Message-Id: <119997719911-git-send-email-ezk@cs.sunysb.edu>
Date:	Thu, 10 Jan 2008 09:59:38 -0500
From:	Erez Zadok <ezk@...sunysb.edu>
To:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	hch@...radead.org, viro@....linux.org.uk
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Erez Zadok <ezk@...sunysb.edu>
Subject: [PATCH 19/29] Unionfs: mount-time and stacking-interposition functions

Includes read_super and module-linkage routines.

Signed-off-by: Erez Zadok <ezk@...sunysb.edu>
---
 fs/unionfs/main.c |  794 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 794 insertions(+), 0 deletions(-)
 create mode 100644 fs/unionfs/main.c

diff --git a/fs/unionfs/main.c b/fs/unionfs/main.c
new file mode 100644
index 0000000..23c18f7
--- /dev/null
+++ b/fs/unionfs/main.c
@@ -0,0 +1,794 @@
+/*
+ * Copyright (c) 2003-2007 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2007 Stony Brook University
+ * Copyright (c) 2003-2007 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+
+static void unionfs_fill_inode(struct dentry *dentry,
+			       struct inode *inode)
+{
+	struct inode *lower_inode;
+	struct dentry *lower_dentry;
+	int bindex, bstart, bend;
+
+	bstart = dbstart(dentry);
+	bend = dbend(dentry);
+
+	for (bindex = bstart; bindex <= bend; bindex++) {
+		lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+		if (!lower_dentry) {
+			unionfs_set_lower_inode_idx(inode, bindex, NULL);
+			continue;
+		}
+
+		/* Initialize the lower inode to the new lower inode. */
+		if (!lower_dentry->d_inode)
+			continue;
+
+		unionfs_set_lower_inode_idx(inode, bindex,
+					    igrab(lower_dentry->d_inode));
+	}
+
+	ibstart(inode) = dbstart(dentry);
+	ibend(inode) = dbend(dentry);
+
+	/* Use attributes from the first branch. */
+	lower_inode = unionfs_lower_inode(inode);
+
+	/* Use different set of inode ops for symlinks & directories */
+	if (S_ISLNK(lower_inode->i_mode))
+		inode->i_op = &unionfs_symlink_iops;
+	else if (S_ISDIR(lower_inode->i_mode))
+		inode->i_op = &unionfs_dir_iops;
+
+	/* Use different set of file ops for directories */
+	if (S_ISDIR(lower_inode->i_mode))
+		inode->i_fop = &unionfs_dir_fops;
+
+	/* properly initialize special inodes */
+	if (S_ISBLK(lower_inode->i_mode) || S_ISCHR(lower_inode->i_mode) ||
+	    S_ISFIFO(lower_inode->i_mode) || S_ISSOCK(lower_inode->i_mode))
+		init_special_inode(inode, lower_inode->i_mode,
+				   lower_inode->i_rdev);
+
+	/* all well, copy inode attributes */
+	unionfs_copy_attr_all(inode, lower_inode);
+	fsstack_copy_inode_size(inode, lower_inode);
+}
+
+/*
+ * Connect a unionfs inode dentry/inode with several lower ones.  This is
+ * the classic stackable file system "vnode interposition" action.
+ *
+ * @sb: unionfs's super_block
+ */
+struct dentry *unionfs_interpose(struct dentry *dentry, struct super_block *sb,
+				 int flag)
+{
+	int err = 0;
+	struct inode *inode;
+	int is_negative_dentry = 1;
+	int bindex, bstart, bend;
+	int need_fill_inode = 1;
+	struct dentry *spliced = NULL;
+
+	verify_locked(dentry);
+
+	bstart = dbstart(dentry);
+	bend = dbend(dentry);
+
+	/* Make sure that we didn't get a negative dentry. */
+	for (bindex = bstart; bindex <= bend; bindex++) {
+		if (unionfs_lower_dentry_idx(dentry, bindex) &&
+		    unionfs_lower_dentry_idx(dentry, bindex)->d_inode) {
+			is_negative_dentry = 0;
+			break;
+		}
+	}
+	BUG_ON(is_negative_dentry);
+
+	/*
+	 * We allocate our new inode below, by calling iget.
