[net-next-2.6.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 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 ecryptfs_inode_info *inode_info;
	mm_segment_t fs_save;
	ssize_t rc;

	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());
	rc = vfs_write(inode_info->lower_file, data, size,
		       &inode_info->lower_file->f_pos);
	set_fs(fs_save);
	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);
	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);
		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_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, 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);
		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 ((offset + size) > ecryptfs_file_size) {
		i_size_write(ecryptfs_inode, (offset + size));
		if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
			rc = ecryptfs_write_inode_size_to_metadata(
								ecryptfs_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 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 ecryptfs_inode_info *inode_info =
		ecryptfs_inode_to_private(ecryptfs_inode);
	mm_segment_t fs_save;
	ssize_t rc;

	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());
	rc = vfs_read(inode_info->lower_file, data, size,
		      &inode_info->lower_file->f_pos);
	set_fs(fs_save);
	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);
	if (rc > 0)
		rc = 0;
	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 inode *ecryptfs_inode = ecryptfs_file->f_dentry->d_inode;
	struct page *ecryptfs_page;
	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;

	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_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, 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	*
96a7b9c2	37	* Returns bytes written on success; less than zero on error
da0102a1 MH	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;
da0102a1	43	mm_segment_t fs_save;
96a7b9c2	44	ssize_t rc;
da0102a1 MH	45
	46	inode_info = ecryptfs_inode_to_private(ecryptfs_inode);
	47	mutex_lock(&inode_info->lower_file_mutex);
	48	BUG_ON(!inode_info->lower_file);
	49	inode_info->lower_file->f_pos = offset;
	50	fs_save = get_fs();
	51	set_fs(get_ds());
96a7b9c2 TH	52	rc = vfs_write(inode_info->lower_file, data, size,
96a7b9c2 TH	53	&inode_info->lower_file->f_pos);
da0102a1	54	set_fs(fs_save);
da0102a1 MH	55	mutex_unlock(&inode_info->lower_file_mutex);
	56	mark_inode_dirty_sync(ecryptfs_inode);
	57	return rc;
	58	}
	59
	60	/**
	61	* ecryptfs_write_lower_page_segment
	62	* @ecryptfs_inode: The eCryptfs inode
	63	* @page_for_lower: The page containing the data to be written to the
	64	* lower file
	65	* @offset_in_page: The offset in the @page_for_lower from which to
	66	* start writing the data
	67	* @size: The amount of data from @page_for_lower to write to the
	68	* lower file
	69	*
	70	* Determines the byte offset in the file for the given page and
	71	* offset within the page, maps the page, and makes the call to write
	72	* the contents of @page_for_lower to the lower inode.
	73	*
	74	* Returns zero on success; non-zero otherwise
	75	*/
	76	int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
	77	struct page *page_for_lower,
	78	size_t offset_in_page, size_t size)
	79	{
	80	char *virt;
	81	loff_t offset;
	82	int rc;
	83
8a146a2b	84	offset = ((((loff_t)page_for_lower->index) << PAGE_CACHE_SHIFT)
d6a13c17	85	+ offset_in_page);
da0102a1 MH	86	virt = kmap(page_for_lower);
da0102a1 MH	87	rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
96a7b9c2 TH	88	if (rc > 0)
96a7b9c2 TH	89	rc = 0;
da0102a1 MH	90	kunmap(page_for_lower);
	91	return rc;
	92	}
	93
	94	/**
	95	* ecryptfs_write
48c1e44a	96	* @ecryptfs_inode: The eCryptfs file into which to write
da0102a1 MH	97	* @data: Virtual address where data to write is located
	98	* @offset: Offset in the eCryptfs file at which to begin writing the
	99	* data from @data
	100	* @size: The number of bytes to write from @data
	101	*
	102	* Write an arbitrary amount of data to an arbitrary location in the
	103	* eCryptfs inode page cache. This is done on a page-by-page, and then
	104	* by an extent-by-extent, basis; individual extents are encrypted and
	105	* written to the lower page cache (via VFS writes). This function
	106	* takes care of all the address translation to locations in the lower
	107	* filesystem; it also handles truncate events, writing out zeros
	108	* where necessary.
	109	*
	110	* Returns zero on success; non-zero otherwise
	111	*/
48c1e44a	112	int ecryptfs_write(struct inode ecryptfs_inode, char data, loff_t offset,
da0102a1 MH	113	size_t size)
	114	{
	115	struct page *ecryptfs_page;
13a791b4	116	struct ecryptfs_crypt_stat *crypt_stat;
da0102a1	117	char *ecryptfs_page_virt;
13a791b4	118	loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
da0102a1 MH	119	loff_t data_offset = 0;
	120	loff_t pos;
	121	int rc = 0;
	122
13a791b4	123	crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
7a3f595c ES	124	/*
	125	* if we are writing beyond current size, then start pos
	126	* at the current size - we'll fill in zeros from there.
