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// SPDX-License-Identifier: GPL-2.0-or-later
/* getroot.c: get the root dentry for an NFS mount
*
* Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/unistd.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/stats.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>
#include <linux/lockd/bind.h>
#include <linux/seq_file.h>
#include <linux/mount.h>
#include <linux/vfs.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/uaccess.h>
#include "internal.h"
#define NFSDBG_FACILITY NFSDBG_CLIENT
/*
* Set the superblock root dentry.
* Note that this function frees the inode in case of error.
*/
static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *inode)
{
/* The mntroot acts as the dummy root dentry for this superblock */
if (sb->s_root == NULL) {
sb->s_root = d_make_root(inode);
if (sb->s_root == NULL)
return -ENOMEM;
ihold(inode);
/*
* Ensure that this dentry is invisible to d_find_alias().
* Otherwise, it may be spliced into the tree by
* d_splice_alias if a parent directory from the same
* filesystem gets mounted at a later time.
* This again causes shrink_dcache_for_umount_subtree() to
* Oops, since the test for IS_ROOT() will fail.
*/
spin_lock(&d_inode(sb->s_root)->i_lock);
spin_lock(&sb->s_root->d_lock);
hlist_del_init(&sb->s_root->d_u.d_alias);
spin_unlock(&sb->s_root->d_lock);
spin_unlock(&d_inode(sb->s_root)->i_lock);
}
return 0;
}
/*
* get an NFS2/NFS3 root dentry from the root filehandle
*/
int nfs_get_root(struct super_block *s, struct fs_context *fc)
{
struct nfs_fs_context *ctx = nfs_fc2context(fc);
struct nfs_server *server = NFS_SB(s);
struct nfs_fsinfo fsinfo;
struct dentry *root;
struct inode *inode;
char *name;
int error = -ENOMEM;
name = kstrdup(fc->source, GFP_KERNEL);
if (!name)
goto out;
/* get the actual root for this mount */
fsinfo.fattr = nfs_alloc_fattr();
if (fsinfo.fattr == NULL)
goto out_name;
error = server->nfs_client->rpc_ops->getroot(server, ctx->mntfh, &fsinfo);
if (error < 0) {
dprintk("nfs_get_root: getattr error = %d\n", -error);
nfs_errorf(fc, "NFS: Couldn't getattr on root");
goto out_fattr;
}
inode = nfs_fhget(s, ctx->mntfh, fsinfo.fattr, NULL);
if (IS_ERR(inode)) {
dprintk("nfs_get_root: get root inode failed\n");
error = PTR_ERR(inode);
nfs_errorf(fc, "NFS: Couldn't get root inode");
goto out_fattr;
}
error = nfs_superblock_set_dummy_root(s, inode);
if (error != 0)
goto out_fattr;
/* root dentries normally start off anonymous and get spliced in later
* if the dentry tree reaches them; however if the dentry already
* exists, we'll pick it up at this point and use it as the root
*/
root = d_obtain_root(inode);
if (IS_ERR(root)) {
dprintk("nfs_get_root: get root dentry failed\n");
error = PTR_ERR(root);
nfs_errorf(fc, "NFS: Couldn't get root dentry");
goto out_fattr;
}
security_d_instantiate(root, inode);
spin_lock(&root->d_lock);
if (IS_ROOT(root) && !root->d_fsdata &&
!(root->d_flags & DCACHE_NFSFS_RENAMED)) {
root->d_fsdata = name;
name = NULL;
}
spin_unlock(&root->d_lock);
fc->root = root;
error = 0;
out_fattr:
nfs_free_fattr(fsinfo.fattr);
out_name:
kfree(name);
out:
return error;
}
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