+	 * iget will call our read_inode which will initialize some
+	 * of the new inode's fields
+	 */
+
+	/*
+	 * On revalidate we've already got our own inode and just need
+	 * to fix it up.
+	 */
+	if (flag == INTERPOSE_REVAL) {
+		inode = dentry->d_inode;
+		UNIONFS_I(inode)->bstart = -1;
+		UNIONFS_I(inode)->bend = -1;
+		atomic_set(&UNIONFS_I(inode)->generation,
+			   atomic_read(&UNIONFS_SB(sb)->generation));
+
+		UNIONFS_I(inode)->lower_inodes =
+			kcalloc(sbmax(sb), sizeof(struct inode *), GFP_KERNEL);
+		if (unlikely(!UNIONFS_I(inode)->lower_inodes)) {
+			err = -ENOMEM;
+			goto out;
+		}
+	} else {
+		/* get unique inode number for unionfs */
+		inode = iget(sb, iunique(sb, UNIONFS_ROOT_INO));
+		if (!inode) {
+			err = -EACCES;
+			goto out;
+		}
+		if (atomic_read(&inode->i_count) > 1)
+			goto skip;
+	}
+
+	need_fill_inode = 0;
+	unionfs_fill_inode(dentry, inode);
+
+skip:
+	/* only (our) lookup wants to do a d_add */
+	switch (flag) {
+	case INTERPOSE_DEFAULT:
+	case INTERPOSE_REVAL_NEG:
+		d_instantiate(dentry, inode);
+		break;
+	case INTERPOSE_LOOKUP:
+		spliced = d_splice_alias(inode, dentry);
+		if (spliced && spliced != dentry) {
+			/*
+			 * d_splice can return a dentry if it was
+			 * disconnected and had to be moved.  We must ensure
+			 * that the private data of the new dentry is
+			 * correct and that the inode info was filled
+			 * properly.  Finally we must return this new
+			 * dentry.
+			 */
+			spliced->d_op = &unionfs_dops;
+			spliced->d_fsdata = dentry->d_fsdata;
+			dentry->d_fsdata = NULL;
+			dentry = spliced;
+			if (need_fill_inode) {
+				need_fill_inode = 0;
+				unionfs_fill_inode(dentry, inode);
+			}
+			goto out_spliced;
+		} else if (!spliced) {
+			if (need_fill_inode) {
+				need_fill_inode = 0;
+				unionfs_fill_inode(dentry, inode);
+				goto out_spliced;
+			}
+		}
+		break;
+	case INTERPOSE_REVAL:
+		/* Do nothing. */
+		break;
+	default:
+		printk(KERN_CRIT "unionfs: invalid interpose flag passed!\n");
+		BUG();
+	}
+	goto out;
+
+out_spliced:
+	if (!err)
+		return spliced;
+out:
+	return ERR_PTR(err);
+}
+
+/* like interpose above, but for an already existing dentry */
+void unionfs_reinterpose(struct dentry *dentry)
+{
+	struct dentry *lower_dentry;
+	struct inode *inode;
+	int bindex, bstart, bend;
+
+	verify_locked(dentry);
+
+	/* This is pre-allocated inode */
+	inode = dentry->d_inode;
+
+	bstart = dbstart(dentry);
+	bend = dbend(dentry);
+	for (bindex = bstart; bindex <= bend; bindex++) {
