release/src/router/samba3/source/smbd/oplock_linux.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    kernel oplock processing for Linux
   4    Copyright (C) Andrew Tridgell 2000
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19 */
  20
  21 #define DBGC_CLASS DBGC_LOCKING
  22 #include "includes.h"
  23
  24 #if HAVE_KERNEL_OPLOCKS_LINUX
  25
  26 /* these can be removed when they are in glibc headers */
  27 struct  cap_user_header {
  28         uint32 version;
  29         int pid;
  30 } header;
  31 struct cap_user_data {
  32         uint32 effective;
  33         uint32 permitted;
  34         uint32 inheritable;
  35 } data;
  36
  37 extern int capget(struct cap_user_header * hdrp,
  38                   struct cap_user_data * datap);
  39 extern int capset(struct cap_user_header * hdrp,
  40                   const struct cap_user_data * datap);
  41
  42 static SIG_ATOMIC_T signals_received;
  43 #define FD_PENDING_SIZE 100
  44 static SIG_ATOMIC_T fd_pending_array[FD_PENDING_SIZE];
  45
  46 #ifndef F_SETLEASE
  47 #define F_SETLEASE      1024
  48 #endif
  49
  50 #ifndef F_GETLEASE
  51 #define F_GETLEASE      1025
  52 #endif
  53
  54 #ifndef CAP_LEASE
  55 #define CAP_LEASE 28
  56 #endif
  57
  58 #ifndef RT_SIGNAL_LEASE
  59 #define RT_SIGNAL_LEASE (SIGRTMIN+1)
  60 #endif
  61
  62 #ifndef F_SETSIG
  63 #define F_SETSIG 10
  64 #endif
  65
  66 /****************************************************************************
  67  Handle a LEASE signal, incrementing the signals_received and blocking the signal.
  68 ****************************************************************************/
  69
  70 static void signal_handler(int sig, siginfo_t *info, void *unused)
  71 {
  72         if (signals_received < FD_PENDING_SIZE - 1) {
  73                 fd_pending_array[signals_received] = (SIG_ATOMIC_T)info->si_fd;
  74                 signals_received++;
  75         } /* Else signal is lost. */
  76         sys_select_signal(RT_SIGNAL_LEASE);
  77 }
  78
  79 /****************************************************************************
  80  Try to gain a linux capability.
  81 ****************************************************************************/
  82
  83 static void set_capability(unsigned capability)
  84 {
  85 #ifndef _LINUX_CAPABILITY_VERSION
  86 #define _LINUX_CAPABILITY_VERSION 0x19980330
  87 #endif
  88         header.version = _LINUX_CAPABILITY_VERSION;
  89         header.pid = 0;
  90
  91         if (capget(&header, &data) == -1) {
  92                 DEBUG(3,("Unable to get kernel capabilities (%s)\n", strerror(errno)));
  93                 return;
  94         }
  95
  96         data.effective |= (1<<capability);
  97
  98         if (capset(&header, &data) == -1) {
  99                 DEBUG(3,("Unable to set %d capability (%s)\n",
 100                          capability, strerror(errno)));
 101         }
 102 }
 103
 104 /****************************************************************************
 105  Call SETLEASE. If we get EACCES then we try setting up the right capability and
 106  try again
 107 ****************************************************************************/
 108
 109 static int linux_setlease(int fd, int leasetype)
 110 {
 111         int ret;
 112
 113         if (fcntl(fd, F_SETSIG, RT_SIGNAL_LEASE) == -1) {
 114                 DEBUG(3,("Failed to set signal handler for kernel lease\n"));
 115                 return -1;
 116         }
 117
 118         ret = fcntl(fd, F_SETLEASE, leasetype);
 119         if (ret == -1 && errno == EACCES) {
 120                 set_capability(CAP_LEASE);
 121                 ret = fcntl(fd, F_SETLEASE, leasetype);
 122         }
 123
 124         return ret;
 125 }
 126
 127 /****************************************************************************
 128  * Deal with the Linux kernel <--> smbd
 129  * oplock break protocol.
 130 ****************************************************************************/
 131
 132 static files_struct *linux_oplock_receive_message(fd_set *fds)
 133 {
 134         int fd;
 135         files_struct *fsp;
 136
 137         BlockSignals(True, RT_SIGNAL_LEASE);
 138         fd = fd_pending_array[0];
 139         fsp = file_find_fd(fd);
 140         fd_pending_array[0] = (SIG_ATOMIC_T)-1;
 141         if (signals_received > 1)
 142                 memmove(CONST_DISCARD(void *, &fd_pending_array[0]),
 143                         CONST_DISCARD(void *, &fd_pending_array[1]),
 144                         sizeof(SIG_ATOMIC_T)*(signals_received-1));
 145         signals_received--;
 146         /* now we can receive more signals */
 147         BlockSignals(False, RT_SIGNAL_LEASE);
 148
 149         return fsp;
 150 }
 151
 152 /****************************************************************************
