/* 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);
}

/* 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))
		dbstart(upper) = bindex;
	if (likely(dbend(upper) < bindex))
		dbend(upper) = bindex;
}

/*
 * return to user-space the branch indices containing the file in question
 *
 * We use fd_set and therefore we are limited to the number of the branches
 * to FD_SETSIZE, which is currently 1024 - plenty for most people
 */
static int unionfs_ioctl_queryfile(struct file *file, struct dentry *parent,
				   unsigned int cmd, unsigned long arg)
{
	int err = 0;
	fd_set branchlist;
	int bstart = 0, bend = 0, bindex = 0;
	int orig_bstart, orig_bend;
	struct dentry *dentry, *lower_dentry;
	struct vfsmount *mnt;

	dentry = file->f_path.dentry;
	orig_bstart = dbstart(dentry);
	orig_bend = dbend(dentry);
	err = unionfs_partial_lookup(dentry, parent);
	if (err)
		goto out;
	bstart = dbstart(dentry);
	bend = dbend(dentry);

	FD_ZERO(&branchlist);

	for (bindex = bstart; bindex <= bend; bindex++) {
		lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
		if (!lower_dentry)
			continue;
		if (likely(lower_dentry->d_inode))
			FD_SET(bindex, &branchlist);
		/* purge any lower objects after partial_lookup */
		if (bindex < orig_bstart || bindex > orig_bend) {
			dput(lower_dentry);
			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);
			mnt = unionfs_lower_mnt_idx(dentry, bindex);
			if (!mnt)
				continue;
			unionfs_mntput(dentry, bindex);
			unionfs_set_lower_mnt_idx(dentry, bindex, NULL);
		}
	}
	/* restore original dentry's offsets */
	dbstart(dentry) = orig_bstart;
	dbend(dentry) = orig_bend;
	ibstart(dentry->d_inode) = orig_bstart;
	ibend(dentry->d_inode) = orig_bend;

	err = copy_to_user((void __user *)arg, &branchlist, sizeof(fd_set));
	if (unlikely(err))
		err = -EFAULT;

out:
	return err < 0 ? err : bend;
}

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);
}

/*
 * 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 bstart, bend;

	BUG_ON(S_ISDIR(dentry->d_inode->i_mode));
	bstart = dbstart(dentry);
	bend = dbend(dentry);

	path_put_lowers(dentry, bstart + 1, bend, false);
	iput_lowers(dentry->d_inode, bstart + 1, bend, false);

	dbend(dentry) = bstart;
	ibend(dentry->d_inode) = ibstart(dentry->d_inode) = bstart;
}

/* unionfs_open helper function: open a directory */
static int __open_dir(struct inode *inode, struct file *file)
{
	struct dentry *lower_dentry;
	struct file *lower_file;
	int bindex, bstart, bend;
	struct vfsmount *mnt;

	bstart = fbstart(file) = dbstart(file->f_path.dentry);
	bend = fbend(file) = dbend(file->f_path.dentry);

	for (bindex = bstart; bindex <= bend; bindex++) {
		lower_dentry =
			unionfs_lower_dentry_idx(file->f_path.dentry, bindex);
		if (!lower_dentry)
			continue;

		dget(lower_dentry);
		unionfs_mntget(file->f_path.dentry, bindex);
		mnt = unionfs_lower_mnt_idx(file->f_path.dentry, bindex);
		lower_file = dentry_open(lower_dentry, mnt, file->f_flags,
					 current_cred());
		if (IS_ERR(lower_file))
			return PTR_ERR(lower_file);

		unionfs_set_lower_file_idx(file, bindex, lower_file);

		/*
		 * The branchget goes after the open, because otherwise
		 * we would miss the reference on release.
		 */
		branchget(inode->i_sb, bindex);
	}

	return 0;
}

/* open all lower files for a given file */
static int open_all_files(struct file *file)
{
	int bindex, bstart, bend, err = 0;
	struct file *lower_file;
	struct dentry *lower_dentry;
	struct dentry *dentry = file->f_path.dentry;
	struct super_block *sb = dentry->d_sb;

	bstart = dbstart(dentry);
	bend = dbend(dentry);

	for (bindex = bstart; bindex <= bend; bindex++) {
		lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
		if (!lower_dentry)
			continue;

