staging: iio: Documentation fixes

[zen-stable.git] / fs / cifs / transport.c

/*
 *   fs/cifs/transport.c
 *
 *   Copyright (C) International Business Machines  Corp., 2002,2008
 *   Author(s): Steve French (sfrench@us.ibm.com)
 *   Jeremy Allison (jra@samba.org) 2006.
 *
 *   This library is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as published
 *   by the Free Software Foundation; either version 2.1 of the License, or
 *   (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
 *   the GNU Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public License
 *   along with this library; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include <linux/fs.h>
#include <linux/list.h>
#include <linux/gfp.h>
#include <linux/wait.h>
#include <linux/net.h>
#include <linux/delay.h>
#include <asm/uaccess.h>
#include <asm/processor.h>
#include <linux/mempool.h>
#include "cifspdu.h"
#include "cifsglob.h"
#include "cifsproto.h"
#include "cifs_debug.h"

extern mempool_t *cifs_mid_poolp;
extern struct kmem_cache *cifs_oplock_cachep;

static struct mid_q_entry *
AllocMidQEntry(const struct smb_hdr *smb_buffer, struct TCP_Server_Info *server)
{
        struct mid_q_entry *temp;

        if (server == NULL) {
                cERROR(1, ("Null TCP session in AllocMidQEntry"));
                return NULL;
        }

        temp = mempool_alloc(cifs_mid_poolp, GFP_NOFS);
        if (temp == NULL)
                return temp;
        else {
                memset(temp, 0, sizeof(struct mid_q_entry));
                temp->mid = smb_buffer->Mid;    /* always LE */
                temp->pid = current->pid;
                temp->command = smb_buffer->Command;
                cFYI(1, ("For smb_command %d", temp->command));
        /*      do_gettimeofday(&temp->when_sent);*/ /* easier to use jiffies */
                /* when mid allocated can be before when sent */
                temp->when_alloc = jiffies;
                temp->tsk = current;
        }

        spin_lock(&GlobalMid_Lock);
        list_add_tail(&temp->qhead, &server->pending_mid_q);
        atomic_inc(&midCount);
        temp->midState = MID_REQUEST_ALLOCATED;
        spin_unlock(&GlobalMid_Lock);
        return temp;
}

static void
DeleteMidQEntry(struct mid_q_entry *midEntry)
{
#ifdef CONFIG_CIFS_STATS2
        unsigned long now;
#endif
        spin_lock(&GlobalMid_Lock);
        midEntry->midState = MID_FREE;
        list_del(&midEntry->qhead);
        atomic_dec(&midCount);
        spin_unlock(&GlobalMid_Lock);
        if (midEntry->largeBuf)
                cifs_buf_release(midEntry->resp_buf);
        else
                cifs_small_buf_release(midEntry->resp_buf);
#ifdef CONFIG_CIFS_STATS2
        now = jiffies;
        /* commands taking longer than one second are indications that
           something is wrong, unless it is quite a slow link or server */
        if ((now - midEntry->when_alloc) > HZ) {
                if ((cifsFYI & CIFS_TIMER) &&
                   (midEntry->command != SMB_COM_LOCKING_ANDX)) {
                        printk(KERN_DEBUG " CIFS slow rsp: cmd %d mid %d",
                               midEntry->command, midEntry->mid);
                        printk(" A: 0x%lx S: 0x%lx R: 0x%lx\n",
                               now - midEntry->when_alloc,
                               now - midEntry->when_sent,
                               now - midEntry->when_received);
                }
        }
#endif
        mempool_free(midEntry, cifs_mid_poolp);
}

static int
smb_sendv(struct TCP_Server_Info *server, struct kvec *iov, int n_vec)
{
        int rc = 0;
        int i = 0;
        struct msghdr smb_msg;
        struct smb_hdr *smb_buffer = iov[0].iov_base;
        unsigned int len = iov[0].iov_len;
        unsigned int total_len;
        int first_vec = 0;
        unsigned int smb_buf_length = smb_buffer->smb_buf_length;
        struct socket *ssocket = server->ssocket;

        if (ssocket == NULL)
                return -ENOTSOCK; /* BB eventually add reconnect code here */

        smb_msg.msg_name = (struct sockaddr *) &server->addr.sockAddr;
        smb_msg.msg_namelen = sizeof(struct sockaddr);
        smb_msg.msg_control = NULL;
        smb_msg.msg_controllen = 0;
        if (server->noblocksnd)
                smb_msg.msg_flags = MSG_DONTWAIT + MSG_NOSIGNAL;
        else
                smb_msg.msg_flags = MSG_NOSIGNAL;

