1 /* 2 * linux/fs/nfs/namespace.c 3 * 4 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com> 5 * 6 * NFS namespace 7 */ 8 9 #include <linux/config.h> 10 11 #include <linux/dcache.h> 12 #include <linux/mount.h> 13 #include <linux/namei.h> 14 #include <linux/nfs_fs.h> 15 #include <linux/string.h> 16 #include <linux/sunrpc/clnt.h> 17 #include <linux/vfs.h> 18 #include "internal.h" 19 20 #define NFSDBG_FACILITY NFSDBG_VFS 21 22 static void nfs_expire_automounts(void *list); 23 24 LIST_HEAD(nfs_automount_list); 25 static DECLARE_WORK(nfs_automount_task, nfs_expire_automounts, &nfs_automount_list); 26 int nfs_mountpoint_expiry_timeout = 500 * HZ; 27 28 /* 29 * nfs_path - reconstruct the path given an arbitrary dentry 30 * @base - arbitrary string to prepend to the path 31 * @dentry - pointer to dentry 32 * @buffer - result buffer 33 * @buflen - length of buffer 34 * 35 * Helper function for constructing the path from the 36 * root dentry to an arbitrary hashed dentry. 37 * 38 * This is mainly for use in figuring out the path on the 39 * server side when automounting on top of an existing partition. 40 */ 41 char *nfs_path(const char *base, const struct dentry *dentry, 42 char *buffer, ssize_t buflen) 43 { 44 char *end = buffer+buflen; 45 int namelen; 46 47 *--end = '\0'; 48 buflen--; 49 spin_lock(&dcache_lock); 50 while (!IS_ROOT(dentry)) { 51 namelen = dentry->d_name.len; 52 buflen -= namelen + 1; 53 if (buflen < 0) 54 goto Elong_unlock; 55 end -= namelen; 56 memcpy(end, dentry->d_name.name, namelen); 57 *--end = '/'; 58 dentry = dentry->d_parent; 59 } 60 spin_unlock(&dcache_lock); 61 namelen = strlen(base); 62 /* Strip off excess slashes in base string */ 63 while (namelen > 0 && base[namelen - 1] == '/') 64 namelen--; 65 buflen -= namelen; 66 if (buflen < 0) 67 goto Elong; 68 end -= namelen; 69 memcpy(end, base, namelen); 70 return end; 71 Elong_unlock: 72 spin_unlock(&dcache_lock); 73 Elong: 74 return ERR_PTR(-ENAMETOOLONG); 75 } 76 77 /* 78 * nfs_follow_mountpoint - handle crossing a mountpoint on the server 79 * @dentry - dentry of mountpoint 80 * @nd - nameidata info 81 * 82 * When we encounter a mountpoint on the server, we want to set up 83 * a mountpoint on the client too, to prevent inode numbers from 84 * colliding, and to allow "df" to work properly. 85 * On NFSv4, we also want to allow for the fact that different 86 * filesystems may be migrated to different servers in a failover 87 * situation, and that different filesystems may want to use 88 * different security flavours. 89 */ 90 static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd) 91 { 92 struct vfsmount *mnt; 93 struct nfs_server *server = NFS_SERVER(dentry->d_inode); 94 struct dentry *parent; 95 struct nfs_fh fh; 96 struct nfs_fattr fattr; 97 int err; 98 99 BUG_ON(IS_ROOT(dentry)); 100 dprintk("%s: enter\n", __FUNCTION__); 101 dput(nd->dentry); 102 nd->dentry = dget(dentry); 103 if (d_mountpoint(nd->dentry)) 104 goto out_follow; 105 /* Look it up again */ 106 parent = dget_parent(nd->dentry); 107 err = server->rpc_ops->lookup(parent->d_inode, &nd->dentry->d_name, &fh, &fattr); 108 dput(parent); 109 if (err != 0) 110 goto out_err; 111 112 if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) 113 mnt = nfs_do_refmount(nd->mnt, nd->dentry); 114 else 115 mnt = nfs_do_submount(nd->mnt, nd->dentry, &fh, &fattr); 116 err = PTR_ERR(mnt); 117 if (IS_ERR(mnt)) 118 goto out_err; 119 120 mntget(mnt); 121 err = do_add_mount(mnt, nd, nd->mnt->mnt_flags|MNT_SHRINKABLE, &nfs_automount_list); 122 if (err < 0) { 123 mntput(mnt); 124 if (err == -EBUSY) 125 goto out_follow; 126 goto out_err; 127 } 128 mntput(nd->mnt); 129 dput(nd->dentry); 130 nd->mnt = mnt; 131 nd->dentry = dget(mnt->mnt_root); 132 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 133 out: 134 dprintk("%s: done, returned %d\n", __FUNCTION__, err); 135 return ERR_PTR(err); 136 out_err: 137 path_release(nd); 138 goto out; 139 out_follow: 140 while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) 141 ; 142 err = 0; 143 goto out; 144 } 145 146 struct inode_operations nfs_mountpoint_inode_operations = { 147 .follow_link = nfs_follow_mountpoint, 148 .getattr = nfs_getattr, 149 }; 150 151 struct inode_operations nfs_referral_inode_operations = { 152 .follow_link = nfs_follow_mountpoint, 153 }; 154 155 static void nfs_expire_automounts(void *data) 156 { 157 struct list_head *list = (struct list_head *)data; 158 159 mark_mounts_for_expiry(list); 160 if (!list_empty(list)) 161 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 162 } 163 164 void nfs_release_automount_timer(void) 165 { 166 if (list_empty(&nfs_automount_list)) { 167 cancel_delayed_work(&nfs_automount_task); 168 flush_scheduled_work(); 169 } 170 } 171 172 /* 173 * Clone a mountpoint of the appropriate type 174 */ 175 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server, char *devname, 176 struct nfs_clone_mount *mountdata) 177 { 178 #ifdef CONFIG_NFS_V4 179 struct vfsmount *mnt = NULL; 180 switch (server->rpc_ops->version) { 181 case 2: 182 case 3: 183 mnt = vfs_kern_mount(&clone_nfs_fs_type, 0, devname, mountdata); 184 break; 185 case 4: 186 mnt = vfs_kern_mount(&clone_nfs4_fs_type, 0, devname, mountdata); 187 } 188 return mnt; 189 #else 190 return vfs_kern_mount(&clone_nfs_fs_type, 0, devname, mountdata); 191 #endif 192 } 193 194 /** 195 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary 196 * @mnt_parent - mountpoint of parent directory 197 * @dentry - parent directory 198 * @fh - filehandle for new root dentry 199 * @fattr - attributes for new root inode 200 * 201 */ 202 struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent, 203 const struct dentry *dentry, struct nfs_fh *fh, 204 struct nfs_fattr *fattr) 205 { 206 struct nfs_clone_mount mountdata = { 207 .sb = mnt_parent->mnt_sb, 208 .dentry = dentry, 209 .fh = fh, 210 .fattr = fattr, 211 }; 212 struct vfsmount *mnt = ERR_PTR(-ENOMEM); 213 char *page = (char *) __get_free_page(GFP_USER); 214 char *devname; 215 216 dprintk("%s: submounting on %s/%s\n", __FUNCTION__, 217 dentry->d_parent->d_name.name, 218 dentry->d_name.name); 219 if (page == NULL) 220 goto out; 221 devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE); 222 mnt = (struct vfsmount *)devname; 223 if (IS_ERR(devname)) 224 goto free_page; 225 mnt = nfs_do_clone_mount(NFS_SB(mnt_parent->mnt_sb), devname, &mountdata); 226 free_page: 227 free_page((unsigned long)page); 228 out: 229 dprintk("%s: done\n", __FUNCTION__); 230 return mnt; 231 } 232