+		lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+		if (!lower_dentry)
+			continue;
+
+		if (!lower_dentry->d_inode)
+			continue;
+		if (unionfs_lower_inode_idx(inode, bindex))
+			continue;
+		unionfs_set_lower_inode_idx(inode, bindex,
+					    igrab(lower_dentry->d_inode));
+	}
+	ibstart(inode) = dbstart(dentry);
+	ibend(inode) = dbend(dentry);
+}
+
+/*
+ * make sure the branch we just looked up (nd) makes sense:
+ *
+ * 1) we're not trying to stack unionfs on top of unionfs
+ * 2) it exists
+ * 3) is a directory
+ */
+int check_branch(struct nameidata *nd)
+{
+	/* XXX: remove in ODF code -- stacking unions allowed there */
+	if (!strcmp(nd->dentry->d_sb->s_type->name, UNIONFS_NAME))
+		return -EINVAL;
+	if (!nd->dentry->d_inode)
+		return -ENOENT;
+	if (!S_ISDIR(nd->dentry->d_inode->i_mode))
+		return -ENOTDIR;
+	return 0;
+}
+
+/* checks if two lower_dentries have overlapping branches */
+static int is_branch_overlap(struct dentry *dent1, struct dentry *dent2)
+{
+	struct dentry *dent = NULL;
+
+	dent = dent1;
+	while ((dent != dent2) && (dent->d_parent != dent))
+		dent = dent->d_parent;
+
+	if (dent == dent2)
+		return 1;
+
+	dent = dent2;
+	while ((dent != dent1) && (dent->d_parent != dent))
+		dent = dent->d_parent;
+
+	return (dent == dent1);
+}
+
+/*
+ * Parse "ro" or "rw" options, but default to "rw" if no mode options was
+ * specified.  Fill the mode bits in @perms.  If encounter an unknown
+ * string, return -EINVAL.  Otherwise return 0.
+ */
+int parse_branch_mode(const char *name, int *perms)
+{
+	if (!name || !strcmp(name, "rw")) {
+		*perms = MAY_READ | MAY_WRITE;
+		return 0;
+	}
+	if (!strcmp(name, "ro")) {
+		*perms = MAY_READ;
+		return 0;
+	}
+	return -EINVAL;
+}
+
+/*
+ * parse the dirs= mount argument
+ *
+ * We don't need to lock the superblock private data's rwsem, as we get
+ * called only by unionfs_read_super - it is still a long time before anyone
+ * can even get a reference to us.
+ */
+static int parse_dirs_option(struct super_block *sb, struct unionfs_dentry_info
+			     *lower_root_info, char *options)
+{
+	struct nameidata nd;
+	char *name;
+	int err = 0;
+	int branches = 1;
+	int bindex = 0;
+	int i = 0;
+	int j = 0;
+	struct dentry *dent1;
+	struct dentry *dent2;
+
+	if (options[0] == '\0') {
+		printk(KERN_ERR "unionfs: no branches specified\n");
+		err = -EINVAL;
+		goto out;
+	}
+
+	/*
+	 * Each colon means we have a separator, this is really just a rough
+	 * guess, since strsep will handle empty fields for us.