        /* smb header is converted in header_assemble. bcc and rest of SMB word
           area, and byte area if necessary, is converted to littleendian in
           cifssmb.c and RFC1001 len is converted to bigendian in smb_send
           Flags2 is converted in SendReceive */


        total_len = 0;
        for (i = 0; i < n_vec; i++)
                total_len += iov[i].iov_len;

        smb_buffer->smb_buf_length = cpu_to_be32(smb_buffer->smb_buf_length);
        cFYI(1, ("Sending smb:  total_len %d", total_len));
        dump_smb(smb_buffer, len);

        i = 0;
        while (total_len) {
                rc = kernel_sendmsg(ssocket, &smb_msg, &iov[first_vec],
                                    n_vec - first_vec, total_len);
                if ((rc == -ENOSPC) || (rc == -EAGAIN)) {
                        i++;
                        /* if blocking send we try 3 times, since each can block
                           for 5 seconds. For nonblocking  we have to try more
                           but wait increasing amounts of time allowing time for
                           socket to clear.  The overall time we wait in either
                           case to send on the socket is about 15 seconds.
                           Similarly we wait for 15 seconds for
                           a response from the server in SendReceive[2]
                           for the server to send a response back for
                           most types of requests (except SMB Write
                           past end of file which can be slow, and
                           blocking lock operations). NFS waits slightly longer
                           than CIFS, but this can make it take longer for
                           nonresponsive servers to be detected and 15 seconds
                           is more than enough time for modern networks to
                           send a packet.  In most cases if we fail to send
                           after the retries we will kill the socket and
                           reconnect which may clear the network problem.
                        */
                        if ((i >= 14) || (!server->noblocksnd && (i > 2))) {
                                cERROR(1,
                                   ("sends on sock %p stuck for 15 seconds",
                                    ssocket));
                                rc = -EAGAIN;
                                break;
                        }
                        msleep(1 << i);
                        continue;
                }
                if (rc < 0)
                        break;

                if (rc == total_len) {
                        total_len = 0;
                        break;
                } else if (rc > total_len) {
                        cERROR(1, ("sent %d requested %d", rc, total_len));
                        break;
                }
                if (rc == 0) {
                        /* should never happen, letting socket clear before
                           retrying is our only obvious option here */
                        cERROR(1, ("tcp sent no data"));
                        msleep(500);
                        continue;
                }
                total_len -= rc;
                /* the line below resets i */
                for (i = first_vec; i < n_vec; i++) {
                        if (iov[i].iov_len) {
                                if (rc > iov[i].iov_len) {
                                        rc -= iov[i].iov_len;
                                        iov[i].iov_len = 0;
                                } else {
                                        iov[i].iov_base += rc;
                                        iov[i].iov_len -= rc;
                                        first_vec = i;
                                        break;
                                }
                        }
                }
                i = 0; /* in case we get ENOSPC on the next send */
        }

        if ((total_len > 0) && (total_len != smb_buf_length + 4)) {
                cFYI(1, ("partial send (%d remaining), terminating session",
                        total_len));
                /* If we have only sent part of an SMB then the next SMB
                   could be taken as the remainder of this one.  We need
                   to kill the socket so the server throws away the partial
                   SMB */
                server->tcpStatus = CifsNeedReconnect;
        }

        if (rc < 0) {
                cERROR(1, ("Error %d sending data on socket to server", rc));
        } else
                rc = 0;

        /* Don't want to modify the buffer as a
           side effect of this call. */
        smb_buffer->smb_buf_length = smb_buf_length;

        return rc;
}

int
smb_send(struct TCP_Server_Info *server, struct smb_hdr *smb_buffer,
         unsigned int smb_buf_length)
{
        struct kvec iov;

        iov.iov_base = smb_buffer;
        iov.iov_len = smb_buf_length + 4;

        return smb_sendv(server, &iov, 1);
}

static int wait_for_free_request(struct cifsSesInfo *ses, const int long_op)
{
        if (long_op == CIFS_ASYNC_OP) {
                /* oplock breaks must not be held up */
                atomic_inc(&ses->server->inFlight);
                return 0;
        }

