/**
 * eCryptfs: Linux filesystem encryption layer
 *
 * Copyright (C) 1997-2004 Erez Zadok
 * Copyright (C) 2001-2004 Stony Brook University
 * Copyright (C) 2004-2007 International Business Machines Corp.
 *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
 *              Michael C. Thompsion <mcthomps@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/file.h>
#include <linux/vmalloc.h>
#include <linux/pagemap.h>
#include <linux/dcache.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/fs_stack.h>
#include <linux/slab.h>
#include <linux/xattr.h>
#include <asm/unaligned.h>
#include "ecryptfs_kernel.h"

static struct dentry *lock_parent(struct dentry *dentry)
{
        struct dentry *dir;

        dir = dget_parent(dentry);
        inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);
        return dir;
}

static void unlock_dir(struct dentry *dir)
{
        inode_unlock(d_inode(dir));
        dput(dir);
}

static int ecryptfs_inode_test(struct inode *inode, void *lower_inode)
{
        return ecryptfs_inode_to_lower(inode) == lower_inode;
}

static int ecryptfs_inode_set(struct inode *inode, void *opaque)
{
        struct inode *lower_inode = opaque;

        ecryptfs_set_inode_lower(inode, lower_inode);
        fsstack_copy_attr_all(inode, lower_inode);
        /* i_size will be overwritten for encrypted regular files */
        fsstack_copy_inode_size(inode, lower_inode);
        inode->i_ino = lower_inode->i_ino;
        inode->i_version++;
        inode->i_mapping->a_ops = &ecryptfs_aops;

        if (S_ISLNK(inode->i_mode))
                inode->i_op = &ecryptfs_symlink_iops;
        else if (S_ISDIR(inode->i_mode))
                inode->i_op = &ecryptfs_dir_iops;
        else
                inode->i_op = &ecryptfs_main_iops;

        if (S_ISDIR(inode->i_mode))
                inode->i_fop = &ecryptfs_dir_fops;
        else if (special_file(inode->i_mode))
                init_special_inode(inode, inode->i_mode, inode->i_rdev);
        else
                inode->i_fop = &ecryptfs_main_fops;

        return 0;
}

static struct inode *__ecryptfs_get_inode(struct inode *lower_inode,
                                          struct super_block *sb)
{
        struct inode *inode;

        if (lower_inode->i_sb != ecryptfs_superblock_to_lower(sb))
                return ERR_PTR(-EXDEV);
        if (!igrab(lower_inode))
                return ERR_PTR(-ESTALE);
        inode = iget5_locked(sb, (unsigned long)lower_inode,
                             ecryptfs_inode_test, ecryptfs_inode_set,
                             lower_inode);
        if (!inode) {
                iput(lower_inode);
                return ERR_PTR(-EACCES);
        }
        if (!(inode->i_state & I_NEW))
                iput(lower_inode);

        return inode;
}

struct inode *ecryptfs_get_inode(struct inode *lower_inode,
                                 struct super_block *sb)
{
        struct inode *inode = __ecryptfs_get_inode(lower_inode, sb);

        if (!IS_ERR(inode) && (inode->i_state & I_NEW))
                unlock_new_inode(inode);

        return inode;
}

/**
 * ecryptfs_interpose
 * @lower_dentry: Existing dentry in the lower filesystem
 * @dentry: ecryptfs' dentry
 * @sb: ecryptfs's super_block
 *
 * Interposes upper and lower dentries.
 *
 * Returns zero on success; non-zero otherwise
 */
static int ecryptfs_interpose(struct dentry *lower_dentry,
                              struct dentry *dentry, struct super_block *sb)
{
        struct inode *inode = ecryptfs_get_inode(d_inode(lower_dentry), sb);

        if (IS_ERR(inode))
                return PTR_ERR(inode);
        d_instantiate(dentry, inode);

        return 0;
}

static int ecryptfs_do_unlink(struct inode *dir, struct dentry *dentry,
                              struct inode *inode)
{
        struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);
        struct inode *lower_dir_inode = ecryptfs_inode_to_lower(dir);
        struct dentry *lower_dir_dentry;
        int rc;

        dget(lower_dentry);
        lower_dir_dentry = lock_parent(lower_dentry);
        rc = vfs_unlink(lower_dir_inode, lower_dentry, NULL);
        if (rc) {
                printk(KERN_ERR "Error in vfs_unlink; rc = [%d]\n", rc);
                goto out_unlock;
        }
        fsstack_copy_attr_times(dir, lower_dir_inode);
        set_nlink(inode, ecryptfs_inode_to_lower(inode)->i_nlink);
        inode->i_ctime = dir->i_ctime;
        d_drop(dentry);
out_unlock:
        unlock_dir(lower_dir_dentry);
        dput(lower_dentry);
        return rc;
}

