[PATCH 14/42] Unionfs: lower-level copyup routines

[Erez Zadok]

Signed-off-by: Erez Zadok <ezk@xxxxxxxxxxxxx>
---
 fs/unionfs/copyup.c |  897 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 897 insertions(+), 0 deletions(-)
 create mode 100644 fs/unionfs/copyup.c

diff --git a/fs/unionfs/copyup.c b/fs/unionfs/copyup.c
new file mode 100644
index 0000000..3fe4865
--- /dev/null
+++ b/fs/unionfs/copyup.c
@@ -0,0 +1,897 @@
+/*
+ * 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"
+
+/*
+ * For detailed explanation of copyup see:
+ * Documentation/filesystems/unionfs/concepts.txt
+ */
+
+#ifdef CONFIG_UNION_FS_XATTR
+/* copyup all extended attrs for a given dentry */
+static int copyup_xattrs(struct dentry *old_lower_dentry,
+			 struct dentry *new_lower_dentry)
+{
+	int err = 0;
+	ssize_t list_size = -1;
+	char *name_list = NULL;
+	char *attr_value = NULL;
+	char *name_list_buf = NULL;
+
+	/* query the actual size of the xattr list */
+	list_size = vfs_listxattr(old_lower_dentry, NULL, 0);
+	if (list_size <= 0) {
+		err = list_size;
+		goto out;
+	}
+
+	/* allocate space for the actual list */
+	name_list = unionfs_xattr_alloc(list_size + 1, XATTR_LIST_MAX);
+	if (unlikely(!name_list || IS_ERR(name_list))) {
+		err = PTR_ERR(name_list);
+		goto out;
+	}
+
+	name_list_buf = name_list; /* save for kfree at end */
+
+	/* now get the actual xattr list of the source file */
+	list_size = vfs_listxattr(old_lower_dentry, name_list, list_size);
+	if (list_size <= 0) {
+		err = list_size;
+		goto out;
+	}
+
+	/* allocate space to hold each xattr's value */
+	attr_value = unionfs_xattr_alloc(XATTR_SIZE_MAX, XATTR_SIZE_MAX);
+	if (unlikely(!attr_value || IS_ERR(attr_value))) {
+		err = PTR_ERR(name_list);
+		goto out;
+	}
+
+	/* in a loop, get and set each xattr from src to dst file */
+	while (*name_list) {
+		ssize_t size;
+
+		/* Lock here since vfs_getxattr doesn't lock for us */
+		mutex_lock(&old_lower_dentry->d_inode->i_mutex);
+		size = vfs_getxattr(old_lower_dentry, name_list,
+				    attr_value, XATTR_SIZE_MAX);
+		mutex_unlock(&old_lower_dentry->d_inode->i_mutex);
+		if (size < 0) {
+			err = size;
+			goto out;
+		}
+		if (size > XATTR_SIZE_MAX) {
+			err = -E2BIG;
+			goto out;
+		}
+		/* Don't lock here since vfs_setxattr does it for us. */
+		err = vfs_setxattr(new_lower_dentry, name_list, attr_value,
+				   size, 0);
+		/*
+		 * Selinux depends on "security.*" xattrs, so to maintain
+		 * the security of copied-up files, if Selinux is active,
+		 * then we must copy these xattrs as well.  So we need to
+		 * temporarily get FOWNER privileges.
+		 * XXX: move entire copyup code to SIOQ.
+		 */
+		if (err == -EPERM && !capable(CAP_FOWNER)) {
+			cap_raise(current->cap_effective, CAP_FOWNER);
+			err = vfs_setxattr(new_lower_dentry, name_list,
+					   attr_value, size, 0);
+			cap_lower(current->cap_effective, CAP_FOWNER);
+		}
+		if (err < 0)
+			goto out;
+		name_list += strlen(name_list) + 1;
+	}
+out:
+	unionfs_xattr_kfree(name_list_buf);
+	unionfs_xattr_kfree(attr_value);
+	/* Ignore if xattr isn't supported */
+	if (err == -ENOTSUPP || err == -EOPNOTSUPP)
+		err = 0;
+	return err;
+}
+#endif /* CONFIG_UNION_FS_XATTR */
+
+/*
+ * Determine the mode based on the copyup flags, and the existing dentry.