        spin_lock(&GlobalMid_Lock);
        while (1) {
                if (atomic_read(&ses->server->inFlight) >=
                                cifs_max_pending){
                        spin_unlock(&GlobalMid_Lock);
#ifdef CONFIG_CIFS_STATS2
                        atomic_inc(&ses->server->num_waiters);
#endif
                        wait_event(ses->server->request_q,
                                   atomic_read(&ses->server->inFlight)
                                     < cifs_max_pending);
#ifdef CONFIG_CIFS_STATS2
                        atomic_dec(&ses->server->num_waiters);
#endif
                        spin_lock(&GlobalMid_Lock);
                } else {
                        if (ses->server->tcpStatus == CifsExiting) {
                                spin_unlock(&GlobalMid_Lock);
                                return -ENOENT;
                        }

                        /* can not count locking commands against total
                           as they are allowed to block on server */

                        /* update # of requests on the wire to server */
                        if (long_op != CIFS_BLOCKING_OP)
                                atomic_inc(&ses->server->inFlight);
                        spin_unlock(&GlobalMid_Lock);
                        break;
                }
        }
        return 0;
}

static int allocate_mid(struct cifsSesInfo *ses, struct smb_hdr *in_buf,
                        struct mid_q_entry **ppmidQ)
{
        if (ses->server->tcpStatus == CifsExiting) {
                return -ENOENT;
        }

        if (ses->server->tcpStatus == CifsNeedReconnect) {
                cFYI(1, ("tcp session dead - return to caller to retry"));
                return -EAGAIN;
        }

        if (ses->status != CifsGood) {
                /* check if SMB session is bad because we are setting it up */
                if ((in_buf->Command != SMB_COM_SESSION_SETUP_ANDX) &&
                        (in_buf->Command != SMB_COM_NEGOTIATE))
                        return -EAGAIN;
                /* else ok - we are setting up session */
        }
        *ppmidQ = AllocMidQEntry(in_buf, ses->server);
        if (*ppmidQ == NULL)
                return -ENOMEM;
        return 0;
}

static int wait_for_response(struct cifsSesInfo *ses,
                        struct mid_q_entry *midQ,
                        unsigned long timeout,
                        unsigned long time_to_wait)
{
        unsigned long curr_timeout;

        for (;;) {
                curr_timeout = timeout + jiffies;
                wait_event_timeout(ses->server->response_q,
                        midQ->midState != MID_REQUEST_SUBMITTED, timeout);

                if (time_after(jiffies, curr_timeout) &&
                        (midQ->midState == MID_REQUEST_SUBMITTED) &&
                        ((ses->server->tcpStatus == CifsGood) ||
                         (ses->server->tcpStatus == CifsNew))) {

                        unsigned long lrt;

                        /* We timed out. Is the server still
                           sending replies ? */
                        spin_lock(&GlobalMid_Lock);
                        lrt = ses->server->lstrp;
                        spin_unlock(&GlobalMid_Lock);

                        /* Calculate time_to_wait past last receive time.
                         Although we prefer not to time out if the
                         server is still responding - we will time
                         out if the server takes more than 15 (or 45
                         or 180) seconds to respond to this request
                         and has not responded to any request from
                         other threads on the client within 10 seconds */
                        lrt += time_to_wait;
                        if (time_after(jiffies, lrt)) {
                                /* No replies for time_to_wait. */
                                cERROR(1, ("server not responding"));
                                return -1;
                        }
                } else {
                        return 0;
                }
        }
}


/*
 *
 * Send an SMB Request.  No response info (other than return code)
 * needs to be parsed.
 *
 * flags indicate the type of request buffer and how long to wait
 * and whether to log NT STATUS code (error) before mapping it to POSIX error
 *
 */
int
SendReceiveNoRsp(const unsigned int xid, struct cifsSesInfo *ses,
                struct smb_hdr *in_buf, int flags)
{
        int rc;
        struct kvec iov[1];
        int resp_buf_type;

        iov[0].iov_base = (char *)in_buf;
        iov[0].iov_len = in_buf->smb_buf_length + 4;
        flags |= CIFS_NO_RESP;
        rc = SendReceive2(xid, ses, iov, 1, &resp_buf_type, flags);
        cFYI(DBG2, ("SendRcvNoRsp flags %d rc %d", flags, rc));

        return rc;
}

int
SendReceive2(const unsigned int xid, struct cifsSesInfo *ses,
             struct kvec *iov, int n_vec, int *pRespBufType /* ret */,
             const int flags)
{
        int rc = 0;
        int long_op;
        unsigned int receive_len;
        unsigned long timeout;
        struct mid_q_entry *midQ;
        struct smb_hdr *in_buf = iov[0].iov_base;

        long_op = flags & CIFS_TIMEOUT_MASK;

