release/src-rt-6.x.4708/linux/linux-2.6.36/fs/dlm/midcomms.c

   1 /******************************************************************************
   2 *******************************************************************************
   3 **
   4 **  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
   5 **  Copyright (C) 2004-2008 Red Hat, Inc.  All rights reserved.
   6 **
   7 **  This copyrighted material is made available to anyone wishing to use,
   8 **  modify, copy, or redistribute it subject to the terms and conditions
   9 **  of the GNU General Public License v.2.
  10 **
  11 *******************************************************************************
  12 ******************************************************************************/
  13
  14 /*
  15  * midcomms.c
  16  *
  17  * This is the appallingly named "mid-level" comms layer.
  18  *
  19  * Its purpose is to take packets from the "real" comms layer,
  20  * split them up into packets and pass them to the interested
  21  * part of the locking mechanism.
  22  *
  23  * It also takes messages from the locking layer, formats them
  24  * into packets and sends them to the comms layer.
  25  */
  26
  27 #include "dlm_internal.h"
  28 #include "lowcomms.h"
  29 #include "config.h"
  30 #include "lock.h"
  31 #include "midcomms.h"
  32
  33
  34 static void copy_from_cb(void *dst, const void *base, unsigned offset,
  35                          unsigned len, unsigned limit)
  36 {
  37         unsigned copy = len;
  38
  39         if ((copy + offset) > limit)
  40                 copy = limit - offset;
  41         memcpy(dst, base + offset, copy);
  42         len -= copy;
  43         if (len)
  44                 memcpy(dst + copy, base, len);
  45 }
  46
  47 /*
  48  * Called from the low-level comms layer to process a buffer of
  49  * commands.
  50  *
  51  * Only complete messages are processed here, any "spare" bytes from
  52  * the end of a buffer are saved and tacked onto the front of the next
  53  * message that comes in. I doubt this will happen very often but we
  54  * need to be able to cope with it and I don't want the task to be waiting
  55  * for packets to come in when there is useful work to be done.
  56  */
  57
  58 int dlm_process_incoming_buffer(int nodeid, const void *base,
  59                                 unsigned offset, unsigned len, unsigned limit)
  60 {
  61         union {
  62                 unsigned char __buf[DLM_INBUF_LEN];
  63                 /* this is to force proper alignment on some arches */
  64                 union dlm_packet p;
  65         } __tmp;
  66         union dlm_packet *p = &__tmp.p;
  67         int ret = 0;
  68         int err = 0;
  69         uint16_t msglen;
  70         uint32_t lockspace;
  71
  72         while (len > sizeof(struct dlm_header)) {
  73
  74                 /* Copy just the header to check the total length.  The
  75                    message may wrap around the end of the buffer back to the
  76                    start, so we need to use a temp buffer and copy_from_cb. */
  77
  78                 copy_from_cb(p, base, offset, sizeof(struct dlm_header),
  79                              limit);
  80
  81                 msglen = le16_to_cpu(p->header.h_length);
  82                 lockspace = p->header.h_lockspace;
  83
  84                 err = -EINVAL;
  85                 if (msglen < sizeof(struct dlm_header))
  86                         break;
  87                 if (p->header.h_cmd == DLM_MSG) {
  88                         if (msglen < sizeof(struct dlm_message))
  89                                 break;
  90                 } else {
  91                         if (msglen < sizeof(struct dlm_rcom))
  92                                 break;
  93                 }
  94                 err = -E2BIG;
  95                 if (msglen > dlm_config.ci_buffer_size) {
  96                         log_print("message size %d from %d too big, buf len %d",
  97                                   msglen, nodeid, len);
  98                         break;
  99                 }
 100                 err = 0;
 101
 102                 /* If only part of the full message is contained in this
 103                    buffer, then do nothing and wait for lowcomms to call
 104                    us again later with more data.  We return 0 meaning
 105                    we've consumed none of the input buffer. */
 106
 107                 if (msglen > len)
 108                         break;
 109
 110                 /* Allocate a larger temp buffer if the full message won't fit
 111                    in the buffer on the stack (which should work for most
 112                    ordinary messages). */
 113
 114                 if (msglen > sizeof(__tmp) && p == &__tmp.p) {
 115                         p = kmalloc(dlm_config.ci_buffer_size, GFP_NOFS);
 116                         if (p == NULL)
 117                                 return ret;
 118                 }
 119
 120                 copy_from_cb(p, base, offset, msglen, limit);
 121
 122                 BUG_ON(lockspace != p->header.h_lockspace);
 123
 124                 ret += msglen;
 125                 offset += msglen;
 126                 offset &= (limit - 1);
 127                 len -= msglen;
 128
 129                 dlm_receive_buffer(p, nodeid);
 130         }
 131
 132         if (p != &__tmp.p)
 133                 kfree(p);
 134
 135         return err ? err : ret;
 136 }