+ *
+ * Handle file systems which may not support certain options.  For example
+ * jffs2 doesn't allow one to chmod a symlink.  So we ignore such harmless
+ * errors, rather than propagating them up, which results in copyup errors
+ * and errors returned back to users.
+ */
+static int copyup_permissions(struct super_block *sb,
+			      struct dentry *old_lower_dentry,
+			      struct dentry *new_lower_dentry)
+{
+	struct inode *i = old_lower_dentry->d_inode;
+	struct iattr newattrs;
+	int err;
+
+	newattrs.ia_atime = i->i_atime;
+	newattrs.ia_mtime = i->i_mtime;
+	newattrs.ia_ctime = i->i_ctime;
+	newattrs.ia_gid = i->i_gid;
+	newattrs.ia_uid = i->i_uid;
+	newattrs.ia_valid = ATTR_CTIME | ATTR_ATIME | ATTR_MTIME |
+		ATTR_ATIME_SET | ATTR_MTIME_SET | ATTR_FORCE |
+		ATTR_GID | ATTR_UID;
+	err = notify_change(new_lower_dentry, &newattrs);
+	if (err)
+		goto out;
+
+	/* now try to change the mode and ignore EOPNOTSUPP on symlinks */
+	newattrs.ia_mode = i->i_mode;
+	newattrs.ia_valid = ATTR_MODE | ATTR_FORCE;
+	err = notify_change(new_lower_dentry, &newattrs);
+	if (err == -EOPNOTSUPP &&
+	    S_ISLNK(new_lower_dentry->d_inode->i_mode)) {
+		printk(KERN_WARNING
+		       "unionfs: changing \"%s\" symlink mode unsupported\n",
+		       new_lower_dentry->d_name.name);
+		err = 0;
+	}
+
+out:
+	return err;
+}
+
+/*
+ * create the new device/file/directory - use copyup_permission to copyup
+ * times, and mode
+ *
+ * if the object being copied up is a regular file, the file is only created,
+ * the contents have to be copied up separately
+ */
+static int __copyup_ndentry(struct dentry *old_lower_dentry,
+			    struct dentry *new_lower_dentry,
+			    struct dentry *new_lower_parent_dentry,
+			    char *symbuf)
+{
+	int err = 0;
+	umode_t old_mode = old_lower_dentry->d_inode->i_mode;
+	struct sioq_args args;
+
+	if (S_ISDIR(old_mode)) {
+		args.mkdir.parent = new_lower_parent_dentry->d_inode;
+		args.mkdir.dentry = new_lower_dentry;
+		args.mkdir.mode = old_mode;
+
+		run_sioq(__unionfs_mkdir, &args);
+		err = args.err;
+	} else if (S_ISLNK(old_mode)) {
+		args.symlink.parent = new_lower_parent_dentry->d_inode;
+		args.symlink.dentry = new_lower_dentry;
+		args.symlink.symbuf = symbuf;
+		args.symlink.mode = old_mode;
+
+		run_sioq(__unionfs_symlink, &args);
+		err = args.err;
+	} else if (S_ISBLK(old_mode) || S_ISCHR(old_mode) ||
+		   S_ISFIFO(old_mode) || S_ISSOCK(old_mode)) {
+		args.mknod.parent = new_lower_parent_dentry->d_inode;
+		args.mknod.dentry = new_lower_dentry;
+		args.mknod.mode = old_mode;
+		args.mknod.dev = old_lower_dentry->d_inode->i_rdev;
+
+		run_sioq(__unionfs_mknod, &args);
+		err = args.err;
+	} else if (S_ISREG(old_mode)) {
+		struct nameidata nd;
+		err = init_lower_nd(&nd, LOOKUP_CREATE);
+		if (unlikely(err < 0))
+			goto out;
+		args.create.nd = &nd;
+		args.create.parent = new_lower_parent_dentry->d_inode;
+		args.create.dentry = new_lower_dentry;
+		args.create.mode = old_mode;
+
+		run_sioq(__unionfs_create, &args);
+		err = args.err;
+		release_lower_nd(&nd, err);
+	} else {
+		printk(KERN_CRIT "unionfs: unknown inode type %d\n",
+		       old_mode);
+		BUG();
+	}
+
+out:
+	return err;
+}
+
+static int __copyup_reg_data(struct dentry *dentry,