        *pRespBufType = CIFS_NO_BUFFER;  /* no response buf yet */

        if ((ses == NULL) || (ses->server == NULL)) {
                cifs_small_buf_release(in_buf);
                cERROR(1, ("Null session"));
                return -EIO;
        }

        if (ses->server->tcpStatus == CifsExiting) {
                cifs_small_buf_release(in_buf);
                return -ENOENT;
        }

        /* Ensure that we do not send more than 50 overlapping requests
           to the same server. We may make this configurable later or
           use ses->maxReq */

        rc = wait_for_free_request(ses, long_op);
        if (rc) {
                cifs_small_buf_release(in_buf);
                return rc;
        }

        /* make sure that we sign in the same order that we send on this socket
           and avoid races inside tcp sendmsg code that could cause corruption
           of smb data */

        mutex_lock(&ses->server->srv_mutex);

        rc = allocate_mid(ses, in_buf, &midQ);
        if (rc) {
                mutex_unlock(&ses->server->srv_mutex);
                cifs_small_buf_release(in_buf);
                /* Update # of requests on wire to server */
                atomic_dec(&ses->server->inFlight);
                wake_up(&ses->server->request_q);
                return rc;
        }
        rc = cifs_sign_smb2(iov, n_vec, ses->server, &midQ->sequence_number);
        if (rc) {
                mutex_unlock(&ses->server->srv_mutex);
                cifs_small_buf_release(in_buf);
                goto out;
        }

        midQ->midState = MID_REQUEST_SUBMITTED;
#ifdef CONFIG_CIFS_STATS2
        atomic_inc(&ses->server->inSend);
#endif
        rc = smb_sendv(ses->server, iov, n_vec);
#ifdef CONFIG_CIFS_STATS2
        atomic_dec(&ses->server->inSend);
        midQ->when_sent = jiffies;
#endif

        mutex_unlock(&ses->server->srv_mutex);
        cifs_small_buf_release(in_buf);

        if (rc < 0)
                goto out;

        if (long_op == CIFS_STD_OP)
                timeout = 15 * HZ;
        else if (long_op == CIFS_VLONG_OP) /* e.g. slow writes past EOF */
                timeout = 180 * HZ;
        else if (long_op == CIFS_LONG_OP)
                timeout = 45 * HZ; /* should be greater than
                        servers oplock break timeout (about 43 seconds) */
        else if (long_op == CIFS_ASYNC_OP)
                goto out;
        else if (long_op == CIFS_BLOCKING_OP)
                timeout = 0x7FFFFFFF; /*  large, but not so large as to wrap */
        else {
                cERROR(1, ("unknown timeout flag %d", long_op));
                rc = -EIO;
                goto out;
        }

        /* wait for 15 seconds or until woken up due to response arriving or
           due to last connection to this server being unmounted */
        if (signal_pending(current)) {
                /* if signal pending do not hold up user for full smb timeout
                but we still give response a chance to complete */
                timeout = 2 * HZ;
        }

        /* No user interrupts in wait - wreaks havoc with performance */
        wait_for_response(ses, midQ, timeout, 10 * HZ);

        spin_lock(&GlobalMid_Lock);

        if (midQ->resp_buf == NULL) {
                cERROR(1, ("No response to cmd %d mid %d",
                        midQ->command, midQ->mid));
                if (midQ->midState == MID_REQUEST_SUBMITTED) {
                        if (ses->server->tcpStatus == CifsExiting)
                                rc = -EHOSTDOWN;
                        else {
                                ses->server->tcpStatus = CifsNeedReconnect;
                                midQ->midState = MID_RETRY_NEEDED;
                        }
                }

                if (rc != -EHOSTDOWN) {
                        if (midQ->midState == MID_RETRY_NEEDED) {
                                rc = -EAGAIN;
                                cFYI(1, ("marking request for retry"));
                        } else {
                                rc = -EIO;
                        }
                }
                spin_unlock(&GlobalMid_Lock);
                DeleteMidQEntry(midQ);
                /* Update # of requests on wire to server */
                atomic_dec(&ses->server->inFlight);
                wake_up(&ses->server->request_q);
                return rc;
        }

        spin_unlock(&GlobalMid_Lock);
        receive_len = midQ->resp_buf->smb_buf_length;

        if (receive_len > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE) {
                cERROR(1, ("Frame too large received.  Length: %d  Xid: %d",
                        receive_len, xid));
                rc = -EIO;
                goto out;
        }