/**
 * ecryptfs_do_create
 * @directory_inode: inode of the new file's dentry's parent in ecryptfs
 * @ecryptfs_dentry: New file's dentry in ecryptfs
 * @mode: The mode of the new file
 *
 * Creates the underlying file and the eCryptfs inode which will link to
 * it. It will also update the eCryptfs directory inode to mimic the
 * stat of the lower directory inode.
 *
 * Returns the new eCryptfs inode on success; an ERR_PTR on error condition
 */
static struct inode *
ecryptfs_do_create(struct inode *directory_inode,
                   struct dentry *ecryptfs_dentry, umode_t mode)
{
        int rc;
        struct dentry *lower_dentry;
        struct dentry *lower_dir_dentry;
        struct inode *inode;

        lower_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry);
        lower_dir_dentry = lock_parent(lower_dentry);
        rc = vfs_create(d_inode(lower_dir_dentry), lower_dentry, mode, true);
        if (rc) {
                printk(KERN_ERR "%s: Failure to create dentry in lower fs; "
                       "rc = [%d]\n", __func__, rc);
                inode = ERR_PTR(rc);
                goto out_lock;
        }
        inode = __ecryptfs_get_inode(d_inode(lower_dentry),
                                     directory_inode->i_sb);
        if (IS_ERR(inode)) {
                vfs_unlink(d_inode(lower_dir_dentry), lower_dentry, NULL);
                goto out_lock;
        }
        fsstack_copy_attr_times(directory_inode, d_inode(lower_dir_dentry));
        fsstack_copy_inode_size(directory_inode, d_inode(lower_dir_dentry));
out_lock:
        unlock_dir(lower_dir_dentry);
        return inode;
}

/**
 * ecryptfs_initialize_file
 *
 * Cause the file to be changed from a basic empty file to an ecryptfs
 * file with a header and first data page.
 *
 * Returns zero on success
 */
int ecryptfs_initialize_file(struct dentry *ecryptfs_dentry,
                             struct inode *ecryptfs_inode)
{
        struct ecryptfs_crypt_stat *crypt_stat =
                &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
        int rc = 0;

        if (S_ISDIR(ecryptfs_inode->i_mode)) {
                ecryptfs_printk(KERN_DEBUG, "This is a directory\n");
                crypt_stat->flags &= ~(ECRYPTFS_ENCRYPTED);
                goto out;
        }
        ecryptfs_printk(KERN_DEBUG, "Initializing crypto context\n");
        rc = ecryptfs_new_file_context(ecryptfs_inode);
        if (rc) {
                ecryptfs_printk(KERN_ERR, "Error creating new file "
                                "context; rc = [%d]\n", rc);
                goto out;
        }
        rc = ecryptfs_get_lower_file(ecryptfs_dentry, ecryptfs_inode);
        if (rc) {
                printk(KERN_ERR "%s: Error attempting to initialize "
                        "the lower file for the dentry with name "
                        "[%pd]; rc = [%d]\n", __func__,
                        ecryptfs_dentry, rc);
                goto out;
        }
        rc = ecryptfs_write_metadata(ecryptfs_dentry, ecryptfs_inode);
        if (rc)
                printk(KERN_ERR "Error writing headers; rc = [%d]\n", rc);
        ecryptfs_put_lower_file(ecryptfs_inode);
out:
        return rc;
}

/**
 * ecryptfs_create
 * @dir: The inode of the directory in which to create the file.
 * @dentry: The eCryptfs dentry
 * @mode: The mode of the new file.
 *
 * Creates a new file.
 *
 * Returns zero on success; non-zero on error condition
 */
static int
ecryptfs_create(struct inode *directory_inode, struct dentry *ecryptfs_dentry,
                umode_t mode, bool excl)
{
        struct inode *ecryptfs_inode;
        int rc;

        ecryptfs_inode = ecryptfs_do_create(directory_inode, ecryptfs_dentry,
                                            mode);
        if (IS_ERR(ecryptfs_inode)) {
                ecryptfs_printk(KERN_WARNING, "Failed to create file in"
                                "lower filesystem\n");
                rc = PTR_ERR(ecryptfs_inode);
                goto out;
        }
        /* At this point, a file exists on "disk"; we need to make sure
         * that this on disk file is prepared to be an ecryptfs file */
        rc = ecryptfs_initialize_file(ecryptfs_dentry, ecryptfs_inode);
        if (rc) {
                ecryptfs_do_unlink(directory_inode, ecryptfs_dentry,
                                   ecryptfs_inode);
                iget_failed(ecryptfs_inode);
                goto out;
        }
        unlock_new_inode(ecryptfs_inode);
        d_instantiate(ecryptfs_dentry, ecryptfs_inode);
out:
        return rc;
}

static int ecryptfs_i_size_read(struct dentry *dentry, struct inode *inode)
{
        struct ecryptfs_crypt_stat *crypt_stat;
        int rc;

        rc = ecryptfs_get_lower_file(dentry, inode);
        if (rc) {
                printk(KERN_ERR "%s: Error attempting to initialize "
                        "the lower file for the dentry with name "
                        "[%pd]; rc = [%d]\n", __func__,
                        dentry, rc);
                return rc;
        }

        crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
        /* TODO: lock for crypt_stat comparison */
        if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED))
                ecryptfs_set_default_sizes(crypt_stat);

        rc = ecryptfs_read_and_validate_header_region(inode);
        ecryptfs_put_lower_file(inode);
        if (rc) {
                rc = ecryptfs_read_and_validate_xattr_region(dentry, inode);
                if (!rc)
                        crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
        }

