init android origin source code

1 files changed, 3501 insertions, 0 deletions

diff --git a/ANDROID_3.4.5/fs/namei.c b/ANDROID_3.4.5/fs/namei.c
new file mode 100644
index 00000000..c4279191
--- /dev/null
+++ b/ANDROID_3.4.5/fs/namei.c
@@ -0,0 +1,3501 @@
+/*
+ *  linux/fs/namei.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ */
+
+/*
+ * Some corrections by tytso.
+ */
+
+/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
+ * lookup logic.
+ */
+/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
+ */
+
+#include <linux/init.h>
+#include <linux/export.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/pagemap.h>
+#include <linux/fsnotify.h>
+#include <linux/personality.h>
+#include <linux/security.h>
+#include <linux/ima.h>
+#include <linux/syscalls.h>
+#include <linux/mount.h>
+#include <linux/audit.h>
+#include <linux/capability.h>
+#include <linux/file.h>
+#include <linux/fcntl.h>
+#include <linux/device_cgroup.h>
+#include <linux/fs_struct.h>
+#include <linux/posix_acl.h>
+#include <asm/uaccess.h>
+
+#include "internal.h"
+#include "mount.h"
+
+/* [Feb-1997 T. Schoebel-Theuer]
+ * Fundamental changes in the pathname lookup mechanisms (namei)
+ * were necessary because of omirr.  The reason is that omirr needs
+ * to know the _real_ pathname, not the user-supplied one, in case
+ * of symlinks (and also when transname replacements occur).
+ *
+ * The new code replaces the old recursive symlink resolution with
+ * an iterative one (in case of non-nested symlink chains).  It does
+ * this with calls to <fs>_follow_link().
+ * As a side effect, dir_namei(), _namei() and follow_link() are now 
+ * replaced with a single function lookup_dentry() that can handle all 
+ * the special cases of the former code.
+ *
+ * With the new dcache, the pathname is stored at each inode, at least as
+ * long as the refcount of the inode is positive.  As a side effect, the
+ * size of the dcache depends on the inode cache and thus is dynamic.
+ *
+ * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
+ * resolution to correspond with current state of the code.
+ *
+ * Note that the symlink resolution is not *completely* iterative.
+ * There is still a significant amount of tail- and mid- recursion in
+ * the algorithm.  Also, note that <fs>_readlink() is not used in
+ * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
+ * may return different results than <fs>_follow_link().  Many virtual
+ * filesystems (including /proc) exhibit this behavior.
+ */
+
+/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
+ * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
+ * and the name already exists in form of a symlink, try to create the new
+ * name indicated by the symlink. The old code always complained that the
+ * name already exists, due to not following the symlink even if its target
+ * is nonexistent.  The new semantics affects also mknod() and link() when
+ * the name is a symlink pointing to a non-existent name.
+ *
+ * I don't know which semantics is the right one, since I have no access
+ * to standards. But I found by trial that HP-UX 9.0 has the full "new"
+ * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
+ * "old" one. Personally, I think the new semantics is much more logical.
+ * Note that "ln old new" where "new" is a symlink pointing to a non-existing
+ * file does succeed in both HP-UX and SunOs, but not in Solaris
+ * and in the old Linux semantics.
+ */
+
+/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
+ * semantics.  See the comments in "open_namei" and "do_link" below.
+ *
+ * [10-Sep-98 Alan Modra] Another symlink change.
+ */
+
+/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
+ *	inside the path - always follow.
+ *	in the last component in creation/removal/renaming - never follow.
+ *	if LOOKUP_FOLLOW passed - follow.
+ *	if the pathname has trailing slashes - follow.
+ *	otherwise - don't follow.
+ * (applied in that order).
+ *
+ * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
+ * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
+ * During the 2.4 we need to fix the userland stuff depending on it -
+ * hopefully we will be able to get rid of that wart in 2.5. So far only
+ * XEmacs seems to be relying on it...
+ */
+/*
+ * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
+ * implemented.  Let's see if raised priority of ->s_vfs_rename_mutex gives
+ * any extra contention...
+ */
+
+/* In order to reduce some races, while at the same time doing additional
+ * checking and hopefully speeding things up, we copy filenames to the
+ * kernel data space before using them..
+ *
+ * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
+ * PATH_MAX includes the nul terminator --RR.
+ */
+static int do_getname(const char __user *filename, char *page)
+{
+	int retval;
+	unsigned long len = PATH_MAX;
+
+	if (!segment_eq(get_fs(), KERNEL_DS)) {
+		if ((unsigned long) filename >= TASK_SIZE)
+			return -EFAULT;
+		if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
+			len = TASK_SIZE - (unsigned long) filename;
+	}
+
+	retval = strncpy_from_user(page, filename, len);
+	if (retval > 0) {
+		if (retval < len)
+			return 0;
+		return -ENAMETOOLONG;
+	} else if (!retval)
+		retval = -ENOENT;
+	return retval;
+}
+
+static char *getname_flags(const char __user *filename, int flags, int *empty)
+{
+	char *result = __getname();
+	int retval;
+
+	if (!result)
+		return ERR_PTR(-ENOMEM);
+
+	retval = do_getname(filename, result);
+	if (retval < 0) {
+		if (retval == -ENOENT && empty)
+			*empty = 1;
+		if (retval != -ENOENT || !(flags & LOOKUP_EMPTY)) {
+			__putname(result);
+			return ERR_PTR(retval);
+		}
+	}
+	audit_getname(result);
+	return result;
+}
+
+char *getname(const char __user * filename)
+{
+	return getname_flags(filename, 0, NULL);
+}
+
+#ifdef CONFIG_AUDITSYSCALL
+void putname(const char *name)
+{
+	if (unlikely(!audit_dummy_context()))
+		audit_putname(name);
+	else
+		__putname(name);
+}
+EXPORT_SYMBOL(putname);
+#endif
+
+static int check_acl(struct inode *inode, int mask)
+{
+#ifdef CONFIG_FS_POSIX_ACL
+	struct posix_acl *acl;
+
+	if (mask & MAY_NOT_BLOCK) {
+		acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
+	        if (!acl)
+	                return -EAGAIN;
+		/* no ->get_acl() calls in RCU mode... */
+		if (acl == ACL_NOT_CACHED)
+			return -ECHILD;
+	        return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
+	}
+
+	acl = get_cached_acl(inode, ACL_TYPE_ACCESS);
+
+	/*
+	 * A filesystem can force a ACL callback by just never filling the
+	 * ACL cache. But normally you'd fill the cache either at inode
+	 * instantiation time, or on the first ->get_acl call.
+	 *
+	 * If the filesystem doesn't have a get_acl() function at all, we'll
+	 * just create the negative cache entry.
+	 */
+	if (acl == ACL_NOT_CACHED) {
+	        if (inode->i_op->get_acl) {
+			acl = inode->i_op->get_acl(inode, ACL_TYPE_ACCESS);
+			if (IS_ERR(acl))
+				return PTR_ERR(acl);
+		} else {
+		        set_cached_acl(inode, ACL_TYPE_ACCESS, NULL);
+		        return -EAGAIN;
+		}
+	}
+
+	if (acl) {
+	        int error = posix_acl_permission(inode, acl, mask);
+	        posix_acl_release(acl);
+	        return error;
+	}
+#endif
+
+	return -EAGAIN;
+}
+
+/*
+ * This does the basic permission checking
+ */
+static int acl_permission_check(struct inode *inode, int mask)
+{
+	unsigned int mode = inode->i_mode;
+
+	if (current_user_ns() != inode_userns(inode))
+		goto other_perms;
+
+	if (likely(current_fsuid() == inode->i_uid))
+		mode >>= 6;
+	else {
+		if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
+			int error = check_acl(inode, mask);
+			if (error != -EAGAIN)
+				return error;
+		}
+
+		if (in_group_p(inode->i_gid))
+			mode >>= 3;
+	}
+
+other_perms:
+	/*
+	 * If the DACs are ok we don't need any capability check.
+	 */
+	if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
+		return 0;
+	return -EACCES;
+}
+
+/**
+ * generic_permission -  check for access rights on a Posix-like filesystem
+ * @inode:	inode to check access rights for
+ * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
+ *
+ * Used to check for read/write/execute permissions on a file.
+ * We use "fsuid" for this, letting us set arbitrary permissions
+ * for filesystem access without changing the "normal" uids which
+ * are used for other things.
+ *
+ * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
+ * request cannot be satisfied (eg. requires blocking or too much complexity).
+ * It would then be called again in ref-walk mode.
+ */
+int generic_permission(struct inode *inode, int mask)
+{
+	int ret;
+
+	/*
+	 * Do the basic permission checks.
+	 */
+	ret = acl_permission_check(inode, mask);
+	if (ret != -EACCES)
+		return ret;
+
+	if (S_ISDIR(inode->i_mode)) {
+		/* DACs are overridable for directories */
+		if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
+			return 0;
+		if (!(mask & MAY_WRITE))
+			if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
+				return 0;
+		return -EACCES;
+	}
+	/*
+	 * Read/write DACs are always overridable.
+	 * Executable DACs are overridable when there is
+	 * at least one exec bit set.
+	 */
+	if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
+		if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
+			return 0;
+
+	/*
+	 * Searching includes executable on directories, else just read.
+	 */
+	mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
+	if (mask == MAY_READ)
+		if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
+			return 0;
+
+	return -EACCES;
+}
+
+/*
+ * We _really_ want to just do "generic_permission()" without
+ * even looking at the inode->i_op values. So we keep a cache
+ * flag in inode->i_opflags, that says "this has not special
+ * permission function, use the fast case".
+ */
+static inline int do_inode_permission(struct inode *inode, int mask)
+{
+	if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
+		if (likely(inode->i_op->permission))
+			return inode->i_op->permission(inode, mask);
+
+		/* This gets set once for the inode lifetime */
+		spin_lock(&inode->i_lock);
+		inode->i_opflags |= IOP_FASTPERM;
+		spin_unlock(&inode->i_lock);
+	}
+	return generic_permission(inode, mask);
+}
+
+/**
+ * inode_permission  -  check for access rights to a given inode
+ * @inode:	inode to check permission on
+ * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
+ *
+ * Used to check for read/write/execute permissions on an inode.
+ * We use "fsuid" for this, letting us set arbitrary permissions
+ * for filesystem access without changing the "normal" uids which
+ * are used for other things.
+ *
+ * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
+ */
+int inode_permission(struct inode *inode, int mask)
+{
+	int retval;
+
+	if (unlikely(mask & MAY_WRITE)) {
+		umode_t mode = inode->i_mode;
+
+		/*
+		 * Nobody gets write access to a read-only fs.
+		 */
+		if (IS_RDONLY(inode) &&
+		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
+			return -EROFS;
+
+		/*
+		 * Nobody gets write access to an immutable file.
+		 */
+		if (IS_IMMUTABLE(inode))
+			return -EACCES;
+	}
+
+	retval = do_inode_permission(inode, mask);
+	if (retval)
+		return retval;
+
+	retval = devcgroup_inode_permission(inode, mask);
+	if (retval)
+		return retval;
+
+	return security_inode_permission(inode, mask);
+}
+
+/**
+ * path_get - get a reference to a path
+ * @path: path to get the reference to
+ *
+ * Given a path increment the reference count to the dentry and the vfsmount.
+ */
+void path_get(struct path *path)
+{
+	mntget(path->mnt);
+	dget(path->dentry);
+}
+EXPORT_SYMBOL(path_get);
+
+/**
+ * path_put - put a reference to a path
+ * @path: path to put the reference to
+ *
+ * Given a path decrement the reference count to the dentry and the vfsmount.
+ */
+void path_put(struct path *path)
+{
+	dput(path->dentry);
+	mntput(path->mnt);
+}
+EXPORT_SYMBOL(path_put);
+
+/*
+ * Path walking has 2 modes, rcu-walk and ref-walk (see
+ * Documentation/filesystems/path-lookup.txt).  In situations when we can't
+ * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
+ * normal reference counts on dentries and vfsmounts to transition to rcu-walk
+ * mode.  Refcounts are grabbed at the last known good point before rcu-walk
+ * got stuck, so ref-walk may continue from there. If this is not successful
+ * (eg. a seqcount has changed), then failure is returned and it's up to caller
+ * to restart the path walk from the beginning in ref-walk mode.
+ */
+
+/**
+ * unlazy_walk - try to switch to ref-walk mode.
+ * @nd: nameidata pathwalk data
+ * @dentry: child of nd->path.dentry or NULL
+ * Returns: 0 on success, -ECHILD on failure
+ *
+ * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
+ * for ref-walk mode.  @dentry must be a path found by a do_lookup call on
+ * @nd or NULL.  Must be called from rcu-walk context.