+			     struct dentry *new_lower_dentry, int new_bindex,
+			     struct dentry *old_lower_dentry, int old_bindex,
+			     struct file **copyup_file, loff_t len)
+{
+	struct super_block *sb = dentry->d_sb;
+	struct file *input_file;
+	struct file *output_file;
+	struct vfsmount *output_mnt;
+	mm_segment_t old_fs;
+	char *buf = NULL;
+	ssize_t read_bytes, write_bytes;
+	loff_t size;
+	int err = 0;
+
+	/* open old file */
+	unionfs_mntget(dentry, old_bindex);
+	branchget(sb, old_bindex);
+	/* dentry_open calls dput and mntput if it returns an error */
+	input_file = dentry_open(old_lower_dentry,
+				 unionfs_lower_mnt_idx(dentry, old_bindex),
+				 O_RDONLY | O_LARGEFILE);
+	if (IS_ERR(input_file)) {
+		dput(old_lower_dentry);
+		err = PTR_ERR(input_file);
+		goto out;
+	}
+	if (unlikely(!input_file->f_op || !input_file->f_op->read)) {
+		err = -EINVAL;
+		goto out_close_in;
+	}
+
+	/* open new file */
+	dget(new_lower_dentry);
+	output_mnt = unionfs_mntget(sb->s_root, new_bindex);
+	branchget(sb, new_bindex);
+	output_file = dentry_open(new_lower_dentry, output_mnt,
+				  O_RDWR | O_LARGEFILE);
+	if (IS_ERR(output_file)) {
+		err = PTR_ERR(output_file);
+		goto out_close_in2;
+	}
+	if (unlikely(!output_file->f_op || !output_file->f_op->write)) {
+		err = -EINVAL;
+		goto out_close_out;
+	}
+
+	/* allocating a buffer */
+	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (unlikely(!buf)) {
+		err = -ENOMEM;
+		goto out_close_out;
+	}
+
+	input_file->f_pos = 0;
+	output_file->f_pos = 0;
+
+	old_fs = get_fs();
+	set_fs(KERNEL_DS);
+
+	size = len;
+	err = 0;
+	do {
+		if (len >= PAGE_SIZE)
+			size = PAGE_SIZE;
+		else if ((len < PAGE_SIZE) && (len > 0))
+			size = len;
+
+		len -= PAGE_SIZE;
+
+		read_bytes =
+			input_file->f_op->read(input_file,
+					       (char __user *)buf, size,
+					       &input_file->f_pos);
+		if (read_bytes <= 0) {
+			err = read_bytes;
+			break;
+		}
+
+		write_bytes =
+			output_file->f_op->write(output_file,
+						 (char __user *)buf,
+						 read_bytes,
+						 &output_file->f_pos);
+		if ((write_bytes < 0) || (write_bytes < read_bytes)) {
+			err = write_bytes;
+			break;
+		}
+	} while ((read_bytes > 0) && (len > 0));
+
+	set_fs(old_fs);
+
+	kfree(buf);
+
+	if (!err)
+		err = output_file->f_op->fsync(output_file,
+					       new_lower_dentry, 0);
+
+	if (err)
+		goto out_close_out;
+
+	if (copyup_file) {
+		*copyup_file = output_file;
+		goto out_close_in;
+	}
+
+out_close_out:
+	fput(output_file);
+
+out_close_in2:
+	branchput(sb, new_bindex);
+
+out_close_in:
+	fput(input_file);
+
+out:
+	branchput(sb, old_bindex);
+
+	return err;
+}
+
+/*
+ * dput the lower references for old and new dentry & clear a lower dentry
+ * pointer
+ */
+static void __clear(struct dentry *dentry, struct dentry *old_lower_dentry,
+		    int old_bstart, int old_bend,
+		    struct dentry *new_lower_dentry, int new_bindex)
+{
+	/* get rid of the lower dentry and all its traces */
+	unionfs_set_lower_dentry_idx(dentry, new_bindex, NULL);
+	set_dbstart(dentry, old_bstart);
+	set_dbend(dentry, old_bend);
+
+	dput(new_lower_dentry);
+	dput(old_lower_dentry);
+}
+
+/*
+ * Copy up a dentry to a file of specified name.