        /* Must return 0 to allow non-eCryptfs files to be looked up, too */
        return 0;
}

/**
 * ecryptfs_lookup_interpose - Dentry interposition for a lookup
 */
static struct dentry *ecryptfs_lookup_interpose(struct dentry *dentry,
                                     struct dentry *lower_dentry)
{
        struct inode *inode, *lower_inode = d_inode(lower_dentry);
        struct ecryptfs_dentry_info *dentry_info;
        struct vfsmount *lower_mnt;
        int rc = 0;

        dentry_info = kmem_cache_alloc(ecryptfs_dentry_info_cache, GFP_KERNEL);
        if (!dentry_info) {
                printk(KERN_ERR "%s: Out of memory whilst attempting "
                       "to allocate ecryptfs_dentry_info struct\n",
                        __func__);
                dput(lower_dentry);
                return ERR_PTR(-ENOMEM);
        }

        lower_mnt = mntget(ecryptfs_dentry_to_lower_mnt(dentry->d_parent));
        fsstack_copy_attr_atime(d_inode(dentry->d_parent),
                                d_inode(lower_dentry->d_parent));
        BUG_ON(!d_count(lower_dentry));

        ecryptfs_set_dentry_private(dentry, dentry_info);
        dentry_info->lower_path.mnt = lower_mnt;
        dentry_info->lower_path.dentry = lower_dentry;

        if (d_really_is_negative(lower_dentry)) {
                /* We want to add because we couldn't find in lower */
                d_add(dentry, NULL);
                return NULL;
        }
        inode = __ecryptfs_get_inode(lower_inode, dentry->d_sb);
        if (IS_ERR(inode)) {
                printk(KERN_ERR "%s: Error interposing; rc = [%ld]\n",
                       __func__, PTR_ERR(inode));
                return ERR_CAST(inode);
        }
        if (S_ISREG(inode->i_mode)) {
                rc = ecryptfs_i_size_read(dentry, inode);
                if (rc) {
                        make_bad_inode(inode);
                        return ERR_PTR(rc);
                }
        }

        if (inode->i_state & I_NEW)
                unlock_new_inode(inode);
        return d_splice_alias(inode, dentry);
}

/**
 * ecryptfs_lookup
 * @ecryptfs_dir_inode: The eCryptfs directory inode
 * @ecryptfs_dentry: The eCryptfs dentry that we are looking up
 * @flags: lookup flags
 *
 * Find a file on disk. If the file does not exist, then we'll add it to the
 * dentry cache and continue on to read it from the disk.
 */
static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
                                      struct dentry *ecryptfs_dentry,
                                      unsigned int flags)
{
        char *encrypted_and_encoded_name = NULL;
        struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
        struct dentry *lower_dir_dentry, *lower_dentry;
        const char *name = ecryptfs_dentry->d_name.name;
        size_t len = ecryptfs_dentry->d_name.len;
        struct dentry *res;
        int rc = 0;

        lower_dir_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry->d_parent);

        mount_crypt_stat = &ecryptfs_superblock_to_private(
                                ecryptfs_dentry->d_sb)->mount_crypt_stat;
        if (mount_crypt_stat
            && (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)) {
                rc = ecryptfs_encrypt_and_encode_filename(
                        &encrypted_and_encoded_name, &len,
                        mount_crypt_stat, name, len);
                if (rc) {
                        printk(KERN_ERR "%s: Error attempting to encrypt and encode "
                               "filename; rc = [%d]\n", __func__, rc);
                        return ERR_PTR(rc);
                }
                name = encrypted_and_encoded_name;
        }

        lower_dentry = lookup_one_len_unlocked(name, lower_dir_dentry, len);
        if (IS_ERR(lower_dentry)) {
                ecryptfs_printk(KERN_DEBUG, "%s: lookup_one_len() returned "
                                "[%ld] on lower_dentry = [%s]\n", __func__,
                                PTR_ERR(lower_dentry),
                                name);
                res = ERR_CAST(lower_dentry);
        } else {
                res = ecryptfs_lookup_interpose(ecryptfs_dentry, lower_dentry);
        }
        kfree(encrypted_and_encoded_name);
        return res;
}

static int ecryptfs_link(struct dentry *old_dentry, struct inode *dir,
                         struct dentry *new_dentry)
{
        struct dentry *lower_old_dentry;
        struct dentry *lower_new_dentry;
        struct dentry *lower_dir_dentry;
        u64 file_size_save;
        int rc;