		dget(lower_dentry);
		unionfs_mntget(dentry, bindex);
		branchget(sb, bindex);

		lower_file =
			dentry_open(lower_dentry,
				    unionfs_lower_mnt_idx(dentry, bindex),
				    file->f_flags, current_cred());
		if (IS_ERR(lower_file)) {
			branchput(sb, bindex);
			err = PTR_ERR(lower_file);
			goto out;
		} else {
			unionfs_set_lower_file_idx(file, bindex, lower_file);
		}
	}
out:
	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);
	dbstart(dentry) = old_bstart;
	dbend(dentry) = old_bend;

	dput(new_lower_dentry);
	dput(old_lower_dentry);
}

/* perform a delayed copyup of a read-write file on a read-only branch */
static int do_delayed_copyup(struct file *file, struct dentry *parent)
{
	int bindex, bstart, bend, err = 0;
	struct dentry *dentry = file->f_path.dentry;
	struct inode *parent_inode = parent->d_inode;

	bstart = fbstart(file);
	bend = fbend(file);

	BUG_ON(!S_ISREG(dentry->d_inode->i_mode));

	unionfs_check_file(file);
	for (bindex = bstart - 1; bindex >= 0; bindex--) {
		if (!d_deleted(dentry))
			err = copyup_file(parent_inode, file, bstart,
					  bindex,
					  i_size_read(dentry->d_inode));
		else
			err = copyup_deleted_file(file, dentry, parent,
						  bstart, bindex);
		/* if succeeded, set lower open-file flags and break */
		if (!err) {
			struct file *lower_file;
			lower_file = unionfs_lower_file_idx(file, bindex);
			lower_file->f_flags = file->f_flags;
			break;
		}
	}
	if (err || (bstart <= fbstart(file)))
		goto out;
	bend = fbend(file);
	for (bindex = bstart; bindex <= bend; bindex++) {
		if (unionfs_lower_file_idx(file, bindex)) {
			branchput(dentry->d_sb, bindex);
			fput(unionfs_lower_file_idx(file, bindex));
			unionfs_set_lower_file_idx(file, bindex, NULL);
		}
	}
	path_put_lowers(dentry, bstart, bend, false);
	iput_lowers(dentry->d_inode, bstart, bend, false);
	/* for reg file, we only open it "once" */
	fbend(file) = fbstart(file);
	dbend(dentry) = dbstart(dentry);
	ibend(dentry->d_inode) = ibstart(dentry->d_inode);

out:
	unionfs_check_file(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;
	dbstart(dentry) = new_bstart;
	dbend(dentry) = new_bend;

}

/* open the highest priority file for a given upper file */
static int open_highest_file(struct file *file, bool willwrite)
{
	int bindex, bstart, bend, err = 0;
	struct file *lower_file;
	struct dentry *lower_dentry;
	struct dentry *dentry = file->f_path.dentry;
	struct dentry *parent = dget_parent(dentry);
	struct inode *parent_inode = parent->d_inode;
	struct super_block *sb = dentry->d_sb;

	bstart = dbstart(dentry);
	bend = dbend(dentry);

	lower_dentry = unionfs_lower_dentry(dentry);
	if (willwrite && IS_WRITE_FLAG(file->f_flags) && is_robranch(dentry)) {
		for (bindex = bstart - 1; bindex >= 0; bindex--) {
			err = copyup_file(parent_inode, file, bstart, bindex,
					  i_size_read(dentry->d_inode));
			if (!err)
				break;
		}
		atomic_set(&UNIONFS_F(file)->generation,
			   atomic_read(&UNIONFS_I(dentry->d_inode)->
				       generation));
		goto out;
	}

	dget(lower_dentry);
	unionfs_mntget(dentry, bstart);
	lower_file = dentry_open(lower_dentry,
				 unionfs_lower_mnt_idx(dentry, bstart),
				 file->f_flags, current_cred());
	if (IS_ERR(lower_file)) {
		err = PTR_ERR(lower_file);
		goto out;
	}
	branchget(sb, bstart);
	unionfs_set_lower_file(file, lower_file);
	/* Fix up the position. */
	lower_file->f_pos = file->f_pos;

	memcpy(&lower_file->f_ra, &file->f_ra, sizeof(struct file_ra_state));
out:
	dput(parent);
	return err;
}

