1 /* getroot.c: get the root dentry for an NFS mount
3 * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
12 #include <linux/module.h>
13 #include <linux/init.h>
15 #include <linux/time.h>
16 #include <linux/kernel.h>
18 #include <linux/string.h>
19 #include <linux/stat.h>
20 #include <linux/errno.h>
21 #include <linux/unistd.h>
22 #include <linux/sunrpc/clnt.h>
23 #include <linux/sunrpc/stats.h>
24 #include <linux/nfs_fs.h>
25 #include <linux/nfs_mount.h>
26 #include <linux/lockd/bind.h>
27 #include <linux/seq_file.h>
28 #include <linux/mount.h>
29 #include <linux/vfs.h>
30 #include <linux/namei.h>
31 #include <linux/security.h>
33 #include <asm/uaccess.h>
37 #define NFSDBG_FACILITY NFSDBG_CLIENT
40 * Set the superblock root dentry.
41 * Note that this function frees the inode in case of error.
43 static int nfs_superblock_set_dummy_root(struct super_block
*sb
, struct inode
*inode
)
45 /* The mntroot acts as the dummy root dentry for this superblock */
46 if (sb
->s_root
== NULL
) {
47 sb
->s_root
= d_make_root(inode
);
48 if (sb
->s_root
== NULL
)
52 * Ensure that this dentry is invisible to d_find_alias().
53 * Otherwise, it may be spliced into the tree by
54 * d_splice_alias if a parent directory from the same
55 * filesystem gets mounted at a later time.
56 * This again causes shrink_dcache_for_umount_subtree() to
57 * Oops, since the test for IS_ROOT() will fail.
59 spin_lock(&d_inode(sb
->s_root
)->i_lock
);
60 spin_lock(&sb
->s_root
->d_lock
);
61 hlist_del_init(&sb
->s_root
->d_u
.d_alias
);
62 spin_unlock(&sb
->s_root
->d_lock
);
63 spin_unlock(&d_inode(sb
->s_root
)->i_lock
);
69 * get an NFS2/NFS3 root dentry from the root filehandle
71 struct dentry
*nfs_get_root(struct super_block
*sb
, struct nfs_fh
*mntfh
,
74 struct nfs_server
*server
= NFS_SB(sb
);
75 struct nfs_fsinfo fsinfo
;
78 void *name
= kstrdup(devname
, GFP_KERNEL
);
82 return ERR_PTR(-ENOMEM
);
84 /* get the actual root for this mount */
85 fsinfo
.fattr
= nfs_alloc_fattr();
86 if (fsinfo
.fattr
== NULL
) {
88 return ERR_PTR(-ENOMEM
);
91 error
= server
->nfs_client
->rpc_ops
->getroot(server
, mntfh
, &fsinfo
);
93 dprintk("nfs_get_root: getattr error = %d\n", -error
);
98 inode
= nfs_fhget(sb
, mntfh
, fsinfo
.fattr
, NULL
);
100 dprintk("nfs_get_root: get root inode failed\n");
101 ret
= ERR_CAST(inode
);
105 error
= nfs_superblock_set_dummy_root(sb
, inode
);
107 ret
= ERR_PTR(error
);
111 /* root dentries normally start off anonymous and get spliced in later
112 * if the dentry tree reaches them; however if the dentry already
113 * exists, we'll pick it up at this point and use it as the root
115 ret
= d_obtain_root(inode
);
117 dprintk("nfs_get_root: get root dentry failed\n");
121 security_d_instantiate(ret
, inode
);
122 spin_lock(&ret
->d_lock
);
123 if (IS_ROOT(ret
) && !ret
->d_fsdata
&&
124 !(ret
->d_flags
& DCACHE_NFSFS_RENAMED
)) {
125 ret
->d_fsdata
= name
;
128 spin_unlock(&ret
->d_lock
);
131 nfs_free_fattr(fsinfo
.fattr
);
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