        file_size_save = i_size_read(d_inode(old_dentry));
        lower_old_dentry = ecryptfs_dentry_to_lower(old_dentry);
        lower_new_dentry = ecryptfs_dentry_to_lower(new_dentry);
        dget(lower_old_dentry);
        dget(lower_new_dentry);
        lower_dir_dentry = lock_parent(lower_new_dentry);
        rc = vfs_link(lower_old_dentry, d_inode(lower_dir_dentry),
                      lower_new_dentry, NULL);
        if (rc || d_really_is_negative(lower_new_dentry))
                goto out_lock;
        rc = ecryptfs_interpose(lower_new_dentry, new_dentry, dir->i_sb);
        if (rc)
                goto out_lock;
        fsstack_copy_attr_times(dir, d_inode(lower_dir_dentry));
        fsstack_copy_inode_size(dir, d_inode(lower_dir_dentry));
        set_nlink(d_inode(old_dentry),
                  ecryptfs_inode_to_lower(d_inode(old_dentry))->i_nlink);
        i_size_write(d_inode(new_dentry), file_size_save);
out_lock:
        unlock_dir(lower_dir_dentry);
        dput(lower_new_dentry);
        dput(lower_old_dentry);
        return rc;
}

static int ecryptfs_unlink(struct inode *dir, struct dentry *dentry)
{
        return ecryptfs_do_unlink(dir, dentry, d_inode(dentry));
}

static int ecryptfs_symlink(struct inode *dir, struct dentry *dentry,
                            const char *symname)
{
        int rc;
        struct dentry *lower_dentry;
        struct dentry *lower_dir_dentry;
        char *encoded_symname;
        size_t encoded_symlen;
        struct ecryptfs_mount_crypt_stat *mount_crypt_stat = NULL;

        lower_dentry = ecryptfs_dentry_to_lower(dentry);
        dget(lower_dentry);
        lower_dir_dentry = lock_parent(lower_dentry);
        mount_crypt_stat = &ecryptfs_superblock_to_private(
                dir->i_sb)->mount_crypt_stat;
        rc = ecryptfs_encrypt_and_encode_filename(&encoded_symname,
                                                  &encoded_symlen,
                                                  mount_crypt_stat, symname,
                                                  strlen(symname));
        if (rc)
                goto out_lock;
        rc = vfs_symlink(d_inode(lower_dir_dentry), lower_dentry,
                         encoded_symname);
        kfree(encoded_symname);
        if (rc || d_really_is_negative(lower_dentry))
                goto out_lock;
        rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb);
        if (rc)
                goto out_lock;
        fsstack_copy_attr_times(dir, d_inode(lower_dir_dentry));
        fsstack_copy_inode_size(dir, d_inode(lower_dir_dentry));
out_lock:
        unlock_dir(lower_dir_dentry);
        dput(lower_dentry);
        if (d_really_is_negative(dentry))
                d_drop(dentry);
        return rc;
}

static int ecryptfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
        int rc;
        struct dentry *lower_dentry;
        struct dentry *lower_dir_dentry;

        lower_dentry = ecryptfs_dentry_to_lower(dentry);
        lower_dir_dentry = lock_parent(lower_dentry);
        rc = vfs_mkdir(d_inode(lower_dir_dentry), lower_dentry, mode);
        if (rc || d_really_is_negative(lower_dentry))
                goto out;
        rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb);
        if (rc)
                goto out;
        fsstack_copy_attr_times(dir, d_inode(lower_dir_dentry));
        fsstack_copy_inode_size(dir, d_inode(lower_dir_dentry));
        set_nlink(dir, d_inode(lower_dir_dentry)->i_nlink);
out:
        unlock_dir(lower_dir_dentry);
        if (d_really_is_negative(dentry))
                d_drop(dentry);
        return rc;
}

static int ecryptfs_rmdir(struct inode *dir, struct dentry *dentry)
{
        struct dentry *lower_dentry;
        struct dentry *lower_dir_dentry;
        int rc;

        lower_dentry = ecryptfs_dentry_to_lower(dentry);
        dget(dentry);
        lower_dir_dentry = lock_parent(lower_dentry);
        dget(lower_dentry);
        rc = vfs_rmdir(d_inode(lower_dir_dentry), lower_dentry);
        dput(lower_dentry);
        if (!rc && d_really_is_positive(dentry))
                clear_nlink(d_inode(dentry));
        fsstack_copy_attr_times(dir, d_inode(lower_dir_dentry));
        set_nlink(dir, d_inode(lower_dir_dentry)->i_nlink);
        unlock_dir(lower_dir_dentry);
        if (!rc)
                d_drop(dentry);
        dput(dentry);
        return rc;
}

static int
ecryptfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
{
        int rc;
        struct dentry *lower_dentry;
        struct dentry *lower_dir_dentry;

        lower_dentry = ecryptfs_dentry_to_lower(dentry);
        lower_dir_dentry = lock_parent(lower_dentry);
        rc = vfs_mknod(d_inode(lower_dir_dentry), lower_dentry, mode, dev);
        if (rc || d_really_is_negative(lower_dentry))
                goto out;
        rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb);
        if (rc)
                goto out;
        fsstack_copy_attr_times(dir, d_inode(lower_dir_dentry));
        fsstack_copy_inode_size(dir, d_inode(lower_dir_dentry));
out:
        unlock_dir(lower_dir_dentry);
        if (d_really_is_negative(dentry))
                d_drop(dentry);
        return rc;
}