+	 */
+	for (i = 0; options[i]; i++)
+		if (options[i] == ':')
+			branches++;
+
+	/* allocate space for underlying pointers to lower dentry */
+	UNIONFS_SB(sb)->data =
+		kcalloc(branches, sizeof(struct unionfs_data), GFP_KERNEL);
+	if (unlikely(!UNIONFS_SB(sb)->data)) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	lower_root_info->lower_paths =
+		kcalloc(branches, sizeof(struct path), GFP_KERNEL);
+	if (unlikely(!lower_root_info->lower_paths)) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	/* now parsing a string such as "b1:b2=rw:b3=ro:b4" */
+	branches = 0;
+	while ((name = strsep(&options, ":")) != NULL) {
+		int perms;
+		char *mode = strchr(name, '=');
+
+		if (!name)
+			continue;
+		if (!*name) {	/* bad use of ':' (extra colons) */
+			err = -EINVAL;
+			goto out;
+		}
+
+		branches++;
+
+		/* strip off '=' if any */
+		if (mode)
+			*mode++ = '\0';
+
+		err = parse_branch_mode(mode, &perms);
+		if (err) {
+			printk(KERN_ERR "unionfs: invalid mode \"%s\" for "
+			       "branch %d\n", mode, bindex);
+			goto out;
+		}
+		/* ensure that leftmost branch is writeable */
+		if (!bindex && !(perms & MAY_WRITE)) {
+			printk(KERN_ERR "unionfs: leftmost branch cannot be "
+			       "read-only (use \"-o ro\" to create a "
+			       "read-only union)\n");
+			err = -EINVAL;
+			goto out;
+		}
+
+		err = path_lookup(name, LOOKUP_FOLLOW, &nd);
+		if (err) {
+			printk(KERN_ERR "unionfs: error accessing "
+			       "lower directory '%s' (error %d)\n",
+			       name, err);
+			goto out;
+		}
+
+		err = check_branch(&nd);
+		if (err) {
+			printk(KERN_ERR "unionfs: lower directory "
+			       "'%s' is not a valid branch\n", name);
+			path_release(&nd);
+			goto out;
+		}
+
+		lower_root_info->lower_paths[bindex].dentry = nd.dentry;
+		lower_root_info->lower_paths[bindex].mnt = nd.mnt;
+
+		set_branchperms(sb, bindex, perms);
+		set_branch_count(sb, bindex, 0);
+		new_branch_id(sb, bindex);
+
+		if (lower_root_info->bstart < 0)
+			lower_root_info->bstart = bindex;
+		lower_root_info->bend = bindex;
+		bindex++;
+	}
+
+	if (branches == 0) {
+		printk(KERN_ERR "unionfs: no branches specified\n");
+		err = -EINVAL;
+		goto out;
+	}
+
+	BUG_ON(branches != (lower_root_info->bend + 1));
+
+	/*
+	 * Ensure that no overlaps exist in the branches.
+	 *
+	 * This test is required because the Linux kernel has no support
+	 * currently for ensuring coherency between stackable layers and
+	 * branches.  If we were to allow overlapping branches, it would be
+	 * possible, for example, to delete a file via one branch, which
+	 * would not be reflected in another branch.  Such incoherency could
+	 * lead to inconsistencies and even kernel oopses.  Rather than
+	 * implement hacks to work around some of these cache-coherency
+	 * problems, we prevent branch overlapping, for now.  A complete
+	 * solution will involve proper kernel/VFS support for cache
+	 * coherency, at which time we could safely remove this
+	 * branch-overlapping test.
+	 */
+	for (i = 0; i < branches; i++) {
+		dent1 = lower_root_info->lower_paths[i].dentry;
+		for (j = i + 1; j < branches; j++) {
+			dent2 = lower_root_info->lower_paths[j].dentry;
+			if (is_branch_overlap(dent1, dent2)) {
+				printk(KERN_ERR "unionfs: branches %d and "
+				       "%d overlap\n", i, j);
+				err = -EINVAL;
+				goto out;
+			}
+		}
+	}
+
+out:
+	if (err) {
+		for (i = 0; i < branches; i++)
+			if (lower_root_info->lower_paths[i].dentry) {
+				dput(lower_root_info->lower_paths[i].dentry);
+				/* initialize: can't use unionfs_mntput here */
+				mntput(lower_root_info->lower_paths[i].mnt);
+			}
+
+		kfree(lower_root_info->lower_paths);
+		kfree(UNIONFS_SB(sb)->data);
+
+		/*
+		 * MUST clear the pointers to prevent potential double free if
+		 * the caller dies later on
+		 */
+		lower_root_info->lower_paths = NULL;
+		UNIONFS_SB(sb)->data = NULL;
+	}
+	return err;
+}
+
+/*
+ * Parse mount options.  See the manual page for usage instructions.
+ *
+ * Returns the dentry object of the lower-level (lower) directory;
+ * We want to mount our stackable file system on top of that lower directory.