+ */
+static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
+{
+	struct fs_struct *fs = current->fs;
+	struct dentry *parent = nd->path.dentry;
+	int want_root = 0;
+
+	BUG_ON(!(nd->flags & LOOKUP_RCU));
+	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
+		want_root = 1;
+		spin_lock(&fs->lock);
+		if (nd->root.mnt != fs->root.mnt ||
+				nd->root.dentry != fs->root.dentry)
+			goto err_root;
+	}
+	spin_lock(&parent->d_lock);
+	if (!dentry) {
+		if (!__d_rcu_to_refcount(parent, nd->seq))
+			goto err_parent;
+		BUG_ON(nd->inode != parent->d_inode);
+	} else {
+		if (dentry->d_parent != parent)
+			goto err_parent;
+		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+		if (!__d_rcu_to_refcount(dentry, nd->seq))
+			goto err_child;
+		/*
+		 * If the sequence check on the child dentry passed, then
+		 * the child has not been removed from its parent. This
+		 * means the parent dentry must be valid and able to take
+		 * a reference at this point.
+		 */
+		BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
+		BUG_ON(!parent->d_count);
+		parent->d_count++;
+		spin_unlock(&dentry->d_lock);
+	}
+	spin_unlock(&parent->d_lock);
+	if (want_root) {
+		path_get(&nd->root);
+		spin_unlock(&fs->lock);
+	}
+	mntget(nd->path.mnt);
+
+	rcu_read_unlock();
+	br_read_unlock(vfsmount_lock);
+	nd->flags &= ~LOOKUP_RCU;
+	return 0;
+
+err_child:
+	spin_unlock(&dentry->d_lock);
+err_parent:
+	spin_unlock(&parent->d_lock);
+err_root:
+	if (want_root)
+		spin_unlock(&fs->lock);
+	return -ECHILD;
+}
+
+/**
+ * release_open_intent - free up open intent resources
+ * @nd: pointer to nameidata
+ */
+void release_open_intent(struct nameidata *nd)
+{
+	struct file *file = nd->intent.open.file;
+
+	if (file && !IS_ERR(file)) {
+		if (file->f_path.dentry == NULL)
+			put_filp(file);
+		else
+			fput(file);
+	}
+}
+
+static inline int d_revalidate(struct dentry *dentry, struct nameidata *nd)
+{
+	return dentry->d_op->d_revalidate(dentry, nd);
+}
+
+/**
+ * complete_walk - successful completion of path walk
+ * @nd:  pointer nameidata
+ *
+ * If we had been in RCU mode, drop out of it and legitimize nd->path.
+ * Revalidate the final result, unless we'd already done that during
+ * the path walk or the filesystem doesn't ask for it.  Return 0 on
+ * success, -error on failure.  In case of failure caller does not
+ * need to drop nd->path.
+ */
+static int complete_walk(struct nameidata *nd)
+{
+	struct dentry *dentry = nd->path.dentry;
+	int status;
+
+	if (nd->flags & LOOKUP_RCU) {
+		nd->flags &= ~LOOKUP_RCU;
+		if (!(nd->flags & LOOKUP_ROOT))
+			nd->root.mnt = NULL;
+		spin_lock(&dentry->d_lock);
+		if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) {
+			spin_unlock(&dentry->d_lock);
+			rcu_read_unlock();
+			br_read_unlock(vfsmount_lock);
+			return -ECHILD;
+		}
+		BUG_ON(nd->inode != dentry->d_inode);
+		spin_unlock(&dentry->d_lock);
+		mntget(nd->path.mnt);
+		rcu_read_unlock();
+		br_read_unlock(vfsmount_lock);
+	}
+
+	if (likely(!(nd->flags & LOOKUP_JUMPED)))
+		return 0;
+
+	if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
+		return 0;
+
+	if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
+		return 0;
+
+	/* Note: we do not d_invalidate() */
+	status = d_revalidate(dentry, nd);
+	if (status > 0)
+		return 0;
+
+	if (!status)
+		status = -ESTALE;
+
+	path_put(&nd->path);
+	return status;
+}
+
+static __always_inline void set_root(struct nameidata *nd)
+{
+	if (!nd->root.mnt)
+		get_fs_root(current->fs, &nd->root);
+}
+
+static int link_path_walk(const char *, struct nameidata *);
+
+static __always_inline void set_root_rcu(struct nameidata *nd)
+{
+	if (!nd->root.mnt) {
+		struct fs_struct *fs = current->fs;
+		unsigned seq;
+
+		do {
+			seq = read_seqcount_begin(&fs->seq);
+			nd->root = fs->root;
+			nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
+		} while (read_seqcount_retry(&fs->seq, seq));
+	}
+}
+
+static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
+{
+	int ret;
+
+	if (IS_ERR(link))
+		goto fail;
+
+	if (*link == '/') {
+		set_root(nd);
+		path_put(&nd->path);
+		nd->path = nd->root;
+		path_get(&nd->root);
+		nd->flags |= LOOKUP_JUMPED;
+	}
+	nd->inode = nd->path.dentry->d_inode;
+
+	ret = link_path_walk(link, nd);
+	return ret;
+fail:
+	path_put(&nd->path);
+	return PTR_ERR(link);
+}
+
+static void path_put_conditional(struct path *path, struct nameidata *nd)
+{
+	dput(path->dentry);
+	if (path->mnt != nd->path.mnt)
+		mntput(path->mnt);
+}
+
+static inline void path_to_nameidata(const struct path *path,
+					struct nameidata *nd)
+{
+	if (!(nd->flags & LOOKUP_RCU)) {
+		dput(nd->path.dentry);
+		if (nd->path.mnt != path->mnt)
+			mntput(nd->path.mnt);
+	}
+	nd->path.mnt = path->mnt;
+	nd->path.dentry = path->dentry;
+}
+
+static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
+{
+	struct inode *inode = link->dentry->d_inode;
+	if (!IS_ERR(cookie) && inode->i_op->put_link)
+		inode->i_op->put_link(link->dentry, nd, cookie);
+	path_put(link);
+}
+
+static __always_inline int
+follow_link(struct path *link, struct nameidata *nd, void **p)
+{
+	int error;
+	struct dentry *dentry = link->dentry;
+
+	BUG_ON(nd->flags & LOOKUP_RCU);
+
+	if (link->mnt == nd->path.mnt)
+		mntget(link->mnt);
+
+	if (unlikely(current->total_link_count >= 40)) {
+		*p = ERR_PTR(-ELOOP); /* no ->put_link(), please */
+		path_put(&nd->path);
+		return -ELOOP;
+	}
+	cond_resched();
+	current->total_link_count++;
+
+	touch_atime(link);
+	nd_set_link(nd, NULL);
+
+	error = security_inode_follow_link(link->dentry, nd);
+	if (error) {
+		*p = ERR_PTR(error); /* no ->put_link(), please */
+		path_put(&nd->path);
+		return error;
+	}
+
+	nd->last_type = LAST_BIND;
+	*p = dentry->d_inode->i_op->follow_link(dentry, nd);
+	error = PTR_ERR(*p);
+	if (!IS_ERR(*p)) {
+		char *s = nd_get_link(nd);
+		error = 0;
+		if (s)
+			error = __vfs_follow_link(nd, s);
+		else if (nd->last_type == LAST_BIND) {
+			nd->flags |= LOOKUP_JUMPED;
+			nd->inode = nd->path.dentry->d_inode;
+			if (nd->inode->i_op->follow_link) {
+				/* stepped on a _really_ weird one */
+				path_put(&nd->path);
+				error = -ELOOP;
+			}
+		}
+	}
+	return error;
+}
+
+static int follow_up_rcu(struct path *path)
+{
+	struct mount *mnt = real_mount(path->mnt);
+	struct mount *parent;
+	struct dentry *mountpoint;
+
+	parent = mnt->mnt_parent;
+	if (&parent->mnt == path->mnt)
+		return 0;
+	mountpoint = mnt->mnt_mountpoint;
+	path->dentry = mountpoint;
+	path->mnt = &parent->mnt;
+	return 1;
+}
+
+int follow_up(struct path *path)
+{
+	struct mount *mnt = real_mount(path->mnt);
+	struct mount *parent;
+	struct dentry *mountpoint;
+
+	br_read_lock(vfsmount_lock);
+	parent = mnt->mnt_parent;
+	if (&parent->mnt == path->mnt) {
+		br_read_unlock(vfsmount_lock);
+		return 0;
+	}
+	mntget(&parent->mnt);
+	mountpoint = dget(mnt->mnt_mountpoint);
+	br_read_unlock(vfsmount_lock);
+	dput(path->dentry);
+	path->dentry = mountpoint;
+	mntput(path->mnt);
+	path->mnt = &parent->mnt;
+	return 1;
+}
+
+/*
+ * Perform an automount
+ * - return -EISDIR to tell follow_managed() to stop and return the path we
+ *   were called with.
+ */
+static int follow_automount(struct path *path, unsigned flags,
+			    bool *need_mntput)
+{
+	struct vfsmount *mnt;
+	int err;
+
+	if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
+		return -EREMOTE;
+
+	/* We don't want to mount if someone's just doing a stat -
+	 * unless they're stat'ing a directory and appended a '/' to
+	 * the name.
+	 *
+	 * We do, however, want to mount if someone wants to open or
+	 * create a file of any type under the mountpoint, wants to
+	 * traverse through the mountpoint or wants to open the
+	 * mounted directory.  Also, autofs may mark negative dentries
+	 * as being automount points.  These will need the attentions
+	 * of the daemon to instantiate them before they can be used.
+	 */
+	if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
+		     LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
+	    path->dentry->d_inode)
+		return -EISDIR;
+
+	current->total_link_count++;
+	if (current->total_link_count >= 40)
+		return -ELOOP;
+
+	mnt = path->dentry->d_op->d_automount(path);
+	if (IS_ERR(mnt)) {
+		/*
+		 * The filesystem is allowed to return -EISDIR here to indicate
+		 * it doesn't want to automount.  For instance, autofs would do
+		 * this so that its userspace daemon can mount on this dentry.
+		 *
+		 * However, we can only permit this if it's a terminal point in
+		 * the path being looked up; if it wasn't then the remainder of
+		 * the path is inaccessible and we should say so.
+		 */
+		if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT))
+			return -EREMOTE;
+		return PTR_ERR(mnt);
+	}
+
+	if (!mnt) /* mount collision */
+		return 0;
+
+	if (!*need_mntput) {
+		/* lock_mount() may release path->mnt on error */
+		mntget(path->mnt);
+		*need_mntput = true;
+	}
+	err = finish_automount(mnt, path);
+
+	switch (err) {
+	case -EBUSY:
+		/* Someone else made a mount here whilst we were busy */
+		return 0;
+	case 0:
+		path_put(path);
+		path->mnt = mnt;
+		path->dentry = dget(mnt->mnt_root);
+		return 0;
+	default:
+		return err;
+	}
+
+}
+
+/*
+ * Handle a dentry that is managed in some way.
+ * - Flagged for transit management (autofs)
+ * - Flagged as mountpoint
+ * - Flagged as automount point
+ *
+ * This may only be called in refwalk mode.
+ *
+ * Serialization is taken care of in namespace.c
+ */
+static int follow_managed(struct path *path, unsigned flags)
+{
+	struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
+	unsigned managed;
+	bool need_mntput = false;
+	int ret = 0;
+
+	/* Given that we're not holding a lock here, we retain the value in a
+	 * local variable for each dentry as we look at it so that we don't see
+	 * the components of that value change under us */
+	while (managed = ACCESS_ONCE(path->dentry->d_flags),
+	       managed &= DCACHE_MANAGED_DENTRY,
+	       unlikely(managed != 0)) {
+		/* Allow the filesystem to manage the transit without i_mutex
+		 * being held. */
+		if (managed & DCACHE_MANAGE_TRANSIT) {
+			BUG_ON(!path->dentry->d_op);
+			BUG_ON(!path->dentry->d_op->d_manage);
+			ret = path->dentry->d_op->d_manage(path->dentry, false);
+			if (ret < 0)
+				break;
+		}
+
+		/* Transit to a mounted filesystem. */
+		if (managed & DCACHE_MOUNTED) {
+			struct vfsmount *mounted = lookup_mnt(path);
+			if (mounted) {
+				dput(path->dentry);
+				if (need_mntput)
+					mntput(path->mnt);
+				path->mnt = mounted;
+				path->dentry = dget(mounted->mnt_root);
+				need_mntput = true;
+				continue;
+			}
+
+			/* Something is mounted on this dentry in another
+			 * namespace and/or whatever was mounted there in this
+			 * namespace got unmounted before we managed to get the
+			 * vfsmount_lock */
+		}
+
+		/* Handle an automount point */
+		if (managed & DCACHE_NEED_AUTOMOUNT) {
+			ret = follow_automount(path, flags, &need_mntput);
+			if (ret < 0)
+				break;
+			continue;
+		}
+
+		/* We didn't change the current path point */
+		break;
+	}
+
+	if (need_mntput && path->mnt == mnt)
+		mntput(path->mnt);
+	if (ret == -EISDIR)
+		ret = 0;
+	return ret < 0 ? ret : need_mntput;
+}
+
+int follow_down_one(struct path *path)
+{
+	struct vfsmount *mounted;
+
+	mounted = lookup_mnt(path);
+	if (mounted) {
+		dput(path->dentry);
+		mntput(path->mnt);
+		path->mnt = mounted;
+		path->dentry = dget(mounted->mnt_root);
+		return 1;
+	}
+	return 0;
+}
+
+static inline bool managed_dentry_might_block(struct dentry *dentry)
+{
+	return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
+		dentry->d_op->d_manage(dentry, true) < 0);
+}
+
+/*
+ * Try to skip to top of mountpoint pile in rcuwalk mode.  Fail if
+ * we meet a managed dentry that would need blocking.
