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