+ */
+static struct unionfs_dentry_info *unionfs_parse_options(
+					 struct super_block *sb,
+					 char *options)
+{
+	struct unionfs_dentry_info *lower_root_info;
+	char *optname;
+	int err = 0;
+	int bindex;
+	int dirsfound = 0;
+
+	/* allocate private data area */
+	err = -ENOMEM;
+	lower_root_info =
+		kzalloc(sizeof(struct unionfs_dentry_info), GFP_KERNEL);
+	if (unlikely(!lower_root_info))
+		goto out_error;
+	lower_root_info->bstart = -1;
+	lower_root_info->bend = -1;
+	lower_root_info->bopaque = -1;
+
+	while ((optname = strsep(&options, ",")) != NULL) {
+		char *optarg;
+		char *endptr;
+		int intval;
+
+		if (!optname || !*optname)
+			continue;
+
+		optarg = strchr(optname, '=');
+		if (optarg)
+			*optarg++ = '\0';
+
+		/*
+		 * All of our options take an argument now. Insert ones that
+		 * don't, above this check.
+		 */
+		if (!optarg) {
+			printk(KERN_ERR "unionfs: %s requires an argument\n",
+			       optname);
+			err = -EINVAL;
+			goto out_error;
+		}
+
+		if (!strcmp("dirs", optname)) {
+			if (++dirsfound > 1) {
+				printk(KERN_ERR
+				       "unionfs: multiple dirs specified\n");
+				err = -EINVAL;
+				goto out_error;
+			}
+			err = parse_dirs_option(sb, lower_root_info, optarg);
+			if (err)
+				goto out_error;
+			continue;
+		}
+
+		/* All of these options require an integer argument. */
+		intval = simple_strtoul(optarg, &endptr, 0);
+		if (*endptr) {
+			printk(KERN_ERR
+			       "unionfs: invalid %s option '%s'\n",
+			       optname, optarg);
+			err = -EINVAL;
+			goto out_error;
+		}
+
+		err = -EINVAL;
+		printk(KERN_ERR
+		       "unionfs: unrecognized option '%s'\n", optname);
+		goto out_error;
+	}
+	if (dirsfound != 1) {
+		printk(KERN_ERR "unionfs: dirs option required\n");
+		err = -EINVAL;
+		goto out_error;
+	}
+	goto out;
+
+out_error:
+	if (lower_root_info && lower_root_info->lower_paths) {
+		for (bindex = lower_root_info->bstart;
+		     bindex >= 0 && bindex <= lower_root_info->bend;
+		     bindex++) {
+			struct dentry *d;
+			struct vfsmount *m;
+
+			d = lower_root_info->lower_paths[bindex].dentry;
+			m = lower_root_info->lower_paths[bindex].mnt;
+
+			dput(d);
+			/* initializing: can't use unionfs_mntput here */
+			mntput(m);
+		}
+	}
+
+	kfree(lower_root_info->lower_paths);
+	kfree(lower_root_info);
+
+	kfree(UNIONFS_SB(sb)->data);
+	UNIONFS_SB(sb)->data = NULL;
+
+	lower_root_info = ERR_PTR(err);
+out:
+	return lower_root_info;
+}
+
+/*
+ * our custom d_alloc_root work-alike
+ *
+ * we can't use d_alloc_root if we want to use our own interpose function
+ * unchanged, so we simply call our own "fake" d_alloc_root
+ */
+static struct dentry *unionfs_d_alloc_root(struct super_block *sb)
+{
+	struct dentry *ret = NULL;
+
+	if (sb) {
+		static const struct qstr name = {
+			.name = "/",
+			.len = 1
+		};
+
+		ret = d_alloc(NULL, &name);
+		if (likely(ret)) {
+			ret->d_op = &unionfs_dops;
+			ret->d_sb = sb;
+			ret->d_parent = ret;
+		}
+	}
+	return ret;
+}
+
+/*
+ * There is no need to lock the unionfs_super_info's rwsem as there is no
+ * way anyone can have a reference to the superblock at this point in time.