 153  Attempt to set an kernel oplock on a file.
 154 ****************************************************************************/
 155
 156 static BOOL linux_set_kernel_oplock(files_struct *fsp, int oplock_type)
 157 {
 158         if (linux_setlease(fsp->fh->fd, F_WRLCK) == -1) {
 159                 DEBUG(3,("linux_set_kernel_oplock: Refused oplock on file %s, fd = %d, dev = %x, \
 160 inode = %.0f. (%s)\n",
 161                          fsp->fsp_name, fsp->fh->fd,
 162                          (unsigned int)fsp->dev, (double)fsp->inode, strerror(errno)));
 163                 return False;
 164         }
 165
 166         DEBUG(3,("linux_set_kernel_oplock: got kernel oplock on file %s, dev = %x, inode = %.0f, file_id = %lu\n",
 167                   fsp->fsp_name, (unsigned int)fsp->dev, (double)fsp->inode, fsp->fh->file_id));
 168
 169         return True;
 170 }
 171
 172 /****************************************************************************
 173  Release a kernel oplock on a file.
 174 ****************************************************************************/
 175
 176 static void linux_release_kernel_oplock(files_struct *fsp)
 177 {
 178         if (DEBUGLVL(10)) {
 179                 /*
 180                  * Check and print out the current kernel
 181                  * oplock state of this file.
 182                  */
 183                 int state = fcntl(fsp->fh->fd, F_GETLEASE, 0);
 184                 dbgtext("linux_release_kernel_oplock: file %s, dev = %x, inode = %.0f file_id = %lu has kernel \
 185 oplock state of %x.\n", fsp->fsp_name, (unsigned int)fsp->dev,
 186                         (double)fsp->inode, fsp->fh->file_id, state );
 187         }
 188
 189         /*
 190          * Remove the kernel oplock on this file.
 191          */
 192         if (linux_setlease(fsp->fh->fd, F_UNLCK) == -1) {
 193                 if (DEBUGLVL(0)) {
 194                         dbgtext("linux_release_kernel_oplock: Error when removing kernel oplock on file " );
 195                         dbgtext("%s, dev = %x, inode = %.0f, file_id = %lu. Error was %s\n",
 196                                 fsp->fsp_name, (unsigned int)fsp->dev,
 197                                 (double)fsp->inode, fsp->fh->file_id, strerror(errno) );
 198                 }
 199         }
 200 }
 201
 202 /****************************************************************************
 203  See if a oplock message is waiting.
 204 ****************************************************************************/
 205
 206 static BOOL linux_oplock_msg_waiting(fd_set *fds)
 207 {
 208         return signals_received != 0;
 209 }
 210
 211 /****************************************************************************
 212  See if the kernel supports oplocks.
 213 ****************************************************************************/
 214
 215 static BOOL linux_oplocks_available(void)
 216 {
 217         int fd, ret;
 218         fd = open("/dev/null", O_RDONLY);
 219         if (fd == -1)
 220                 return False; /* uggh! */
 221         ret = fcntl(fd, F_GETLEASE, 0);
 222         close(fd);
 223         return ret == F_UNLCK;
 224 }
 225
 226 /****************************************************************************
 227  Setup kernel oplocks.
 228 ****************************************************************************/
 229
 230 struct kernel_oplocks *linux_init_kernel_oplocks(void)
 231 {
 232         static struct kernel_oplocks koplocks;
 233         struct sigaction act;
 234
 235         if (!linux_oplocks_available()) {
 236                 DEBUG(3,("Linux kernel oplocks not available\n"));
 237                 return NULL;
 238         }
 239
 240         ZERO_STRUCT(act);
 241
 242         act.sa_handler = NULL;
 243         act.sa_sigaction = signal_handler;
 244         act.sa_flags = SA_SIGINFO;
 245         sigemptyset( &act.sa_mask );
 246         if (sigaction(RT_SIGNAL_LEASE, &act, NULL) != 0) {
 247                 DEBUG(0,("Failed to setup RT_SIGNAL_LEASE handler\n"));
 248                 return NULL;
 249         }
 250
 251         koplocks.receive_message = linux_oplock_receive_message;
 252         koplocks.set_oplock = linux_set_kernel_oplock;
 253         koplocks.release_oplock = linux_release_kernel_oplock;
 254         koplocks.msg_waiting = linux_oplock_msg_waiting;
 255         koplocks.notification_fd = -1;
 256
 257         /* the signal can start off blocked due to a bug in bash */
 258         BlockSignals(False, RT_SIGNAL_LEASE);
 259
 260         DEBUG(3,("Linux kernel oplocks enabled\n"));
 261
 262         return &koplocks;
 263 }
 264 #else
 265  void oplock_linux_dummy(void);
 266
 267  void oplock_linux_dummy(void) {}
 268 #endif /* HAVE_KERNEL_OPLOCKS_LINUX */