/*
 * scan through the lower dentry objects, and set bstart to reflect the
 * starting branch
 */
void update_bstart(struct dentry *dentry)
{
	int bindex;
	int bstart = dbstart(dentry);
	int bend = dbend(dentry);
	struct dentry *lower_dentry;

	for (bindex = bstart; bindex <= bend; bindex++) {
		lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
		if (!lower_dentry)
			continue;
		if (lower_dentry->d_inode) {
			dbstart(dentry) = bindex;
			break;
		}
		dput(lower_dentry);
		unionfs_set_lower_dentry_idx(dentry, bindex, NULL);
	}
}

int unionfs_ioctl_queryfile(struct file *file, unsigned int cmd,
			    unsigned long arg)
{
	int err = 0;
	fd_set branchlist;

	int bstart = 0, bend = 0, bindex = 0;
	struct dentry *dentry, *hidden_dentry;

	print_entry_location();

	dentry = file->f_dentry;
	lock_dentry(dentry);
	if ((err = unionfs_partial_lookup(dentry)))
		goto out;
	bstart = dbstart(dentry);
	bend = dbend(dentry);

	FD_ZERO(&branchlist);

	for (bindex = bstart; bindex <= bend; bindex++) {
		hidden_dentry = dtohd_index(dentry, bindex);
		if (!hidden_dentry)
			continue;
		if (hidden_dentry->d_inode)
			FD_SET(bindex, &branchlist);
	}

	err = copy_to_user((void *)arg, &branchlist, sizeof(fd_set));
	if (err) {
		err = -EFAULT;
		goto out;
	}

      out:
	unlock_dentry(dentry);
	err = err < 0 ? err : bend;
	print_exit_status(err);
	return (err);
}

static int unionfs_setattr(struct dentry *dentry, struct iattr *ia)
{
	int err = 0;
	struct dentry *lower_dentry;
	struct dentry *parent;
	struct inode *inode;
	struct inode *lower_inode;
	int bstart, bend, bindex;
	loff_t size;
	struct iattr lower_ia;

	/* check if user has permission to change inode */
	err = inode_change_ok(dentry->d_inode, ia);
	if (err)
		goto out_err;

	unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
	parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
	unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);

	if (unlikely(!__unionfs_d_revalidate(dentry, parent, false, 0))) {
		err = -ESTALE;
		goto out;
	}

	bstart = dbstart(dentry);
	bend = dbend(dentry);
	inode = dentry->d_inode;

	/*
	 * mode change is for clearing setuid/setgid. Allow lower filesystem
	 * to reinterpret it in its own way.
	 */
	if (ia->ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID))
		ia->ia_valid &= ~ATTR_MODE;

	lower_dentry = unionfs_lower_dentry(dentry);
	if (!lower_dentry) { /* should never happen after above revalidate */
		err = -EINVAL;
		goto out;
	}

	/*
	 * Get the lower inode directly from lower dentry, in case ibstart
	 * is -1 (which happens when the file is open but unlinked.
	 */
	lower_inode = lower_dentry->d_inode;

	/* check if user has permission to change lower inode */
	err = inode_change_ok(lower_inode, ia);
	if (err)
		goto out;

	/* copyup if the file is on a read only branch */
	if (is_robranch_super(dentry->d_sb, bstart)
	    || __is_rdonly(lower_inode)) {
		/* check if we have a branch to copy up to */
		if (bstart <= 0) {
			err = -EACCES;
			goto out;
		}

		if (ia->ia_valid & ATTR_SIZE)
			size = ia->ia_size;
		else
			size = i_size_read(inode);
		/* copyup to next available branch */
		for (bindex = bstart - 1; bindex >= 0; bindex--) {
			err = copyup_dentry(parent->d_inode,
					    dentry, bstart, bindex,
					    dentry->d_name.name,
					    dentry->d_name.len,
					    NULL, size);
			if (!err)
				break;
		}
		if (err)
			goto out;
		/* get updated lower_dentry/inode after copyup */
		lower_dentry = unionfs_lower_dentry(dentry);
		lower_inode = unionfs_lower_inode(inode);
		/*
		 * check for whiteouts in writeable branch, and remove them
		 * if necessary.
		 */
		if (lower_dentry) {
			err = check_unlink_whiteout(dentry, lower_dentry,
						    bindex);
			if (err > 0) /* ignore if whiteout found and removed */
				err = 0;
		}
	}

