Date: Wed, 3 May 2006 21:41:28 -0600
From: Phillip Hellewell <phillip@hellewell.homeip.net>
To: Andrew Morton <akpm@osdl.org>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
       viro@ftp.linux.org.uk, mike@halcrow.us, mhalcrow@us.ibm.com,
       mcthomps@us.ibm.com, toml@us.ibm.com, yoder1@us.ibm.com,
       James Morris <jmorris@namei.org>, "Stephen C. Tweedie" <sct@redhat.com>,
       Erez Zadok <ezk@cs.sunysb.edu>, David Howells <dhowells@redhat.com>
Subject: [PATCH 10/13: eCryptfs] Mmap operations
Message-ID: <20060504034127.GI28613@hellewell.homeip.net>
References: <20060504031755.GA28257@hellewell.homeip.net>
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This is the 10th patch in a series of 13 constituting the kernel
components of the eCryptfs cryptographic filesystem.

eCryptfs mmap operations. Page read/write code works closely with
encryption/decryption routines in crypto.c.

Signed-off-by: Phillip Hellewell <phillip@hellewell.homeip.net>
Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>

---

 mmap.c |  869 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 869 insertions(+)

Index: linux-2.6.17-rc3-mm1-ecryptfs/fs/ecryptfs/mmap.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.17-rc3-mm1-ecryptfs/fs/ecryptfs/mmap.c	2006-05-02 19:36:03.000000000 -0600
@@ -0,0 +1,869 @@
+/**
+ * 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 <asm/scatterlist.h>
+#include "ecryptfs_kernel.h"
+
+kmem_cache_t *ecryptfs_lower_page_cache;
+
+/**
+ * Get one page from cache or lower f/s, return error otherwise.
+ *
+ * @return 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;
+	int rc;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter\n");
+	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);
+	if (!PageUptodate(page)) {
+		lock_page(page);
+		rc = mapping->a_ops->readpage(file, page);
+		if (rc) {
+			page = ERR_PTR(rc);
+			goto out;
+		}
+		wait_on_page_locked(page);
+		if (!PageUptodate(page)) {
+			page = ERR_PTR(-EIO);
+			goto out;
+		}
+	}
+out:
+	ecryptfs_printk(KERN_DEBUG, "Exit\n");
+	return page;
+}
+
+static
+int write_zeros(struct file *file, pgoff_t index, int start, int num_zeros);
+
+/**
+ * Function for handling lseek-ing past the end of the file.
+ *
+ * This function does not support shrinking, only growing a file.
+ *
+ * @param file The ecryptfs file
+ * @param 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
+ * @return 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);
+
+	ecryptfs_printk(KERN_DEBUG, "Enter; inode->i_size = [0x%.16x]; "
+			"new_length = [0x%.16x]\n", cur_length, new_length);
+	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:
+	ecryptfs_printk(KERN_DEBUG, "Exit; rc = [%d]\n", rc);
+	return rc;
+}
+
+/**
+ * @param page Page that is locked before this call is made
+ * @return Zero on success
+ */
+static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
+{
+	struct ecryptfs_page_crypt_context ctx;
+	int rc = 0;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter; page->index = [0x%.16x]; "
+			"page->mapping->host = [%p]\n", page->index,
+			page->mapping->host);
+	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:
+	ecryptfs_printk(KERN_DEBUG, "Exit; rc = [%d]\n", rc);
+	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 = -EIO;
+	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;
+	struct address_space_operations *lower_a_ops;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter; lower_page_index = [0x%.16x]\n",
+			lower_page_index);
+	dentry = file->f_dentry;
+	if (NULL == ECRYPTFS_FILE_TO_PRIVATE_SM(file)) {
+		rc = -ENOENT;
+		ecryptfs_printk(KERN_ERR, "No lower file info\n");
+		goto out;
+	}
+	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);
+	if (!PageUptodate(lower_page)) {
+		lock_page(lower_page);
+		rc = lower_a_ops->readpage(lower_file, lower_page);
+		if (rc) {
+			lower_page = NULL;
+			rc = -EIO;
+			ecryptfs_printk(KERN_ERR, "Error reading lower "
+					"page at index=[0x%.16x]\n",
+					lower_page_index);
+			goto out;
+		}
+		wait_on_page_locked(lower_page);
+		if (!PageUptodate(lower_page)) {
+			rc = -EIO;
+			ecryptfs_printk(KERN_ERR, "Error reading lower "
+					"page at index=[0x%.16x]\n",
+					lower_page_index);
+			goto out;
+		}
+	}
+	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);
+	ecryptfs_printk(KERN_DEBUG, "Exit; rc = [%d]\n", rc);
+	return rc;
+}
+
+/**
+ * Read in a page, decrypting if necessary.
+ *
+ * @param file This is an ecryptfs file
+ * @param page ecryptfs associated page to stick the read data into
+ * @return 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;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter; page->index = [%ld]\n",
+			page->index);
+	ASSERT(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);
+	ecryptfs_printk(KERN_DEBUG, "Exit; rc = [%d]\n", rc);
+	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;
+
+	ecryptfs_printk(KERN_DEBUG, "Called on page w/ index [0x%.16x] and "
+			"to = [%d]\n", page->index, to);