+ *
+ * @dir: used to pull the ->i_sb to access other branches
+ * @dentry: the non-negative dentry whose lower_inode we should copy
+ * @bstart: the branch of the lower_inode to copy from
+ * @new_bindex: the branch to create the new file in
+ * @name: the name of the file to create
+ * @namelen: length of @name
+ * @copyup_file: the "struct file" to return (optional)
+ * @len: how many bytes to copy-up?
+ */
+int copyup_dentry(struct inode *dir, struct dentry *dentry, int bstart,
+		  int new_bindex, const char *name, int namelen,
+		  struct file **copyup_file, loff_t len)
+{
+	struct dentry *new_lower_dentry;
+	struct dentry *old_lower_dentry = NULL;
+	struct super_block *sb;
+	int err = 0;
+	int old_bindex;
+	int old_bstart;
+	int old_bend;
+	struct dentry *new_lower_parent_dentry = NULL;
+	mm_segment_t oldfs;
+	char *symbuf = NULL;
+
+	verify_locked(dentry);
+
+	old_bindex = bstart;
+	old_bstart = dbstart(dentry);
+	old_bend = dbend(dentry);
+
+	BUG_ON(new_bindex < 0);
+	BUG_ON(new_bindex >= old_bindex);
+
+	sb = dir->i_sb;
+
+	err = is_robranch_super(sb, new_bindex);
+	if (err)
+		goto out;
+
+	/* Create the directory structure above this dentry. */
+	new_lower_dentry = create_parents(dir, dentry, name, new_bindex);
+	if (IS_ERR(new_lower_dentry)) {
+		err = PTR_ERR(new_lower_dentry);
+		goto out;
+	}
+
+	old_lower_dentry = unionfs_lower_dentry_idx(dentry, old_bindex);
+	/* we conditionally dput this old_lower_dentry at end of function */
+	dget(old_lower_dentry);
+
+	/* For symlinks, we must read the link before we lock the directory. */
+	if (S_ISLNK(old_lower_dentry->d_inode->i_mode)) {
+
+		symbuf = kmalloc(PATH_MAX, GFP_KERNEL);
+		if (unlikely(!symbuf)) {
+			__clear(dentry, old_lower_dentry,
+				old_bstart, old_bend,
+				new_lower_dentry, new_bindex);
+			err = -ENOMEM;
+			goto out_free;
+		}
+
+		oldfs = get_fs();
+		set_fs(KERNEL_DS);
+		err = old_lower_dentry->d_inode->i_op->readlink(
+			old_lower_dentry,
+			(char __user *)symbuf,
+			PATH_MAX);
+		set_fs(oldfs);
+		if (err < 0) {
+			__clear(dentry, old_lower_dentry,
+				old_bstart, old_bend,
+				new_lower_dentry, new_bindex);
+			goto out_free;
+		}
+		symbuf[err] = '\0';
+	}
+
+	/* Now we lock the parent, and create the object in the new branch. */
+	new_lower_parent_dentry = lock_parent(new_lower_dentry);
+
+	/* create the new inode */
+	err = __copyup_ndentry(old_lower_dentry, new_lower_dentry,
+			       new_lower_parent_dentry, symbuf);
+
+	if (err) {
+		__clear(dentry, old_lower_dentry,
+			old_bstart, old_bend,
+			new_lower_dentry, new_bindex);
+		goto out_unlock;
+	}
+
+	/* We actually copyup the file here. */
+	if (S_ISREG(old_lower_dentry->d_inode->i_mode))
+		err = __copyup_reg_data(dentry, new_lower_dentry, new_bindex,
+					old_lower_dentry, old_bindex,
+					copyup_file, len);
+	if (err)
+		goto out_unlink;
+
+	/* Set permissions. */
+	err = copyup_permissions(sb, old_lower_dentry, new_lower_dentry);
+	if (err)