static int
ecryptfs_rename(struct inode *old_dir, struct dentry *old_dentry,
                struct inode *new_dir, struct dentry *new_dentry,
                unsigned int flags)
{
        int rc;
        struct dentry *lower_old_dentry;
        struct dentry *lower_new_dentry;
        struct dentry *lower_old_dir_dentry;
        struct dentry *lower_new_dir_dentry;
        struct dentry *trap = NULL;
        struct inode *target_inode;

        if (flags)
                return -EINVAL;

        lower_old_dentry = ecryptfs_dentry_to_lower(old_dentry);
        lower_new_dentry = ecryptfs_dentry_to_lower(new_dentry);
        dget(lower_old_dentry);
        dget(lower_new_dentry);
        lower_old_dir_dentry = dget_parent(lower_old_dentry);
        lower_new_dir_dentry = dget_parent(lower_new_dentry);
        target_inode = d_inode(new_dentry);
        trap = lock_rename(lower_old_dir_dentry, lower_new_dir_dentry);
        /* source should not be ancestor of target */
        if (trap == lower_old_dentry) {
                rc = -EINVAL;
                goto out_lock;
        }
        /* target should not be ancestor of source */
        if (trap == lower_new_dentry) {
                rc = -ENOTEMPTY;
                goto out_lock;
        }
        rc = vfs_rename(d_inode(lower_old_dir_dentry), lower_old_dentry,
                        d_inode(lower_new_dir_dentry), lower_new_dentry,
                        NULL, 0);
        if (rc)
                goto out_lock;
        if (target_inode)
                fsstack_copy_attr_all(target_inode,
                                      ecryptfs_inode_to_lower(target_inode));
        fsstack_copy_attr_all(new_dir, d_inode(lower_new_dir_dentry));
        if (new_dir != old_dir)
                fsstack_copy_attr_all(old_dir, d_inode(lower_old_dir_dentry));
out_lock:
        unlock_rename(lower_old_dir_dentry, lower_new_dir_dentry);
        dput(lower_new_dir_dentry);
        dput(lower_old_dir_dentry);
        dput(lower_new_dentry);
        dput(lower_old_dentry);
        return rc;
}

static char *ecryptfs_readlink_lower(struct dentry *dentry, size_t *bufsiz)
{
        struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);
        char *lower_buf;
        char *buf;
        mm_segment_t old_fs;
        int rc;

        lower_buf = kmalloc(PATH_MAX, GFP_KERNEL);
        if (!lower_buf)
                return ERR_PTR(-ENOMEM);
        old_fs = get_fs();
        set_fs(get_ds());
        rc = d_inode(lower_dentry)->i_op->readlink(lower_dentry,
                                                   (char __user *)lower_buf,
                                                   PATH_MAX);
        set_fs(old_fs);
        if (rc < 0)
                goto out;
        rc = ecryptfs_decode_and_decrypt_filename(&buf, bufsiz, dentry->d_sb,
                                                  lower_buf, rc);
out:
        kfree(lower_buf);
        return rc ? ERR_PTR(rc) : buf;
}

static const char *ecryptfs_get_link(struct dentry *dentry,
                                     struct inode *inode,
                                     struct delayed_call *done)
{
        size_t len;
        char *buf;

        if (!dentry)
                return ERR_PTR(-ECHILD);

        buf = ecryptfs_readlink_lower(dentry, &len);
        if (IS_ERR(buf))
                return buf;
        fsstack_copy_attr_atime(d_inode(dentry),
                                d_inode(ecryptfs_dentry_to_lower(dentry)));
        buf[len] = '\0';
        set_delayed_call(done, kfree_link, buf);
        return buf;
}

/**
 * upper_size_to_lower_size
 * @crypt_stat: Crypt_stat associated with file
 * @upper_size: Size of the upper file
 *
 * Calculate the required size of the lower file based on the
 * specified size of the upper file. This calculation is based on the
 * number of headers in the underlying file and the extent size.
 *
 * Returns Calculated size of the lower file.
 */
static loff_t
upper_size_to_lower_size(struct ecryptfs_crypt_stat *crypt_stat,
                         loff_t upper_size)
{
        loff_t lower_size;

        lower_size = ecryptfs_lower_header_size(crypt_stat);
        if (upper_size != 0) {
                loff_t num_extents;

                num_extents = upper_size >> crypt_stat->extent_shift;
                if (upper_size & ~crypt_stat->extent_mask)
                        num_extents++;
                lower_size += (num_extents * crypt_stat->extent_size);
        }
        return lower_size;
}

