/* * linux/fs/nfs/namespace.c * * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com> * - Modified by David Howells <dhowells@redhat.com> * * NFS namespace */ #include <linux/dcache.h> #include <linux/mount.h> #include <linux/namei.h> #include <linux/nfs_fs.h> #include <linux/string.h> #include <linux/sunrpc/clnt.h> #include <linux/vfs.h> #include "internal.h" #define NFSDBG_FACILITY NFSDBG_VFS static void nfs_expire_automounts(struct work_struct *work); static LIST_HEAD(nfs_automount_list); static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts); int nfs_mountpoint_expiry_timeout = 500 * HZ; static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent, const struct dentry *dentry, struct nfs_fh *fh, struct nfs_fattr *fattr); /* * nfs_path - reconstruct the path given an arbitrary dentry * @base - arbitrary string to prepend to the path * @droot - pointer to root dentry for mountpoint * @dentry - pointer to dentry * @buffer - result buffer * @buflen - length of buffer * * Helper function for constructing the path from the * root dentry to an arbitrary hashed dentry. * * This is mainly for use in figuring out the path on the * server side when automounting on top of an existing partition. */ char *nfs_path(const char *base, const struct dentry *droot, const struct dentry *dentry, char *buffer, ssize_t buflen) { char *end = buffer+buflen; int namelen; *--end = '\0'; buflen--; spin_lock(&dcache_lock); while (!IS_ROOT(dentry) && dentry != droot) { namelen = dentry->d_name.len; buflen -= namelen + 1; if (buflen < 0) goto Elong_unlock; end -= namelen; memcpy(end, dentry->d_name.name, namelen); *--end = '/'; dentry = dentry->d_parent; } spin_unlock(&dcache_lock); namelen = strlen(base); /* Strip off excess slashes in base string */ while (namelen > 0 && base[namelen - 1] == '/') namelen--; buflen -= namelen; if (buflen < 0) goto Elong; end -= namelen; memcpy(end, base, namelen); return end; Elong_unlock: spin_unlock(&dcache_lock); Elong: return ERR_PTR(-ENAMETOOLONG); } /* * nfs_follow_mountpoint - handle crossing a mountpoint on the server * @dentry - dentry of mountpoint * @nd - nameidata info * * When we encounter a mountpoint on the server, we want to set up * a mountpoint on the client too, to prevent inode numbers from * colliding, and to allow "df" to work properly. * On NFSv4, we also want to allow for the fact that different * filesystems may be migrated to different servers in a failover * situation, and that different filesystems may want to use * different security flavours. */ static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd) { struct vfsmount *mnt; struct nfs_server *server = NFS_SERVER(dentry->d_inode); struct dentry *parent; struct nfs_fh fh; struct nfs_fattr fattr; int err; dprintk("--> nfs_follow_mountpoint()\n"); BUG_ON(IS_ROOT(dentry)); dprintk("%s: enter\n", __func__); dput(nd->path.dentry); nd->path.dentry = dget(dentry); /* Look it up again */ parent = dget_parent(nd->path.dentry); err = server->nfs_client->rpc_ops->lookup(parent->d_inode, &nd->path.dentry->d_name, &fh, &fattr); dput(parent); if (err != 0) goto out_err; if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) mnt = nfs_do_refmount(nd->path.mnt, nd->path.dentry); else mnt = nfs_do_submount(nd->path.mnt, nd->path.dentry, &fh, &fattr); err = PTR_ERR(mnt); if (IS_ERR(mnt)) goto out_err; mntget(mnt); err = do_add_mount(mnt, nd, nd->path.mnt->mnt_flags|MNT_SHRINKABLE, &nfs_automount_list); if (err < 0) { mntput(mnt); if (err == -EBUSY) goto out_follow; goto out_err; } path_put(&nd->path); nd->path.mnt = mnt; nd->path.dentry = dget(mnt->mnt_root); schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); out: dprintk("%s: done, returned %d\n", __func__, err); dprintk("<-- nfs_follow_mountpoint() = %d\n", err); return ERR_PTR(err); out_err: path_put(&nd->path); goto out; out_follow: while (d_mountpoint(nd->path.dentry) && follow_down(&nd->path.mnt, &nd->path.dentry)) ; err = 0; goto out; } const struct inode_operations nfs_mountpoint_inode_operations = { .follow_link = nfs_follow_mountpoint, .getattr = nfs_getattr, }; const struct inode_operations nfs_referral_inode_operations = { .follow_link = nfs_follow_mountpoint, }; static void nfs_expire_automounts(struct work_struct *work) { struct list_head *list = &nfs_automount_list; mark_mounts_for_expiry(list); if (!list_empty(list)) schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); } void nfs_release_automount_timer(void) { if (list_empty(&nfs_automount_list)) cancel_delayed_work(&nfs_automount_task); } /* * Clone a mountpoint of the appropriate type */ static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server, const char *devname, struct nfs_clone_mount *mountdata) { #ifdef CONFIG_NFS_V4 struct vfsmount *mnt = NULL; switch (server->nfs_client->rpc_ops->version) { case 2: case 3: mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata); break; case 4: mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata); } return mnt; #else return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata); #endif } /** * nfs_do_submount - set up mountpoint when crossing a filesystem boundary * @mnt_parent - mountpoint of parent directory * @dentry - parent directory * @fh - filehandle for new root dentry * @fattr - attributes for new root inode * */ static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent, const struct dentry *dentry, struct nfs_fh *fh, struct nfs_fattr *fattr) { struct nfs_clone_mount mountdata = { .sb = mnt_parent->mnt_sb, .dentry = dentry, .fh = fh, .fattr = fattr, }; struct vfsmount *mnt = ERR_PTR(-ENOMEM); char *page = (char *) __get_free_page(GFP_USER); char *devname; dprintk("--> nfs_do_submount()\n"); dprintk("%s: submounting on %s/%s\n", __func__, dentry->d_parent->d_name.name, dentry->d_name.name); if (page == NULL) goto out; devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE); mnt = (struct vfsmount *)devname; if (IS_ERR(devname)) goto free_page; mnt = nfs_do_clone_mount(NFS_SB(mnt_parent->mnt_sb), devname, &mountdata); free_page: free_page((unsigned long)page); out: dprintk("%s: done\n", __func__); dprintk("<-- nfs_do_submount() = %p\n", mnt); return mnt; }