	/*
	 * If shrinking, first truncate upper level to cancel writing dirty
	 * pages beyond the new eof; and also if its' maxbytes is more
	 * limiting (fail with -EFBIG before making any change to the lower
	 * level).  There is no need to vmtruncate the upper level
	 * afterwards in the other cases: we fsstack_copy_inode_size from
	 * the lower level.
//.........这里部分代码省略.........

static int unionfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
	int err = 0;
	struct dentry *lower_dentry = NULL;
	struct dentry *lower_parent_dentry = NULL;
	struct dentry *parent;
	int bindex = 0, bstart;
	char *name = NULL;
	int valid;

	unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
	parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
	unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);

	valid = __unionfs_d_revalidate(dentry, parent, false, 0);
	if (unlikely(!valid)) {
		err = -ESTALE;	/* same as what real_lookup does */
		goto out;
	}

	bstart = dbstart(dentry);

	lower_dentry = unionfs_lower_dentry(dentry);

	/* check for a whiteout in new dentry branch, and delete it */
	err = check_unlink_whiteout(dentry, lower_dentry, bstart);
	if (err > 0)	       /* whiteout found and removed successfully */
		err = 0;
	if (err) {
		/* exit if the error returned was NOT -EROFS */
		if (!IS_COPYUP_ERR(err))
			goto out;
		bstart--;
	}

	/* check if copyup's needed, and mkdir */
	for (bindex = bstart; bindex >= 0; bindex--) {
		int i;
		int bend = dbend(dentry);

		if (is_robranch_super(dentry->d_sb, bindex))
			continue;

		lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
		if (!lower_dentry) {
			lower_dentry = create_parents(dir, dentry,
						      dentry->d_name.name,
						      bindex);
			if (!lower_dentry || IS_ERR(lower_dentry)) {
				printk(KERN_ERR "unionfs: lower dentry "
				       " NULL for bindex = %d\n", bindex);
				continue;
			}
		}

		lower_parent_dentry = lock_parent(lower_dentry);

		if (IS_ERR(lower_parent_dentry)) {
			err = PTR_ERR(lower_parent_dentry);
			goto out;
		}

		err = vfs_mkdir(lower_parent_dentry->d_inode, lower_dentry,
				mode);

		unlock_dir(lower_parent_dentry);

		/* did the mkdir succeed? */
		if (err)
			break;

		for (i = bindex + 1; i <= bend; i++) {
			/* XXX: use path_put_lowers? */
			if (unionfs_lower_dentry_idx(dentry, i)) {
				dput(unionfs_lower_dentry_idx(dentry, i));
				unionfs_set_lower_dentry_idx(dentry, i, NULL);
			}
		}
		dbend(dentry) = bindex;

		/*
		 * Only INTERPOSE_LOOKUP can return a value other than 0 on
		 * err.
		 */
		err = PTR_ERR(unionfs_interpose(dentry, dir->i_sb, 0));
		if (!err) {
			unionfs_copy_attr_times(dir);
			fsstack_copy_inode_size(dir,
						lower_parent_dentry->d_inode);

			/* update number of links on parent directory */
			set_nlink(dir, unionfs_get_nlinks(dir));
		}

		err = make_dir_opaque(dentry, dbstart(dentry));
		if (err) {
			printk(KERN_ERR "unionfs: mkdir: error creating "
			       ".wh.__dir_opaque: %d\n", err);
			goto out;
		}
//.........这里部分代码省略.........