+ */
+static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
+			       struct inode **inode)
+{
+	for (;;) {
+		struct mount *mounted;
+		/*
+		 * Don't forget we might have a non-mountpoint managed dentry
+		 * that wants to block transit.
+		 */
+		if (unlikely(managed_dentry_might_block(path->dentry)))
+			return false;
+
+		if (!d_mountpoint(path->dentry))
+			break;
+
+		mounted = __lookup_mnt(path->mnt, path->dentry, 1);
+		if (!mounted)
+			break;
+		path->mnt = &mounted->mnt;
+		path->dentry = mounted->mnt.mnt_root;
+		nd->flags |= LOOKUP_JUMPED;
+		nd->seq = read_seqcount_begin(&path->dentry->d_seq);
+		/*
+		 * Update the inode too. We don't need to re-check the
+		 * dentry sequence number here after this d_inode read,
+		 * because a mount-point is always pinned.
+		 */
+		*inode = path->dentry->d_inode;
+	}
+	return true;
+}
+
+static void follow_mount_rcu(struct nameidata *nd)
+{
+	while (d_mountpoint(nd->path.dentry)) {
+		struct mount *mounted;
+		mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1);
+		if (!mounted)
+			break;
+		nd->path.mnt = &mounted->mnt;
+		nd->path.dentry = mounted->mnt.mnt_root;
+		nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
+	}
+}
+
+static int follow_dotdot_rcu(struct nameidata *nd)
+{
+	set_root_rcu(nd);
+
+	while (1) {
+		if (nd->path.dentry == nd->root.dentry &&
+		    nd->path.mnt == nd->root.mnt) {
+			break;
+		}
+		if (nd->path.dentry != nd->path.mnt->mnt_root) {
+			struct dentry *old = nd->path.dentry;
+			struct dentry *parent = old->d_parent;
+			unsigned seq;
+
+			seq = read_seqcount_begin(&parent->d_seq);
+			if (read_seqcount_retry(&old->d_seq, nd->seq))
+				goto failed;
+			nd->path.dentry = parent;
+			nd->seq = seq;
+			break;
+		}
+		if (!follow_up_rcu(&nd->path))
+			break;
+		nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
+	}
+	follow_mount_rcu(nd);
+	nd->inode = nd->path.dentry->d_inode;
+	return 0;
+
+failed:
+	nd->flags &= ~LOOKUP_RCU;
+	if (!(nd->flags & LOOKUP_ROOT))
+		nd->root.mnt = NULL;
+	rcu_read_unlock();
+	br_read_unlock(vfsmount_lock);
+	return -ECHILD;
+}
+
+/*
+ * Follow down to the covering mount currently visible to userspace.  At each
+ * point, the filesystem owning that dentry may be queried as to whether the
+ * caller is permitted to proceed or not.
+ */
+int follow_down(struct path *path)
+{
+	unsigned managed;
+	int ret;
+
+	while (managed = ACCESS_ONCE(path->dentry->d_flags),
+	       unlikely(managed & DCACHE_MANAGED_DENTRY)) {
+		/* Allow the filesystem to manage the transit without i_mutex
+		 * being held.
+		 *
+		 * We indicate to the filesystem if someone is trying to mount
+		 * something here.  This gives autofs the chance to deny anyone
+		 * other than its daemon the right to mount on its
+		 * superstructure.
+		 *
+		 * The filesystem may sleep at this point.
+		 */
+		if (managed & DCACHE_MANAGE_TRANSIT) {
+			BUG_ON(!path->dentry->d_op);
+			BUG_ON(!path->dentry->d_op->d_manage);
+			ret = path->dentry->d_op->d_manage(
+				path->dentry, false);
+			if (ret < 0)
+				return ret == -EISDIR ? 0 : ret;
+		}
+
+		/* Transit to a mounted filesystem. */
+		if (managed & DCACHE_MOUNTED) {
+			struct vfsmount *mounted = lookup_mnt(path);
+			if (!mounted)
+				break;
+			dput(path->dentry);
+			mntput(path->mnt);
+			path->mnt = mounted;
+			path->dentry = dget(mounted->mnt_root);
+			continue;
+		}
+
+		/* Don't handle automount points here */
+		break;
+	}
+	return 0;
+}
+
+/*
+ * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
+ */
+static void follow_mount(struct path *path)
+{
+	while (d_mountpoint(path->dentry)) {
+		struct vfsmount *mounted = lookup_mnt(path);
+		if (!mounted)
+			break;
+		dput(path->dentry);
+		mntput(path->mnt);
+		path->mnt = mounted;
+		path->dentry = dget(mounted->mnt_root);
+	}
+}
+
+static void follow_dotdot(struct nameidata *nd)
+{
+	set_root(nd);
+
+	while(1) {
+		struct dentry *old = nd->path.dentry;
+
+		if (nd->path.dentry == nd->root.dentry &&
+		    nd->path.mnt == nd->root.mnt) {
+			break;
+		}
+		if (nd->path.dentry != nd->path.mnt->mnt_root) {
+			/* rare case of legitimate dget_parent()... */
+			nd->path.dentry = dget_parent(nd->path.dentry);
+			dput(old);
+			break;
+		}
+		if (!follow_up(&nd->path))
+			break;
+	}
+	follow_mount(&nd->path);
+	nd->inode = nd->path.dentry->d_inode;
+}
+
+/*
+ * This looks up the name in dcache, possibly revalidates the old dentry and
+ * allocates a new one if not found or not valid.  In the need_lookup argument
+ * returns whether i_op->lookup is necessary.
+ *
+ * dir->d_inode->i_mutex must be held
+ */
+static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir,
+				    struct nameidata *nd, bool *need_lookup)
+{
+	struct dentry *dentry;
+	int error;
+
+	*need_lookup = false;
+	dentry = d_lookup(dir, name);
+	if (dentry) {
+		if (d_need_lookup(dentry)) {
+			*need_lookup = true;
+		} else if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
+			error = d_revalidate(dentry, nd);
+			if (unlikely(error <= 0)) {
+				if (error < 0) {
+					dput(dentry);
+					return ERR_PTR(error);
+				} else if (!d_invalidate(dentry)) {
+					dput(dentry);
+					dentry = NULL;
+				}
+			}
+		}
+	}
+
+	if (!dentry) {
+		dentry = d_alloc(dir, name);
+		if (unlikely(!dentry))
+			return ERR_PTR(-ENOMEM);
+
+		*need_lookup = true;
+	}
+	return dentry;
+}
+
+/*
+ * Call i_op->lookup on the dentry.  The dentry must be negative but may be
+ * hashed if it was pouplated with DCACHE_NEED_LOOKUP.
+ *
+ * dir->d_inode->i_mutex must be held
+ */
+static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
+				  struct nameidata *nd)
+{
+	struct dentry *old;
+
+	/* Don't create child dentry for a dead directory. */
+	if (unlikely(IS_DEADDIR(dir))) {
+		dput(dentry);
+		return ERR_PTR(-ENOENT);
+	}
+
+	old = dir->i_op->lookup(dir, dentry, nd);
+	if (unlikely(old)) {
+		dput(dentry);
+		dentry = old;
+	}
+	return dentry;
+}
+
+static struct dentry *__lookup_hash(struct qstr *name,
+		struct dentry *base, struct nameidata *nd)
+{
+	bool need_lookup;
+	struct dentry *dentry;
+
+	dentry = lookup_dcache(name, base, nd, &need_lookup);
+	if (!need_lookup)
+		return dentry;
+
+	return lookup_real(base->d_inode, dentry, nd);
+}
+
+/*
+ *  It's more convoluted than I'd like it to be, but... it's still fairly
+ *  small and for now I'd prefer to have fast path as straight as possible.
+ *  It _is_ time-critical.
+ */
+static int do_lookup(struct nameidata *nd, struct qstr *name,
+			struct path *path, struct inode **inode)
+{
+	struct vfsmount *mnt = nd->path.mnt;
+	struct dentry *dentry, *parent = nd->path.dentry;
+	int need_reval = 1;
+	int status = 1;
+	int err;
+
+	/*
+	 * Rename seqlock is not required here because in the off chance
+	 * of a false negative due to a concurrent rename, we're going to
+	 * do the non-racy lookup, below.
+	 */
+	if (nd->flags & LOOKUP_RCU) {
+		unsigned seq;
+		*inode = nd->inode;
+		dentry = __d_lookup_rcu(parent, name, &seq, inode);
+		if (!dentry)
+			goto unlazy;
+
+		/* Memory barrier in read_seqcount_begin of child is enough */
+		if (__read_seqcount_retry(&parent->d_seq, nd->seq))
+			return -ECHILD;
+		nd->seq = seq;
+
+		if (unlikely(d_need_lookup(dentry)))
+			goto unlazy;
+		if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
+			status = d_revalidate(dentry, nd);
+			if (unlikely(status <= 0)) {
+				if (status != -ECHILD)
+					need_reval = 0;
+				goto unlazy;
+			}
+		}
+		path->mnt = mnt;
+		path->dentry = dentry;
+		if (unlikely(!__follow_mount_rcu(nd, path, inode)))
+			goto unlazy;
+		if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
+			goto unlazy;
+		return 0;
+unlazy:
+		if (unlazy_walk(nd, dentry))
+			return -ECHILD;
+	} else {
+		dentry = __d_lookup(parent, name);
+	}
+
+	if (unlikely(!dentry))
+		goto need_lookup;
+
+	if (unlikely(d_need_lookup(dentry))) {
+		dput(dentry);
+		goto need_lookup;
+	}
+
+	if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
+		status = d_revalidate(dentry, nd);
+	if (unlikely(status <= 0)) {
+		if (status < 0) {
+			dput(dentry);
+			return status;
+		}
+		if (!d_invalidate(dentry)) {
+			dput(dentry);
+			goto need_lookup;
+		}
+	}
+done:
+	path->mnt = mnt;
+	path->dentry = dentry;
+	err = follow_managed(path, nd->flags);
+	if (unlikely(err < 0)) {
+		path_put_conditional(path, nd);
+		return err;
+	}
+	if (err)
+		nd->flags |= LOOKUP_JUMPED;
+	*inode = path->dentry->d_inode;
+	return 0;
+
+need_lookup:
+	BUG_ON(nd->inode != parent->d_inode);
+
+	mutex_lock(&parent->d_inode->i_mutex);
+	dentry = __lookup_hash(name, parent, nd);
+	mutex_unlock(&parent->d_inode->i_mutex);
+	if (IS_ERR(dentry))
+		return PTR_ERR(dentry);
+	goto done;
+}
+
+static inline int may_lookup(struct nameidata *nd)
+{
+	if (nd->flags & LOOKUP_RCU) {
+		int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
+		if (err != -ECHILD)
+			return err;
+		if (unlazy_walk(nd, NULL))
+			return -ECHILD;
+	}
+	return inode_permission(nd->inode, MAY_EXEC);
+}
+
+static inline int handle_dots(struct nameidata *nd, int type)
+{
+	if (type == LAST_DOTDOT) {
+		if (nd->flags & LOOKUP_RCU) {
+			if (follow_dotdot_rcu(nd))
+				return -ECHILD;
+		} else
+			follow_dotdot(nd);
+	}
+	return 0;
+}
+
+static void terminate_walk(struct nameidata *nd)
+{
+	if (!(nd->flags & LOOKUP_RCU)) {
+		path_put(&nd->path);
+	} else {
+		nd->flags &= ~LOOKUP_RCU;
+		if (!(nd->flags & LOOKUP_ROOT))
+			nd->root.mnt = NULL;
+		rcu_read_unlock();
+		br_read_unlock(vfsmount_lock);
+	}
+}
+
+/*
+ * Do we need to follow links? We _really_ want to be able
+ * to do this check without having to look at inode->i_op,
+ * so we keep a cache of "no, this doesn't need follow_link"
+ * for the common case.
