[PATCH 6/12: eCryptfs] Superblock operations

Phillip Hellewell
2005-11-19T04:19:12Z

eCryptfs superblock operations and inode
allocation/deallocation/initialization functions.

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

---

super.c | 250 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 250 insertions(+)
--- linux-2.6.15-rc1-mm1/fs/ecryptfs/super.c 1969-12-31 18:00:00.000000000 -0600
+++ linux-2.6.15-rc1-mm1-ecryptfs/fs/ecryptfs/super.c 2005-11-18 11:20:09.000000000 -0600
@@ -0,0 +1,250 @@
+/**
+ * eCryptfs: Linux filesystem encryption layer
+ *
+ * Copyright (c) 1997-2003 Erez Zadok
+ * Copyright (c) 2001-2003 Stony Brook University
+ * Copyright (c) 2005 International Business Machines Corp.
+ * Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
+ * Michael C. Thompson <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/fs.h>
+#include <linux/mount.h>
+#include <linux/key.h>
+#include "ecryptfs_kernel.h"
+
+kmem_cache_t *ecryptfs_inode_info_cache;
+
+/**
+ * Called to bring an inode into existence.
+ *
+ * Note that setting the self referencing pointer doesn't work here:
+ * i.e. ECRYPTFS_INODE_TO_PRIVATE_SM(inode)=ei;
+ *
+ * Only handle allocation, setting up structures should be done in
+ * ecryptfs_read_inode. This is because the kernel, between now and
+ * then, will 0 out the private data pointer.
+ *
+ * @param sb Pointer to the super block of the filesystem
+ * @return Pointer to a newly allocated inode, NULL otherwise
+ */
+static struct inode *ecryptfs_alloc_inode(struct super_block *sb) {
+ struct ecryptfs_inode_info *ecryptfs_inode = NULL;
+ struct inode *inode = NULL;
+
+ ecryptfs_printk(1, KERN_NOTICE, "Enter; sb = [%p]\n", sb);
+ ecryptfs_inode = kmem_cache_alloc(ecryptfs_inode_info_cache,
+ SLAB_KERNEL);
+ if (unlikely(!ecryptfs_inode)) {
+ ecryptfs_printk(1, KERN_WARNING,
+ "Failed to allocate new inode\n");
+ goto out;
+ }
+ ecryptfs_init_crypt_stats(&(ecryptfs_inode->crypt_stats));
+ inode = &(ecryptfs_inode->vfs_inode);
+ out:
+ ecryptfs_printk(1, KERN_NOTICE, "Exit; inode = [%p]\n", inode);
+ return inode;
+}
+
+/**
+ * This is used during the final destruction of the inode.
+ * All allocation of memory related to the inode, including allocated
+ * memory in the crypt_stats struct, will be released here.
+ * There should be no chance that this deallocation will be missed.
+ */
+static void ecryptfs_destroy_inode(struct inode *inode) {
+ struct ecryptfs_crypt_stats *crypt_stats;
+
+ ecryptfs_printk(1, KERN_NOTICE, "Enter; inode = [%p]\n", inode);
+ crypt_stats = &(ECRYPTFS_INODE_TO_PRIVATE(inode))->crypt_stats;
+ ecryptfs_destruct_crypt_stats(crypt_stats);
+ kmem_cache_free(ecryptfs_inode_info_cache,
+ ECRYPTFS_INODE_TO_PRIVATE(inode));
+ ecryptfs_printk(1, KERN_NOTICE, "Exit\n");
+}
+
+/**
+ * Return a pointer to our ecryptfs_inode_info struct.
+ * This is specified by the kernel documentation for the alloc_inode &
+ * destroy_inode change. We use this function to get a handle to our
+ * ecryptfs specific data.
+ *
+ * @param inode The inode component of the ecryptfs_inode_info we want to find
+ * @return Handle to our ecryptfs_inode_info
+ */
+static inline struct ecryptfs_inode_info *ECRYPTFS_I(struct inode *inode)
+{
+ return list_entry(inode, struct ecryptfs_inode_info, vfs_inode);
+}
+
+/**
+ * Set up the ecryptfs inode.
+ */
+static void ecryptfs_read_inode(struct inode *inode)
+{
+ ecryptfs_printk(1, KERN_NOTICE, "Enter; inode = [%p]\n", inode);
+ /* This is where we setup the self-reference in the vfs_inode's
+ * u.generic_ip. That way we don't have to walk the list again. */
+ ECRYPTFS_INODE_TO_PRIVATE_SM(inode) = ECRYPTFS_I(inode);
+ ECRYPTFS_INODE_TO_LOWER(inode) = NULL;
+ inode->i_version++;
+ inode->i_op = &ecryptfs_main_iops;
+ inode->i_fop = &ecryptfs_main_fops;
+ inode->i_mapping->a_ops = &ecryptfs_aops;
+ ecryptfs_printk(1, KERN_NOTICE, "Exit\n");
+}
+
+
+/**
+ * This is called through iput_final().
+ * This is function will replace generic_drop_inode. The end result of which
+ * is we are skipping the check in inode->i_nlink, which we do not use.
+ */
+static void ecryptfs_drop_inode(struct inode *inode) {
