/*
* Copyright (C) 2006-2009 Red Hat, Inc.
*
* This file is released under the LGPL.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <linux/workqueue.h>
#include <linux/connector.h>
#include <linux/device-mapper.h>
#include <linux/dm-log-userspace.h>
#include "dm-log-userspace-transfer.h"
static uint32_t dm_ulog_seq;
/*
* Netlink/Connector is an unreliable protocol. How long should
* we wait for a response before assuming it was lost and retrying?
* (If we do receive a response after this time, it will be discarded
* and the response to the resent request will be waited for.
*/
#define DM_ULOG_RETRY_TIMEOUT (15 * HZ)
/*
* Pre-allocated space for speed
*/
#define DM_ULOG_PREALLOCED_SIZE 512
static struct cn_msg *prealloced_cn_msg;
static struct dm_ulog_request *prealloced_ulog_tfr;
static struct cb_id ulog_cn_id = {
.idx = CN_IDX_DM,
.val = CN_VAL_DM_USERSPACE_LOG
};
static DEFINE_MUTEX(dm_ulog_lock);
struct receiving_pkg {
struct list_head list;
struct completion complete;
uint32_t seq;
int error;
size_t *data_size;
char *data;
};
static DEFINE_SPINLOCK(receiving_list_lock);
static struct list_head receiving_list;
static int dm_ulog_sendto_server(struct dm_ulog_request *tfr)
{
int r;
struct cn_msg *msg = prealloced_cn_msg;
memset(msg, 0, sizeof(struct cn_msg));
msg->id.idx = ulog_cn_id.idx;
msg->id.val = ulog_cn_id.val;
msg->ack = 0;
msg->seq = tfr->seq;
msg->len = sizeof(struct dm_ulog_request) + tfr->data_size;
r = cn_netlink_send(msg, 0, gfp_any());
return r;
}
/*
* Parameters for this function can be either msg or tfr, but not
* both. This function fills in the reply for a waiting request.
* If just msg is given, then the reply is simply an ACK from userspace
* that the request was received.
*
* Returns: 0 on success, -ENOENT on failure
*/
static int fill_pkg(struct cn_msg *msg, struct dm_ulog_request *tfr)
{
uint32_t rtn_seq = (msg) ? msg->seq : (tfr) ? tfr->seq : 0;
struct receiving_pkg *pkg;
/*
* The 'receiving_pkg' entries in this list are statically
* allocated on the stack in 'dm_consult_userspace'.
* Each process that is waiting for a reply from the user
* space server will have an entry in this list.
*
* We are safe to do it this way because the stack space
* is unique to each process, but still addressable by
* other processes.
*/
list_for_each_entry(pkg, &receiving_list, list) {
if (rtn_seq != pkg->seq)
continue;
if (msg) {
pkg->error = -msg->ack;
/*
* If we are trying again, we will need to know our
* storage capacity. Otherwise, along with the
* error code, we make explicit that we have no data.
*/
if (pkg->error != -EAGAIN)
*(pkg->data_size) = 0;
} else if (tfr->data_size > *(pkg->data_size)) {
DMERR("Insufficient space to receive package [%u] "
"(%u vs %zu)", tfr->request_type,
tfr->data_size, *(pkg->data_size));
*(pkg->data_size) = 0;
pkg->error = -ENOSPC;
} else {
pkg->error = tfr->error;
memcpy(pkg->data, tfr->data, tfr->data_size);
*(pkg->data_size) = tfr->data_size;
}
complete(&pkg->complete);
return 0;
}
return -ENOENT;
}
/*
* This is the connector callback that delivers data
* that was sent from userspace.
*/
static void cn_ulog_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
{
struct dm_ulog_request *tfr = (struct dm_ulog_request *)(msg + 1);
if (!cap_raised(current_cap(), CAP_SYS_ADMIN))
return;
spin_lock(&receiving_list_lock);
if (msg->len == 0)
fill_pkg(msg, NULL);
else if (msg->len < sizeof(*tfr))
DMERR("Incomplete message received (expected %u, got %u): [%u]",
(unsigned)sizeof(*tfr), msg->len, msg->seq);
else
fill_pkg(NULL, tfr);
spin_unlock(&receiving_list_lock);
}
/**
* dm_consult_userspace
* @uuid: log's universal unique identifier (must be DM_UUID_LEN in size)
* @luid: log's local unique identifier
* @request_type: found in include/linux/dm-log-userspace.h
* @data: data to tx to the server
* @data_size: size of data in bytes
* @rdata: place to put return data from server
* @rdata_size: value-result (amount of space given/amount of space used)
*
* rdata_size is undefined on failure.