+ */
+static inline int should_follow_link(struct inode *inode, int follow)
+{
+	if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
+		if (likely(inode->i_op->follow_link))
+			return follow;
+
+		/* This gets set once for the inode lifetime */
+		spin_lock(&inode->i_lock);
+		inode->i_opflags |= IOP_NOFOLLOW;
+		spin_unlock(&inode->i_lock);
+	}
+	return 0;
+}
+
+static inline int walk_component(struct nameidata *nd, struct path *path,
+		struct qstr *name, int type, int follow)
+{
+	struct inode *inode;
+	int err;
+	/*
+	 * "." and ".." are special - ".." especially so because it has
+	 * to be able to know about the current root directory and
+	 * parent relationships.
+	 */
+	if (unlikely(type != LAST_NORM))
+		return handle_dots(nd, type);
+	err = do_lookup(nd, name, path, &inode);
+	if (unlikely(err)) {
+		terminate_walk(nd);
+		return err;
+	}
+	if (!inode) {
+		path_to_nameidata(path, nd);
+		terminate_walk(nd);
+		return -ENOENT;
+	}
+	if (should_follow_link(inode, follow)) {
+		if (nd->flags & LOOKUP_RCU) {
+			if (unlikely(unlazy_walk(nd, path->dentry))) {
+				terminate_walk(nd);
+				return -ECHILD;
+			}
+		}
+		BUG_ON(inode != path->dentry->d_inode);
+		return 1;
+	}
+	path_to_nameidata(path, nd);
+	nd->inode = inode;
+	return 0;
+}
+
+/*
+ * This limits recursive symlink follows to 8, while
+ * limiting consecutive symlinks to 40.
+ *
+ * Without that kind of total limit, nasty chains of consecutive
+ * symlinks can cause almost arbitrarily long lookups.
+ */
+static inline int nested_symlink(struct path *path, struct nameidata *nd)
+{
+	int res;
+
+	if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
+		path_put_conditional(path, nd);
+		path_put(&nd->path);
+		return -ELOOP;
+	}
+	BUG_ON(nd->depth >= MAX_NESTED_LINKS);
+
+	nd->depth++;
+	current->link_count++;
+
+	do {
+		struct path link = *path;
+		void *cookie;
+
+		res = follow_link(&link, nd, &cookie);
+		if (!res)
+			res = walk_component(nd, path, &nd->last,
+					     nd->last_type, LOOKUP_FOLLOW);
+		put_link(nd, &link, cookie);
+	} while (res > 0);
+
+	current->link_count--;
+	nd->depth--;
+	return res;
+}
+
+/*
+ * We really don't want to look at inode->i_op->lookup
+ * when we don't have to. So we keep a cache bit in
+ * the inode ->i_opflags field that says "yes, we can
+ * do lookup on this inode".
+ */
+static inline int can_lookup(struct inode *inode)
+{
+	if (likely(inode->i_opflags & IOP_LOOKUP))
+		return 1;
+	if (likely(!inode->i_op->lookup))
+		return 0;
+
+	/* We do this once for the lifetime of the inode */
+	spin_lock(&inode->i_lock);
+	inode->i_opflags |= IOP_LOOKUP;
+	spin_unlock(&inode->i_lock);
+	return 1;
+}
+
+/*
+ * We can do the critical dentry name comparison and hashing
+ * operations one word at a time, but we are limited to:
+ *
+ * - Architectures with fast unaligned word accesses. We could
+ *   do a "get_unaligned()" if this helps and is sufficiently
+ *   fast.
+ *
+ * - Little-endian machines (so that we can generate the mask
+ *   of low bytes efficiently). Again, we *could* do a byte
+ *   swapping load on big-endian architectures if that is not
+ *   expensive enough to make the optimization worthless.
+ *
+ * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
+ *   do not trap on the (extremely unlikely) case of a page
+ *   crossing operation.
+ *
+ * - Furthermore, we need an efficient 64-bit compile for the
+ *   64-bit case in order to generate the "number of bytes in
+ *   the final mask". Again, that could be replaced with a
+ *   efficient population count instruction or similar.
+ */
+#ifdef CONFIG_DCACHE_WORD_ACCESS
+
+#include <asm/word-at-a-time.h>
+
+#ifdef CONFIG_64BIT
+
+static inline unsigned int fold_hash(unsigned long hash)
+{
+	hash += hash >> (8*sizeof(int));
+	return hash;
+}
+
+#else	/* 32-bit case */
+
+#define fold_hash(x) (x)
+
+#endif
+
+unsigned int full_name_hash(const unsigned char *name, unsigned int len)
+{
+	unsigned long a, mask;
+	unsigned long hash = 0;
+
+	for (;;) {
+		a = load_unaligned_zeropad(name);
+		if (len < sizeof(unsigned long))
+			break;
+		hash += a;
+		hash *= 9;
+		name += sizeof(unsigned long);
+		len -= sizeof(unsigned long);
+		if (!len)
+			goto done;
+	}
+	mask = ~(~0ul << len*8);
+	hash += mask & a;
+done:
+	return fold_hash(hash);
+}
+EXPORT_SYMBOL(full_name_hash);
+
+/*
+ * Calculate the length and hash of the path component, and
+ * return the length of the component;
+ */
+static inline unsigned long hash_name(const char *name, unsigned int *hashp)
+{
+	unsigned long a, mask, hash, len;
+
+	hash = a = 0;
+	len = -sizeof(unsigned long);
+	do {
+		hash = (hash + a) * 9;
+		len += sizeof(unsigned long);
+		a = load_unaligned_zeropad(name+len);
+		/* Do we have any NUL or '/' bytes in this word? */
+		mask = has_zero(a) | has_zero(a ^ REPEAT_BYTE('/'));
+	} while (!mask);
+
+	/* The mask *below* the first high bit set */
+	mask = (mask - 1) & ~mask;
+	mask >>= 7;
+	hash += a & mask;
+	*hashp = fold_hash(hash);
+
+	return len + count_masked_bytes(mask);
+}
+
+#else
+
+unsigned int full_name_hash(const unsigned char *name, unsigned int len)
+{
+	unsigned long hash = init_name_hash();
+	while (len--)
+		hash = partial_name_hash(*name++, hash);
+	return end_name_hash(hash);
+}
+EXPORT_SYMBOL(full_name_hash);
+
+/*
+ * We know there's a real path component here of at least
+ * one character.
+ */
+static inline unsigned long hash_name(const char *name, unsigned int *hashp)
+{
+	unsigned long hash = init_name_hash();
+	unsigned long len = 0, c;
+
+	c = (unsigned char)*name;
+	do {
+		len++;
+		hash = partial_name_hash(c, hash);
+		c = (unsigned char)name[len];
+	} while (c && c != '/');
+	*hashp = end_name_hash(hash);
+	return len;
+}
+
+#endif
+
+/*
+ * Name resolution.
+ * This is the basic name resolution function, turning a pathname into
+ * the final dentry. We expect 'base' to be positive and a directory.
+ *
+ * Returns 0 and nd will have valid dentry and mnt on success.
+ * Returns error and drops reference to input namei data on failure.
+ */
+static int link_path_walk(const char *name, struct nameidata *nd)
+{
+	struct path next;
+	int err;
+	
+	while (*name=='/')
+		name++;
+	if (!*name)
+		return 0;
+
+	/* At this point we know we have a real path component. */
+	for(;;) {
+		struct qstr this;
+		long len;
+		int type;
+
+		err = may_lookup(nd);
+ 		if (err)
+			break;
+
+		len = hash_name(name, &this.hash);
+		this.name = name;
+		this.len = len;
+
+		type = LAST_NORM;
+		if (name[0] == '.') switch (len) {
+			case 2:
+				if (name[1] == '.') {
+					type = LAST_DOTDOT;
+					nd->flags |= LOOKUP_JUMPED;
+				}
+				break;
+			case 1:
+				type = LAST_DOT;
+		}
+		if (likely(type == LAST_NORM)) {
+			struct dentry *parent = nd->path.dentry;
+			nd->flags &= ~LOOKUP_JUMPED;
+			if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
+				err = parent->d_op->d_hash(parent, nd->inode,
+							   &this);
+				if (err < 0)
+					break;
+			}
+		}
+
+		if (!name[len])
+			goto last_component;
+		/*
+		 * If it wasn't NUL, we know it was '/'. Skip that
+		 * slash, and continue until no more slashes.
+		 */
+		do {
+			len++;
+		} while (unlikely(name[len] == '/'));
+		if (!name[len])
+			goto last_component;
+		name += len;
+
+		err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
+		if (err < 0)
+			return err;
+
+		if (err) {
+			err = nested_symlink(&next, nd);
+			if (err)
+				return err;
+		}
+		if (can_lookup(nd->inode))
+			continue;
+		err = -ENOTDIR; 
+		break;
+		/* here ends the main loop */
+
+last_component:
+		nd->last = this;
+		nd->last_type = type;
+		return 0;
+	}
+	terminate_walk(nd);
+	return err;
+}
+
+static int path_init(int dfd, const char *name, unsigned int flags,
+		     struct nameidata *nd, struct file **fp)
+{
+	int retval = 0;
+	int fput_needed;
+	struct file *file;
+
+	nd->last_type = LAST_ROOT; /* if there are only slashes... */
+	nd->flags = flags | LOOKUP_JUMPED;
+	nd->depth = 0;
+	if (flags & LOOKUP_ROOT) {
+		struct inode *inode = nd->root.dentry->d_inode;
+		if (*name) {
+			if (!inode->i_op->lookup)
+				return -ENOTDIR;
+			retval = inode_permission(inode, MAY_EXEC);
+			if (retval)
+				return retval;
+		}
+		nd->path = nd->root;
+		nd->inode = inode;
+		if (flags & LOOKUP_RCU) {
+			br_read_lock(vfsmount_lock);
+			rcu_read_lock();
+			nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
+		} else {
+			path_get(&nd->path);
+		}
+		return 0;
+	}
+
+	nd->root.mnt = NULL;
+
+	if (*name=='/') {
+		if (flags & LOOKUP_RCU) {
+			br_read_lock(vfsmount_lock);
+			rcu_read_lock();
+			set_root_rcu(nd);
+		} else {
+			set_root(nd);
+			path_get(&nd->root);
+		}
+		nd->path = nd->root;
+	} else if (dfd == AT_FDCWD) {
+		if (flags & LOOKUP_RCU) {
+			struct fs_struct *fs = current->fs;
+			unsigned seq;
+
+			br_read_lock(vfsmount_lock);
+			rcu_read_lock();
+
+			do {
+				seq = read_seqcount_begin(&fs->seq);
+				nd->path = fs->pwd;
+				nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
+			} while (read_seqcount_retry(&fs->seq, seq));
+		} else {
+			get_fs_pwd(current->fs, &nd->path);
+		}
+	} else {
+		struct dentry *dentry;
+
+		file = fget_raw_light(dfd, &fput_needed);
+		retval = -EBADF;
+		if (!file)
+			goto out_fail;
+
+		dentry = file->f_path.dentry;
+
+		if (*name) {
+			retval = -ENOTDIR;
+			if (!S_ISDIR(dentry->d_inode->i_mode))
+				goto fput_fail;
+
+			retval = inode_permission(dentry->d_inode, MAY_EXEC);
+			if (retval)
+				goto fput_fail;
+		}
+
+		nd->path = file->f_path;
+		if (flags & LOOKUP_RCU) {
+			if (fput_needed)
+				*fp = file;
+			nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
+			br_read_lock(vfsmount_lock);
+			rcu_read_lock();
+		} else {
+			path_get(&file->f_path);
+			fput_light(file, fput_needed);
+		}
+	}
+
+	nd->inode = nd->path.dentry->d_inode;
+	return 0;
+
+fput_fail:
+	fput_light(file, fput_needed);
+out_fail:
+	return retval;
+}
+
+static inline int lookup_last(struct nameidata *nd, struct path *path)
+{
+	if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
+		nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
+
+	nd->flags &= ~LOOKUP_PARENT;
+	return walk_component(nd, path, &nd->last, nd->last_type,
+					nd->flags & LOOKUP_FOLLOW);
+}
+
+/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
+static int path_lookupat(int dfd, const char *name,
+				unsigned int flags, struct nameidata *nd)
+{
+	struct file *base = NULL;
+	struct path path;
+	int err;
+
+	/*
+	 * Path walking is largely split up into 2 different synchronisation
+	 * schemes, rcu-walk and ref-walk (explained in
+	 * Documentation/filesystems/path-lookup.txt). These share much of the
+	 * path walk code, but some things particularly setup, cleanup, and
+	 * following mounts are sufficiently divergent that functions are
+	 * duplicated. Typically there is a function foo(), and its RCU
+	 * analogue, foo_rcu().
