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afs: Support the AFS dynamic root

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Support the AFS dynamic root which is a pseudo-volume that doesn't connect
to any server resource, but rather is just a root directory that
dynamically creates mountpoint directories where the name of such a
directory is the name of the cell.

Such a mount can be created thus:

	mount -t afs none /afs -o dyn

Dynamic root superblocks aren't shared except by bind mounts and
propagation.  Cell root volumes can then be mounted by referring to them by
name, e.g.:

	ls /afs/grand.central.org/
	ls /afs/.grand.central.org/

The kernel will upcall to consult the DNS if the address wasn't supplied
directly.

Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2018-02-06 06:26:30 +00:00
parent 16280a15be
commit 4d673da145
7 changed files with 277 additions and 98 deletions
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17
Documentation/filesystems/afs.txt
View File

@ -7,6 +7,7 @@ Contents:
- Overview.
- Usage.
- Mountpoints.
- Dynamic root.
- Proc filesystem.
- The cell database.
- Security.
@ -127,6 +128,22 @@ mounted on /afs in one go by doing:
umount /afs
============
DYNAMIC ROOT
============
A mount option is available to create a serverless mount that is only usable
for dynamic lookup. Creating such a mount can be done by, for example:
mount -t afs none /afs -o dyn
This creates a mount that just has an empty directory at the root. Attempting
to look up a name in this directory will cause a mountpoint to be created that
looks up a cell of the same name, for example:
ls /afs/grand.central.org/
===============
PROC FILESYSTEM
===============

122
fs/afs/dir.c
View File

@ -17,10 +17,13 @@
#include <linux/pagemap.h>
#include <linux/ctype.h>
#include <linux/sched.h>
#include <linux/dns_resolver.h>
#include "internal.h"
static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags);
static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags);
static int afs_dir_open(struct inode *inode, struct file *file);
static int afs_readdir(struct file *file, struct dir_context *ctx);
static int afs_d_revalidate(struct dentry *dentry, unsigned int flags);
@ -64,6 +67,17 @@ const struct inode_operations afs_dir_inode_operations = {
.listxattr = afs_listxattr,
};
const struct file_operations afs_dynroot_file_operations = {
.open = dcache_dir_open,
.release = dcache_dir_close,
.iterate_shared = dcache_readdir,
.llseek = dcache_dir_lseek,
};
const struct inode_operations afs_dynroot_inode_operations = {
.lookup = afs_dynroot_lookup,
};
const struct dentry_operations afs_fs_dentry_operations = {
.d_revalidate = afs_d_revalidate,
.d_delete = afs_d_delete,
@ -467,26 +481,59 @@ static int afs_do_lookup(struct inode *dir, struct dentry *dentry,
return 0;
}
/*
* 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.
*/
static struct inode *afs_try_auto_mntpt(
int ret, struct dentry *dentry, struct inode *dir, struct key *key,
struct afs_fid *fid)
static struct inode *afs_try_auto_mntpt(struct dentry *dentry,
struct inode *dir, struct afs_fid *fid)
{
const char *devname = dentry->d_name.name;
struct afs_vnode *vnode = AFS_FS_I(dir);
struct inode *inode;
int ret = -ENOENT;
_enter("%d, %p{%pd}, {%x:%u}, %p",
ret, dentry, dentry, vnode->fid.vid, vnode->fid.vnode, key);
_enter("%p{%pd}, {%x:%u}",
dentry, dentry, vnode->fid.vid, vnode->fid.vnode);
if (ret != -ENOENT ||
!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
goto out;
inode = afs_iget_autocell(dir, devname, strlen(devname), key);
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;
@ -545,13 +592,16 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
ret = afs_do_lookup(dir, dentry, &fid, key);
if (ret < 0) {
inode = afs_try_auto_mntpt(ret, dentry, dir, key, &fid);
if (!IS_ERR(inode)) {
key_put(key);
goto success;
if (ret == -ENOENT) {
inode = afs_try_auto_mntpt(dentry, dir, &fid);
if (!IS_ERR(inode)) {
key_put(key);
goto success;
}
ret = PTR_ERR(inode);
}
ret = PTR_ERR(inode);
key_put(key);
if (ret == -ENOENT) {
d_add(dentry, NULL);
@ -582,6 +632,46 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
return NULL;
}
/*
* 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 afs_fid fid;
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);
}
inode = afs_try_auto_mntpt(dentry, dir, &fid);
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;
}
/*
* check that a dentry lookup hit has found a valid entry
* - NOTE! the hit can be a negative hit too, so we can't assume we have an
@ -589,6 +679,7 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
*/
static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
{
struct afs_super_info *as = dentry->d_sb->s_fs_info;
struct afs_vnode *vnode, *dir;
struct afs_fid uninitialized_var(fid);
struct dentry *parent;
@ -600,6 +691,9 @@ static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
if (flags & LOOKUP_RCU)
return -ECHILD;
if (as->dyn_root)
return 1;
if (d_really_is_positive(dentry)) {
vnode = AFS_FS_I(d_inode(dentry));
_enter("{v={%x:%u} n=%pd fl=%lx},",

