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/* dir.c: AFS dynamic root handling
*
* Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/dns_resolver.h>
#include "internal.h"
const struct file_operations afs_dynroot_file_operations = {
.open = dcache_dir_open,
.release = dcache_dir_close,
.iterate_shared = dcache_readdir,
.llseek = dcache_dir_lseek,
};
/*
* 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;
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(afs_d2net(dentry), name, len);
if (!IS_ERR(cell)) {
afs_put_cell(afs_d2net(dentry), cell);
return 0;
}
ret = dns_query("afsdb", name, len, "ipv4", NULL, NULL);
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}, {%x:%u}",
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 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)
{
struct afs_vnode *vnode;
struct inode *inode;
int ret;
vnode = AFS_FS_I(dir);
_enter("%pd", dentry);
ASSERTCMP(d_inode(dentry), ==, NULL);
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);
inode = afs_try_auto_mntpt(dentry, dir);
if (IS_ERR(inode)) {
ret = PTR_ERR(inode);
if (ret == -ENOENT) {
d_add(dentry, NULL);
_leave(" = NULL [negative]");
return NULL;
}
_leave(" = %d [do]", ret);
return ERR_PTR(ret);
}
d_add(dentry, inode);
_leave(" = 0 { ino=%lu v=%u }",
d_inode(dentry)->i_ino, d_inode(dentry)->i_generation);
return NULL;
}
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,
};
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