Staging: pohmelfs: directory operations.

This patch implementes all supported directory operations
like directory reading, object lookup, creation, removal
and so on.

Currently object removal is not optimized at all.
Signed-off-by: NEvgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/staging/pohmelfs/path_entry.c

+/*
+ * 2007+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net>
+ * All rights reserved.
+ *
+ * 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.
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/ktime.h>
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+#include <linux/writeback.h>
+#include <linux/mount.h>
+#include <linux/mm.h>
+
+#include "netfs.h"
+
+#define UNHASHED_OBSCURE_STRING_SIZE		sizeof(" (deleted)")
+
+/*
+ * Create path from root for given inode.
+ * Path is formed as set of stuctures, containing name of the object
+ * and its inode data (mode, permissions and so on).
+ */
+int pohmelfs_construct_path_string(struct pohmelfs_inode *pi, void *data, int len)
+{
+	struct path path;
+	struct dentry *d;
+	char *ptr;
+	int err = 0, strlen, reduce = 0;
+
+	d = d_find_alias(&pi->vfs_inode);
+	if (!d) {
+		printk("%s: no alias, list_empty: %d.\n", __func__, list_empty(&pi->vfs_inode.i_dentry));
+		return -ENOENT;
+	}
+
+	read_lock(&current->fs->lock);
+	path.mnt = mntget(current->fs->root.mnt);
+	read_unlock(&current->fs->lock);
+
+	path.dentry = d;
+
+	if (!IS_ROOT(d) && d_unhashed(d))
+		reduce = 1;
+
+	ptr = d_path(&path, data, len);
+	if (IS_ERR(ptr)) {
+		err = PTR_ERR(ptr);
+		goto out;
+	}
+
+	if (reduce && len >= UNHASHED_OBSCURE_STRING_SIZE) {
+		char *end = data + len - UNHASHED_OBSCURE_STRING_SIZE;
+		*end = '\0';
+	}
+
+	strlen = len - (ptr - (char *)data);
+	memmove(data, ptr, strlen);
+	ptr = data;
+
+	err = strlen;
+
+	dprintk("%s: dname: '%s', len: %u, maxlen: %u, name: '%s', strlen: %d.\n",
+			__func__, d->d_name.name, d->d_name.len, len, ptr, strlen);
+
+out:
+	dput(d);
+	mntput(path.mnt);
+
+	return err;
+}
+
+int pohmelfs_path_length(struct pohmelfs_inode *pi)
+{
+	struct dentry *d, *root, *first;
+	int len = 1; /* Root slash */
+
+	first = d = d_find_alias(&pi->vfs_inode);
+	if (!d) {
+		dprintk("%s: ino: %llu, mode: %o.\n", __func__, pi->ino, pi->vfs_inode.i_mode);
+		return -ENOENT;
+	}
+
+	read_lock(&current->fs->lock);
+	root = dget(current->fs->root.dentry);
+	read_unlock(&current->fs->lock);
+
+	spin_lock(&dcache_lock);
+
+	if (!IS_ROOT(d) && d_unhashed(d))
+		len += UNHASHED_OBSCURE_STRING_SIZE; /* Obscure " (deleted)" string */
+
+	while (d && d != root && !IS_ROOT(d)) {
+		len += d->d_name.len + 1; /* Plus slash */
+		d = d->d_parent;
+	}
+	spin_unlock(&dcache_lock);
+
+	dput(root);
+	dput(first);
+
+	return len + 1; /* Including zero-byte */
+}