48
fs/afs/inode.c
View File

@ -147,7 +147,7 @@ int afs_iget5_test(struct inode *inode, void *opaque)
*
* These pseudo inodes don't match anything.
*/
static int afs_iget5_autocell_test(struct inode *inode, void *opaque)
static int afs_iget5_pseudo_dir_test(struct inode *inode, void *opaque)
{
return 0;
}
@ -169,31 +169,34 @@ static int afs_iget5_set(struct inode *inode, void *opaque)
}
/*
* inode retrieval for autocell
* Create an inode for a dynamic root directory or an autocell dynamic
* automount dir.
*/
struct inode *afs_iget_autocell(struct inode *dir, const char *dev_name,
int namesz, struct key *key)
struct inode *afs_iget_pseudo_dir(struct super_block *sb, bool root)
{
struct afs_iget_data data;
struct afs_super_info *as;
struct afs_vnode *vnode;
struct super_block *sb;
struct inode *inode;
static atomic_t afs_autocell_ino;
_enter("{%x:%u},%*.*s,",
AFS_FS_I(dir)->fid.vid, AFS_FS_I(dir)->fid.vnode,
namesz, namesz, dev_name ?: "");
_enter("");
sb = dir->i_sb;
as = sb->s_fs_info;
data.volume = as->volume;
data.fid.vid = as->volume->vid;
data.fid.unique = 0;
data.fid.vnode = 0;
if (as->volume) {
data.volume = as->volume;
data.fid.vid = as->volume->vid;
}
if (root) {
data.fid.vnode = 1;
data.fid.unique = 1;
} else {
data.fid.vnode = atomic_inc_return(&afs_autocell_ino);
data.fid.unique = 0;
}
inode = iget5_locked(sb, atomic_inc_return(&afs_autocell_ino),
afs_iget5_autocell_test, afs_iget5_set,
inode = iget5_locked(sb, data.fid.vnode,
afs_iget5_pseudo_dir_test, afs_iget5_set,
&data);
if (!inode) {
_leave(" = -ENOMEM");
@ -211,7 +214,12 @@ struct inode *afs_iget_autocell(struct inode *dir, const char *dev_name,
inode->i_size = 0;
inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
inode->i_op = &afs_autocell_inode_operations;
if (root) {
inode->i_op = &afs_dynroot_inode_operations;
inode->i_fop = &afs_dynroot_file_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;
@ -223,8 +231,12 @@ struct inode *afs_iget_autocell(struct inode *dir, const char *dev_name,
inode->i_generation = 0;
set_bit(AFS_VNODE_PSEUDODIR, &vnode->flags);
set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
inode->i_flags |= S_AUTOMOUNT | S_NOATIME;
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;