/* This function replicates the directory structure upto given dentry
 * in the bindex branch.  */
struct dentry *create_parents_named(struct inode *dir, struct dentry *dentry,
				    const char *name, int bindex)
{
	int err;
	struct dentry *child_dentry;
	struct dentry *parent_dentry;
	struct dentry *hidden_parent_dentry = NULL;
	struct dentry *hidden_dentry = NULL;
	const char *childname;
	unsigned int childnamelen;

	int old_kmalloc_size;
	int kmalloc_size;
	int num_dentry;
	int count;

	int old_bstart;
	int old_bend;
	struct dentry **path = NULL;
	struct dentry **tmp_path;

	print_entry_location();

	verify_locked(dentry);

	/* There is no sense allocating any less than the minimum. */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,0)
	kmalloc_size = malloc_sizes[0].cs_size;
#else
	kmalloc_size = 32;
#endif
	num_dentry = kmalloc_size / sizeof(struct dentry *);

	if ((err = is_robranch_super(dir->i_sb, bindex))) {
		hidden_dentry = ERR_PTR(err);
		goto out;
	}

	fist_print_dentry("IN: create_parents_named", dentry);
	fist_dprint(8, "name = %s\n", name);

	old_bstart = dbstart(dentry);
	old_bend = dbend(dentry);

	path = (struct dentry **)KMALLOC(kmalloc_size, GFP_KERNEL);
	memset(path, 0, kmalloc_size);

	/* assume the negative dentry of unionfs as the parent dentry */
	parent_dentry = dentry;

	count = 0;
	/* 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;
		lock_dentry(parent_dentry);

		/* find out the hidden_parent_dentry in the given branch */
		hidden_parent_dentry = dtohd_index(parent_dentry, bindex);

		/* store the child dentry */
		path[count++] = child_dentry;
		if (count == num_dentry) {
			old_kmalloc_size = kmalloc_size;
			kmalloc_size *= 2;
			num_dentry = kmalloc_size / sizeof(struct dentry *);

			tmp_path =
			    (struct dentry **)KMALLOC(kmalloc_size, GFP_KERNEL);
			if (!tmp_path) {
				hidden_dentry = ERR_PTR(-ENOMEM);
				goto out;
			}
			memset(tmp_path, 0, kmalloc_size);
			memcpy(tmp_path, path, old_kmalloc_size);
			KFREE(path);
			path = tmp_path;
			tmp_path = NULL;
		}

	} while (!hidden_parent_dentry);
	count--;

	/* This is basically while(child_dentry != dentry).  This loop is
	 * horrible to follow and should be replaced with cleaner code. */
	while (1) {
		PASSERT(child_dentry);
		PASSERT(parent_dentry);
		PASSERT(parent_dentry->d_inode);
//.........这里部分代码省略.........

int copyup_named_dentry(struct inode *dir, struct dentry *dentry,
			int bstart, int new_bindex, char *name,
			int namelen, struct file **copyup_file, int len)
{
	struct dentry *new_hidden_dentry;
	struct dentry *old_hidden_dentry = NULL;
	struct super_block *sb;
	struct file *input_file = NULL;
	struct file *output_file = NULL;
	ssize_t read_bytes, write_bytes;
	mm_segment_t old_fs;
	int err = 0;
	char *buf;
	int old_bindex;
	int got_branch_input = -1;
	int got_branch_output = -1;
	int old_bstart;
	int old_bend;
	int size = len;
	struct dentry *new_hidden_parent_dentry;
	mm_segment_t oldfs;
	char *symbuf = NULL;
	uid_t saved_uid = current->fsuid;
	gid_t saved_gid = current->fsgid;

	print_entry_location();
	verify_locked(dentry);
	fist_print_dentry("IN: copyup_named_dentry", dentry);

	old_bindex = bstart;
	old_bstart = dbstart(dentry);
	old_bend = dbend(dentry);

	ASSERT(new_bindex >= 0);
	ASSERT(new_bindex < old_bindex);
	PASSERT(dir);
	PASSERT(dentry);

	sb = dir->i_sb;

	if ((err = is_robranch_super(sb, new_bindex)))
		goto out;

	/* Create the directory structure above this dentry. */
	new_hidden_dentry = create_parents_named(dir, dentry, name, new_bindex);
	PASSERT(new_hidden_dentry);
	if (IS_ERR(new_hidden_dentry)) {
		err = PTR_ERR(new_hidden_dentry);
		goto out;
	}

	fist_print_generic_dentry("Copyup Object", new_hidden_dentry);

	/* Now we actually create the object. */
	old_hidden_dentry = dtohd_index(dentry, old_bindex);
	PASSERT(old_hidden_dentry);
	PASSERT(old_hidden_dentry->d_inode);
	DGET(old_hidden_dentry);