+		goto out_unlink;
+
+#ifdef CONFIG_UNION_FS_XATTR
+	/* Selinux uses extended attributes for permissions. */
+	err = copyup_xattrs(old_lower_dentry, new_lower_dentry);
+	if (err)
+		goto out_unlink;
+#endif /* CONFIG_UNION_FS_XATTR */
+
+	/* do not allow files getting deleted to be re-interposed */
+	if (!d_deleted(dentry))
+		unionfs_reinterpose(dentry);
+
+	goto out_unlock;
+
+out_unlink:
+	/*
+	 * copyup failed, because we possibly ran out of space or
+	 * quota, or something else happened so let's unlink; we don't
+	 * really care about the return value of vfs_unlink
+	 */
+	vfs_unlink(new_lower_parent_dentry->d_inode, new_lower_dentry);
+
+	if (copyup_file) {
+		/* need to close the file */
+
+		fput(*copyup_file);
+		branchput(sb, new_bindex);
+	}
+
+	/*
+	 * TODO: should we reset the error to something like -EIO?
+	 *
+	 * If we don't reset, the user may get some nonsensical errors, but
+	 * on the other hand, if we reset to EIO, we guarantee that the user
+	 * will get a "confusing" error message.
+	 */
+
+out_unlock:
+	unlock_dir(new_lower_parent_dentry);
+
+out_free:
+	/*
+	 * If old_lower_dentry was a directory, we need to dput it.  If it
+	 * was a file, then it was already dput indirectly by other
+	 * functions we call above which operate on regular files.
+	 */
+	if (old_lower_dentry && old_lower_dentry->d_inode &&
+	    (S_ISDIR(old_lower_dentry->d_inode->i_mode) ||
+	     S_ISLNK(old_lower_dentry->d_inode->i_mode)))
+		dput(old_lower_dentry);
+	kfree(symbuf);
+
+	if (err)
+		goto out;
+	if (!S_ISDIR(dentry->d_inode->i_mode)) {
+		unionfs_postcopyup_release(dentry);
+		if (!unionfs_lower_inode(dentry->d_inode)) {
+			/*
+			 * If we got here, then we copied up to an
+			 * unlinked-open file, whose name is .unionfsXXXXX.
+			 */
+			struct inode *inode = new_lower_dentry->d_inode;
+			atomic_inc(&inode->i_count);
+			unionfs_set_lower_inode_idx(dentry->d_inode,
+						    ibstart(dentry->d_inode),
+						    inode);
+		}
+	}
+	unionfs_postcopyup_setmnt(dentry);
+	/* sync inode times from copied-up inode to our inode */
+	unionfs_copy_attr_times(dentry->d_inode);
+	unionfs_check_inode(dir);
+	unionfs_check_dentry(dentry);
+out:
+	return err;
+}
+
+/*
+ * This function creates a copy of a file represented by 'file' which
+ * currently resides in branch 'bstart' to branch 'new_bindex.'  The copy
+ * will be named "name".
+ */
+int copyup_named_file(struct inode *dir, struct file *file, char *name,
+		      int bstart, int new_bindex, loff_t len)
+{
+	int err = 0;
+	struct file *output_file = NULL;
+
+	err = copyup_dentry(dir, file->f_path.dentry, bstart, new_bindex,
+			    name, strlen(name), &output_file, len);
+	if (!err) {
+		fbstart(file) = new_bindex;
+		unionfs_set_lower_file_idx(file, new_bindex, output_file);
+	}
+
+	return err;
+}
+
+/*
+ * This function creates a copy of a file represented by 'file' which
+ * currently resides in branch 'bstart' to branch 'new_bindex'.