14
fs/afs/internal.h
View File

@ -36,6 +36,7 @@ struct afs_mount_params {
bool rwpath; /* T if the parent should be considered R/W */
bool force; /* T to force cell type */
bool autocell; /* T if set auto mount operation */
bool dyn_root; /* T if dynamic root */
afs_voltype_t type; /* type of volume requested */
int volnamesz; /* size of volume name */
const char *volname; /* name of volume to mount */
@ -186,6 +187,7 @@ struct afs_super_info {
struct afs_net *net; /* Network namespace */
struct afs_cell *cell; /* The cell in which the volume resides */
struct afs_volume *volume; /* volume record */
bool dyn_root; /* True if dynamic root */
};
static inline struct afs_super_info *AFS_FS_S(struct super_block *sb)
@ -634,10 +636,13 @@ extern bool afs_cm_incoming_call(struct afs_call *);
/*
* dir.c
*/
extern bool afs_dir_check_page(struct inode *, struct page *);
extern const struct inode_operations afs_dir_inode_operations;
extern const struct dentry_operations afs_fs_dentry_operations;
extern const struct file_operations afs_dir_file_operations;
extern const struct inode_operations afs_dir_inode_operations;
extern const struct file_operations afs_dynroot_file_operations;
extern const struct inode_operations afs_dynroot_inode_operations;
extern const struct dentry_operations afs_fs_dentry_operations;
extern bool afs_dir_check_page(struct inode *, struct page *);
/*
* file.c
@ -695,8 +700,7 @@ extern int afs_fs_get_capabilities(struct afs_net *, struct afs_server *,
*/
extern int afs_fetch_status(struct afs_vnode *, struct key *);
extern int afs_iget5_test(struct inode *, void *);
extern struct inode *afs_iget_autocell(struct inode *, const char *, int,
struct key *);
extern struct inode *afs_iget_pseudo_dir(struct super_block *, bool);
extern struct inode *afs_iget(struct super_block *, struct key *,
struct afs_fid *, struct afs_file_status *,
struct afs_callback *,

20
fs/afs/mntpt.c
View File

@ -72,7 +72,7 @@ static int afs_mntpt_open(struct inode *inode, struct file *file)
*/
static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
{
struct afs_super_info *super;
struct afs_super_info *as;
struct vfsmount *mnt;
struct afs_vnode *vnode;
struct page *page;
@ -104,13 +104,13 @@ static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
goto error_no_page;
if (mntpt->d_name.name[0] == '.') {
devname[0] = '#';
memcpy(devname + 1, mntpt->d_name.name, size - 1);
devname[0] = '%';
memcpy(devname + 1, mntpt->d_name.name + 1, size - 1);
memcpy(devname + size, afs_root_cell,
sizeof(afs_root_cell));
rwpath = true;
} else {
devname[0] = '%';
devname[0] = '#';
memcpy(devname + 1, mntpt->d_name.name, size);
memcpy(devname + size + 1, afs_root_cell,
sizeof(afs_root_cell));
@ -142,11 +142,13 @@ static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
}
/* work out what options we want */
super = AFS_FS_S(mntpt->d_sb);
memcpy(options, "cell=", 5);
strcpy(options + 5, super->volume->cell->name);
if (super->volume->type == AFSVL_RWVOL || rwpath)
strcat(options, ",rwpath");
as = AFS_FS_S(mntpt->d_sb);
if (as->cell) {
memcpy(options, "cell=", 5);
strcpy(options + 5, as->cell->name);
if ((as->volume && as->volume->type == AFSVL_RWVOL) || rwpath)
strcat(options, ",rwpath");
}
/* try and do the mount */
_debug("--- attempting mount %s -o %s ---", devname, options);