/**
 * truncate_upper
 * @dentry: The ecryptfs layer dentry
 * @ia: Address of the ecryptfs inode's attributes
 * @lower_ia: Address of the lower inode's attributes
 *
 * Function to handle truncations modifying the size of the file. Note
 * that the file sizes are interpolated. When expanding, we are simply
 * writing strings of 0's out. When truncating, we truncate the upper
 * inode and update the lower_ia according to the page index
 * interpolations. If ATTR_SIZE is set in lower_ia->ia_valid upon return,
 * the caller must use lower_ia in a call to notify_change() to perform
 * the truncation of the lower inode.
 *
 * Returns zero on success; non-zero otherwise
 */
static int truncate_upper(struct dentry *dentry, struct iattr *ia,
                          struct iattr *lower_ia)
{
        int rc = 0;
        struct inode *inode = d_inode(dentry);
        struct ecryptfs_crypt_stat *crypt_stat;
        loff_t i_size = i_size_read(inode);
        loff_t lower_size_before_truncate;
        loff_t lower_size_after_truncate;

        if (unlikely((ia->ia_size == i_size))) {
                lower_ia->ia_valid &= ~ATTR_SIZE;
                return 0;
        }
        rc = ecryptfs_get_lower_file(dentry, inode);
        if (rc)
                return rc;
        crypt_stat = &ecryptfs_inode_to_private(d_inode(dentry))->crypt_stat;
        /* Switch on growing or shrinking file */
        if (ia->ia_size > i_size) {
                char zero[] = { 0x00 };

                lower_ia->ia_valid &= ~ATTR_SIZE;
                /* Write a single 0 at the last position of the file;
                 * this triggers code that will fill in 0's throughout
                 * the intermediate portion of the previous end of the
                 * file and the new and of the file */
                rc = ecryptfs_write(inode, zero,
                                    (ia->ia_size - 1), 1);
        } else { /* ia->ia_size < i_size_read(inode) */
                /* We're chopping off all the pages down to the page
                 * in which ia->ia_size is located. Fill in the end of
                 * that page from (ia->ia_size & ~PAGE_MASK) to
                 * PAGE_SIZE with zeros. */
                size_t num_zeros = (PAGE_SIZE
                                    - (ia->ia_size & ~PAGE_MASK));

                if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
                        truncate_setsize(inode, ia->ia_size);
                        lower_ia->ia_size = ia->ia_size;
                        lower_ia->ia_valid |= ATTR_SIZE;
                        goto out;
                }
                if (num_zeros) {
                        char *zeros_virt;

                        zeros_virt = kzalloc(num_zeros, GFP_KERNEL);
                        if (!zeros_virt) {
                                rc = -ENOMEM;
                                goto out;
                        }
                        rc = ecryptfs_write(inode, zeros_virt,
                                            ia->ia_size, num_zeros);
                        kfree(zeros_virt);
                        if (rc) {
                                printk(KERN_ERR "Error attempting to zero out "
                                       "the remainder of the end page on "
                                       "reducing truncate; rc = [%d]\n", rc);
                                goto out;
                        }
                }
                truncate_setsize(inode, ia->ia_size);
                rc = ecryptfs_write_inode_size_to_metadata(inode);
                if (rc) {
                        printk(KERN_ERR "Problem with "
                               "ecryptfs_write_inode_size_to_metadata; "
                               "rc = [%d]\n", rc);
                        goto out;
                }
                /* We are reducing the size of the ecryptfs file, and need to
                 * know if we need to reduce the size of the lower file. */
                lower_size_before_truncate =
                    upper_size_to_lower_size(crypt_stat, i_size);
                lower_size_after_truncate =
                    upper_size_to_lower_size(crypt_stat, ia->ia_size);
                if (lower_size_after_truncate < lower_size_before_truncate) {
                        lower_ia->ia_size = lower_size_after_truncate;
                        lower_ia->ia_valid |= ATTR_SIZE;
                } else
                        lower_ia->ia_valid &= ~ATTR_SIZE;
        }
out:
        ecryptfs_put_lower_file(inode);
        return rc;
}

static int ecryptfs_inode_newsize_ok(struct inode *inode, loff_t offset)
{
        struct ecryptfs_crypt_stat *crypt_stat;
        loff_t lower_oldsize, lower_newsize;

        crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
        lower_oldsize = upper_size_to_lower_size(crypt_stat,
                                                 i_size_read(inode));
        lower_newsize = upper_size_to_lower_size(crypt_stat, offset);
        if (lower_newsize > lower_oldsize) {
                /*
                 * The eCryptfs inode and the new *lower* size are mixed here
                 * because we may not have the lower i_mutex held and/or it may
                 * not be appropriate to call inode_newsize_ok() with inodes
                 * from other filesystems.
                 */
                return inode_newsize_ok(inode, lower_newsize);
        }

        return 0;
}

/**
 * ecryptfs_truncate
 * @dentry: The ecryptfs layer dentry
 * @new_length: The length to expand the file to
 *
 * Simple function that handles the truncation of an eCryptfs inode and
 * its corresponding lower inode.
 *
 * Returns zero on success; non-zero otherwise
 */
int ecryptfs_truncate(struct dentry *dentry, loff_t new_length)
{
        struct iattr ia = { .ia_valid = ATTR_SIZE, .ia_size = new_length };
        struct iattr lower_ia = { .ia_valid = 0 };
        int rc;

        rc = ecryptfs_inode_newsize_ok(d_inode(dentry), new_length);
        if (rc)
                return rc;

        rc = truncate_upper(dentry, &ia, &lower_ia);
        if (!rc && lower_ia.ia_valid & ATTR_SIZE) {
                struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);

                inode_lock(d_inode(lower_dentry));
                rc = notify_change(lower_dentry, &lower_ia, NULL);
                inode_unlock(d_inode(lower_dentry));
        }
        return rc;
}

static int
ecryptfs_permission(struct inode *inode, int mask)
{
        return inode_permission(ecryptfs_inode_to_lower(inode), mask);
}

