linux/fs/exportfs/expfs.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) Neil Brown 2002
 * Copyright (C) Christoph Hellwig 2007
 *
 * This file contains the code mapping from inodes to NFS file handles,
 * and for mapping back from file handles to dentries.
 *
 * For details on why we do all the strange and hairy things in here
 * take a look at Documentation/filesystems/nfs/exporting.rst.
 */
#include <linux/exportfs.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/sched.h>
#include <linux/cred.h>

#define dprintk(fmt, args...) …


static int get_name(const struct path *path, char *name, struct dentry *child);


static int exportfs_get_name(struct vfsmount *mnt, struct dentry *dir,
		char *name, struct dentry *child)
{ … }

/*
 * Check if the dentry or any of it's aliases is acceptable.
 */
static struct dentry *
find_acceptable_alias(struct dentry *result,
		int (*acceptable)(void *context, struct dentry *dentry),
		void *context)
{ … }

static bool dentry_connected(struct dentry *dentry)
{ … }

static void clear_disconnected(struct dentry *dentry)
{ … }

/*
 * Reconnect a directory dentry with its parent.
 *
 * This can return a dentry, or NULL, or an error.
 *
 * In the first case the returned dentry is the parent of the given
 * dentry, and may itself need to be reconnected to its parent.
 *
 * In the NULL case, a concurrent VFS operation has either renamed or
 * removed this directory.  The concurrent operation has reconnected our
 * dentry, so we no longer need to.
 */
static struct dentry *reconnect_one(struct vfsmount *mnt,
		struct dentry *dentry, char *nbuf)
{ … }

/*
 * Make sure target_dir is fully connected to the dentry tree.
 *
 * On successful return, DCACHE_DISCONNECTED will be cleared on
 * target_dir, and target_dir->d_parent->...->d_parent will reach the
 * root of the filesystem.
 *
 * Whenever DCACHE_DISCONNECTED is unset, target_dir is fully connected.
 * But the converse is not true: target_dir may have DCACHE_DISCONNECTED
 * set but already be connected.  In that case we'll verify the
 * connection to root and then clear the flag.
 *
 * Note that target_dir could be removed by a concurrent operation.  In
 * that case reconnect_path may still succeed with target_dir fully
 * connected, but further operations using the filehandle will fail when
 * necessary (due to S_DEAD being set on the directory).
 */
static int
reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
{ … }

struct getdents_callback { … };

/*
 * A rather strange filldir function to capture
 * the name matching the specified inode number.
 */
static bool filldir_one(struct dir_context *ctx, const char *name, int len,
			loff_t pos, u64 ino, unsigned int d_type)
{ … }

/**
 * get_name - default export_operations->get_name function
 * @path:   the directory in which to find a name
 * @name:   a pointer to a %NAME_MAX+1 char buffer to store the name
 * @child:  the dentry for the child directory.
 *
 * calls readdir on the parent until it finds an entry with
 * the same inode number as the child, and returns that.
 */
static int get_name(const struct path *path, char *name, struct dentry *child)
{ … }

#define FILEID_INO64_GEN_LEN …

/**
 * exportfs_encode_ino64_fid - encode non-decodeable 64bit ino file id
 * @inode:   the object to encode
 * @fid:     where to store the file handle fragment
 * @max_len: maximum length to store there (in 4 byte units)
 *
 * This generic function is used to encode a non-decodeable file id for
 * fanotify for filesystems that do not support NFS export.
 */
static int exportfs_encode_ino64_fid(struct inode *inode, struct fid *fid,
				     int *max_len)
{ … }

/**
 * exportfs_encode_inode_fh - encode a file handle from inode
 * @inode:   the object to encode
 * @fid:     where to store the file handle fragment
 * @max_len: maximum length to store there
 * @parent:  parent directory inode, if wanted
 * @flags:   properties of the requested file handle
 *
 * Returns an enum fid_type or a negative errno.
 */
int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
			     int *max_len, struct inode *parent, int flags)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * exportfs_encode_fh - encode a file handle from dentry
 * @dentry:  the object to encode
 * @fid:     where to store the file handle fragment
 * @max_len: maximum length to store there
 * @flags:   properties of the requested file handle
 *
 * Returns an enum fid_type or a negative errno.
 */
int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
		       int flags)
{ … }
EXPORT_SYMBOL_GPL(…);

struct dentry *
exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
		       int fileid_type, unsigned int flags,
		       int (*acceptable)(void *, struct dentry *),
		       void *context)
{ … }
EXPORT_SYMBOL_GPL(…);

struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
				  int fh_len, int fileid_type,
				  int (*acceptable)(void *, struct dentry *),
				  void *context)
{ … }
EXPORT_SYMBOL_GPL(…);

MODULE_LICENSE(…) …;