	127	*/
da0102a1 MH	128	if (offset > ecryptfs_file_size)
	129	pos = ecryptfs_file_size;
	130	else
	131	pos = offset;
	132	while (pos < (offset + size)) {
	133	pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
	134	size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
	135	size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
	136	size_t total_remaining_bytes = ((offset + size) - pos);
	137
	138	if (num_bytes > total_remaining_bytes)
	139	num_bytes = total_remaining_bytes;
	140	if (pos < offset) {
7a3f595c	141	/* remaining zeros to write, up to destination offset */
da0102a1 MH	142	size_t total_remaining_zeros = (offset - pos);
	143
	144	if (num_bytes > total_remaining_zeros)
	145	num_bytes = total_remaining_zeros;
	146	}
02bd9799	147	ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode,
16a72c45	148	ecryptfs_page_idx);
da0102a1 MH	149	if (IS_ERR(ecryptfs_page)) {
	150	rc = PTR_ERR(ecryptfs_page);
	151	printk(KERN_ERR "%s: Error getting page at "
	152	"index [%ld] from eCryptfs inode "
18d1dbf1	153	"mapping; rc = [%d]\n", __func__,
da0102a1 MH	154	ecryptfs_page_idx, rc);
	155	goto out;
	156	}
da0102a1	157	ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
7a3f595c ES	158
	159	/*
	160	* pos: where we're now writing, offset: where the request was
	161	* If current pos is before request, we are filling zeros
	162	* If we are at or beyond request, we are writing the data
	163	* If we're in a fresh page beyond eof, zero it in either case
	164	*/
	165	if (pos < offset \|\| !start_offset_in_page) {
	166	/* We are extending past the previous end of the file.
	167	* Fill in zero values to the end of the page */
	168	memset(((char *)ecryptfs_page_virt
	169	+ start_offset_in_page), 0,
	170	PAGE_CACHE_SIZE - start_offset_in_page);
	171	}
	172
	173	/* pos >= offset, we are now writing the data request */
da0102a1 MH	174	if (pos >= offset) {
	175	memcpy(((char *)ecryptfs_page_virt
	176	+ start_offset_in_page),
	177	(data + data_offset), num_bytes);
	178	data_offset += num_bytes;
da0102a1 MH	179	}
	180	kunmap_atomic(ecryptfs_page_virt, KM_USER0);
	181	flush_dcache_page(ecryptfs_page);
16a72c45 MH	182	SetPageUptodate(ecryptfs_page);
16a72c45 MH	183	unlock_page(ecryptfs_page);
13a791b4 TH	184	if (crypt_stat->flags & ECRYPTFS_ENCRYPTED)
	185	rc = ecryptfs_encrypt_page(ecryptfs_page);
	186	else
	187	rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
	188	ecryptfs_page,
	189	start_offset_in_page,
	190	data_offset);
16a72c45	191	page_cache_release(ecryptfs_page);
da0102a1 MH	192	if (rc) {
da0102a1 MH	193	printk(KERN_ERR "%s: Error encrypting "
18d1dbf1	194	"page; rc = [%d]\n", __func__, rc);
da0102a1 MH	195	goto out;
da0102a1 MH	196	}
da0102a1 MH	197	pos += num_bytes;
	198	}
	199	if ((offset + size) > ecryptfs_file_size) {
13a791b4 TH	200	i_size_write(ecryptfs_inode, (offset + size));
	201	if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
	202	rc = ecryptfs_write_inode_size_to_metadata(
	203	ecryptfs_inode);
	204	if (rc) {
	205	printk(KERN_ERR "Problem with "
	206	"ecryptfs_write_inode_size_to_metadata; "
	207	"rc = [%d]\n", rc);
	208	goto out;
	209	}
da0102a1 MH	210	}
	211	}
	212	out:
	213	return rc;
	214	}
	215
	216	/**
	217	* ecryptfs_read_lower
	218	* @data: The read data is stored here by this function
	219	* @offset: Byte offset in the lower file from which to read the data
	220	* @size: Number of bytes to read from @offset of the lower file and
	221	* store into @data
	222	* @ecryptfs_inode: The eCryptfs inode
	223	*
	224	* Read @size bytes of data at byte offset @offset from the lower
	225	* inode into memory location @data.