+ */
+int copyup_file(struct inode *dir, struct file *file, int bstart,
+		int new_bindex, loff_t len)
+{
+	int err = 0;
+	struct file *output_file = NULL;
+	struct dentry *dentry = file->f_path.dentry;
+
+	err = copyup_dentry(dir, dentry, bstart, new_bindex,
+			    dentry->d_name.name, dentry->d_name.len,
+			    &output_file, len);
+	if (!err) {
+		fbstart(file) = new_bindex;
+		unionfs_set_lower_file_idx(file, new_bindex, output_file);
+	}
+
+	return err;
+}
+
+/* purge a dentry's lower-branch states (dput/mntput, etc.) */
+static void __cleanup_dentry(struct dentry *dentry, int bindex,
+			     int old_bstart, int old_bend)
+{
+	int loop_start;
+	int loop_end;
+	int new_bstart = -1;
+	int new_bend = -1;
+	int i;
+
+	loop_start = min(old_bstart, bindex);
+	loop_end = max(old_bend, bindex);
+
+	/*
+	 * This loop sets the bstart and bend for the new dentry by
+	 * traversing from left to right.  It also dputs all negative
+	 * dentries except bindex
+	 */
+	for (i = loop_start; i <= loop_end; i++) {
+		if (!unionfs_lower_dentry_idx(dentry, i))
+			continue;
+
+		if (i == bindex) {
+			new_bend = i;
+			if (new_bstart < 0)
+				new_bstart = i;
+			continue;
+		}
+
+		if (!unionfs_lower_dentry_idx(dentry, i)->d_inode) {
+			dput(unionfs_lower_dentry_idx(dentry, i));
+			unionfs_set_lower_dentry_idx(dentry, i, NULL);
+
+			unionfs_mntput(dentry, i);
+			unionfs_set_lower_mnt_idx(dentry, i, NULL);
+		} else {
+			if (new_bstart < 0)
+				new_bstart = i;
+			new_bend = i;
+		}
+	}
+
+	if (new_bstart < 0)
+		new_bstart = bindex;
+	if (new_bend < 0)
+		new_bend = bindex;
+	set_dbstart(dentry, new_bstart);
+	set_dbend(dentry, new_bend);
+
+}
+
+/* set lower inode ptr and update bstart & bend if necessary */
+static void __set_inode(struct dentry *upper, struct dentry *lower,
+			int bindex)
+{
+	unionfs_set_lower_inode_idx(upper->d_inode, bindex,
+				    igrab(lower->d_inode));
+	if (likely(ibstart(upper->d_inode) > bindex))
+		ibstart(upper->d_inode) = bindex;
+	if (likely(ibend(upper->d_inode) < bindex))
+		ibend(upper->d_inode) = bindex;
+
+}
+
+/* set lower dentry ptr and update bstart & bend if necessary */
+static void __set_dentry(struct dentry *upper, struct dentry *lower,
+			 int bindex)
+{
+	unionfs_set_lower_dentry_idx(upper, bindex, lower);
+	if (likely(dbstart(upper) > bindex))
+		set_dbstart(upper, bindex);
+	if (likely(dbend(upper) < bindex))
+		set_dbend(upper, bindex);
+}
+
+/*
+ * This function replicates the directory structure up-to given dentry
+ * in the bindex branch.
