// SPDX-License-Identifier: GPL-2.0-only /* * 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/module.h> #include <linux/dcache.h> #include <linux/gfp.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 <linux/sunrpc/gss_api.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; /* * nfs_path - reconstruct the path given an arbitrary dentry * @base - used to return pointer to the end of devname part of path * @dentry - pointer to dentry * @buffer - result buffer * @buflen - length of buffer * @flags - options (see below) * * Helper function for constructing the server pathname * by 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 * and in generating /proc/mounts and friends. * * Supported flags: * NFS_PATH_CANONICAL: ensure there is exactly one slash after * the original device (export) name * (if unset, the original name is returned verbatim) */ char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen, unsigned flags) { char *end; int namelen; unsigned seq; const char *base; rename_retry: end = buffer+buflen; *--end = '\0'; buflen--; seq = read_seqbegin(&rename_lock); rcu_read_lock(); while (1) { spin_lock(&dentry->d_lock); if (IS_ROOT(dentry)) break; namelen = dentry->d_name.len; buflen -= namelen + 1; if (buflen < 0) goto Elong_unlock; end -= namelen; memcpy(end, dentry->d_name.name, namelen); *--end = '/'; spin_unlock(&dentry->d_lock); dentry = dentry->d_parent; } if (read_seqretry(&rename_lock, seq)) { spin_unlock(&dentry->d_lock); rcu_read_unlock(); goto rename_retry; } if ((flags & NFS_PATH_CANONICAL) && *end != '/') { if (--buflen < 0) { spin_unlock(&dentry->d_lock); rcu_read_unlock(); goto Elong; } *--end = '/'; } *p = end; base = dentry->d_fsdata; if (!base) { spin_unlock(&dentry->d_lock); rcu_read_unlock(); WARN_ON(1); return end; } namelen = strlen(base); if (*end == '/') { /* Strip off excess slashes in base string */ while (namelen > 0 && base[namelen - 1] == '/') namelen--; } buflen -= namelen; if (buflen < 0) { spin_unlock(&dentry->d_lock); rcu_read_unlock(); goto Elong; } end -= namelen; memcpy(end, base, namelen); spin_unlock(&dentry->d_lock); rcu_read_unlock(); return end; Elong_unlock: spin_unlock(&dentry->d_lock); rcu_read_unlock(); if (read_seqretry(&rename_lock, seq)) goto rename_retry; Elong: return ERR_PTR(-ENAMETOOLONG); } EXPORT_SYMBOL_GPL(nfs_path); /* * nfs_d_automount - Handle crossing a mountpoint on the server * @path - The mountpoint * * 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. */ struct vfsmount *nfs_d_automount(struct path *path) { struct vfsmount *mnt; struct nfs_server *server = NFS_SERVER(d_inode(path->dentry)); struct nfs_fh *fh = NULL; struct nfs_fattr *fattr = NULL; if (IS_ROOT(path->dentry)) return ERR_PTR(-ESTALE); mnt = ERR_PTR(-ENOMEM); fh = nfs_alloc_fhandle(); fattr = nfs_alloc_fattr(); if (fh == NULL || fattr == NULL) goto out; mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr); if (IS_ERR(mnt)) goto out; mntget(mnt); /* prevent immediate expiration */ mnt_set_expiry(mnt, &nfs_automount_list); schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); out: nfs_free_fattr(fattr); nfs_free_fhandle(fh); return mnt; } static int nfs_namespace_getattr(const struct path *path, struct kstat *stat, u32 request_mask, unsigned int query_flags) { if (NFS_FH(d_inode(path->dentry))->size != 0) return nfs_getattr(path, stat, request_mask, query_flags); generic_fillattr(d_inode(path->dentry), stat); return 0; } static int nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr) { if (NFS_FH(d_inode(dentry))->size != 0) return nfs_setattr(dentry, attr); return -EACCES; } const struct inode_operations nfs_mountpoint_inode_operations = { .getattr = nfs_getattr, .setattr = nfs_setattr, }; const struct inode_operations nfs_referral_inode_operations = { .getattr = nfs_namespace_getattr, .setattr = nfs_namespace_setattr, }; 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) { return vfs_submount(mountdata->dentry, &nfs_xdev_fs_type, devname, mountdata); } /** * nfs_do_submount - set up mountpoint when crossing a filesystem boundary * @dentry: parent directory * @fh: filehandle for new root dentry * @fattr: attributes for new root inode * @authflavor: security flavor to use when performing the mount * */ struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh, struct nfs_fattr *fattr, rpc_authflavor_t authflavor) { struct nfs_clone_mount mountdata = { .sb = dentry->d_sb, .dentry = dentry, .fh = fh, .fattr = fattr, .authflavor = authflavor, }; struct vfsmount *mnt; char *page = (char *) __get_free_page(GFP_USER); char *devname; if (page == NULL) return ERR_PTR(-ENOMEM); devname = nfs_devname(dentry, page, PAGE_SIZE); if (IS_ERR(devname)) mnt = ERR_CAST(devname); else mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata); free_page((unsigned long)page); return mnt; } EXPORT_SYMBOL_GPL(nfs_do_submount); struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry, struct nfs_fh *fh, struct nfs_fattr *fattr) { int err; struct dentry *parent = dget_parent(dentry); /* Look it up again to get its attributes */ err = server->nfs_client->rpc_ops->lookup(d_inode(parent), &dentry->d_name, fh, fattr, NULL); dput(parent); if (err != 0) return ERR_PTR(err); return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor); } EXPORT_SYMBOL_GPL(nfs_submount);