blob: b79879aacc02e80ddaa7cfdcd1706d547eca9a6d [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0-or-later
/* AFS dynamic root handling
*
* Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/dns_resolver.h>
#include "internal.h"
static atomic_t afs_autocell_ino;
/*
* iget5() comparator for inode created by autocell operations
*
* These pseudo inodes don't match anything.
*/
static int afs_iget5_pseudo_test(struct inode *inode, void *opaque)
{
return 0;
}
/*
* iget5() inode initialiser
*/
static int afs_iget5_pseudo_set(struct inode *inode, void *opaque)
{
struct afs_super_info *as = AFS_FS_S(inode->i_sb);
struct afs_vnode *vnode = AFS_FS_I(inode);
struct afs_fid *fid = opaque;
vnode->volume = as->volume;
vnode->fid = *fid;
inode->i_ino = fid->vnode;
inode->i_generation = fid->unique;
return 0;
}
/*
* Create an inode for a dynamic root directory or an autocell dynamic
* automount dir.
*/
struct inode *afs_iget_pseudo_dir(struct super_block *sb, bool root)
{
struct afs_super_info *as = AFS_FS_S(sb);
struct afs_vnode *vnode;
struct inode *inode;
struct afs_fid fid = {};
_enter("");
if (as->volume)
fid.vid = as->volume->vid;
if (root) {
fid.vnode = 1;
fid.unique = 1;
} else {
fid.vnode = atomic_inc_return(&afs_autocell_ino);
fid.unique = 0;
}
inode = iget5_locked(sb, fid.vnode,
afs_iget5_pseudo_test, afs_iget5_pseudo_set, &fid);
if (!inode) {
_leave(" = -ENOMEM");
return ERR_PTR(-ENOMEM);
}
_debug("GOT INODE %p { ino=%lu, vl=%llx, vn=%llx, u=%x }",
inode, inode->i_ino, fid.vid, fid.vnode, fid.unique);
vnode = AFS_FS_I(inode);
/* there shouldn't be an existing inode */
BUG_ON(!(inode->i_state & I_NEW));
inode->i_size = 0;
inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
if (root) {
inode->i_op = &afs_dynroot_inode_operations;
inode->i_fop = &simple_dir_operations;
} else {
inode->i_op = &afs_autocell_inode_operations;
}
set_nlink(inode, 2);
inode->i_uid = GLOBAL_ROOT_UID;
inode->i_gid = GLOBAL_ROOT_GID;
inode->i_ctime = inode->i_atime = inode->i_mtime = current_time(inode);
inode->i_blocks = 0;
inode->i_generation = 0;
set_bit(AFS_VNODE_PSEUDODIR, &vnode->flags);
if (!root) {
set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
inode->i_flags |= S_AUTOMOUNT;
}
inode->i_flags |= S_NOATIME;
unlock_new_inode(inode);
_leave(" = %p", inode);
return inode;
}
/*
* Probe to see if a cell may exist. This prevents positive dentries from
* being created unnecessarily.
*/
static int afs_probe_cell_name(struct dentry *dentry)
{
struct afs_cell *cell;
struct afs_net *net = afs_d2net(dentry);
const char *name = dentry->d_name.name;
size_t len = dentry->d_name.len;
int ret;
/* Names prefixed with a dot are R/W mounts. */
if (name[0] == '.') {
if (len == 1)
return -EINVAL;
name++;
len--;
}
cell = afs_lookup_cell_rcu(net, name, len);
if (!IS_ERR(cell)) {
afs_put_cell(net, cell);
return 0;
}
ret = dns_query(net->net, "afsdb", name, len, "srv=1",
NULL, NULL, false);
if (ret == -ENODATA)
ret = -EDESTADDRREQ;
return ret;
}
/*
* Try to auto mount the mountpoint with pseudo directory, if the autocell
* operation is setted.
*/
struct inode *afs_try_auto_mntpt(struct dentry *dentry, struct inode *dir)
{
struct afs_vnode *vnode = AFS_FS_I(dir);
struct inode *inode;
int ret = -ENOENT;
_enter("%p{%pd}, {%llx:%llu}",
dentry, dentry, vnode->fid.vid, vnode->fid.vnode);
if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
goto out;
ret = afs_probe_cell_name(dentry);
if (ret < 0)
goto out;
inode = afs_iget_pseudo_dir(dir->i_sb, false);
if (IS_ERR(inode)) {
ret = PTR_ERR(inode);
goto out;
}
_leave("= %p", inode);
return inode;
out:
_leave("= %d", ret);
return ret == -ENOENT ? NULL : ERR_PTR(ret);
}
/*
* Look up @cell in a dynroot directory. This is a substitution for the
* local cell name for the net namespace.