/**
 * ecryptfs_setattr
 * @dentry: dentry handle to the inode to modify
 * @ia: Structure with flags of what to change and values
 *
 * Updates the metadata of an inode. If the update is to the size
 * i.e. truncation, then ecryptfs_truncate will handle the size modification
 * of both the ecryptfs inode and the lower inode.
 *
 * All other metadata changes will be passed right to the lower filesystem,
 * and we will just update our inode to look like the lower.
 */
static int ecryptfs_setattr(struct dentry *dentry, struct iattr *ia)
{
        int rc = 0;
        struct dentry *lower_dentry;
        struct iattr lower_ia;
        struct inode *inode;
        struct inode *lower_inode;
        struct ecryptfs_crypt_stat *crypt_stat;

        crypt_stat = &ecryptfs_inode_to_private(d_inode(dentry))->crypt_stat;
        if (!(crypt_stat->flags & ECRYPTFS_STRUCT_INITIALIZED)) {
                rc = ecryptfs_init_crypt_stat(crypt_stat);
                if (rc)
                        return rc;
        }
        inode = d_inode(dentry);
        lower_inode = ecryptfs_inode_to_lower(inode);
        lower_dentry = ecryptfs_dentry_to_lower(dentry);
        mutex_lock(&crypt_stat->cs_mutex);
        if (d_is_dir(dentry))
                crypt_stat->flags &= ~(ECRYPTFS_ENCRYPTED);
        else if (d_is_reg(dentry)
                 && (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED)
                     || !(crypt_stat->flags & ECRYPTFS_KEY_VALID))) {
                struct ecryptfs_mount_crypt_stat *mount_crypt_stat;

                mount_crypt_stat = &ecryptfs_superblock_to_private(
                        dentry->d_sb)->mount_crypt_stat;
                rc = ecryptfs_get_lower_file(dentry, inode);
                if (rc) {
                        mutex_unlock(&crypt_stat->cs_mutex);
                        goto out;
                }
                rc = ecryptfs_read_metadata(dentry);
                ecryptfs_put_lower_file(inode);
                if (rc) {
                        if (!(mount_crypt_stat->flags
                              & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED)) {
                                rc = -EIO;
                                printk(KERN_WARNING "Either the lower file "
                                       "is not in a valid eCryptfs format, "
                                       "or the key could not be retrieved. "
                                       "Plaintext passthrough mode is not "
                                       "enabled; returning -EIO\n");
                                mutex_unlock(&crypt_stat->cs_mutex);
                                goto out;
                        }
                        rc = 0;
                        crypt_stat->flags &= ~(ECRYPTFS_I_SIZE_INITIALIZED
                                               | ECRYPTFS_ENCRYPTED);
                }
        }
        mutex_unlock(&crypt_stat->cs_mutex);

        rc = setattr_prepare(dentry, ia);
        if (rc)
                goto out;
        if (ia->ia_valid & ATTR_SIZE) {
                rc = ecryptfs_inode_newsize_ok(inode, ia->ia_size);
                if (rc)
                        goto out;
        }

        memcpy(&lower_ia, ia, sizeof(lower_ia));
        if (ia->ia_valid & ATTR_FILE)
                lower_ia.ia_file = ecryptfs_file_to_lower(ia->ia_file);
        if (ia->ia_valid & ATTR_SIZE) {
                rc = truncate_upper(dentry, ia, &lower_ia);
                if (rc < 0)
                        goto out;
        }

        /*
         * mode change is for clearing setuid/setgid bits. Allow lower fs
         * to interpret this in its own way.
         */
        if (lower_ia.ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID))
                lower_ia.ia_valid &= ~ATTR_MODE;

        inode_lock(d_inode(lower_dentry));
        rc = notify_change(lower_dentry, &lower_ia, NULL);
        inode_unlock(d_inode(lower_dentry));
out:
        fsstack_copy_attr_all(inode, lower_inode);
        return rc;
}

static int ecryptfs_getattr_link(struct vfsmount *mnt, struct dentry *dentry,
                                 struct kstat *stat)
{
        struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
        int rc = 0;

        mount_crypt_stat = &ecryptfs_superblock_to_private(
                                                dentry->d_sb)->mount_crypt_stat;
        generic_fillattr(d_inode(dentry), stat);
        if (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES) {
                char *target;
                size_t targetsiz;

                target = ecryptfs_readlink_lower(dentry, &targetsiz);
                if (!IS_ERR(target)) {
                        kfree(target);
                        stat->size = targetsiz;
                } else {
                        rc = PTR_ERR(target);
                }
        }
        return rc;
}

static int ecryptfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
                            struct kstat *stat)
{
        struct kstat lower_stat;
        int rc;

        rc = vfs_getattr(ecryptfs_dentry_to_lower_path(dentry), &lower_stat);
        if (!rc) {
                fsstack_copy_attr_all(d_inode(dentry),
                                      ecryptfs_inode_to_lower(d_inode(dentry)));