+ */
+struct dentry *create_parents(struct inode *dir, struct dentry *dentry,
+			      const char *name, int bindex)
+{
+	int err;
+	struct dentry *child_dentry;
+	struct dentry *parent_dentry;
+	struct dentry *lower_parent_dentry = NULL;
+	struct dentry *lower_dentry = NULL;
+	const char *childname;
+	unsigned int childnamelen;
+	int nr_dentry;
+	int count = 0;
+	int old_bstart;
+	int old_bend;
+	struct dentry **path = NULL;
+	struct super_block *sb;
+
+	verify_locked(dentry);
+
+	err = is_robranch_super(dir->i_sb, bindex);
+	if (err) {
+		lower_dentry = ERR_PTR(err);
+		goto out;
+	}
+
+	old_bstart = dbstart(dentry);
+	old_bend = dbend(dentry);
+
+	lower_dentry = ERR_PTR(-ENOMEM);
+
+	/* There is no sense allocating any less than the minimum. */
+	nr_dentry = 1;
+	path = kmalloc(nr_dentry * sizeof(struct dentry *), GFP_KERNEL);
+	if (unlikely(!path))
+		goto out;
+
+	/* assume the negative dentry of unionfs as the parent dentry */
+	parent_dentry = dentry;
+
+	/*
+	 * This loop finds the first parent that exists in the given branch.
+	 * We start building the directory structure from there.  At the end
+	 * of the loop, the following should hold:
+	 *  - child_dentry is the first nonexistent child
+	 *  - parent_dentry is the first existent parent
+	 *  - path[0] is the = deepest child
+	 *  - path[count] is the first child to create
+	 */
+	do {
+		child_dentry = parent_dentry;
+
+		/* find the parent directory dentry in unionfs */
+		parent_dentry = child_dentry->d_parent;
+		unionfs_lock_dentry(parent_dentry);
+
+		/* find out the lower_parent_dentry in the given branch */
+		lower_parent_dentry =
+			unionfs_lower_dentry_idx(parent_dentry, bindex);
+
+		/* grow path table */
+		if (count == nr_dentry) {
+			void *p;
+
+			nr_dentry *= 2;
+			p = krealloc(path, nr_dentry * sizeof(struct dentry *),
+				     GFP_KERNEL);
+			if (unlikely(!p)) {
+				lower_dentry = ERR_PTR(-ENOMEM);
+				goto out;
+			}
+			path = p;
+		}
+
+		/* store the child dentry */
+		path[count++] = child_dentry;
+	} while (!lower_parent_dentry);
+	count--;
+
+	sb = dentry->d_sb;
+
+	/*
+	 * This code goes between the begin/end labels and basically
+	 * emulates a while(child_dentry != dentry), only cleaner and
+	 * shorter than what would be a much longer while loop.
+	 */
+begin:
+	/* get lower parent dir in the current branch */
+	lower_parent_dentry = unionfs_lower_dentry_idx(parent_dentry, bindex);
+	unionfs_unlock_dentry(parent_dentry);
+
+	/* init the values to lookup */
+	childname = child_dentry->d_name.name;
+	childnamelen = child_dentry->d_name.len;
+
+	if (child_dentry != dentry) {
+		/* lookup child in the underlying file system */
+		lower_dentry = lookup_one_len(childname, lower_parent_dentry,
+					      childnamelen);
+		if (IS_ERR(lower_dentry))
+			goto out;
+	} else {
+		/*
+		 * Is the name a whiteout of the child name ?  lookup the
+		 * whiteout child in the underlying file system
+		 */
+		lower_dentry = lookup_one_len(name, lower_parent_dentry,
+					      strlen(name));
+		if (IS_ERR(lower_dentry))
+			goto out;
+
+		/* Replace the current dentry (if any) with the new one */
+		dput(unionfs_lower_dentry_idx(dentry, bindex));
+		unionfs_set_lower_dentry_idx(dentry, bindex,
+					     lower_dentry);
+
+		__cleanup_dentry(dentry, bindex, old_bstart, old_bend);
+		goto out;
+	}
+
+	if (lower_dentry->d_inode) {
+		/*
+		 * since this already exists we dput to avoid
+		 * multiple references on the same dentry
+		 */
+		dput(lower_dentry);
+	} else {
+		struct sioq_args args;
+
+		/* it's a negative dentry, create a new dir */
+		lower_parent_dentry = lock_parent(lower_dentry);
+
+		args.mkdir.parent = lower_parent_dentry->d_inode;
+		args.mkdir.dentry = lower_dentry;
+		args.mkdir.mode = child_dentry->d_inode->i_mode;
+
+		run_sioq(__unionfs_mkdir, &args);
+		err = args.err;
+
+		if (!err)
+			err = copyup_permissions(dir->i_sb, child_dentry,
+						 lower_dentry);
+		unlock_dir(lower_parent_dentry);
+		if (err) {
+			struct inode *inode = lower_dentry->d_inode;
+			/*
+			 * If we get here, it means that we created a new
+			 * dentry+inode, but copying permissions failed.