+	 *
+	 * -ECHILD is the error number of choice (just to avoid clashes) that
+	 * is returned if some aspect of an rcu-walk fails. Such an error must
+	 * be handled by restarting a traditional ref-walk (which will always
+	 * be able to complete).
+	 */
+	err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);
+
+	if (unlikely(err))
+		return err;
+
+	current->total_link_count = 0;
+	err = link_path_walk(name, nd);
+
+	if (!err && !(flags & LOOKUP_PARENT)) {
+		err = lookup_last(nd, &path);
+		while (err > 0) {
+			void *cookie;
+			struct path link = path;
+			nd->flags |= LOOKUP_PARENT;
+			err = follow_link(&link, nd, &cookie);
+			if (!err)
+				err = lookup_last(nd, &path);
+			put_link(nd, &link, cookie);
+		}
+	}
+
+	if (!err)
+		err = complete_walk(nd);
+
+	if (!err && nd->flags & LOOKUP_DIRECTORY) {
+		if (!nd->inode->i_op->lookup) {
+			path_put(&nd->path);
+			err = -ENOTDIR;
+		}
+	}
+
+	if (base)
+		fput(base);
+
+	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
+		path_put(&nd->root);
+		nd->root.mnt = NULL;
+	}
+	return err;
+}
+
+static int do_path_lookup(int dfd, const char *name,
+				unsigned int flags, struct nameidata *nd)
+{
+	int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
+	if (unlikely(retval == -ECHILD))
+		retval = path_lookupat(dfd, name, flags, nd);
+	if (unlikely(retval == -ESTALE))
+		retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd);
+
+	if (likely(!retval)) {
+		if (unlikely(!audit_dummy_context())) {
+			if (nd->path.dentry && nd->inode)
+				audit_inode(name, nd->path.dentry);
+		}
+	}
+	return retval;
+}
+
+int kern_path_parent(const char *name, struct nameidata *nd)
+{
+	return do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, nd);
+}
+
+int kern_path(const char *name, unsigned int flags, struct path *path)
+{
+	struct nameidata nd;
+	int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
+	if (!res)
+		*path = nd.path;
+	return res;
+}
+
+/**
+ * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
+ * @dentry:  pointer to dentry of the base directory
+ * @mnt: pointer to vfs mount of the base directory
+ * @name: pointer to file name
+ * @flags: lookup flags
+ * @path: pointer to struct path to fill
+ */
+int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
+		    const char *name, unsigned int flags,
+		    struct path *path)
+{
+	struct nameidata nd;
+	int err;
+	nd.root.dentry = dentry;
+	nd.root.mnt = mnt;
+	BUG_ON(flags & LOOKUP_PARENT);
+	/* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
+	err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd);
+	if (!err)
+		*path = nd.path;
+	return err;
+}
+
+/*
+ * Restricted form of lookup. Doesn't follow links, single-component only,
+ * needs parent already locked. Doesn't follow mounts.
+ * SMP-safe.
+ */
+static struct dentry *lookup_hash(struct nameidata *nd)
+{
+	return __lookup_hash(&nd->last, nd->path.dentry, nd);
+}
+
+/**
+ * lookup_one_len - filesystem helper to lookup single pathname component
+ * @name:	pathname component to lookup
+ * @base:	base directory to lookup from
+ * @len:	maximum length @len should be interpreted to
+ *
+ * Note that this routine is purely a helper for filesystem usage and should
+ * not be called by generic code.  Also note that by using this function the
+ * nameidata argument is passed to the filesystem methods and a filesystem
+ * using this helper needs to be prepared for that.
+ */
+struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
+{
+	struct qstr this;
+	unsigned int c;
+	int err;
+
+	WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
+
+	this.name = name;
+	this.len = len;
+	this.hash = full_name_hash(name, len);
+	if (!len)
+		return ERR_PTR(-EACCES);
+
+	while (len--) {
+		c = *(const unsigned char *)name++;
+		if (c == '/' || c == '\0')
+			return ERR_PTR(-EACCES);
+	}
+	/*
+	 * See if the low-level filesystem might want
+	 * to use its own hash..
+	 */
+	if (base->d_flags & DCACHE_OP_HASH) {
+		int err = base->d_op->d_hash(base, base->d_inode, &this);
+		if (err < 0)
+			return ERR_PTR(err);
+	}
+
+	err = inode_permission(base->d_inode, MAY_EXEC);
+	if (err)
+		return ERR_PTR(err);
+
+	return __lookup_hash(&this, base, NULL);
+}
+
+int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
+		 struct path *path, int *empty)
+{
+	struct nameidata nd;
+	char *tmp = getname_flags(name, flags, empty);
+	int err = PTR_ERR(tmp);
+	if (!IS_ERR(tmp)) {
+
+		BUG_ON(flags & LOOKUP_PARENT);
+
+		err = do_path_lookup(dfd, tmp, flags, &nd);
+		putname(tmp);
+		if (!err)
+			*path = nd.path;
+	}
+	return err;
+}
+
+int user_path_at(int dfd, const char __user *name, unsigned flags,
+		 struct path *path)
+{
+	return user_path_at_empty(dfd, name, flags, path, NULL);
+}
+
+static int user_path_parent(int dfd, const char __user *path,
+			struct nameidata *nd, char **name)
+{
+	char *s = getname(path);
+	int error;
+
+	if (IS_ERR(s))
+		return PTR_ERR(s);
+
+	error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
+	if (error)
+		putname(s);
+	else
+		*name = s;
+
+	return error;
+}
+
+/*
+ * It's inline, so penalty for filesystems that don't use sticky bit is
+ * minimal.
+ */
+static inline int check_sticky(struct inode *dir, struct inode *inode)
+{
+	uid_t fsuid = current_fsuid();
+
+	if (!(dir->i_mode & S_ISVTX))
+		return 0;
+	if (current_user_ns() != inode_userns(inode))
+		goto other_userns;
+	if (inode->i_uid == fsuid)
+		return 0;
+	if (dir->i_uid == fsuid)
+		return 0;
+
+other_userns:
+	return !ns_capable(inode_userns(inode), CAP_FOWNER);
+}
+
+/*
+ *	Check whether we can remove a link victim from directory dir, check
+ *  whether the type of victim is right.
+ *  1. We can't do it if dir is read-only (done in permission())
+ *  2. We should have write and exec permissions on dir
+ *  3. We can't remove anything from append-only dir
+ *  4. We can't do anything with immutable dir (done in permission())
+ *  5. If the sticky bit on dir is set we should either
+ *	a. be owner of dir, or
+ *	b. be owner of victim, or
+ *	c. have CAP_FOWNER capability
+ *  6. If the victim is append-only or immutable we can't do antyhing with
+ *     links pointing to it.
+ *  7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
+ *  8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
+ *  9. We can't remove a root or mountpoint.
+ * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
+ *     nfs_async_unlink().
+ */
+static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
+{
+	int error;
+
+	if (!victim->d_inode)
+		return -ENOENT;
+
+	BUG_ON(victim->d_parent->d_inode != dir);
+	audit_inode_child(victim, dir);
+
+	error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
+	if (error)
+		return error;
+	if (IS_APPEND(dir))
+		return -EPERM;
+	if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
+	    IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
+		return -EPERM;
+	if (isdir) {
+		if (!S_ISDIR(victim->d_inode->i_mode))
+			return -ENOTDIR;
+		if (IS_ROOT(victim))
+			return -EBUSY;
+	} else if (S_ISDIR(victim->d_inode->i_mode))
+		return -EISDIR;
+	if (IS_DEADDIR(dir))
+		return -ENOENT;
+	if (victim->d_flags & DCACHE_NFSFS_RENAMED)
+		return -EBUSY;
+	return 0;
+}
+
+/*	Check whether we can create an object with dentry child in directory
+ *  dir.
+ *  1. We can't do it if child already exists (open has special treatment for
+ *     this case, but since we are inlined it's OK)
+ *  2. We can't do it if dir is read-only (done in permission())
+ *  3. We should have write and exec permissions on dir
+ *  4. We can't do it if dir is immutable (done in permission())
+ */
+static inline int may_create(struct inode *dir, struct dentry *child)
+{
+	if (child->d_inode)
+		return -EEXIST;
+	if (IS_DEADDIR(dir))
+		return -ENOENT;
+	return inode_permission(dir, MAY_WRITE | MAY_EXEC);
+}
+
+/*
+ * p1 and p2 should be directories on the same fs.
+ */
+struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
+{
+	struct dentry *p;
+
+	if (p1 == p2) {
+		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
+		return NULL;
+	}
+
+	mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
+
+	p = d_ancestor(p2, p1);
+	if (p) {
+		mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
+		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
+		return p;
+	}
+
+	p = d_ancestor(p1, p2);
+	if (p) {
+		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
+		mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
+		return p;
+	}
+
+	mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
+	mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
+	return NULL;
+}
+
+void unlock_rename(struct dentry *p1, struct dentry *p2)
+{
+	mutex_unlock(&p1->d_inode->i_mutex);
+	if (p1 != p2) {
+		mutex_unlock(&p2->d_inode->i_mutex);
+		mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
+	}
+}
+
+int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
+		struct nameidata *nd)
+{
+	int error = may_create(dir, dentry);
+
+	if (error)
+		return error;
+
+	if (!dir->i_op->create)
+		return -EACCES;	/* shouldn't it be ENOSYS? */
+	mode &= S_IALLUGO;
+	mode |= S_IFREG;
+	error = security_inode_create(dir, dentry, mode);
+	if (error)
+		return error;
+	error = dir->i_op->create(dir, dentry, mode, nd);
+	if (!error)
+		fsnotify_create(dir, dentry);
+	return error;
+}
+
+static int may_open(struct path *path, int acc_mode, int flag)
+{
+	struct dentry *dentry = path->dentry;
+	struct inode *inode = dentry->d_inode;
+	int error;
+
+	/* O_PATH? */
+	if (!acc_mode)
+		return 0;
+
+	if (!inode)
+		return -ENOENT;
+
+	switch (inode->i_mode & S_IFMT) {
+	case S_IFLNK:
+		return -ELOOP;
+	case S_IFDIR:
+		if (acc_mode & MAY_WRITE)
+			return -EISDIR;
+		break;
+	case S_IFBLK:
+	case S_IFCHR:
+		if (path->mnt->mnt_flags & MNT_NODEV)
+			return -EACCES;
+		/*FALLTHRU*/
+	case S_IFIFO:
+	case S_IFSOCK:
+		flag &= ~O_TRUNC;
+		break;
+	}
+
+	error = inode_permission(inode, acc_mode);
+	if (error)
+		return error;
+
+	/*
+	 * An append-only file must be opened in append mode for writing.
+	 */
+	if (IS_APPEND(inode)) {
+		if  ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
+			return -EPERM;
+		if (flag & O_TRUNC)
+			return -EPERM;
+	}
+
+	/* O_NOATIME can only be set by the owner or superuser */
+	if (flag & O_NOATIME && !inode_owner_or_capable(inode))
+		return -EPERM;
+
+	return 0;
+}
+
+static int handle_truncate(struct file *filp)
+{
+	struct path *path = &filp->f_path;
+	struct inode *inode = path->dentry->d_inode;
+	int error = get_write_access(inode);
+	if (error)
+		return error;
+	/*
+	 * Refuse to truncate files with mandatory locks held on them.