	226	*
96a7b9c2	227	* Returns bytes read on success; 0 on EOF; less than zero on error
da0102a1 MH	228	*/
	229	int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
	230	struct inode *ecryptfs_inode)
	231	{
	232	struct ecryptfs_inode_info *inode_info =
	233	ecryptfs_inode_to_private(ecryptfs_inode);
da0102a1	234	mm_segment_t fs_save;
96a7b9c2	235	ssize_t rc;
da0102a1 MH	236
	237	mutex_lock(&inode_info->lower_file_mutex);
	238	BUG_ON(!inode_info->lower_file);
	239	inode_info->lower_file->f_pos = offset;
	240	fs_save = get_fs();
	241	set_fs(get_ds());
96a7b9c2 TH	242	rc = vfs_read(inode_info->lower_file, data, size,
96a7b9c2 TH	243	&inode_info->lower_file->f_pos);
da0102a1	244	set_fs(fs_save);
da0102a1	245	mutex_unlock(&inode_info->lower_file_mutex);
da0102a1 MH	246	return rc;
	247	}
	248
	249	/**
	250	* ecryptfs_read_lower_page_segment
	251	* @page_for_ecryptfs: The page into which data for eCryptfs will be
	252	* written
	253	* @offset_in_page: Offset in @page_for_ecryptfs from which to start
	254	* writing
	255	* @size: The number of bytes to write into @page_for_ecryptfs
	256	* @ecryptfs_inode: The eCryptfs inode
	257	*
	258	* Determines the byte offset in the file for the given page and
	259	* offset within the page, maps the page, and makes the call to read
	260	* the contents of @page_for_ecryptfs from the lower inode.
	261	*
	262	* Returns zero on success; non-zero otherwise
	263	*/
	264	int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
	265	pgoff_t page_index,
	266	size_t offset_in_page, size_t size,
	267	struct inode *ecryptfs_inode)
	268	{
	269	char *virt;
	270	loff_t offset;
	271	int rc;
	272
d6a13c17	273	offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page);
da0102a1 MH	274	virt = kmap(page_for_ecryptfs);
da0102a1 MH	275	rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
96a7b9c2 TH	276	if (rc > 0)
96a7b9c2 TH	277	rc = 0;
da0102a1	278	kunmap(page_for_ecryptfs);
16a72c45	279	flush_dcache_page(page_for_ecryptfs);
da0102a1 MH	280	return rc;
	281	}
	282
7896b631	283	#if 0
da0102a1 MH	284	/**
	285	* ecryptfs_read
	286	* @data: The virtual address into which to write the data read (and
	287	* possibly decrypted) from the lower file
	288	* @offset: The offset in the decrypted view of the file from which to
	289	* read into @data
	290	* @size: The number of bytes to read into @data
	291	* @ecryptfs_file: The eCryptfs file from which to read
	292	*
	293	* Read an arbitrary amount of data from an arbitrary location in the
	294	* eCryptfs page cache. This is done on an extent-by-extent basis;
	295	* individual extents are decrypted and read from the lower page
	296	* cache (via VFS reads). This function takes care of all the
	297	* address translation to locations in the lower filesystem.
	298	*
	299	* Returns zero on success; non-zero otherwise
	300	*/
	301	int ecryptfs_read(char *data, loff_t offset, size_t size,
	302	struct file *ecryptfs_file)
	303	{
02bd9799	304	struct inode *ecryptfs_inode = ecryptfs_file->f_dentry->d_inode;
da0102a1 MH	305	struct page *ecryptfs_page;
da0102a1 MH	306	char *ecryptfs_page_virt;
02bd9799	307	loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
da0102a1 MH	308	loff_t data_offset = 0;
	309	loff_t pos;
	310	int rc = 0;
	311
	312	if ((offset + size) > ecryptfs_file_size) {
	313	rc = -EINVAL;
	314	printk(KERN_ERR "%s: Attempt to read data past the end of the "
	315	"file; offset = [%lld]; size = [%td]; "
	316	"ecryptfs_file_size = [%lld]\n",
18d1dbf1	317	__func__, offset, size, ecryptfs_file_size);
da0102a1 MH	318	goto out;
	319	}
	320	pos = offset;
	321	while (pos < (offset + size)) {
	322	pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
	323	size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
	324	size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
	325	size_t total_remaining_bytes = ((offset + size) - pos);
	326
	327	if (num_bytes > total_remaining_bytes)
	328	num_bytes = total_remaining_bytes;
02bd9799	329	ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode,
16a72c45	330	ecryptfs_page_idx);
da0102a1 MH	331	if (IS_ERR(ecryptfs_page)) {
	332	rc = PTR_ERR(ecryptfs_page);
	333	printk(KERN_ERR "%s: Error getting page at "
	334	"index [%ld] from eCryptfs inode "
18d1dbf1	335	"mapping; rc = [%d]\n", __func__,
da0102a1 MH	336	ecryptfs_page_idx, rc);
	337	goto out;
	338	}
da0102a1 MH	339	ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
	340	memcpy((data + data_offset),
	341	((char *)ecryptfs_page_virt + start_offset_in_page),
	342	num_bytes);
	343	kunmap_atomic(ecryptfs_page_virt, KM_USER0);
16a72c45 MH	344	flush_dcache_page(ecryptfs_page);
	345	SetPageUptodate(ecryptfs_page);
	346	unlock_page(ecryptfs_page);
da0102a1 MH	347	page_cache_release(ecryptfs_page);
	348	pos += num_bytes;
	349	data_offset += num_bytes;
	350	}
	351	out:
	352	return rc;
	353	}
7896b631	354	#endif /* 0 */