto out;
	159	}
da0102a1	160	ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
7a3f595c ES	161
	162	/*
	163	* pos: where we're now writing, offset: where the request was
	164	* If current pos is before request, we are filling zeros
	165	* If we are at or beyond request, we are writing the data
	166	* If we're in a fresh page beyond eof, zero it in either case
	167	*/
	168	if (pos < offset \|\| !start_offset_in_page) {
	169	/* We are extending past the previous end of the file.
	170	* Fill in zero values to the end of the page */
	171	memset(((char *)ecryptfs_page_virt
	172	+ start_offset_in_page), 0,
	173	PAGE_CACHE_SIZE - start_offset_in_page);
	174	}
	175
	176	/* pos >= offset, we are now writing the data request */
da0102a1 MH	177	if (pos >= offset) {
	178	memcpy(((char *)ecryptfs_page_virt
	179	+ start_offset_in_page),
	180	(data + data_offset), num_bytes);
	181	data_offset += num_bytes;
da0102a1 MH	182	}
	183	kunmap_atomic(ecryptfs_page_virt, KM_USER0);
	184	flush_dcache_page(ecryptfs_page);
16a72c45 MH	185	SetPageUptodate(ecryptfs_page);
16a72c45 MH	186	unlock_page(ecryptfs_page);
0216f7f7	187	rc = ecryptfs_encrypt_page(ecryptfs_page);
16a72c45	188	page_cache_release(ecryptfs_page);
da0102a1 MH	189	if (rc) {
da0102a1 MH	190	printk(KERN_ERR "%s: Error encrypting "
18d1dbf1	191	"page; rc = [%d]\n", __func__, rc);
da0102a1 MH	192	goto out;
da0102a1 MH	193	}
da0102a1 MH	194	pos += num_bytes;
	195	}
	196	if ((offset + size) > ecryptfs_file_size) {
	197	i_size_write(ecryptfs_file->f_dentry->d_inode, (offset + size));
0216f7f7 MH	198	rc = ecryptfs_write_inode_size_to_metadata(
0216f7f7 MH	199	ecryptfs_file->f_dentry->d_inode);
da0102a1 MH	200	if (rc) {
	201	printk(KERN_ERR "Problem with "
	202	"ecryptfs_write_inode_size_to_metadata; "
	203	"rc = [%d]\n", rc);
	204	goto out;
	205	}
	206	}
	207	out:
	208	return rc;
	209	}
	210
	211	/**
	212	* ecryptfs_read_lower
	213	* @data: The read data is stored here by this function
	214	* @offset: Byte offset in the lower file from which to read the data
	215	* @size: Number of bytes to read from @offset of the lower file and
	216	* store into @data
	217	* @ecryptfs_inode: The eCryptfs inode
	218	*
	219	* Read @size bytes of data at byte offset @offset from the lower
	220	* inode into memory location @data.
	221	*
	222	* Returns zero on success; non-zero on error
	223	*/
	224	int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
	225	struct inode *ecryptfs_inode)
	226	{
	227	struct ecryptfs_inode_info *inode_info =
	228	ecryptfs_inode_to_private(ecryptfs_inode);
	229	ssize_t octets_read;
	230	mm_segment_t fs_save;
da0102a1 MH	231	int rc = 0;
	232
	233	mutex_lock(&inode_info->lower_file_mutex);
	234	BUG_ON(!inode_info->lower_file);
	235	inode_info->lower_file->f_pos = offset;
	236	fs_save = get_fs();
	237	set_fs(get_ds());
	238	octets_read = vfs_read(inode_info->lower_file, data, size,
	239	&inode_info->lower_file->f_pos);
	240	set_fs(fs_save);
	241	if (octets_read < 0) {
	242	printk(KERN_ERR "%s: octets_read = [%td]; "
18d1dbf1	243	"expected [%td]\n", __func__, octets_read, size);
da0102a1 MH	244	rc = -EINVAL;
	245	}
	246	mutex_unlock(&inode_info->lower_file_mutex);
da0102a1 MH	247	return rc;
	248	}
	249
	250	/**
	251	* ecryptfs_read_lower_page_segment
	252	* @page_for_ecryptfs: The page into which data for eCryptfs will be
	253	* written
	254	* @offset_in_page: Offset in @page_for_ecryptfs from which to start
	255	* writing
	256	* @size: The number of bytes to write into @page_for_ecryptfs
	257	* @ecryptfs_inode: The eCryptfs inode
	258	*
	259	* Determines the byte offset in the file for the given page and
	260	* offset within the page, maps the page, and makes the call to read
	261	* the contents of @page_for_ecryptfs from the lower inode.