+	 */
+	error = locks_verify_locked(inode);
+	if (!error)
+		error = security_path_truncate(path);
+	if (!error) {
+		error = do_truncate(path->dentry, 0,
+				    ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
+				    filp);
+	}
+	put_write_access(inode);
+	return error;
+}
+
+static inline int open_to_namei_flags(int flag)
+{
+	if ((flag & O_ACCMODE) == 3)
+		flag--;
+	return flag;
+}
+
+/*
+ * Handle the last step of open()
+ */
+static struct file *do_last(struct nameidata *nd, struct path *path,
+			    const struct open_flags *op, const char *pathname)
+{
+	struct dentry *dir = nd->path.dentry;
+	struct dentry *dentry;
+	int open_flag = op->open_flag;
+	int will_truncate = open_flag & O_TRUNC;
+	int want_write = 0;
+	int acc_mode = op->acc_mode;
+	struct file *filp;
+	int error;
+
+	nd->flags &= ~LOOKUP_PARENT;
+	nd->flags |= op->intent;
+
+	switch (nd->last_type) {
+	case LAST_DOTDOT:
+	case LAST_DOT:
+		error = handle_dots(nd, nd->last_type);
+		if (error)
+			return ERR_PTR(error);
+		/* fallthrough */
+	case LAST_ROOT:
+		error = complete_walk(nd);
+		if (error)
+			return ERR_PTR(error);
+		audit_inode(pathname, nd->path.dentry);
+		if (open_flag & O_CREAT) {
+			error = -EISDIR;
+			goto exit;
+		}
+		goto ok;
+	case LAST_BIND:
+		error = complete_walk(nd);
+		if (error)
+			return ERR_PTR(error);
+		audit_inode(pathname, dir);
+		goto ok;
+	}
+
+	if (!(open_flag & O_CREAT)) {
+		int symlink_ok = 0;
+		if (nd->last.name[nd->last.len])
+			nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
+		if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
+			symlink_ok = 1;
+		/* we _can_ be in RCU mode here */
+		error = walk_component(nd, path, &nd->last, LAST_NORM,
+					!symlink_ok);
+		if (error < 0)
+			return ERR_PTR(error);
+		if (error) /* symlink */
+			return NULL;
+		/* sayonara */
+		error = complete_walk(nd);
+		if (error)
+			return ERR_PTR(error);
+
+		error = -ENOTDIR;
+		if (nd->flags & LOOKUP_DIRECTORY) {
+			if (!nd->inode->i_op->lookup)
+				goto exit;
+		}
+		audit_inode(pathname, nd->path.dentry);
+		goto ok;
+	}
+
+	/* create side of things */
+	/*
+	 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED has been
+	 * cleared when we got to the last component we are about to look up
+	 */
+	error = complete_walk(nd);
+	if (error)
+		return ERR_PTR(error);
+
+	audit_inode(pathname, dir);
+	error = -EISDIR;
+	/* trailing slashes? */
+	if (nd->last.name[nd->last.len])
+		goto exit;
+
+	mutex_lock(&dir->d_inode->i_mutex);
+
+	dentry = lookup_hash(nd);
+	error = PTR_ERR(dentry);
+	if (IS_ERR(dentry)) {
+		mutex_unlock(&dir->d_inode->i_mutex);
+		goto exit;
+	}
+
+	path->dentry = dentry;
+	path->mnt = nd->path.mnt;
+
+	/* Negative dentry, just create the file */
+	if (!dentry->d_inode) {
+		umode_t mode = op->mode;
+		if (!IS_POSIXACL(dir->d_inode))
+			mode &= ~current_umask();
+		/*
+		 * This write is needed to ensure that a
+		 * rw->ro transition does not occur between
+		 * the time when the file is created and when
+		 * a permanent write count is taken through
+		 * the 'struct file' in nameidata_to_filp().
+		 */
+		error = mnt_want_write(nd->path.mnt);
+		if (error)
+			goto exit_mutex_unlock;
+		want_write = 1;
+		/* Don't check for write permission, don't truncate */
+		open_flag &= ~O_TRUNC;
+		will_truncate = 0;
+		acc_mode = MAY_OPEN;
+		error = security_path_mknod(&nd->path, dentry, mode, 0);
+		if (error)
+			goto exit_mutex_unlock;
+		error = vfs_create(dir->d_inode, dentry, mode, nd);
+		if (error)
+			goto exit_mutex_unlock;
+		mutex_unlock(&dir->d_inode->i_mutex);
+		dput(nd->path.dentry);
+		nd->path.dentry = dentry;
+		goto common;
+	}
+
+	/*
+	 * It already exists.
+	 */
+	mutex_unlock(&dir->d_inode->i_mutex);
+	audit_inode(pathname, path->dentry);
+
+	error = -EEXIST;
+	if (open_flag & O_EXCL)
+		goto exit_dput;
+
+	error = follow_managed(path, nd->flags);
+	if (error < 0)
+		goto exit_dput;
+
+	if (error)
+		nd->flags |= LOOKUP_JUMPED;
+
+	error = -ENOENT;
+	if (!path->dentry->d_inode)
+		goto exit_dput;
+
+	if (path->dentry->d_inode->i_op->follow_link)
+		return NULL;
+
+	path_to_nameidata(path, nd);
+	nd->inode = path->dentry->d_inode;
+	/* Why this, you ask?  _Now_ we might have grown LOOKUP_JUMPED... */
+	error = complete_walk(nd);
+	if (error)
+		return ERR_PTR(error);
+	error = -EISDIR;
+	if (S_ISDIR(nd->inode->i_mode))
+		goto exit;
+ok:
+	if (!S_ISREG(nd->inode->i_mode))
+		will_truncate = 0;
+
+	if (will_truncate) {
+		error = mnt_want_write(nd->path.mnt);
+		if (error)
+			goto exit;
+		want_write = 1;
+	}
+common:
+	error = may_open(&nd->path, acc_mode, open_flag);
+	if (error)
+		goto exit;
+	filp = nameidata_to_filp(nd);
+	if (!IS_ERR(filp)) {
+		error = ima_file_check(filp, op->acc_mode);
+		if (error) {
+			fput(filp);
+			filp = ERR_PTR(error);
+		}
+	}
+	if (!IS_ERR(filp)) {
+		if (will_truncate) {
+			error = handle_truncate(filp);
+			if (error) {
+				fput(filp);
+				filp = ERR_PTR(error);
+			}
+		}
+	}
+out:
+	if (want_write)
+		mnt_drop_write(nd->path.mnt);
+	path_put(&nd->path);
+	return filp;
+
+exit_mutex_unlock:
+	mutex_unlock(&dir->d_inode->i_mutex);
+exit_dput:
+	path_put_conditional(path, nd);
+exit:
+	filp = ERR_PTR(error);
+	goto out;
+}
+
+static struct file *path_openat(int dfd, const char *pathname,
+		struct nameidata *nd, const struct open_flags *op, int flags)
+{
+	struct file *base = NULL;
+	struct file *filp;
+	struct path path;
+	int error;
+
+	filp = get_empty_filp();
+	if (!filp)
+		return ERR_PTR(-ENFILE);
+
+	filp->f_flags = op->open_flag;
+	nd->intent.open.file = filp;
+	nd->intent.open.flags = open_to_namei_flags(op->open_flag);
+	nd->intent.open.create_mode = op->mode;
+
+	error = path_init(dfd, pathname, flags | LOOKUP_PARENT, nd, &base);
+	if (unlikely(error))
+		goto out_filp;
+
+	current->total_link_count = 0;
+	error = link_path_walk(pathname, nd);
+	if (unlikely(error))
+		goto out_filp;
+
+	filp = do_last(nd, &path, op, pathname);
+	while (unlikely(!filp)) { /* trailing symlink */
+		struct path link = path;
+		void *cookie;
+		if (!(nd->flags & LOOKUP_FOLLOW)) {
+			path_put_conditional(&path, nd);
+			path_put(&nd->path);
+			filp = ERR_PTR(-ELOOP);
+			break;
+		}
+		nd->flags |= LOOKUP_PARENT;
+		nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
+		error = follow_link(&link, nd, &cookie);
+		if (unlikely(error))
+			filp = ERR_PTR(error);
+		else
+			filp = do_last(nd, &path, op, pathname);
+		put_link(nd, &link, cookie);
+	}
+out:
+	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
+		path_put(&nd->root);
+	if (base)
+		fput(base);
+	release_open_intent(nd);
+	return filp;
+
+out_filp:
+	filp = ERR_PTR(error);
+	goto out;
+}
+
+struct file *do_filp_open(int dfd, const char *pathname,
+		const struct open_flags *op, int flags)
+{
+	struct nameidata nd;
+	struct file *filp;
+
+	filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
+	if (unlikely(filp == ERR_PTR(-ECHILD)))
+		filp = path_openat(dfd, pathname, &nd, op, flags);
+	if (unlikely(filp == ERR_PTR(-ESTALE)))
+		filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
+	return filp;
+}
+
+struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
+		const char *name, const struct open_flags *op, int flags)
+{
+	struct nameidata nd;
+	struct file *file;
+
+	nd.root.mnt = mnt;
+	nd.root.dentry = dentry;
+
+	flags |= LOOKUP_ROOT;
+
+	if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
+		return ERR_PTR(-ELOOP);
+
+	file = path_openat(-1, name, &nd, op, flags | LOOKUP_RCU);
+	if (unlikely(file == ERR_PTR(-ECHILD)))
+		file = path_openat(-1, name, &nd, op, flags);
+	if (unlikely(file == ERR_PTR(-ESTALE)))
+		file = path_openat(-1, name, &nd, op, flags | LOOKUP_REVAL);
+	return file;
+}
+
+struct dentry *kern_path_create(int dfd, const char *pathname, struct path *path, int is_dir)
+{
+	struct dentry *dentry = ERR_PTR(-EEXIST);
+	struct nameidata nd;
+	int error = do_path_lookup(dfd, pathname, LOOKUP_PARENT, &nd);
+	if (error)
+		return ERR_PTR(error);
+
+	/*
+	 * Yucky last component or no last component at all?
+	 * (foo/., foo/.., /////)
+	 */
+	if (nd.last_type != LAST_NORM)
+		goto out;
+	nd.flags &= ~LOOKUP_PARENT;
+	nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;
+	nd.intent.open.flags = O_EXCL;
+
+	/*
+	 * Do the final lookup.
+	 */
+	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
+	dentry = lookup_hash(&nd);
+	if (IS_ERR(dentry))
+		goto fail;
+
+	if (dentry->d_inode)
+		goto eexist;
+	/*
+	 * Special case - lookup gave negative, but... we had foo/bar/
+	 * From the vfs_mknod() POV we just have a negative dentry -
+	 * all is fine. Let's be bastards - you had / on the end, you've
+	 * been asking for (non-existent) directory. -ENOENT for you.
+	 */
+	if (unlikely(!is_dir && nd.last.name[nd.last.len])) {
+		dput(dentry);
+		dentry = ERR_PTR(-ENOENT);
+		goto fail;
+	}
+	*path = nd.path;
+	return dentry;
+eexist:
+	dput(dentry);
+	dentry = ERR_PTR(-EEXIST);
+fail:
+	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+out:
+	path_put(&nd.path);
+	return dentry;
+}
+EXPORT_SYMBOL(kern_path_create);
+
+struct dentry *user_path_create(int dfd, const char __user *pathname, struct path *path, int is_dir)
+{
+	char *tmp = getname(pathname);
+	struct dentry *res;
+	if (IS_ERR(tmp))
+		return ERR_CAST(tmp);
+	res = kern_path_create(dfd, tmp, path, is_dir);
+	putname(tmp);
+	return res;
+}
+EXPORT_SYMBOL(user_path_create);
+
+int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
+{
+	int error = may_create(dir, dentry);
+
+	if (error)
+		return error;
+
+	if ((S_ISCHR(mode) || S_ISBLK(mode)) &&
+	    !ns_capable(inode_userns(dir), CAP_MKNOD))
+		return -EPERM;
+
+	if (!dir->i_op->mknod)
+		return -EPERM;
+
+	error = devcgroup_inode_mknod(mode, dev);
+	if (error)
+		return error;
+
+	error = security_inode_mknod(dir, dentry, mode, dev);
+	if (error)
+		return error;
+
+	error = dir->i_op->mknod(dir, dentry, mode, dev);
+	if (!error)
+		fsnotify_create(dir, dentry);
+	return error;
+}
+
+static int may_mknod(umode_t mode)
+{
+	switch (mode & S_IFMT) {
+	case S_IFREG:
+	case S_IFCHR:
+	case S_IFBLK:
+	case S_IFIFO:
+	case S_IFSOCK:
+	case 0: /* zero mode translates to S_IFREG */
+		return 0;
+	case S_IFDIR:
+		return -EPERM;
+	default:
+		return -EINVAL;
+	}
+}
+
+SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
+		unsigned, dev)
+{
+	struct dentry *dentry;
+	struct path path;
+	int error;
+
+	if (S_ISDIR(mode))
+		return -EPERM;
+
+	dentry = user_path_create(dfd, filename, &path, 0);
+	if (IS_ERR(dentry))
+		return PTR_ERR(dentry);
+
+	if (!IS_POSIXACL(path.dentry->d_inode))
+		mode &= ~current_umask();
+	error = may_mknod(mode);
+	if (error)
+		goto out_dput;
+	error = mnt_want_write(path.mnt);
+	if (error)
+		goto out_dput;
+	error = security_path_mknod(&path, dentry, mode, dev);
+	if (error)
+		goto out_drop_write;
+	switch (mode & S_IFMT) {
+		case 0: case S_IFREG:
+			error = vfs_create(path.dentry->d_inode,dentry,mode,NULL);
+			break;
+		case S_IFCHR: case S_IFBLK:
+			error = vfs_mknod(path.dentry->d_inode,dentry,mode,
+					new_decode_dev(dev));
+			break;
+		case S_IFIFO: case S_IFSOCK:
+			error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
+			break;
+	}
+out_drop_write:
+	mnt_drop_write(path.mnt);
+out_dput:
+	dput(dentry);
+	mutex_unlock(&path.dentry->d_inode->i_mutex);
+	path_put(&path);
+
+	return error;
+}
+
+SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
+{
+	return sys_mknodat(AT_FDCWD, filename, mode, dev);
+}
+
+int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
+{
+	int error = may_create(dir, dentry);
+	unsigned max_links = dir->i_sb->s_max_links;
+
+	if (error)
+		return error;
+
+	if (!dir->i_op->mkdir)
+		return -EPERM;
+
+	mode &= (S_IRWXUGO|S_ISVTX);
+	error = security_inode_mkdir(dir, dentry, mode);
+	if (error)
+		return error;
+
+	if (max_links && dir->i_nlink >= max_links)
+		return -EMLINK;
+
+	error = dir->i_op->mkdir(dir, dentry, mode);
+	if (!error)
+		fsnotify_mkdir(dir, dentry);
+	return error;
+}
+
+SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
+{
+	struct dentry *dentry;
+	struct path path;
+	int error;
+
+	dentry = user_path_create(dfd, pathname, &path, 1);
+	if (IS_ERR(dentry))
+		return PTR_ERR(dentry);
+
+	if (!IS_POSIXACL(path.dentry->d_inode))
+		mode &= ~current_umask();
+	error = mnt_want_write(path.mnt);
+	if (error)
+		goto out_dput;
+	error = security_path_mkdir(&path, dentry, mode);
+	if (error)
+		goto out_drop_write;
+	error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
+out_drop_write:
+	mnt_drop_write(path.mnt);
+out_dput:
+	dput(dentry);
+	mutex_unlock(&path.dentry->d_inode->i_mutex);
+	path_put(&path);
+	return error;
+}
+
+SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
+{
+	return sys_mkdirat(AT_FDCWD, pathname, mode);
+}
+
+/*
+ * The dentry_unhash() helper will try to drop the dentry early: we
+ * should have a usage count of 1 if we're the only user of this
+ * dentry, and if that is true (possibly after pruning the dcache),
+ * then we drop the dentry now.