        /* rcvd frame is ok */

        if (midQ->resp_buf &&
            (midQ->midState == MID_RESPONSE_RECEIVED)) {

                iov[0].iov_base = (char *)midQ->resp_buf;
                if (midQ->largeBuf)
                        *pRespBufType = CIFS_LARGE_BUFFER;
                else
                        *pRespBufType = CIFS_SMALL_BUFFER;
                iov[0].iov_len = receive_len + 4;

                dump_smb(midQ->resp_buf, 80);
                /* convert the length into a more usable form */
                if ((receive_len > 24) &&
                    (ses->server->secMode & (SECMODE_SIGN_REQUIRED |
                                             SECMODE_SIGN_ENABLED))) {
                        rc = cifs_verify_signature(midQ->resp_buf,
                                                &ses->server->mac_signing_key,
                                                midQ->sequence_number+1);
                        if (rc) {
                                cERROR(1, ("Unexpected SMB signature"));
                                /* BB FIXME add code to kill session */
                        }
                }

                /* BB special case reconnect tid and uid here? */
                rc = map_smb_to_linux_error(midQ->resp_buf,
                                            flags & CIFS_LOG_ERROR);

                /* convert ByteCount if necessary */
                if (receive_len >= sizeof(struct smb_hdr) - 4
                    /* do not count RFC1001 header */  +
                    (2 * midQ->resp_buf->WordCount) + 2 /* bcc */ )
                        BCC(midQ->resp_buf) =
                                le16_to_cpu(BCC_LE(midQ->resp_buf));
                if ((flags & CIFS_NO_RESP) == 0)
                        midQ->resp_buf = NULL;  /* mark it so buf will
                                                   not be freed by
                                                   DeleteMidQEntry */
        } else {
                rc = -EIO;
                cFYI(1, ("Bad MID state?"));
        }

out:
        DeleteMidQEntry(midQ);
        atomic_dec(&ses->server->inFlight);
        wake_up(&ses->server->request_q);

        return rc;
}

int
SendReceive(const unsigned int xid, struct cifsSesInfo *ses,
            struct smb_hdr *in_buf, struct smb_hdr *out_buf,
            int *pbytes_returned, const int long_op)
{
        int rc = 0;
        unsigned int receive_len;
        unsigned long timeout;
        struct mid_q_entry *midQ;

        if (ses == NULL) {
                cERROR(1, ("Null smb session"));
                return -EIO;
        }
        if (ses->server == NULL) {
                cERROR(1, ("Null tcp session"));
                return -EIO;
        }

        if (ses->server->tcpStatus == CifsExiting)
                return -ENOENT;

        /* Ensure that we do not send more than 50 overlapping requests
           to the same server. We may make this configurable later or
           use ses->maxReq */

        if (in_buf->smb_buf_length > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE - 4) {
                cERROR(1, ("Illegal length, greater than maximum frame, %d",
                           in_buf->smb_buf_length));
                return -EIO;
        }

        rc = wait_for_free_request(ses, long_op);
        if (rc)
                return rc;

        /* make sure that we sign in the same order that we send on this socket
           and avoid races inside tcp sendmsg code that could cause corruption
           of smb data */

        mutex_lock(&ses->server->srv_mutex);

        rc = allocate_mid(ses, in_buf, &midQ);
        if (rc) {
                mutex_unlock(&ses->server->srv_mutex);
                /* Update # of requests on wire to server */
                atomic_dec(&ses->server->inFlight);
                wake_up(&ses->server->request_q);
                return rc;
        }

        rc = cifs_sign_smb(in_buf, ses->server, &midQ->sequence_number);
        if (rc) {
                mutex_unlock(&ses->server->srv_mutex);
                goto out;
        }