	/* For symlinks, we must read the link before we lock the directory. */
	if (S_ISLNK(old_hidden_dentry->d_inode->i_mode)) {
		PASSERT(old_hidden_dentry->d_inode->i_op);
		PASSERT(old_hidden_dentry->d_inode->i_op->readlink);

		symbuf = KMALLOC(PATH_MAX, GFP_UNIONFS);
		if (!symbuf) {
			err = -ENOMEM;
			goto copyup_readlink_err;
		}

		oldfs = get_fs();
		set_fs(KERNEL_DS);
		err =
		    old_hidden_dentry->d_inode->i_op->
		    readlink(old_hidden_dentry, symbuf, PATH_MAX);
		set_fs(oldfs);
		if (err < 0)
			goto copyup_readlink_err;
		symbuf[err] = '\0';
	}

	/* Now we lock the parent, and create the object in the new branch. */
	new_hidden_parent_dentry = lock_parent(new_hidden_dentry);
	current->fsuid = new_hidden_parent_dentry->d_inode->i_uid;
	current->fsgid = new_hidden_parent_dentry->d_inode->i_gid;
	if (S_ISDIR(old_hidden_dentry->d_inode->i_mode)) {
		err = vfs_mkdir(new_hidden_parent_dentry->d_inode,
				new_hidden_dentry, S_IRWXU);
	} else if (S_ISLNK(old_hidden_dentry->d_inode->i_mode)) {
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
		err = vfs_symlink(new_hidden_parent_dentry->d_inode,
				  new_hidden_dentry, symbuf);
#else
		err = vfs_symlink(new_hidden_parent_dentry->d_inode,
				  new_hidden_dentry, symbuf, S_IRWXU);
#endif
	} else if (S_ISBLK(old_hidden_dentry->d_inode->i_mode)
		   || S_ISCHR(old_hidden_dentry->d_inode->i_mode)
		   || S_ISFIFO(old_hidden_dentry->d_inode->i_mode)
		   || S_ISSOCK(old_hidden_dentry->d_inode->i_mode)) {
//.........这里部分代码省略.........

/*
 * Main (and complex) driver function for Unionfs's lookup
 *
 * Returns: NULL (ok), ERR_PTR if an error occurred, or a non-null non-error
 * PTR if d_splice returned a different dentry.
 *
 * If lookupmode is INTERPOSE_PARTIAL/REVAL/REVAL_NEG, the passed dentry's
 * inode info must be locked.  If lookupmode is INTERPOSE_LOOKUP (i.e., a
 * newly looked-up dentry), then unionfs_lookup_backend will return a locked
 * dentry's info, which the caller must unlock.
 */
struct dentry *unionfs_lookup_full(struct dentry *dentry,
				   struct dentry *parent, int lookupmode)
{
	int err = 0;
	struct dentry *lower_dentry = NULL;
	struct vfsmount *lower_mnt;
	struct vfsmount *lower_dir_mnt;
	struct dentry *wh_lower_dentry = NULL;
	struct dentry *lower_dir_dentry = NULL;
	struct dentry *d_interposed = NULL;
	int bindex, bstart, bend, bopaque;
	int opaque, num_positive = 0;
	const char *name;
	int namelen;
	int pos_start, pos_end;

	/*
	 * We should already have a lock on this dentry in the case of a
	 * partial lookup, or a revalidation.  Otherwise it is returned from
	 * new_dentry_private_data already locked.
	 */
	verify_locked(dentry);
	verify_locked(parent);

	/* must initialize dentry operations */
	dentry->d_op = &unionfs_dops;

	/* We never partial lookup the root directory. */
	if (IS_ROOT(dentry))
		goto out;

	name = dentry->d_name.name;
	namelen = dentry->d_name.len;

	/* No dentries should get created for possible whiteout names. */
	if (!is_validname(name)) {
		err = -EPERM;
		goto out_free;
	}

	/* Now start the actual lookup procedure. */
	bstart = dbstart(parent);
	bend = dbend(parent);
	bopaque = dbopaque(parent);
	BUG_ON(bstart < 0);

	/* adjust bend to bopaque if needed */
	if ((bopaque >= 0) && (bopaque < bend))
		bend = bopaque;

	/* lookup all possible dentries */
	for (bindex = bstart; bindex <= bend; bindex++) {

		lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
		lower_mnt = unionfs_lower_mnt_idx(dentry, bindex);