	262	*
	263	* Returns zero on success; non-zero otherwise
	264	*/
	265	int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
	266	pgoff_t page_index,
	267	size_t offset_in_page, size_t size,
	268	struct inode *ecryptfs_inode)
	269	{
	270	char *virt;
	271	loff_t offset;
	272	int rc;
	273
d6a13c17	274	offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page);
da0102a1 MH	275	virt = kmap(page_for_ecryptfs);
	276	rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
	277	kunmap(page_for_ecryptfs);
16a72c45	278	flush_dcache_page(page_for_ecryptfs);
da0102a1 MH	279	return rc;
	280	}
	281
7896b631	282	#if 0
da0102a1 MH	283	/**
	284	* ecryptfs_read
	285	* @data: The virtual address into which to write the data read (and
	286	* possibly decrypted) from the lower file
	287	* @offset: The offset in the decrypted view of the file from which to
	288	* read into @data
	289	* @size: The number of bytes to read into @data
	290	* @ecryptfs_file: The eCryptfs file from which to read
	291	*
	292	* Read an arbitrary amount of data from an arbitrary location in the
	293	* eCryptfs page cache. This is done on an extent-by-extent basis;
	294	* individual extents are decrypted and read from the lower page
	295	* cache (via VFS reads). This function takes care of all the
	296	* address translation to locations in the lower filesystem.
	297	*
	298	* Returns zero on success; non-zero otherwise
	299	*/
	300	int ecryptfs_read(char *data, loff_t offset, size_t size,
	301	struct file *ecryptfs_file)
	302	{
	303	struct page *ecryptfs_page;
	304	char *ecryptfs_page_virt;
d6a13c17 MH	305	loff_t ecryptfs_file_size =
d6a13c17 MH	306	i_size_read(ecryptfs_file->f_dentry->d_inode);
da0102a1 MH	307	loff_t data_offset = 0;
	308	loff_t pos;
	309	int rc = 0;
	310
	311	if ((offset + size) > ecryptfs_file_size) {
	312	rc = -EINVAL;
	313	printk(KERN_ERR "%s: Attempt to read data past the end of the "
	314	"file; offset = [%lld]; size = [%td]; "
	315	"ecryptfs_file_size = [%lld]\n",
18d1dbf1	316	__func__, offset, size, ecryptfs_file_size);
da0102a1 MH	317	goto out;
	318	}
	319	pos = offset;
	320	while (pos < (offset + size)) {
	321	pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
	322	size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
	323	size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
	324	size_t total_remaining_bytes = ((offset + size) - pos);
	325
	326	if (num_bytes > total_remaining_bytes)
	327	num_bytes = total_remaining_bytes;
16a72c45 MH	328	ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file,
16a72c45 MH	329	ecryptfs_page_idx);
da0102a1 MH	330	if (IS_ERR(ecryptfs_page)) {
	331	rc = PTR_ERR(ecryptfs_page);
	332	printk(KERN_ERR "%s: Error getting page at "
	333	"index [%ld] from eCryptfs inode "
18d1dbf1	334	"mapping; rc = [%d]\n", __func__,
da0102a1 MH	335	ecryptfs_page_idx, rc);
	336	goto out;
	337	}
da0102a1 MH	338	ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
	339	memcpy((data + data_offset),
	340	((char *)ecryptfs_page_virt + start_offset_in_page),
	341	num_bytes);
	342	kunmap_atomic(ecryptfs_page_virt, KM_USER0);
16a72c45 MH	343	flush_dcache_page(ecryptfs_page);
	344	SetPageUptodate(ecryptfs_page);
	345	unlock_page(ecryptfs_page);
da0102a1 MH	346	page_cache_release(ecryptfs_page);
	347	pos += num_bytes;
	348	data_offset += num_bytes;
	349	}
	350	out:
	351	return rc;
	352	}
7896b631	353	#endif /* 0 */