1/* 2 * linux/fs/nfs/namespace.c 3 * 4 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com> 5 * - Modified by David Howells <dhowells@redhat.com> 6 * 7 * NFS namespace 8 */ 9 10#include <linux/dcache.h> 11#include <linux/mount.h> 12#include <linux/namei.h> 13#include <linux/nfs_fs.h> 14#include <linux/string.h> 15#include <linux/sunrpc/clnt.h> 16#include <linux/vfs.h> 17#include "internal.h" 18 19#define NFSDBG_FACILITY NFSDBG_VFS 20 21static void nfs_expire_automounts(struct work_struct *work); 22 23LIST_HEAD(nfs_automount_list); 24static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts); 25int nfs_mountpoint_expiry_timeout = 500 * HZ; 26 27static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent, 28 const struct dentry *dentry, 29 struct nfs_fh *fh, 30 struct nfs_fattr *fattr); 31 32/* 33 * nfs_path - reconstruct the path given an arbitrary dentry 34 * @base - arbitrary string to prepend to the path 35 * @droot - pointer to root dentry for mountpoint 36 * @dentry - pointer to dentry 37 * @buffer - result buffer 38 * @buflen - length of buffer 39 * 40 * Helper function for constructing the path from the 41 * root dentry to an arbitrary hashed dentry. 42 * 43 * This is mainly for use in figuring out the path on the 44 * server side when automounting on top of an existing partition. 45 */ 46char *nfs_path(const char *base, 47 const struct dentry *droot, 48 const struct dentry *dentry, 49 char *buffer, ssize_t buflen) 50{ 51 char *end = buffer+buflen; 52 int namelen; 53 54 *--end = '\0'; 55 buflen--; 56 spin_lock(&dcache_lock); 57 while (!IS_ROOT(dentry) && dentry != droot) { 58 namelen = dentry->d_name.len; 59 buflen -= namelen + 1; 60 if (buflen < 0) 61 goto Elong_unlock; 62 end -= namelen; 63 memcpy(end, dentry->d_name.name, namelen); 64 *--end = '/'; 65 dentry = dentry->d_parent; 66 } 67 spin_unlock(&dcache_lock); 68 namelen = strlen(base); 69 /* Strip off excess slashes in base string */ 70 while (namelen > 0 && base[namelen - 1] == '/') 71 namelen--; 72 buflen -= namelen; 73 if (buflen < 0) 74 goto Elong; 75 end -= namelen; 76 memcpy(end, base, namelen); 77 return end; 78Elong_unlock: 79 spin_unlock(&dcache_lock); 80Elong: 81 return ERR_PTR(-ENAMETOOLONG); 82} 83 84/* 85 * nfs_follow_mountpoint - handle crossing a mountpoint on the server 86 * @dentry - dentry of mountpoint 87 * @nd - nameidata info 88 * 89 * When we encounter a mountpoint on the server, we want to set up 90 * a mountpoint on the client too, to prevent inode numbers from 91 * colliding, and to allow "df" to work properly. 92 * On NFSv4, we also want to allow for the fact that different 93 * filesystems may be migrated to different servers in a failover 94 * situation, and that different filesystems may want to use 95 * different security flavours. 96 */ 97static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd) 98{ 99 struct vfsmount *mnt; 100 struct nfs_server *server = NFS_SERVER(dentry->d_inode); 101 struct dentry *parent; 102 struct nfs_fh fh; 103 struct nfs_fattr fattr; 104 int err; 105 106 dprintk("--> nfs_follow_mountpoint()\n"); 107 108 BUG_ON(IS_ROOT(dentry)); 109 dprintk("%s: enter\n", __FUNCTION__); 110 dput(nd->dentry); 111 nd->dentry = dget(dentry); 112 113 /* Look it up again */ 114 parent = dget_parent(nd->dentry); 115 err = server->nfs_client->rpc_ops->lookup(parent->d_inode, 116 &nd->dentry->d_name, 117 &fh, &fattr); 118 dput(parent); 119 if (err != 0) 120 goto out_err; 121 122 