        midQ->midState = MID_REQUEST_SUBMITTED;
#ifdef CONFIG_CIFS_STATS2
        atomic_inc(&ses->server->inSend);
#endif
        rc = smb_send(ses->server, in_buf, in_buf->smb_buf_length);
#ifdef CONFIG_CIFS_STATS2
        atomic_dec(&ses->server->inSend);
        midQ->when_sent = jiffies;
#endif
        mutex_unlock(&ses->server->srv_mutex);

        if (rc < 0)
                goto out;

        if (long_op == CIFS_STD_OP)
                timeout = 15 * HZ;
        /* wait for 15 seconds or until woken up due to response arriving or
           due to last connection to this server being unmounted */
        else if (long_op == CIFS_ASYNC_OP)
                goto out;
        else if (long_op == CIFS_VLONG_OP) /* writes past EOF can be slow */
                timeout = 180 * HZ;
        else if (long_op == CIFS_LONG_OP)
                timeout = 45 * HZ; /* should be greater than
                        servers oplock break timeout (about 43 seconds) */
        else if (long_op == CIFS_BLOCKING_OP)
                timeout = 0x7FFFFFFF; /* large but no so large as to wrap */
        else {
                cERROR(1, ("unknown timeout flag %d", long_op));
                rc = -EIO;
                goto out;
        }

        if (signal_pending(current)) {
                /* if signal pending do not hold up user for full smb timeout
                but we still give response a chance to complete */
                timeout = 2 * HZ;
        }

        /* No user interrupts in wait - wreaks havoc with performance */
        wait_for_response(ses, midQ, timeout, 10 * HZ);

        spin_lock(&GlobalMid_Lock);
        if (midQ->resp_buf == NULL) {
                cERROR(1, ("No response for cmd %d mid %d",
                          midQ->command, midQ->mid));
                if (midQ->midState == MID_REQUEST_SUBMITTED) {
                        if (ses->server->tcpStatus == CifsExiting)
                                rc = -EHOSTDOWN;
                        else {
                                ses->server->tcpStatus = CifsNeedReconnect;
                                midQ->midState = MID_RETRY_NEEDED;
                        }
                }

                if (rc != -EHOSTDOWN) {
                        if (midQ->midState == MID_RETRY_NEEDED) {
                                rc = -EAGAIN;
                                cFYI(1, ("marking request for retry"));
                        } else {
                                rc = -EIO;
                        }
                }
                spin_unlock(&GlobalMid_Lock);
                DeleteMidQEntry(midQ);
                /* Update # of requests on wire to server */
                atomic_dec(&ses->server->inFlight);
                wake_up(&ses->server->request_q);
                return rc;
        }

        spin_unlock(&GlobalMid_Lock);
        receive_len = midQ->resp_buf->smb_buf_length;

        if (receive_len > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE) {
                cERROR(1, ("Frame too large received.  Length: %d  Xid: %d",
                        receive_len, xid));
                rc = -EIO;
                goto out;
        }

        /* rcvd frame is ok */

        if (midQ->resp_buf && out_buf
            && (midQ->midState == MID_RESPONSE_RECEIVED)) {
                out_buf->smb_buf_length = receive_len;
                memcpy((char *)out_buf + 4,
                       (char *)midQ->resp_buf + 4,
                       receive_len);

                dump_smb(out_buf, 92);
                /* convert the length into a more usable form */
                if ((receive_len > 24) &&
                    (ses->server->secMode & (SECMODE_SIGN_REQUIRED |
                                             SECMODE_SIGN_ENABLED))) {
                        rc = cifs_verify_signature(out_buf,
                                                &ses->server->mac_signing_key,
                                                midQ->sequence_number+1);
                        if (rc) {
                                cERROR(1, ("Unexpected SMB signature"));
                                /* BB FIXME add code to kill session */
                        }
                }

                *pbytes_returned = out_buf->smb_buf_length;

                /* BB special case reconnect tid and uid here? */
                rc = map_smb_to_linux_error(out_buf, 0 /* no log */ );