+ */
+static int unionfs_read_super(struct super_block *sb, void *raw_data,
+			      int silent)
+{
+	int err = 0;
+	struct unionfs_dentry_info *lower_root_info = NULL;
+	int bindex, bstart, bend;
+
+	if (!raw_data) {
+		printk(KERN_ERR
+		       "unionfs: read_super: missing data argument\n");
+		err = -EINVAL;
+		goto out;
+	}
+
+	/* Allocate superblock private data */
+	sb->s_fs_info = kzalloc(sizeof(struct unionfs_sb_info), GFP_KERNEL);
+	if (unlikely(!UNIONFS_SB(sb))) {
+		printk(KERN_CRIT "unionfs: read_super: out of memory\n");
+		err = -ENOMEM;
+		goto out;
+	}
+
+	UNIONFS_SB(sb)->bend = -1;
+	atomic_set(&UNIONFS_SB(sb)->generation, 1);
+	init_rwsem(&UNIONFS_SB(sb)->rwsem);
+	UNIONFS_SB(sb)->high_branch_id = -1; /* -1 == invalid branch ID */
+
+	lower_root_info = unionfs_parse_options(sb, raw_data);
+	if (IS_ERR(lower_root_info)) {
+		printk(KERN_ERR
+		       "unionfs: read_super: error while parsing options "
+		       "(err = %ld)\n", PTR_ERR(lower_root_info));
+		err = PTR_ERR(lower_root_info);
+		lower_root_info = NULL;
+		goto out_free;
+	}
+	if (lower_root_info->bstart == -1) {
+		err = -ENOENT;
+		goto out_free;
+	}
+
+	/* set the lower superblock field of upper superblock */
+	bstart = lower_root_info->bstart;
+	BUG_ON(bstart != 0);
+	sbend(sb) = bend = lower_root_info->bend;
+	for (bindex = bstart; bindex <= bend; bindex++) {
+		struct dentry *d = lower_root_info->lower_paths[bindex].dentry;
+		unionfs_set_lower_super_idx(sb, bindex, d->d_sb);
+	}
+
+	/* max Bytes is the maximum bytes from highest priority branch */
+	sb->s_maxbytes = unionfs_lower_super_idx(sb, 0)->s_maxbytes;
+
+	/*
+	 * Our c/m/atime granularity is 1 ns because we may stack on file
+	 * systems whose granularity is as good.  This is important for our
+	 * time-based cache coherency.
+	 */
+	sb->s_time_gran = 1;
+
+	sb->s_op = &unionfs_sops;
+
+	/* See comment next to the definition of unionfs_d_alloc_root */
+	sb->s_root = unionfs_d_alloc_root(sb);
+	if (unlikely(!sb->s_root)) {
+		err = -ENOMEM;
+		goto out_dput;
+	}
+
+	/* link the upper and lower dentries */
+	sb->s_root->d_fsdata = NULL;
+	err = new_dentry_private_data(sb->s_root, UNIONFS_DMUTEX_ROOT);
+	if (unlikely(err))
+		goto out_freedpd;
+
+	/* Set the lower dentries for s_root */
+	for (bindex = bstart; bindex <= bend; bindex++) {
+		struct dentry *d;
+		struct vfsmount *m;
+
+		d = lower_root_info->lower_paths[bindex].dentry;
+		m = lower_root_info->lower_paths[bindex].mnt;
+
+		unionfs_set_lower_dentry_idx(sb->s_root, bindex, d);
+		unionfs_set_lower_mnt_idx(sb->s_root, bindex, m);
+	}
+	set_dbstart(sb->s_root, bstart);
+	set_dbend(sb->s_root, bend);
+
+	/* Set the generation number to one, since this is for the mount. */
+	atomic_set(&UNIONFS_D(sb->s_root)->generation, 1);
+
+	/*
+	 * Call interpose to create the upper level inode.  Only
+	 * INTERPOSE_LOOKUP can return a value other than 0 on err.