                generic_fillattr(d_inode(dentry), stat);
                stat->blocks = lower_stat.blocks;
        }
        return rc;
}

int
ecryptfs_setxattr(struct dentry *dentry, struct inode *inode,
                  const char *name, const void *value,
                  size_t size, int flags)
{
        int rc;
        struct dentry *lower_dentry;

        lower_dentry = ecryptfs_dentry_to_lower(dentry);
        if (!(d_inode(lower_dentry)->i_opflags & IOP_XATTR)) {
                rc = -EOPNOTSUPP;
                goto out;
        }
        rc = vfs_setxattr(lower_dentry, name, value, size, flags);
        if (!rc && inode)
                fsstack_copy_attr_all(inode, d_inode(lower_dentry));
out:
        return rc;
}

ssize_t
ecryptfs_getxattr_lower(struct dentry *lower_dentry, struct inode *lower_inode,
                        const char *name, void *value, size_t size)
{
        int rc;

        if (!(lower_inode->i_opflags & IOP_XATTR)) {
                rc = -EOPNOTSUPP;
                goto out;
        }
        inode_lock(lower_inode);
        rc = __vfs_getxattr(lower_dentry, lower_inode, name, value, size);
        inode_unlock(lower_inode);
out:
        return rc;
}

static ssize_t
ecryptfs_getxattr(struct dentry *dentry, struct inode *inode,
                  const char *name, void *value, size_t size)
{
        return ecryptfs_getxattr_lower(ecryptfs_dentry_to_lower(dentry),
                                       ecryptfs_inode_to_lower(inode),
                                       name, value, size);
}

static ssize_t
ecryptfs_listxattr(struct dentry *dentry, char *list, size_t size)
{
        int rc = 0;
        struct dentry *lower_dentry;

        lower_dentry = ecryptfs_dentry_to_lower(dentry);
        if (!d_inode(lower_dentry)->i_op->listxattr) {
                rc = -EOPNOTSUPP;
                goto out;
        }
        inode_lock(d_inode(lower_dentry));
        rc = d_inode(lower_dentry)->i_op->listxattr(lower_dentry, list, size);
        inode_unlock(d_inode(lower_dentry));
out:
        return rc;
}

static int ecryptfs_removexattr(struct dentry *dentry, struct inode *inode,
                                const char *name)
{
        int rc;
        struct dentry *lower_dentry;
        struct inode *lower_inode;

        lower_dentry = ecryptfs_dentry_to_lower(dentry);
        lower_inode = ecryptfs_inode_to_lower(inode);
        if (!(lower_inode->i_opflags & IOP_XATTR)) {
                rc = -EOPNOTSUPP;
                goto out;
        }
        inode_lock(lower_inode);
        rc = __vfs_removexattr(lower_dentry, name);
        inode_unlock(lower_inode);
out:
        return rc;
}

const struct inode_operations ecryptfs_symlink_iops = {
        .readlink = generic_readlink,
        .get_link = ecryptfs_get_link,
        .permission = ecryptfs_permission,
        .setattr = ecryptfs_setattr,
        .getattr = ecryptfs_getattr_link,
        .listxattr = ecryptfs_listxattr,
};

const struct inode_operations ecryptfs_dir_iops = {
        .create = ecryptfs_create,
        .lookup = ecryptfs_lookup,
        .link = ecryptfs_link,
        .unlink = ecryptfs_unlink,
        .symlink = ecryptfs_symlink,
        .mkdir = ecryptfs_mkdir,
        .rmdir = ecryptfs_rmdir,
        .mknod = ecryptfs_mknod,
        .rename = ecryptfs_rename,
        .permission = ecryptfs_permission,
        .setattr = ecryptfs_setattr,
        .listxattr = ecryptfs_listxattr,
};

const struct inode_operations ecryptfs_main_iops = {
        .permission = ecryptfs_permission,
        .setattr = ecryptfs_setattr,
        .getattr = ecryptfs_getattr,
        .listxattr = ecryptfs_listxattr,
};

static int ecryptfs_xattr_get(const struct xattr_handler *handler,
                              struct dentry *dentry, struct inode *inode,
                              const char *name, void *buffer, size_t size)
{
        return ecryptfs_getxattr(dentry, inode, name, buffer, size);
}

static int ecryptfs_xattr_set(const struct xattr_handler *handler,
                              struct dentry *dentry, struct inode *inode,
                              const char *name, const void *value, size_t size,
                              int flags)
{
        if (value)
                return ecryptfs_setxattr(dentry, inode, name, value, size, flags);
        else {
                BUG_ON(flags != XATTR_REPLACE);
                return ecryptfs_removexattr(dentry, inode, name);
        }
}

const struct xattr_handler ecryptfs_xattr_handler = {
        .prefix = "",  /* match anything */
        .get = ecryptfs_xattr_get,
        .set = ecryptfs_xattr_set,
};

const struct xattr_handler *ecryptfs_xattr_handlers[] = {
        &ecryptfs_xattr_handler,
        NULL
};