*
* Memory used to communicate with userspace is zero'ed
* before populating to ensure that no unwanted bits leak
* from kernel space to user-space. All userspace log communications
* between kernel and user space go through this function.
*
* Returns: 0 on success, -EXXX on failure
**/
int dm_consult_userspace(const char *uuid, uint64_t luid, int request_type,
char *data, size_t data_size,
char *rdata, size_t *rdata_size)
{
int r = 0;
size_t dummy = 0;
int overhead_size = sizeof(struct dm_ulog_request) + sizeof(struct cn_msg);
struct dm_ulog_request *tfr = prealloced_ulog_tfr;
struct receiving_pkg pkg;
/*
* Given the space needed to hold the 'struct cn_msg' and
* 'struct dm_ulog_request' - do we have enough payload
* space remaining?
*/
if (data_size > (DM_ULOG_PREALLOCED_SIZE - overhead_size)) {
DMINFO("Size of tfr exceeds preallocated size");
return -EINVAL;
}
if (!rdata_size)
rdata_size = &dummy;
resend:
/*
* We serialize the sending of requests so we can
* use the preallocated space.
*/
mutex_lock(&dm_ulog_lock);
memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - sizeof(struct cn_msg));
memcpy(tfr->uuid, uuid, DM_UUID_LEN);
tfr->version = DM_ULOG_REQUEST_VERSION;
tfr->luid = luid;
tfr->seq = dm_ulog_seq++;
/*
* Must be valid request type (all other bits set to
* zero). This reserves other bits for possible future
* use.
*/
tfr->request_type = request_type & DM_ULOG_REQUEST_MASK;
tfr->data_size = data_size;
if (data && data_size)
memcpy(tfr->data, data, data_size);
memset(&pkg, 0, sizeof(pkg));
init_completion(&pkg.complete);
pkg.seq = tfr->seq;
pkg.data_size = rdata_size;
pkg.data = rdata;
spin_lock(&receiving_list_lock);
list_add(&(pkg.list), &receiving_list);
spin_unlock(&receiving_list_lock);
r = dm_ulog_sendto_server(tfr);
mutex_unlock(&dm_ulog_lock);
if (r) {
DMERR("Unable to send log request [%u] to userspace: %d",
request_type, r);
spin_lock(&receiving_list_lock);
list_del_init(&(pkg.list));
spin_unlock(&receiving_list_lock);
goto out;
}
r = wait_for_completion_timeout(&(pkg.complete), DM_ULOG_RETRY_TIMEOUT);
spin_lock(&receiving_list_lock);
list_del_init(&(pkg.list));
spin_unlock(&receiving_list_lock);
if (!r) {
DMWARN("[%s] Request timed out: [%u/%u] - retrying",
(strlen(uuid) > 8) ?
(uuid + (strlen(uuid) - 8)) : (uuid),
request_type, pkg.seq);
goto resend;
}
r = pkg.error;
if (r == -EAGAIN)
goto resend;
out:
return r;
}
int dm_ulog_tfr_init(void)
{
int r;
void *prealloced;
INIT_LIST_HEAD(&receiving_list);
prealloced = kmalloc(DM_ULOG_PREALLOCED_SIZE, GFP_KERNEL);
if (!prealloced)
return -ENOMEM;
prealloced_cn_msg = prealloced;
prealloced_ulog_tfr = prealloced + sizeof(struct cn_msg);
r = cn_add_callback(&ulog_cn_id, "dmlogusr", cn_ulog_callback);
if (r) {
cn_del_callback(&ulog_cn_id);
return r;
}
return 0;
}
void dm_ulog_tfr_exit(void)
{
cn_del_callback(&ulog_cn_id);
kfree(prealloced_cn_msg);
}