+ *
+ * A low-level filesystem can, if it choses, legally
+ * do a
+ *
+ *	if (!d_unhashed(dentry))
+ *		return -EBUSY;
+ *
+ * if it cannot handle the case of removing a directory
+ * that is still in use by something else..
+ */
+void dentry_unhash(struct dentry *dentry)
+{
+	shrink_dcache_parent(dentry);
+	spin_lock(&dentry->d_lock);
+	if (dentry->d_count == 1)
+		__d_drop(dentry);
+	spin_unlock(&dentry->d_lock);
+}
+
+int vfs_rmdir(struct inode *dir, struct dentry *dentry)
+{
+	int error = may_delete(dir, dentry, 1);
+
+	if (error)
+		return error;
+
+	if (!dir->i_op->rmdir)
+		return -EPERM;
+
+	dget(dentry);
+	mutex_lock(&dentry->d_inode->i_mutex);
+
+	error = -EBUSY;
+	if (d_mountpoint(dentry))
+		goto out;
+
+	error = security_inode_rmdir(dir, dentry);
+	if (error)
+		goto out;
+
+	shrink_dcache_parent(dentry);
+	error = dir->i_op->rmdir(dir, dentry);
+	if (error)
+		goto out;
+
+	dentry->d_inode->i_flags |= S_DEAD;
+	dont_mount(dentry);
+
+out:
+	mutex_unlock(&dentry->d_inode->i_mutex);
+	dput(dentry);
+	if (!error)
+		d_delete(dentry);
+	return error;
+}
+
+static long do_rmdir(int dfd, const char __user *pathname)
+{
+	int error = 0;
+	char * name;
+	struct dentry *dentry;
+	struct nameidata nd;
+
+	error = user_path_parent(dfd, pathname, &nd, &name);
+	if (error)
+		return error;
+
+	switch(nd.last_type) {
+	case LAST_DOTDOT:
+		error = -ENOTEMPTY;
+		goto exit1;
+	case LAST_DOT:
+		error = -EINVAL;
+		goto exit1;
+	case LAST_ROOT:
+		error = -EBUSY;
+		goto exit1;
+	}
+
+	nd.flags &= ~LOOKUP_PARENT;
+
+	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
+	dentry = lookup_hash(&nd);
+	error = PTR_ERR(dentry);
+	if (IS_ERR(dentry))
+		goto exit2;
+	if (!dentry->d_inode) {
+		error = -ENOENT;
+		goto exit3;
+	}
+	error = mnt_want_write(nd.path.mnt);
+	if (error)
+		goto exit3;
+	error = security_path_rmdir(&nd.path, dentry);
+	if (error)
+		goto exit4;
+	error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
+exit4:
+	mnt_drop_write(nd.path.mnt);
+exit3:
+	dput(dentry);
+exit2:
+	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+exit1:
+	path_put(&nd.path);
+	putname(name);
+	return error;
+}
+
+SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
+{
+	return do_rmdir(AT_FDCWD, pathname);
+}
+
+int vfs_unlink(struct inode *dir, struct dentry *dentry)
+{
+	int error = may_delete(dir, dentry, 0);
+
+	if (error)
+		return error;
+
+	if (!dir->i_op->unlink)
+		return -EPERM;
+
+	mutex_lock(&dentry->d_inode->i_mutex);
+	if (d_mountpoint(dentry))
+		error = -EBUSY;
+	else {
+		error = security_inode_unlink(dir, dentry);
+		if (!error) {
+			error = dir->i_op->unlink(dir, dentry);
+			if (!error)
+				dont_mount(dentry);
+		}
+	}
+	mutex_unlock(&dentry->d_inode->i_mutex);
+
+	/* We don't d_delete() NFS sillyrenamed files--they still exist. */
+	if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
+		fsnotify_link_count(dentry->d_inode);
+		d_delete(dentry);
+	}
+
+	return error;
+}
+
+/*
+ * Make sure that the actual truncation of the file will occur outside its
+ * directory's i_mutex.  Truncate can take a long time if there is a lot of
+ * writeout happening, and we don't want to prevent access to the directory
+ * while waiting on the I/O.
+ */
+static long do_unlinkat(int dfd, const char __user *pathname)
+{
+	int error;
+	char *name;
+	struct dentry *dentry;
+	struct nameidata nd;
+	struct inode *inode = NULL;
+
+	error = user_path_parent(dfd, pathname, &nd, &name);
+	if (error)
+		return error;
+
+	error = -EISDIR;
+	if (nd.last_type != LAST_NORM)
+		goto exit1;
+
+	nd.flags &= ~LOOKUP_PARENT;
+
+	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
+	dentry = lookup_hash(&nd);
+	error = PTR_ERR(dentry);
+	if (!IS_ERR(dentry)) {
+		/* Why not before? Because we want correct error value */
+		if (nd.last.name[nd.last.len])
+			goto slashes;
+		inode = dentry->d_inode;
+		if (!inode)
+			goto slashes;
+		ihold(inode);
+		error = mnt_want_write(nd.path.mnt);
+		if (error)
+			goto exit2;
+		error = security_path_unlink(&nd.path, dentry);
+		if (error)
+			goto exit3;
+		error = vfs_unlink(nd.path.dentry->d_inode, dentry);
+exit3:
+		mnt_drop_write(nd.path.mnt);
+	exit2:
+		dput(dentry);
+	}
+	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+	if (inode)
+		iput(inode);	/* truncate the inode here */
+exit1:
+	path_put(&nd.path);
+	putname(name);
+	return error;
+
+slashes:
+	error = !dentry->d_inode ? -ENOENT :
+		S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
+	goto exit2;
+}
+
+SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
+{
+	if ((flag & ~AT_REMOVEDIR) != 0)
+		return -EINVAL;
+
+	if (flag & AT_REMOVEDIR)
+		return do_rmdir(dfd, pathname);
+
+	return do_unlinkat(dfd, pathname);
+}
+
+SYSCALL_DEFINE1(unlink, const char __user *, pathname)
+{
+	return do_unlinkat(AT_FDCWD, pathname);
+}
+
+int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
+{
+	int error = may_create(dir, dentry);
+
+	if (error)
+		return error;
+
+	if (!dir->i_op->symlink)
+		return -EPERM;
+
+	error = security_inode_symlink(dir, dentry, oldname);
+	if (error)
+		return error;
+
+	error = dir->i_op->symlink(dir, dentry, oldname);
+	if (!error)
+		fsnotify_create(dir, dentry);
+	return error;
+}
+
+SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
+		int, newdfd, const char __user *, newname)
+{
+	int error;
+	char *from;
+	struct dentry *dentry;
+	struct path path;
+
+	from = getname(oldname);
+	if (IS_ERR(from))
+		return PTR_ERR(from);
+
+	dentry = user_path_create(newdfd, newname, &path, 0);
+	error = PTR_ERR(dentry);
+	if (IS_ERR(dentry))
+		goto out_putname;
+
+	error = mnt_want_write(path.mnt);
+	if (error)
+		goto out_dput;
+	error = security_path_symlink(&path, dentry, from);
+	if (error)
+		goto out_drop_write;
+	error = vfs_symlink(path.dentry->d_inode, dentry, from);
+out_drop_write:
+	mnt_drop_write(path.mnt);
+out_dput:
+	dput(dentry);
+	mutex_unlock(&path.dentry->d_inode->i_mutex);
+	path_put(&path);
+out_putname:
+	putname(from);
+	return error;
+}
+
+SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
+{
+	return sys_symlinkat(oldname, AT_FDCWD, newname);
+}
+
+int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
+{
+	struct inode *inode = old_dentry->d_inode;
+	unsigned max_links = dir->i_sb->s_max_links;
+	int error;
+
+	if (!inode)
+		return -ENOENT;
+
+	error = may_create(dir, new_dentry);
+	if (error)
+		return error;
+
+	if (dir->i_sb != inode->i_sb)
+		return -EXDEV;
+
+	/*
+	 * A link to an append-only or immutable file cannot be created.
+	 */
+	if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
+		return -EPERM;
+	if (!dir->i_op->link)
+		return -EPERM;
+	if (S_ISDIR(inode->i_mode))
+		return -EPERM;
+
+	error = security_inode_link(old_dentry, dir, new_dentry);
+	if (error)
+		return error;
+
+	mutex_lock(&inode->i_mutex);
+	/* Make sure we don't allow creating hardlink to an unlinked file */
+	if (inode->i_nlink == 0)
+		error =  -ENOENT;
+	else if (max_links && inode->i_nlink >= max_links)
+		error = -EMLINK;
+	else
+		error = dir->i_op->link(old_dentry, dir, new_dentry);
+	mutex_unlock(&inode->i_mutex);
+	if (!error)
+		fsnotify_link(dir, inode, new_dentry);
+	return error;
+}
+
+/*
+ * Hardlinks are often used in delicate situations.  We avoid
+ * security-related surprises by not following symlinks on the
+ * newname.  --KAB
+ *
+ * We don't follow them on the oldname either to be compatible
+ * with linux 2.0, and to avoid hard-linking to directories
+ * and other special files.  --ADM
+ */
+SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
+		int, newdfd, const char __user *, newname, int, flags)
+{
+	struct dentry *new_dentry;
+	struct path old_path, new_path;
+	int how = 0;
+	int error;
+
+	if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
+		return -EINVAL;
+	/*
+	 * To use null names we require CAP_DAC_READ_SEARCH
+	 * This ensures that not everyone will be able to create
+	 * handlink using the passed filedescriptor.
+	 */
+	if (flags & AT_EMPTY_PATH) {
+		if (!capable(CAP_DAC_READ_SEARCH))
+			return -ENOENT;
+		how = LOOKUP_EMPTY;
+	}
+
+	if (flags & AT_SYMLINK_FOLLOW)
+		how |= LOOKUP_FOLLOW;
+
+	error = user_path_at(olddfd, oldname, how, &old_path);
+	if (error)
+		return error;
+
+	new_dentry = user_path_create(newdfd, newname, &new_path, 0);
+	error = PTR_ERR(new_dentry);
+	if (IS_ERR(new_dentry))
+		goto out;
+
+	error = -EXDEV;
+	if (old_path.mnt != new_path.mnt)
+		goto out_dput;
+	error = mnt_want_write(new_path.mnt);
+	if (error)
+		goto out_dput;
+	error = security_path_link(old_path.dentry, &new_path, new_dentry);
+	if (error)
+		goto out_drop_write;
+	error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry);
+out_drop_write:
+	mnt_drop_write(new_path.mnt);
+out_dput:
+	dput(new_dentry);
+	mutex_unlock(&new_path.dentry->d_inode->i_mutex);
+	path_put(&new_path);
+out:
+	path_put(&old_path);
+
+	return error;
+}
+
+SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
+{
+	return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
+}
+
+/*
+ * The worst of all namespace operations - renaming directory. "Perverted"
+ * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
+ * Problems:
+ *	a) we can get into loop creation. Check is done in is_subdir().