132
fs/afs/super.c
View File

@ -64,6 +64,7 @@ static atomic_t afs_count_active_inodes;
enum {
afs_no_opt,
afs_opt_cell,
afs_opt_dyn,
afs_opt_rwpath,
afs_opt_vol,
afs_opt_autocell,
@ -71,6 +72,7 @@ enum {
static const match_table_t afs_options_list = {
{ afs_opt_cell, "cell=%s" },
{ afs_opt_dyn, "dyn" },
{ afs_opt_rwpath, "rwpath" },
{ afs_opt_vol, "vol=%s" },
{ afs_opt_autocell, "autocell" },
@ -148,6 +150,11 @@ static int afs_show_devname(struct seq_file *m, struct dentry *root)
const char *suf = "";
char pref = '%';
if (as->dyn_root) {
seq_puts(m, "none");
return 0;
}
switch (volume->type) {
case AFSVL_RWVOL:
break;
@ -171,8 +178,12 @@ static int afs_show_devname(struct seq_file *m, struct dentry *root)
*/
static int afs_show_options(struct seq_file *m, struct dentry *root)
{
struct afs_super_info *as = AFS_FS_S(root->d_sb);
if (as->dyn_root)
seq_puts(m, ",dyn");
if (test_bit(AFS_VNODE_AUTOCELL, &AFS_FS_I(d_inode(root))->flags))
seq_puts(m, "autocell");
seq_puts(m, ",autocell");
return 0;
}
@ -212,7 +223,7 @@ static int afs_parse_options(struct afs_mount_params *params,
break;
case afs_opt_rwpath:
params->rwpath = 1;
params->rwpath = true;
break;
case afs_opt_vol:
@ -220,7 +231,11 @@ static int afs_parse_options(struct afs_mount_params *params,
break;
case afs_opt_autocell:
params->autocell = 1;
params->autocell = true;
break;
case afs_opt_dyn:
params->dyn_root = true;
break;
default:
@ -254,7 +269,7 @@ static int afs_parse_device_name(struct afs_mount_params *params,
int cellnamesz;
_enter(",%s", name);
if (!name) {
printk(KERN_ERR "kAFS: no volume name specified\n");
return -EINVAL;
@ -336,7 +351,14 @@ static int afs_test_super(struct super_block *sb, void *data)
struct afs_super_info *as1 = data;
struct afs_super_info *as = AFS_FS_S(sb);
return as->net == as1->net && as->volume->vid == as1->volume->vid;
return (as->net == as1->net &&
as->volume &&
as->volume->vid == as1->volume->vid);
}
static int afs_dynroot_test_super(struct super_block *sb, void *data)
{
return false;
}
static int afs_set_super(struct super_block *sb, void *data)
@ -365,24 +387,30 @@ static int afs_fill_super(struct super_block *sb,
sb->s_blocksize_bits = PAGE_SHIFT;
sb->s_magic = AFS_FS_MAGIC;
sb->s_op = &afs_super_ops;
sb->s_xattr = afs_xattr_handlers;
if (!as->dyn_root)
sb->s_xattr = afs_xattr_handlers;
ret = super_setup_bdi(sb);
if (ret)
return ret;
sb->s_bdi->ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_SIZE;
sprintf(sb->s_id, "%u", as->volume->vid);
afs_activate_volume(as->volume);
/* allocate the root inode and dentry */
fid.vid = as->volume->vid;
fid.vnode = 1;
fid.unique = 1;
inode = afs_iget(sb, params->key, &fid, NULL, NULL, NULL);
if (as->dyn_root) {
inode = afs_iget_pseudo_dir(sb, true);
sb->s_flags |= SB_RDONLY;
} else {
sprintf(sb->s_id, "%u", as->volume->vid);
afs_activate_volume(as->volume);
fid.vid = as->volume->vid;
fid.vnode = 1;
fid.unique = 1;
inode = afs_iget(sb, params->key, &fid, NULL, NULL, NULL);
}
if (IS_ERR(inode))
return PTR_ERR(inode);
if (params->autocell)
if (params->autocell || params->dyn_root)
set_bit(AFS_VNODE_AUTOCELL, &AFS_FS_I(inode)->flags);
ret = -ENOMEM;
@ -407,7 +435,10 @@ static struct afs_super_info *afs_alloc_sbi(struct afs_mount_params *params)
as = kzalloc(sizeof(struct afs_super_info), GFP_KERNEL);
if (as) {
as->net = afs_get_net(params->net);
as->cell = afs_get_cell(params->cell);
if (params->dyn_root)
as->dyn_root = true;
else
as->cell = afs_get_cell(params->cell);
}
return as;
}
@ -451,18 +482,20 @@ static struct dentry *afs_mount(struct file_system_type *fs_type,
goto error;
}
ret = afs_parse_device_name(&params, dev_name);
if (ret < 0)
goto error;
if (!params.dyn_root) {
ret = afs_parse_device_name(&params, dev_name);
if (ret < 0)
goto error;
/* try and do the mount securely */
key = afs_request_key(params.cell);
if (IS_ERR(key)) {
_leave(" = %ld [key]", PTR_ERR(key));
ret = PTR_ERR(key);
goto error;
/* try and do the mount securely */
key = afs_request_key(params.cell);
if (IS_ERR(key)) {
_leave(" = %ld [key]", PTR_ERR(key));
ret = PTR_ERR(key);
goto error;
}
params.key = key;
}
params.key = key;
/* allocate a superblock info record */
ret = -ENOMEM;
@ -470,20 +503,25 @@ static struct dentry *afs_mount(struct file_system_type *fs_type,
if (!as)
goto error_key;
/* Assume we're going to need a volume record; at the very least we can
* use it to update the volume record if we have one already. This
* checks that the volume exists within the cell.
*/
candidate = afs_create_volume(&params);
if (IS_ERR(candidate)) {
ret = PTR_ERR(candidate);
goto error_as;
if (!params.dyn_root) {
/* Assume we're going to need a volume record; at the very
* least we can use it to update the volume record if we have
* one already. This checks that the volume exists within the
* cell.
*/
candidate = afs_create_volume(&params);
if (IS_ERR(candidate)) {
ret = PTR_ERR(candidate);
goto error_as;
}
as->volume = candidate;
}
as->volume = candidate;
/* allocate a deviceless superblock */
sb = sget(fs_type, afs_test_super, afs_set_super, flags, as);
sb = sget(fs_type,
as->dyn_root ? afs_dynroot_test_super : afs_test_super,
afs_set_super, flags, as);
if (IS_ERR(sb)) {
ret = PTR_ERR(sb);
goto error_as;
@ -529,9 +567,11 @@ static void afs_kill_super(struct super_block *sb)
/* Clear the callback interests (which will do ilookup5) before
* deactivating the superblock.
*/
afs_clear_callback_interests(as->net, as->volume->servers);
if (as->volume)
afs_clear_callback_interests(as->net, as->volume->servers);
kill_anon_super(sb);
afs_deactivate_volume(as->volume);
if (as->volume)
afs_deactivate_volume(as->volume);
afs_destroy_sbi(as);
}
@ -619,12 +659,24 @@ static void afs_destroy_inode(struct inode *inode)
*/
static int afs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
struct afs_super_info *as = AFS_FS_S(dentry->d_sb);
struct afs_fs_cursor fc;
struct afs_volume_status vs;
struct afs_vnode *vnode = AFS_FS_I(d_inode(dentry));
struct key *key;
int ret;
buf->f_type = dentry->d_sb->s_magic;
buf->f_bsize = AFS_BLOCK_SIZE;
buf->f_namelen = AFSNAMEMAX - 1;
if (as->dyn_root) {
buf->f_blocks = 1;
buf->f_bavail = 0;
buf->f_bfree = 0;
return 0;
}
key = afs_request_key(vnode->volume->cell);
if (IS_ERR(key))
return PTR_ERR(key);
@ -645,10 +697,6 @@ static int afs_statfs(struct dentry *dentry, struct kstatfs *buf)
key_put(key);
if (ret == 0) {
buf->f_type = dentry->d_sb->s_magic;
buf->f_bsize = AFS_BLOCK_SIZE;
buf->f_namelen = AFSNAMEMAX - 1;
if (vs.max_quota == 0)
buf->f_blocks = vs.part_max_blocks;
else