		/* skip if we already have a positive lower dentry */
		if (lower_dentry) {
			if (dbstart(dentry) < 0)
				dbstart(dentry) = bindex;
			if (bindex > dbend(dentry))
				dbend(dentry) = bindex;
			if (lower_dentry->d_inode)
				num_positive++;
			continue;
		}

		lower_dir_dentry =
			unionfs_lower_dentry_idx(parent, bindex);
		/* if the lower dentry's parent does not exist, skip this */
		if (!lower_dir_dentry || !lower_dir_dentry->d_inode)
			continue;

		/* also skip it if the parent isn't a directory. */
		if (!S_ISDIR(lower_dir_dentry->d_inode->i_mode))
			continue; /* XXX: should be BUG_ON */

		/* check for whiteouts: stop lookup if found */
		wh_lower_dentry = lookup_whiteout(name, lower_dir_dentry);
		if (IS_ERR(wh_lower_dentry)) {
			err = PTR_ERR(wh_lower_dentry);
			goto out_free;
		}
		if (wh_lower_dentry->d_inode) {
			dbend(dentry) = dbopaque(dentry) = bindex;
			if (dbstart(dentry) < 0)
				dbstart(dentry) = bindex;
			dput(wh_lower_dentry);
			break;
//.........这里部分代码省略.........

void __unionfs_check_file(const struct file *file,
			  const char *fname, const char *fxn, int line)
{
	int bindex;
	int dstart, dend, fstart, fend;
	struct dentry *dentry;
	struct file *lower_file;
	struct inode *inode;
	struct super_block *sb;
	int printed_caller = 0;

	BUG_ON(!file);
	dentry = file->f_path.dentry;
	sb = dentry->d_sb;
	dstart = dbstart(dentry);
	dend = dbend(dentry);
	BUG_ON(dstart > dend);
	fstart = fbstart(file);
	fend = fbend(file);
	BUG_ON(fstart > fend);

	if (unlikely((fstart == -1 && fend != -1) ||
		     (fstart != -1 && fend == -1))) {
		PRINT_CALLER(fname, fxn, line);
		pr_debug(" CF0: file/dentry=%p:%p fstart/end=%d:%d\n",
			 file, dentry, fstart, fend);
	}
	if (unlikely(fstart != dstart)) {
		PRINT_CALLER(fname, fxn, line);
		pr_debug(" CF1: file/dentry=%p:%p fstart=%d dstart=%d\n",
			 file, dentry, fstart, dstart);
	}
	if (unlikely(fend != dend)) {
		PRINT_CALLER(fname, fxn, line);
		pr_debug(" CF2: file/dentry=%p:%p fend=%d dend=%d\n",
			 file, dentry, fend, dend);
	}
	inode = dentry->d_inode;
	if (!S_ISDIR(inode->i_mode)) {
		if (unlikely(fend != fstart)) {
			PRINT_CALLER(fname, fxn, line);
			pr_debug(" CF3: file/inode=%p:%p fstart=%d fend=%d\n",
				 file, inode, fstart, fend);
		}
		if (unlikely(dend != dstart)) {
			PRINT_CALLER(fname, fxn, line);
			pr_debug(" CF4: file/dentry=%p:%p dstart=%d dend=%d\n",
				 file, dentry, dstart, dend);
		}
	}

	/*
	 * check for NULL dentries inside the start/end range, or
	 * non-NULL dentries outside the start/end range.
	 */
	for (bindex = sbstart(sb); bindex < sbmax(sb); bindex++) {
		lower_file = unionfs_lower_file_idx(file, bindex);
		if (lower_file) {
			if (unlikely(bindex < fstart || bindex > fend)) {
				PRINT_CALLER(fname, fxn, line);
				pr_debug(" CF5: file/lower=%p:%p bindex=%d "
					 "fstart/end=%d:%d\n", file,
					 lower_file, bindex, fstart, fend);
			}
		} else {	/* lower_file == NULL */
			if (bindex >= fstart && bindex <= fend) {
				/*
				 * directories can have NULL lower inodes in
				 * b/t start/end, but NOT if at the
				 * start/end range.
				 */
				if (unlikely(!(S_ISDIR(inode->i_mode) &&
					       bindex > fstart &&
					       bindex < fend))) {
					PRINT_CALLER(fname, fxn, line);
					pr_debug(" CF6: file/lower=%p:%p "
						 "bindex=%d fstart/end=%d:%d\n",
						 file, lower_file, bindex,
						 fstart, fend);
				}
			}
		}
	}