+ generic_delete_inode(inode);
+}
+
+/**
+ * Final actions when unmounting a file system.
+ * This will handle deallocation and release of our private data.
+ */
+static void ecryptfs_put_super(struct super_block *sb)
+{
+ struct ecryptfs_sb_info *sb_info = ECRYPTFS_SUPERBLOCK_TO_PRIVATE(sb);
+
+ ecryptfs_printk(1, KERN_NOTICE, "Enter\n");
+ mntput(sb_info->lower_mnt);
+ key_put(sb_info->mount_crypt_stats.global_auth_tok_key);
+ kmem_cache_free(ecryptfs_sb_info_cache, sb_info);
+ ECRYPTFS_SUPERBLOCK_TO_PRIVATE_SM(sb) = NULL;
+ ecryptfs_printk(1, KERN_NOTICE, "Exit\n");
+}
+
+/**
+ * Get the filesystem statistics. Currently, we let this pass right through
+ * to the lower filesystem and take no action ourselves
+ *
+ * TODO: Any stats need to be transposed?
+ */
+static int ecryptfs_statfs(struct super_block *sb, struct kstatfs *buf)
+{
+ int err = 0;
+
+ ecryptfs_printk(1, KERN_NOTICE, "Enter\n");
+ err = vfs_statfs(ECRYPTFS_SUPERBLOCK_TO_LOWER(sb), buf);
+ ecryptfs_printk(1, KERN_NOTICE, "Exit; err = [%d]\n",err);
+ return err;
+}
+
+/**
+ * TODO: Not implemented.
+ * Called to ask filesystem to change mount options.
+ */
+static int ecryptfs_remount_fs(struct super_block *sb, int *flags, char *data)
+{
+ ecryptfs_printk(1, KERN_NOTICE, "Enter\n");
+ ecryptfs_printk(1, KERN_NOTICE, "Exit\n");
+ return -ENOSYS;
+}
+
+/**
+ * Called by iput() when the inode reference count reached zero
+ * and the inode is not hashed anywhere. Used to clear anything
+ * that needs to be, before the inode is completely destroyed and put
+ * on the inode free list. We use this to drop out reference to the
+ * lower inode.
+ *
+ * TODO: Why do we just not drop the reference to the lower inode in
+ * ecryptfs_destroy_inode?
+ */
+static void ecryptfs_clear_inode(struct inode *inode)
+{
+ ecryptfs_printk(1, KERN_NOTICE, "Enter; inode = [%p]; i_ino = [%lu]\n",
+ inode, inode->i_ino);
+ iput(ECRYPTFS_INODE_TO_LOWER(inode));
+ ecryptfs_printk(1, KERN_NOTICE, "Exit\n");
+}
+
+/**
+ * Called in do_umount() if the MNT_FORCE flag was used and this
+ * function is defined. See comment in linux/fs/super.c:do_umount().
+ * Used only in nfs, to kill any pending RPC tasks, so that subsequent
+ * code can actually succeed and won't leave tasks that need handling.
+ *
+ * PS. I wonder if this is somehow useful to undo damage that was
+ * left in the kernel after a user level file server (such as amd)
+ * dies.
+ */
+static void ecryptfs_umount_begin(struct super_block *sb)
+{
+ struct super_block *lower_sb;
+
+ ecryptfs_printk(1, KERN_NOTICE, "Enter\n");
+ /* TODO: Explain why we are umounting the lower superblock */
+ lower_sb = ECRYPTFS_SUPERBLOCK_TO_LOWER(sb);
+ if (lower_sb->s_op->umount_begin)
+ lower_sb->s_op->umount_begin(lower_sb);
+ ecryptfs_printk(1, KERN_NOTICE, "Exit\n");
+}
+
+/* TODO: Where is this normally declared? */
+int seq_printf(struct seq_file *m, const char *f, ...);
+
+/**
+ * Prints the directory we are currently mounted over
+ *
+ * @return Zero on success; non-zero otherwise
+ */
+static int ecryptfs_show_options(struct seq_file *m, struct vfsmount *mnt)
+{
+ struct super_block *sb = mnt->mnt_sb;
+ int ret = 0;
+ char *tmp = NULL;
+ char *path;
+
+ ecryptfs_printk(1, KERN_NOTICE, "Enter\n");
+ tmp = (char *)__get_free_page(GFP_KERNEL);
+ if (!tmp) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ /* TODO: wrap? */
+ path = d_path(ECRYPTFS_DENTRY_TO_LOWER(sb->s_root),
+ ECRYPTFS_SUPERBLOCK_TO_PRIVATE(sb)->lower_mnt, tmp,
+ PAGE_SIZE);
+ seq_printf(m, ",dir=%s", path);
+ free_page((unsigned long)tmp);
+ out:
+ ecryptfs_printk(1, KERN_NOTICE, "Exit; ret = [%d]\n",ret);
+ return ret;
+}
+
+/* TODO: Provide operations? (quota stuff, dirty, sync) */
+struct super_operations ecryptfs_sops = {
+ .alloc_inode = ecryptfs_alloc_inode,
+ .destroy_inode = ecryptfs_destroy_inode,
+ .read_inode = ecryptfs_read_inode,
+ .drop_inode = ecryptfs_drop_inode,
+ .put_super = ecryptfs_put_super,
+ .statfs = ecryptfs_statfs,
+ .remount_fs = ecryptfs_remount_fs,
+ .clear_inode = ecryptfs_clear_inode,
+ .umount_begin = ecryptfs_umount_begin,
+ .show_options = ecryptfs_show_options
+};