if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) 123 mnt = nfs_do_refmount(nd->mnt, nd->dentry); 124 else 125 mnt = nfs_do_submount(nd->mnt, nd->dentry, &fh, &fattr); 126 err = PTR_ERR(mnt); 127 if (IS_ERR(mnt)) 128 goto out_err; 129 130 mntget(mnt); 131 err = do_add_mount(mnt, nd, nd->mnt->mnt_flags|MNT_SHRINKABLE, &nfs_automount_list); 132 if (err < 0) { 133 mntput(mnt); 134 if (err == -EBUSY) 135 goto out_follow; 136 goto out_err; 137 } 138 mntput(nd->mnt); 139 dput(nd->dentry); 140 nd->mnt = mnt; 141 nd->dentry = dget(mnt->mnt_root); 142 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 143out: 144 dprintk("%s: done, returned %d\n", __FUNCTION__, err); 145 146 dprintk("<-- nfs_follow_mountpoint() = %d\n", err); 147 return ERR_PTR(err); 148out_err: 149 path_release(nd); 150 goto out; 151out_follow: 152 while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) 153 ; 154 err = 0; 155 goto out; 156} 157 158const struct inode_operations nfs_mountpoint_inode_operations = { 159 .follow_link = nfs_follow_mountpoint, 160 .getattr = nfs_getattr, 161}; 162 163const struct inode_operations nfs_referral_inode_operations = { 164 .follow_link = nfs_follow_mountpoint, 165}; 166 167static void nfs_expire_automounts(struct work_struct *work) 168{ 169 struct list_head *list = &nfs_automount_list; 170 171 mark_mounts_for_expiry(list); 172 if (!list_empty(list)) 173 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 174} 175 176void nfs_release_automount_timer(void) 177{ 178 if (list_empty(&nfs_automount_list)) { 179 cancel_delayed_work(&nfs_automount_task); 180 flush_scheduled_work(); 181 } 182} 183 184/* 185 * Clone a mountpoint of the appropriate type 186 */ 187static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server, 188 const char *devname, 189 struct nfs_clone_mount *mountdata) 190{ 191#ifdef CONFIG_NFS_V4 192 struct vfsmount *mnt = NULL; 193 switch (server->nfs_client->cl_nfsversion) { 194 case 2: 195 case 3: 196 mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata); 197 break; 198 case 4: 199 mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata); 200 } 201 return mnt; 202#else 203 return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata); 204#endif 205} 206 207/** 208 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary 209 * @mnt_parent - mountpoint of parent directory 210 * @dentry - parent directory 211 * @fh - filehandle for new root dentry 212 * @fattr - attributes for new root inode 213 * 214 */ 215static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent, 216 const struct dentry *dentry, 217 struct nfs_fh *fh, 218 struct nfs_fattr *fattr) 219{ 220 struct nfs_clone_mount mountdata = { 221 .sb = mnt_parent->mnt_sb, 222 .dentry = dentry, 223 .fh = fh, 224 .fattr = fattr, 225 }; 226 struct vfsmount *mnt = ERR_PTR(-ENOMEM); 227 char *page = (char *) __get_free_page(GFP_USER); 228 char *devname; 229 230 dprintk("--> nfs_do_submount()\n"); 231 232 dprintk("%s: submounting on %s/%s\n", __FUNCTION__, 233 dentry->d_parent->d_name.name, 234 dentry->d_name.name); 235 if (page == NULL) 236 goto out; 237 devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE); 238 mnt = (struct vfsmount *)devname; 239 if (IS_ERR(devname)) 240 goto free_page; 241 mnt = nfs_do_clone_mount(NFS_SB(mnt_parent->mnt_sb), devname, &mountdata); 242free_page: 243 free_page((unsigned long)page); 244out: 245 dprintk("%s: done\n", __FUNCTION__); 246 247 dprintk("<-- nfs_do_submount() = %p\n", mnt); 248 return mnt; 249} 250