                /* convert ByteCount if necessary */
                if (receive_len >= sizeof(struct smb_hdr) - 4
                    /* do not count RFC1001 header */  +
                    (2 * out_buf->WordCount) + 2 /* bcc */ )
                        BCC(out_buf) = le16_to_cpu(BCC_LE(out_buf));
        } else {
                rc = -EIO;
                cERROR(1, ("Bad MID state?"));
        }

out:
        DeleteMidQEntry(midQ);
        atomic_dec(&ses->server->inFlight);
        wake_up(&ses->server->request_q);

        return rc;
}

/* Send an NT_CANCEL SMB to cause the POSIX blocking lock to return. */

static int
send_nt_cancel(struct cifsTconInfo *tcon, struct smb_hdr *in_buf,
                struct mid_q_entry *midQ)
{
        int rc = 0;
        struct cifsSesInfo *ses = tcon->ses;
        __u16 mid = in_buf->Mid;

        header_assemble(in_buf, SMB_COM_NT_CANCEL, tcon, 0);
        in_buf->Mid = mid;
        mutex_lock(&ses->server->srv_mutex);
        rc = cifs_sign_smb(in_buf, ses->server, &midQ->sequence_number);
        if (rc) {
                mutex_unlock(&ses->server->srv_mutex);
                return rc;
        }
        rc = smb_send(ses->server, in_buf, in_buf->smb_buf_length);
        mutex_unlock(&ses->server->srv_mutex);
        return rc;
}

/* We send a LOCKINGX_CANCEL_LOCK to cause the Windows
   blocking lock to return. */

static int
send_lock_cancel(const unsigned int xid, struct cifsTconInfo *tcon,
                        struct smb_hdr *in_buf,
                        struct smb_hdr *out_buf)
{
        int bytes_returned;
        struct cifsSesInfo *ses = tcon->ses;
        LOCK_REQ *pSMB = (LOCK_REQ *)in_buf;

        /* We just modify the current in_buf to change
           the type of lock from LOCKING_ANDX_SHARED_LOCK
           or LOCKING_ANDX_EXCLUSIVE_LOCK to
           LOCKING_ANDX_CANCEL_LOCK. */

        pSMB->LockType = LOCKING_ANDX_CANCEL_LOCK|LOCKING_ANDX_LARGE_FILES;
        pSMB->Timeout = 0;
        pSMB->hdr.Mid = GetNextMid(ses->server);

        return SendReceive(xid, ses, in_buf, out_buf,
                        &bytes_returned, CIFS_STD_OP);
}

int
SendReceiveBlockingLock(const unsigned int xid, struct cifsTconInfo *tcon,
            struct smb_hdr *in_buf, struct smb_hdr *out_buf,
            int *pbytes_returned)
{
        int rc = 0;
        int rstart = 0;
        unsigned int receive_len;
        struct mid_q_entry *midQ;
        struct cifsSesInfo *ses;

        if (tcon == NULL || tcon->ses == NULL) {
                cERROR(1, ("Null smb session"));
                return -EIO;
        }
        ses = tcon->ses;

        if (ses->server == NULL) {
                cERROR(1, ("Null tcp session"));
                return -EIO;
        }

        if (ses->server->tcpStatus == CifsExiting)
                return -ENOENT;

        /* Ensure that we do not send more than 50 overlapping requests
           to the same server. We may make this configurable later or
           use ses->maxReq */

        if (in_buf->smb_buf_length > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE - 4) {
                cERROR(1, ("Illegal length, greater than maximum frame, %d",
                           in_buf->smb_buf_length));
                return -EIO;
        }

        rc = wait_for_free_request(ses, CIFS_BLOCKING_OP);
        if (rc)
                return rc;

        /* make sure that we sign in the same order that we send on this socket
           and avoid races inside tcp sendmsg code that could cause corruption
           of smb data */

        mutex_lock(&ses->server->srv_mutex);

        rc = allocate_mid(ses, in_buf, &midQ);
        if (rc) {
                mutex_unlock(&ses->server->srv_mutex);
                return rc;
        }

        rc = cifs_sign_smb(in_buf, ses->server, &midQ->sequence_number);
        if (rc) {
                DeleteMidQEntry(midQ);
                mutex_unlock(&ses->server->srv_mutex);
                return rc;
        }

        midQ->midState = MID_REQUEST_SUBMITTED;
#ifdef CONFIG_CIFS_STATS2
        atomic_inc(&ses->server->inSend);
#endif
        rc = smb_send(ses->server, in_buf, in_buf->smb_buf_length);
#ifdef CONFIG_CIFS_STATS2
        atomic_dec(&ses->server->inSend);
        midQ->when_sent = jiffies;
#endif
        mutex_unlock(&ses->server->srv_mutex);

        if (rc < 0) {
                DeleteMidQEntry(midQ);
                return rc;
        }