+	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;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter; page->index = [0x%.16x]; from = "
+			"[%d]; to = [%d]\n", page->index, from, to);
+	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;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter; lower_page_index = [0x%.16x]\n",
+			lower_page_index);
+	(*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;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter; lower_page->index = [0x%.16x]\n",
+			lower_page->index);
+	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;
+}
+
+void ecryptfs_unmap_and_release_lower_page(struct page *lower_page)
+{
+	ecryptfs_printk(KERN_DEBUG, "Enter; lower_page->index = [0x%.16x]\n",
+			lower_page->index);
+	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);
+}
+
+/**
+ * Writes the lower file size to the first 8 bytes of the header.
+ *
+ * @return Zero on success
+ */
+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;
+	struct address_space_operations *lower_a_ops;
+	u64 file_size;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter\n");
+	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:
+	ecryptfs_printk(KERN_DEBUG, "Exit; rc = [%d]\n", rc);
+	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;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter; lower_page_index = [0x%.16x], "
+			"byte_offset = [%d], region_bytes = [%d]\n",
+			lower_page_index, byte_offset, region_bytes);
+	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;
+}
+
+/**
+ * @return Zero on success
+ */
+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;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter; lower_page->index = [0x%.16x], "
+			"byte_offset = [%d], region_size = [%d]\n",
+			lower_page->index, byte_offset, region_size);
+	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;
+}
+
+/**
+ * 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;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter; page->index = [0x%.16x]\n",
+			page->index);
+	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;
+	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;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter\n");
+	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);
+	ASSERT(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;
+}
+
+/**
+ * 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.
+ *
+ * @param file The eCryptfs file object
+ * @param page The eCryptfs page
+ * @param from Ignored (we rotate the page IV on each write)
+ * @param to Ignored
+ * @return 
+ */
+static int ecryptfs_commit_write(struct file *file, struct page *page,
+				 unsigned from, unsigned to)
+{
+	struct ecryptfs_page_crypt_context ctx;
+	loff_t pos;
+	unsigned bytes = to - from;
+	struct inode *inode;
+	struct inode *lower_inode;
+	struct file *lower_file;
+	struct ecryptfs_crypt_stat *crypt_stat;
+	int rc = -ENOMEM;
+
+	ecryptfs_printk(KERN_DEBUG,
+			"Enter; page->index = [0x%.16x]; from = [%d]; to = "
+			"[%d]\n", page->index, from, to);
+	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;
+	ASSERT(crypt_stat);
+	ASSERT(lower_file);
+	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 = bytes;
+	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);
+	ecryptfs_printk(KERN_DEBUG, "Exit; rc = [%d]\n", rc);
+	return rc;
+}
+
+/**
+ * Write a specified number of zero's to a page.
+ * 
+ * (start + num_zeros) _must_ be less than or equal to PAGE_CACHE_SIZE
+ *
+ * @param file The ecryptfs file
+ * @param index The index in which we are writing
+ * @param start The position after the last block of data
+ * @param num_zeros The number of zeros to write
+ */
+static
+int write_zeros(struct file *file, pgoff_t index, int start, int num_zeros)
+{
+	int rc = 0;
+	struct page *tmp_page;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter; index = [0x%.16x], start offset = "
+			"[%d] num_zeros = [%d]\n", index, start, num_zeros);
+	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:
+	ecryptfs_printk(KERN_DEBUG, "Exit\n");
+	return rc;
+}
+
+static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
+{
+	int rc = 0;
+	struct inode *inode;
+	struct inode *lower_inode;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter\n");
+	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 sync_page(struct page *page)
+{
+	struct address_space *mapping = page->mapping;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter\n");
+	mapping->a_ops->sync_page(page);
+	ecryptfs_printk(KERN_DEBUG, "Exit\n");
+}
+
+static void ecryptfs_sync_page(struct page *page)
+{
+	struct inode *inode;
+	struct inode *lower_inode;
+	struct page *lower_page;
+
+	ecryptfs_printk(KERN_DEBUG, "Enter\n");
+	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_get_page(lower_inode->i_mapping, page->index);
+	if (!lower_page) {
+		ecryptfs_printk(KERN_DEBUG, "find_get_page failed\n");
+		return;
+	}
+	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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