+			 * Therefore, we should delete this inode and dput
+			 * the dentry so as not to leave cruft behind.
+			 */
+			if (lower_dentry->d_op && lower_dentry->d_op->d_iput)
+				lower_dentry->d_op->d_iput(lower_dentry,
+							   inode);
+			else
+				iput(inode);
+			lower_dentry->d_inode = NULL;
+			dput(lower_dentry);
+			lower_dentry = ERR_PTR(err);
+			goto out;
+		}
+
+	}
+
+	__set_inode(child_dentry, lower_dentry, bindex);
+	__set_dentry(child_dentry, lower_dentry, bindex);
+	/*
+	 * update times of this dentry, but also the parent, because if
+	 * we changed, the parent may have changed too.
+	 */
+	unionfs_copy_attr_times(parent_dentry->d_inode);
+	unionfs_copy_attr_times(child_dentry->d_inode);
+
+	parent_dentry = child_dentry;
+	child_dentry = path[--count];
+	goto begin;
+out:
+	/* cleanup any leftover locks from the do/while loop above */
+	if (IS_ERR(lower_dentry))
+		while (count)
+			unionfs_unlock_dentry(path[count--]);
+	kfree(path);
+	return lower_dentry;
+}
+
+/*
+ * Post-copyup helper to ensure we have valid mnts: set lower mnt of
+ * dentry+parents to the first parent node that has an mnt.
+ */
+void unionfs_postcopyup_setmnt(struct dentry *dentry)
+{
+	struct dentry *parent, *hasone;
+	int bindex = dbstart(dentry);
+
+	if (unionfs_lower_mnt_idx(dentry, bindex))
+		return;
+	hasone = dentry->d_parent;
+	/* this loop should stop at root dentry */
+	while (!unionfs_lower_mnt_idx(hasone, bindex))
+		hasone = hasone->d_parent;
+	parent = dentry;
+	while (!unionfs_lower_mnt_idx(parent, bindex)) {
+		unionfs_set_lower_mnt_idx(parent, bindex,
+					  unionfs_mntget(hasone, bindex));
+		parent = parent->d_parent;
+	}
+}
+
+/*
+ * Post-copyup helper to release all non-directory source objects of a
+ * copied-up file.  Regular files should have only one lower object.
+ */
+void unionfs_postcopyup_release(struct dentry *dentry)
+{
+	int bindex;
+
+	BUG_ON(S_ISDIR(dentry->d_inode->i_mode));
+	for (bindex = dbstart(dentry)+1; bindex <= dbend(dentry); bindex++) {
+		if (unionfs_lower_mnt_idx(dentry, bindex)) {
+			unionfs_mntput(dentry, bindex);
+			unionfs_set_lower_mnt_idx(dentry, bindex, NULL);
+		}
+		if (unionfs_lower_dentry_idx(dentry, bindex)) {
+			dput(unionfs_lower_dentry_idx(dentry, bindex));
+			unionfs_set_lower_dentry_idx(dentry, bindex, NULL);
+			iput(unionfs_lower_inode_idx(dentry->d_inode, bindex));
+			unionfs_set_lower_inode_idx(dentry->d_inode, bindex,
+						    NULL);
+		}
+	}
+	bindex = dbstart(dentry);
+	set_dbend(dentry, bindex);
+	ibend(dentry->d_inode) = ibstart(dentry->d_inode) = bindex;
+}
-- 
1.5.2.2

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