+ *	b) race potential - two innocent renames can create a loop together.
+ *	   That's where 4.4 screws up. Current fix: serialization on
+ *	   sb->s_vfs_rename_mutex. We might be more accurate, but that's another
+ *	   story.
+ *	c) we have to lock _three_ objects - parents and victim (if it exists).
+ *	   And that - after we got ->i_mutex on parents (until then we don't know
+ *	   whether the target exists).  Solution: try to be smart with locking
+ *	   order for inodes.  We rely on the fact that tree topology may change
+ *	   only under ->s_vfs_rename_mutex _and_ that parent of the object we
+ *	   move will be locked.  Thus we can rank directories by the tree
+ *	   (ancestors first) and rank all non-directories after them.
+ *	   That works since everybody except rename does "lock parent, lookup,
+ *	   lock child" and rename is under ->s_vfs_rename_mutex.
+ *	   HOWEVER, it relies on the assumption that any object with ->lookup()
+ *	   has no more than 1 dentry.  If "hybrid" objects will ever appear,
+ *	   we'd better make sure that there's no link(2) for them.
+ *	d) conversion from fhandle to dentry may come in the wrong moment - when
+ *	   we are removing the target. Solution: we will have to grab ->i_mutex
+ *	   in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
+ *	   ->i_mutex on parents, which works but leads to some truly excessive
+ *	   locking].
+ */
+static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
+			  struct inode *new_dir, struct dentry *new_dentry)
+{
+	int error = 0;
+	struct inode *target = new_dentry->d_inode;
+	unsigned max_links = new_dir->i_sb->s_max_links;
+
+	/*
+	 * If we are going to change the parent - check write permissions,
+	 * we'll need to flip '..'.
+	 */
+	if (new_dir != old_dir) {
+		error = inode_permission(old_dentry->d_inode, MAY_WRITE);
+		if (error)
+			return error;
+	}
+
+	error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
+	if (error)
+		return error;
+
+	dget(new_dentry);
+	if (target)
+		mutex_lock(&target->i_mutex);
+
+	error = -EBUSY;
+	if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
+		goto out;
+
+	error = -EMLINK;
+	if (max_links && !target && new_dir != old_dir &&
+	    new_dir->i_nlink >= max_links)
+		goto out;
+
+	if (target)
+		shrink_dcache_parent(new_dentry);
+	error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
+	if (error)
+		goto out;
+
+	if (target) {
+		target->i_flags |= S_DEAD;
+		dont_mount(new_dentry);
+	}
+out:
+	if (target)
+		mutex_unlock(&target->i_mutex);
+	dput(new_dentry);
+	if (!error)
+		if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
+			d_move(old_dentry,new_dentry);
+	return error;
+}
+
+static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
+			    struct inode *new_dir, struct dentry *new_dentry)
+{
+	struct inode *target = new_dentry->d_inode;
+	int error;
+
+	error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
+	if (error)
+		return error;
+
+	dget(new_dentry);
+	if (target)
+		mutex_lock(&target->i_mutex);
+
+	error = -EBUSY;
+	if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
+		goto out;
+
+	error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
+	if (error)
+		goto out;
+
+	if (target)
+		dont_mount(new_dentry);
+	if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
+		d_move(old_dentry, new_dentry);
+out:
+	if (target)
+		mutex_unlock(&target->i_mutex);
+	dput(new_dentry);
+	return error;
+}
+
+int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
+	       struct inode *new_dir, struct dentry *new_dentry)
+{
+	int error;
+	int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
+	const unsigned char *old_name;
+
+	if (old_dentry->d_inode == new_dentry->d_inode)
+ 		return 0;
+ 
+	error = may_delete(old_dir, old_dentry, is_dir);
+	if (error)
+		return error;
+
+	if (!new_dentry->d_inode)
+		error = may_create(new_dir, new_dentry);
+	else
+		error = may_delete(new_dir, new_dentry, is_dir);
+	if (error)
+		return error;
+
+	if (!old_dir->i_op->rename)
+		return -EPERM;
+
+	old_name = fsnotify_oldname_init(old_dentry->d_name.name);
+
+	if (is_dir)
+		error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
+	else
+		error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
+	if (!error)
+		fsnotify_move(old_dir, new_dir, old_name, is_dir,
+			      new_dentry->d_inode, old_dentry);
+	fsnotify_oldname_free(old_name);
+
+	return error;
+}
+
+SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
+		int, newdfd, const char __user *, newname)
+{
+	struct dentry *old_dir, *new_dir;
+	struct dentry *old_dentry, *new_dentry;
+	struct dentry *trap;
+	struct nameidata oldnd, newnd;
+	char *from;
+	char *to;
+	int error;
+
+	error = user_path_parent(olddfd, oldname, &oldnd, &from);
+	if (error)
+		goto exit;
+
+	error = user_path_parent(newdfd, newname, &newnd, &to);
+	if (error)
+		goto exit1;
+
+	error = -EXDEV;
+	if (oldnd.path.mnt != newnd.path.mnt)
+		goto exit2;
+
+	old_dir = oldnd.path.dentry;
+	error = -EBUSY;
+	if (oldnd.last_type != LAST_NORM)
+		goto exit2;
+
+	new_dir = newnd.path.dentry;
+	if (newnd.last_type != LAST_NORM)
+		goto exit2;
+
+	oldnd.flags &= ~LOOKUP_PARENT;
+	newnd.flags &= ~LOOKUP_PARENT;
+	newnd.flags |= LOOKUP_RENAME_TARGET;
+
+	trap = lock_rename(new_dir, old_dir);
+
+	old_dentry = lookup_hash(&oldnd);
+	error = PTR_ERR(old_dentry);
+	if (IS_ERR(old_dentry))
+		goto exit3;
+	/* source must exist */
+	error = -ENOENT;
+	if (!old_dentry->d_inode)
+		goto exit4;
+	/* unless the source is a directory trailing slashes give -ENOTDIR */
+	if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
+		error = -ENOTDIR;
+		if (oldnd.last.name[oldnd.last.len])
+			goto exit4;
+		if (newnd.last.name[newnd.last.len])
+			goto exit4;
+	}
+	/* source should not be ancestor of target */
+	error = -EINVAL;
+	if (old_dentry == trap)
+		goto exit4;
+	new_dentry = lookup_hash(&newnd);
+	error = PTR_ERR(new_dentry);
+	if (IS_ERR(new_dentry))
+		goto exit4;
+	/* target should not be an ancestor of source */
+	error = -ENOTEMPTY;
+	if (new_dentry == trap)
+		goto exit5;
+
+	error = mnt_want_write(oldnd.path.mnt);
+	if (error)
+		goto exit5;
+	error = security_path_rename(&oldnd.path, old_dentry,
+				     &newnd.path, new_dentry);
+	if (error)
+		goto exit6;
+	error = vfs_rename(old_dir->d_inode, old_dentry,
+				   new_dir->d_inode, new_dentry);
+exit6:
+	mnt_drop_write(oldnd.path.mnt);
+exit5:
+	dput(new_dentry);
+exit4:
+	dput(old_dentry);
+exit3:
+	unlock_rename(new_dir, old_dir);
+exit2:
+	path_put(&newnd.path);
+	putname(to);
+exit1:
+	path_put(&oldnd.path);
+	putname(from);
+exit:
+	return error;
+}
+
+SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
+{
+	return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
+}
+
+int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
+{
+	int len;
+
+	len = PTR_ERR(link);
+	if (IS_ERR(link))
+		goto out;
+
+	len = strlen(link);
+	if (len > (unsigned) buflen)
+		len = buflen;
+	if (copy_to_user(buffer, link, len))
+		len = -EFAULT;
+out:
+	return len;
+}
+
+/*
+ * A helper for ->readlink().  This should be used *ONLY* for symlinks that
+ * have ->follow_link() touching nd only in nd_set_link().  Using (or not
+ * using) it for any given inode is up to filesystem.
+ */
+int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
+{
+	struct nameidata nd;
+	void *cookie;
+	int res;
+
+	nd.depth = 0;
+	cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
+	if (IS_ERR(cookie))
+		return PTR_ERR(cookie);
+
+	res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
+	if (dentry->d_inode->i_op->put_link)
+		dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
+	return res;
+}
+
+int vfs_follow_link(struct nameidata *nd, const char *link)
+{
+	return __vfs_follow_link(nd, link);
+}
+
+/* get the link contents into pagecache */
+static char *page_getlink(struct dentry * dentry, struct page **ppage)
+{
+	char *kaddr;
+	struct page *page;
+	struct address_space *mapping = dentry->d_inode->i_mapping;
+	page = read_mapping_page(mapping, 0, NULL);
+	if (IS_ERR(page))
+		return (char*)page;
+	*ppage = page;
+	kaddr = kmap(page);
+	nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
+	return kaddr;
+}
+
+int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
+{
+	struct page *page = NULL;
+	char *s = page_getlink(dentry, &page);
+	int res = vfs_readlink(dentry,buffer,buflen,s);
+	if (page) {
+		kunmap(page);
+		page_cache_release(page);
+	}
+	return res;
+}
+
+void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
+{
+	struct page *page = NULL;
+	nd_set_link(nd, page_getlink(dentry, &page));
+	return page;
+}
+
+void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
+{
+	struct page *page = cookie;
+
+	if (page) {
+		kunmap(page);
+		page_cache_release(page);
+	}
+}
+
+/*
+ * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
+ */
+int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct page *page;
+	void *fsdata;
+	int err;
+	char *kaddr;
+	unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
+	if (nofs)
+		flags |= AOP_FLAG_NOFS;
+
+retry:
+	err = pagecache_write_begin(NULL, mapping, 0, len-1,
+				flags, &page, &fsdata);
+	if (err)
+		goto fail;
+
+	kaddr = kmap_atomic(page);
+	memcpy(kaddr, symname, len-1);
+	kunmap_atomic(kaddr);
+
+	err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
+							page, fsdata);
+	if (err < 0)
+		goto fail;
+	if (err < len-1)
+		goto retry;
+
+	mark_inode_dirty(inode);
+	return 0;
+fail:
+	return err;
+}
+
+int page_symlink(struct inode *inode, const char *symname, int len)
+{
+	return __page_symlink(inode, symname, len,
+			!(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
+}
+
+const struct inode_operations page_symlink_inode_operations = {
+	.readlink	= generic_readlink,
+	.follow_link	= page_follow_link_light,
+	.put_link	= page_put_link,
+};
+
+EXPORT_SYMBOL(user_path_at);
+EXPORT_SYMBOL(follow_down_one);
+EXPORT_SYMBOL(follow_down);
+EXPORT_SYMBOL(follow_up);
+EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
+EXPORT_SYMBOL(getname);
+EXPORT_SYMBOL(lock_rename);
+EXPORT_SYMBOL(lookup_one_len);
+EXPORT_SYMBOL(page_follow_link_light);
+EXPORT_SYMBOL(page_put_link);
+EXPORT_SYMBOL(page_readlink);
+EXPORT_SYMBOL(__page_symlink);
+EXPORT_SYMBOL(page_symlink);
+EXPORT_SYMBOL(page_symlink_inode_operations);
+EXPORT_SYMBOL(kern_path);
+EXPORT_SYMBOL(vfs_path_lookup);
+EXPORT_SYMBOL(inode_permission);
+EXPORT_SYMBOL(unlock_rename);
+EXPORT_SYMBOL(vfs_create);
+EXPORT_SYMBOL(vfs_follow_link);
+EXPORT_SYMBOL(vfs_link);
+EXPORT_SYMBOL(vfs_mkdir);
+EXPORT_SYMBOL(vfs_mknod);
+EXPORT_SYMBOL(generic_permission);
+EXPORT_SYMBOL(vfs_readlink);
+EXPORT_SYMBOL(vfs_rename);
+EXPORT_SYMBOL(vfs_rmdir);
+EXPORT_SYMBOL(vfs_symlink);
+EXPORT_SYMBOL(vfs_unlink);
+EXPORT_SYMBOL(dentry_unhash);
+EXPORT_SYMBOL(generic_readlink);