+	 */
+	err = PTR_ERR(unionfs_interpose(sb->s_root, sb, 0));
+	unionfs_unlock_dentry(sb->s_root);
+	if (!err)
+		goto out;
+	/* else fall through */
+
+out_freedpd:
+	if (UNIONFS_D(sb->s_root)) {
+		kfree(UNIONFS_D(sb->s_root)->lower_paths);
+		free_dentry_private_data(sb->s_root);
+	}
+	dput(sb->s_root);
+
+out_dput:
+	if (lower_root_info && !IS_ERR(lower_root_info)) {
+		for (bindex = lower_root_info->bstart;
+		     bindex <= lower_root_info->bend; bindex++) {
+			struct dentry *d;
+			struct vfsmount *m;
+
+			d = lower_root_info->lower_paths[bindex].dentry;
+			m = lower_root_info->lower_paths[bindex].mnt;
+
+			dput(d);
+			/* initializing: can't use unionfs_mntput here */
+			mntput(m);
+		}
+		kfree(lower_root_info->lower_paths);
+		kfree(lower_root_info);
+		lower_root_info = NULL;
+	}
+
+out_free:
+	kfree(UNIONFS_SB(sb)->data);
+	kfree(UNIONFS_SB(sb));
+	sb->s_fs_info = NULL;
+
+out:
+	if (lower_root_info && !IS_ERR(lower_root_info)) {
+		kfree(lower_root_info->lower_paths);
+		kfree(lower_root_info);
+	}
+	return err;
+}
+
+static int unionfs_get_sb(struct file_system_type *fs_type,
+			  int flags, const char *dev_name,
+			  void *raw_data, struct vfsmount *mnt)
+{
+	return get_sb_nodev(fs_type, flags, raw_data, unionfs_read_super, mnt);
+}
+
+static struct file_system_type unionfs_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= UNIONFS_NAME,
+	.get_sb		= unionfs_get_sb,
+	.kill_sb	= generic_shutdown_super,
+	.fs_flags	= FS_REVAL_DOT,
+};
+
+static int __init init_unionfs_fs(void)
+{
+	int err;
+
+	pr_info("Registering unionfs " UNIONFS_VERSION "\n");
+
+	err = unionfs_init_filldir_cache();
+	if (unlikely(err))
+		goto out;
+	err = unionfs_init_inode_cache();
+	if (unlikely(err))
+		goto out;
+	err = unionfs_init_dentry_cache();
+	if (unlikely(err))
+		goto out;
+	err = init_sioq();
+	if (unlikely(err))
+		goto out;
+	err = register_filesystem(&unionfs_fs_type);
+out:
+	if (unlikely(err)) {
+		stop_sioq();
+		unionfs_destroy_filldir_cache();
+		unionfs_destroy_inode_cache();
+		unionfs_destroy_dentry_cache();
+	}
+	return err;
+}
+
+static void __exit exit_unionfs_fs(void)
+{
+	stop_sioq();
+	unionfs_destroy_filldir_cache();
+	unionfs_destroy_inode_cache();
+	unionfs_destroy_dentry_cache();
+	unregister_filesystem(&unionfs_fs_type);
+	pr_info("Completed unionfs module unload\n");
+}
+
+MODULE_AUTHOR("Erez Zadok, Filesystems and Storage Lab, Stony Brook University"
+	      " (http://www.fsl.cs.sunysb.edu)");
+MODULE_DESCRIPTION("Unionfs " UNIONFS_VERSION
+		   " (http://unionfs.filesystems.org)");
+MODULE_LICENSE("GPL");
+
+module_init(init_unionfs_fs);
+module_exit(exit_unionfs_fs);
-- 
1.5.2.2

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