        /* Wait for a reply - allow signals to interrupt. */
        rc = wait_event_interruptible(ses->server->response_q,
                (!(midQ->midState == MID_REQUEST_SUBMITTED)) ||
                ((ses->server->tcpStatus != CifsGood) &&
                 (ses->server->tcpStatus != CifsNew)));

        /* Were we interrupted by a signal ? */
        if ((rc == -ERESTARTSYS) &&
                (midQ->midState == MID_REQUEST_SUBMITTED) &&
                ((ses->server->tcpStatus == CifsGood) ||
                 (ses->server->tcpStatus == CifsNew))) {

                if (in_buf->Command == SMB_COM_TRANSACTION2) {
                        /* POSIX lock. We send a NT_CANCEL SMB to cause the
                           blocking lock to return. */

                        rc = send_nt_cancel(tcon, in_buf, midQ);
                        if (rc) {
                                DeleteMidQEntry(midQ);
                                return rc;
                        }
                } else {
                        /* Windows lock. We send a LOCKINGX_CANCEL_LOCK
                           to cause the blocking lock to return. */

                        rc = send_lock_cancel(xid, tcon, in_buf, out_buf);

                        /* If we get -ENOLCK back the lock may have
                           already been removed. Don't exit in this case. */
                        if (rc && rc != -ENOLCK) {
                                DeleteMidQEntry(midQ);
                                return rc;
                        }
                }

                /* Wait 5 seconds for the response. */
                if (wait_for_response(ses, midQ, 5 * HZ, 5 * HZ) == 0) {
                        /* We got the response - restart system call. */
                        rstart = 1;
                }
        }

        spin_lock(&GlobalMid_Lock);
        if (midQ->resp_buf) {
                spin_unlock(&GlobalMid_Lock);
                receive_len = midQ->resp_buf->smb_buf_length;
        } else {
                cERROR(1, ("No response for cmd %d mid %d",
                          midQ->command, midQ->mid));
                if (midQ->midState == MID_REQUEST_SUBMITTED) {
                        if (ses->server->tcpStatus == CifsExiting)
                                rc = -EHOSTDOWN;
                        else {
                                ses->server->tcpStatus = CifsNeedReconnect;
                                midQ->midState = MID_RETRY_NEEDED;
                        }
                }

                if (rc != -EHOSTDOWN) {
                        if (midQ->midState == MID_RETRY_NEEDED) {
                                rc = -EAGAIN;
                                cFYI(1, ("marking request for retry"));
                        } else {
                                rc = -EIO;
                        }
                }
                spin_unlock(&GlobalMid_Lock);
                DeleteMidQEntry(midQ);
                return rc;
        }

        if (receive_len > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE) {
                cERROR(1, ("Frame too large received.  Length: %d  Xid: %d",
                        receive_len, xid));
                rc = -EIO;
                goto out;
        }

        /* rcvd frame is ok */

        if ((out_buf == NULL) || (midQ->midState != MID_RESPONSE_RECEIVED)) {
                rc = -EIO;
                cERROR(1, ("Bad MID state?"));
                goto out;
        }

        out_buf->smb_buf_length = receive_len;
        memcpy((char *)out_buf + 4,
               (char *)midQ->resp_buf + 4,
               receive_len);

        dump_smb(out_buf, 92);
        /* convert the length into a more usable form */
        if ((receive_len > 24) &&
            (ses->server->secMode & (SECMODE_SIGN_REQUIRED |
                                     SECMODE_SIGN_ENABLED))) {
                rc = cifs_verify_signature(out_buf,
                                           &ses->server->mac_signing_key,
                                           midQ->sequence_number+1);
                if (rc) {
                        cERROR(1, ("Unexpected SMB signature"));
                        /* BB FIXME add code to kill session */
                }
        }

        *pbytes_returned = out_buf->smb_buf_length;

        /* BB special case reconnect tid and uid here? */
        rc = map_smb_to_linux_error(out_buf, 0 /* no log */ );

        /* convert ByteCount if necessary */
        if (receive_len >= sizeof(struct smb_hdr) - 4
            /* do not count RFC1001 header */  +
            (2 * out_buf->WordCount) + 2 /* bcc */ )
                BCC(out_buf) = le16_to_cpu(BCC_LE(out_buf));

out:
        DeleteMidQEntry(midQ);
        if (rstart && rc == -EACCES)
                return -ERESTARTSYS;
        return rc;
}