22
net/dns_resolver/dns_query.c
View File

@ -52,11 +52,11 @@
* @name: Name to look up
* @namelen: Length of name
* @options: Request options (or NULL if no options)
* @_result: Where to place the returned data.
* @_result: Where to place the returned data (or NULL)
* @_expiry: Where to store the result expiry time (or NULL)
*
* The data will be returned in the pointer at *result, and the caller is
* responsible for freeing it.
* The data will be returned in the pointer at *result, if provided, and the
* caller is responsible for freeing it.
*
* The description should be of the form "[<query_type>:]<domain_name>", and
* the options need to be appropriate for the query type requested. If no
@ -81,7 +81,7 @@ int dns_query(const char *type, const char *name, size_t namelen,
kenter("%s,%*.*s,%zu,%s",
type, (int)namelen, (int)namelen, name, namelen, options);
if (!name || namelen == 0 || !_result)
if (!name || namelen == 0)
return -EINVAL;
/* construct the query key description as "[<type>:]<name>" */
@ -146,13 +146,15 @@ int dns_query(const char *type, const char *name, size_t namelen,
upayload = user_key_payload_locked(rkey);
len = upayload->datalen;
ret = -ENOMEM;
*_result = kmalloc(len + 1, GFP_KERNEL);
if (!*_result)
goto put;
if (_result) {
ret = -ENOMEM;
*_result = kmalloc(len + 1, GFP_KERNEL);
if (!*_result)
goto put;
memcpy(*_result, upayload->data, len);
(*_result)[len] = '\0';
memcpy(*_result, upayload->data, len);
(*_result)[len] = '\0';
}
if (_expiry)
*_expiry = rkey->expiry;