| 1 | /* getroot.c: get the root dentry for an NFS mount |
| 2 | * |
| 3 | * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved. |
| 4 | * Written by David Howells (dhowells@redhat.com) |
| 5 | * |
| 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. |
| 10 | */ |
| 11 | |
| 12 | #include <linux/module.h> |
| 13 | #include <linux/init.h> |
| 14 | |
| 15 | #include <linux/time.h> |
| 16 | #include <linux/kernel.h> |
| 17 | #include <linux/mm.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> |
| 32 | |
| 33 | #include <asm/uaccess.h> |
| 34 | |
| 35 | #include "internal.h" |
| 36 | |
| 37 | #define NFSDBG_FACILITY NFSDBG_CLIENT |
| 38 | |
| 39 | /* |
| 40 | * Set the superblock root dentry. |
| 41 | * Note that this function frees the inode in case of error. |
| 42 | */ |
| 43 | static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *inode) |
| 44 | { |
| 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) |
| 49 | return -ENOMEM; |
| 50 | ihold(inode); |
| 51 | /* |
| 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. |
| 58 | */ |
| 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); |
| 64 | } |
| 65 | return 0; |
| 66 | } |
| 67 | |
| 68 | /* |
| 69 | * get an NFS2/NFS3 root dentry from the root filehandle |
| 70 | */ |
| 71 | struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh, |
| 72 | const char *devname) |
| 73 | { |
| 74 | struct nfs_server *server = NFS_SB(sb); |
| 75 | struct nfs_fsinfo fsinfo; |
| 76 | struct dentry *ret; |
| 77 | struct inode *inode; |
| 78 | void *name = kstrdup(devname, GFP_KERNEL); |
| 79 | int error; |
| 80 | |
| 81 | if (!name) |
| 82 | return ERR_PTR(-ENOMEM); |
| 83 | |
| 84 | /* get the actual root for this mount */ |
| 85 | fsinfo.fattr = nfs_alloc_fattr(); |
| 86 | if (fsinfo.fattr == NULL) { |
| 87 | kfree(name); |
| 88 | return ERR_PTR(-ENOMEM); |
| 89 | } |
| 90 | |
| 91 | error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo); |
| 92 | if (error < 0) { |
| 93 | dprintk("nfs_get_root: getattr error = %d\n", -error); |
| 94 | ret = ERR_PTR(error); |
| 95 | goto out; |
| 96 | } |
| 97 | |
| 98 | inode = nfs_fhget(sb, mntfh, fsinfo.fattr, NULL); |
| 99 | if (IS_ERR(inode)) { |
| 100 | dprintk("nfs_get_root: get root inode failed\n"); |
| 101 | ret = ERR_CAST(inode); |
| 102 | goto out; |
| 103 | } |
| 104 | |
| 105 | error = nfs_superblock_set_dummy_root(sb, inode); |
| 106 | if (error != 0) { |
| 107 | ret = ERR_PTR(error); |
| 108 | goto out; |
| 109 | } |
| 110 | |
| 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 |
| 114 | */ |
| 115 | ret = d_obtain_root(inode); |
| 116 | if (IS_ERR(ret)) { |
| 117 | dprintk("nfs_get_root: get root dentry failed\n"); |
| 118 | goto out; |
| 119 | } |
| 120 | |
| 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; |
| 126 | name = NULL; |
| 127 | } |
| 128 | spin_unlock(&ret->d_lock); |
| 129 | out: |
| 130 | kfree(name); |
| 131 | nfs_free_fattr(fsinfo.fattr); |
| 132 | return ret; |
| 133 | } |