	__unionfs_check_dentry(dentry, fname, fxn, line);
}

void __unionfs_check_dentry(const struct dentry *dentry,
			    const char *fname, const char *fxn, int line)
{
	int bindex;
	int dstart, dend, istart, iend;
	struct dentry *lower_dentry;
	struct inode *inode, *lower_inode;
	struct super_block *sb;
	struct vfsmount *lower_mnt;
	int printed_caller = 0;
	void *poison_ptr;

	BUG_ON(!dentry);
	sb = dentry->d_sb;
	inode = dentry->d_inode;
	dstart = dbstart(dentry);
	dend = dbend(dentry);
	/* don't check dentry/mnt if no lower branches */
	if (dstart < 0 && dend < 0)
		goto check_inode;
	BUG_ON(dstart > dend);

	if (unlikely((dstart == -1 && dend != -1) ||
		     (dstart != -1 && dend == -1))) {
		PRINT_CALLER(fname, fxn, line);
		pr_debug(" CD0: dentry=%p dstart/end=%d:%d\n",
			 dentry, dstart, dend);
	}
	/*
	 * check for NULL dentries inside the start/end range, or
	 * non-NULL dentries outside the start/end range.
	 */
	for (bindex = sbstart(sb); bindex < sbmax(sb); bindex++) {
		lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
		if (lower_dentry) {
			if (unlikely(bindex < dstart || bindex > dend)) {
				PRINT_CALLER(fname, fxn, line);
				pr_debug(" CD1: dentry/lower=%p:%p(%p) "
					 "bindex=%d dstart/end=%d:%d\n",
					 dentry, lower_dentry,
					 (lower_dentry ? lower_dentry->d_inode :
					  (void *) -1L),
					 bindex, dstart, dend);
			}
		} else {	/* lower_dentry == NULL */
			if (bindex < dstart || bindex > dend)
				continue;
			/*
			 * Directories can have NULL lower inodes in b/t
			 * start/end, but NOT if at the start/end range.
			 * Ignore this rule, however, if this is a NULL
			 * dentry or a deleted dentry.
			 */
			if (unlikely(!d_deleted((struct dentry *) dentry) &&
				     inode &&
				     !(inode && S_ISDIR(inode->i_mode) &&
				       bindex > dstart && bindex < dend))) {
				PRINT_CALLER(fname, fxn, line);
				pr_debug(" CD2: dentry/lower=%p:%p(%p) "
					 "bindex=%d dstart/end=%d:%d\n",
					 dentry, lower_dentry,
					 (lower_dentry ?
					  lower_dentry->d_inode :
					  (void *) -1L),
					 bindex, dstart, dend);
			}
		}
	}

	/* check for vfsmounts same as for dentries */
	for (bindex = sbstart(sb); bindex < sbmax(sb); bindex++) {
		lower_mnt = unionfs_lower_mnt_idx(dentry, bindex);
		if (lower_mnt) {
			if (unlikely(bindex < dstart || bindex > dend)) {
				PRINT_CALLER(fname, fxn, line);
				pr_debug(" CM0: dentry/lmnt=%p:%p bindex=%d "
					 "dstart/end=%d:%d\n", dentry,
					 lower_mnt, bindex, dstart, dend);
			}
		} else {	/* lower_mnt == NULL */
			if (bindex < dstart || bindex > dend)
				continue;
			/*
			 * Directories can have NULL lower inodes in b/t
			 * start/end, but NOT if at the start/end range.
			 * Ignore this rule, however, if this is a NULL
			 * dentry.
			 */
			if (unlikely(inode &&
				     !(inode && S_ISDIR(inode->i_mode) &&
				       bindex > dstart && bindex < dend))) {
				PRINT_CALLER(fname, fxn, line);
				pr_debug(" CM1: dentry/lmnt=%p:%p "
					 "bindex=%d dstart/end=%d:%d\n",
					 dentry, lower_mnt, bindex,
					 dstart, dend);
			}
		}
	}

//.........这里部分代码省略.........