*/
static struct dentry *afs_lookup_atcell(struct dentry *dentry)
{
struct afs_cell *cell;
struct afs_net *net = afs_d2net(dentry);
struct dentry *ret;
unsigned int seq = 0;
char *name;
int len;
if (!net->ws_cell)
return ERR_PTR(-ENOENT);
ret = ERR_PTR(-ENOMEM);
name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL);
if (!name)
goto out_p;
rcu_read_lock();
do {
read_seqbegin_or_lock(&net->cells_lock, &seq);
cell = rcu_dereference_raw(net->ws_cell);
if (cell) {
len = cell->name_len;
memcpy(name, cell->name, len + 1);
}
} while (need_seqretry(&net->cells_lock, seq));
done_seqretry(&net->cells_lock, seq);
rcu_read_unlock();
ret = ERR_PTR(-ENOENT);
if (!cell)
goto out_n;
ret = lookup_one_len(name, dentry->d_parent, len);
/* We don't want to d_add() the @cell dentry here as we don't want to
* the cached dentry to hide changes to the local cell name.
*/
out_n:
kfree(name);
out_p:
return ret;
}
/*
* Look up an entry in a dynroot directory.
*/
static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
_enter("%pd", dentry);
ASSERTCMP(d_inode(dentry), ==, NULL);
if (flags & LOOKUP_CREATE)
return ERR_PTR(-EOPNOTSUPP);
if (dentry->d_name.len >= AFSNAMEMAX) {
_leave(" = -ENAMETOOLONG");
return ERR_PTR(-ENAMETOOLONG);
}
if (dentry->d_name.len == 5 &&
memcmp(dentry->d_name.name, "@cell", 5) == 0)
return afs_lookup_atcell(dentry);
return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry);
}
const struct inode_operations afs_dynroot_inode_operations = {
.lookup = afs_dynroot_lookup,
};
/*
* Dirs in the dynamic root don't need revalidation.
*/
static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags)
{
return 1;
}
/*
* Allow the VFS to enquire as to whether a dentry should be unhashed (mustn't
* sleep)
* - called from dput() when d_count is going to 0.
* - return 1 to request dentry be unhashed, 0 otherwise
*/
static int afs_dynroot_d_delete(const struct dentry *dentry)
{
return d_really_is_positive(dentry);
}
const struct dentry_operations afs_dynroot_dentry_operations = {
.d_revalidate = afs_dynroot_d_revalidate,
.d_delete = afs_dynroot_d_delete,
.d_release = afs_d_release,
.d_automount = afs_d_automount,
};
/*
* Create a manually added cell mount directory.
* - The caller must hold net->proc_cells_lock
*/
int afs_dynroot_mkdir(struct afs_net *net, struct afs_cell *cell)
{
struct super_block *sb = net->dynroot_sb;
struct dentry *root, *subdir;
int ret;
if (!sb || atomic_read(&sb->s_active) == 0)
return 0;
/* Let the ->lookup op do the creation */
root = sb->s_root;
inode_lock(root->d_inode);
subdir = lookup_one_len(cell->name, root, cell->name_len);
if (IS_ERR(subdir)) {
ret = PTR_ERR(subdir);
goto unlock;
}
/* Note that we're retaining an extra ref on the dentry */
subdir->d_fsdata = (void *)1UL;
ret = 0;
unlock:
inode_unlock(root->d_inode);
return ret;
}
/*
* Remove a manually added cell mount directory.
* - The caller must hold net->proc_cells_lock
*/
void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell)
{
struct super_block *sb = net->dynroot_sb;
struct dentry *root, *subdir;
if (!sb || atomic_read(&sb->s_active) == 0)
return;
root = sb->s_root;
inode_lock(root->d_inode);
/* Don't want to trigger a lookup call, which will re-add the cell */
subdir = try_lookup_one_len(cell->name, root, cell->name_len);
if (IS_ERR_OR_NULL(subdir)) {
_debug("lookup %ld", PTR_ERR(subdir));
goto no_dentry;
}
_debug("rmdir %pd %u", subdir, d_count(subdir));
if (subdir->d_fsdata) {
_debug("unpin %u", d_count(subdir));
subdir->d_fsdata = NULL;
dput(subdir);
}
dput(subdir);
no_dentry:
inode_unlock(root->d_inode);
_leave("");
}
/*
* Populate a newly created dynamic root with cell names.
*/
int afs_dynroot_populate(struct super_block *sb)
{
struct afs_cell *cell;
struct afs_net *net = afs_sb2net(sb);
int ret;
mutex_lock(&net->proc_cells_lock);
net->dynroot_sb = sb;
hlist_for_each_entry(cell, &net->proc_cells, proc_link) {
ret = afs_dynroot_mkdir(net, cell);
if (ret < 0)
goto error;
}
ret = 0;
out:
mutex_unlock(&net->proc_cells_lock);
return ret;
error:
net->dynroot_sb = NULL;
goto out;
}
/*
* When a dynamic root that's in the process of being destroyed, depopulate it
* of pinned directories.
*/
void afs_dynroot_depopulate(struct super_block *sb)
{
struct afs_net *net = afs_sb2net(sb);
struct dentry *root = sb->s_root, *subdir, *tmp;
/* Prevent more subdirs from being created */
mutex_lock(&net->proc_cells_lock);
if (net->dynroot_sb == sb)
net->dynroot_sb = NULL;
mutex_unlock(&net->proc_cells_lock);
inode_lock(root->d_inode);
/* Remove all the pins for dirs created for manually added cells */
list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) {
if (subdir->d_fsdata) {
subdir->d_fsdata = NULL;
dput(subdir);
}
}
inode_unlock(root->d_inode);
}