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 3 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, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #define DBGC_CLASS DBGC_LOCKING
  21 #include "includes.h"
  22
  23 #if HAVE_KERNEL_OPLOCKS_LINUX
  24
  25 static SIG_ATOMIC_T signals_received;
  26 #define FD_PENDING_SIZE 100
  27 static SIG_ATOMIC_T fd_pending_array[FD_PENDING_SIZE];
  28
  29 #ifndef F_SETLEASE
  30 #define F_SETLEASE      1024
  31 #endif
  32
  33 #ifndef F_GETLEASE
  34 #define F_GETLEASE      1025
  35 #endif
  36
  37 #ifndef CAP_LEASE
  38 #define CAP_LEASE 28
  39 #endif
  40
  41 #ifndef RT_SIGNAL_LEASE
  42 #define RT_SIGNAL_LEASE (SIGRTMIN+1)
  43 #endif
  44
  45 #ifndef F_SETSIG
  46 #define F_SETSIG 10
  47 #endif
  48
  49 /****************************************************************************
  50  Handle a LEASE signal, incrementing the signals_received and blocking the signal.
  51 ****************************************************************************/
  52
  53 static void signal_handler(int sig, siginfo_t *info, void *unused)
  54 {
  55         if (signals_received < FD_PENDING_SIZE - 1) {
  56                 fd_pending_array[signals_received] = (SIG_ATOMIC_T)info->si_fd;
  57                 signals_received++;
  58         } /* Else signal is lost. */
  59         sys_select_signal(RT_SIGNAL_LEASE);
  60 }
  61
  62 /*
  63  * public function to get linux lease capability. Needed by some VFS modules (eg. gpfs.c)
  64  */
  65 void linux_set_lease_capability(void)
  66 {
  67         set_effective_capability(LEASE_CAPABILITY);
  68 }
  69
  70 /*
  71  * Call to set the kernel lease signal handler
  72  */
  73 int linux_set_lease_sighandler(int fd)
  74 {
  75         if (fcntl(fd, F_SETSIG, RT_SIGNAL_LEASE) == -1) {
  76                 DEBUG(3,("Failed to set signal handler for kernel lease\n"));
  77                 return -1;
  78         }
  79
  80         return 0;
  81 }
  82
  83 /****************************************************************************
  84  Call SETLEASE. If we get EACCES then we try setting up the right capability and
  85  try again.
  86  Use the SMB_VFS_LINUX_SETLEASE instead of this call directly.
  87 ****************************************************************************/
  88
  89 int linux_setlease(int fd, int leasetype)
  90 {
  91         int ret;
  92
  93         ret = fcntl(fd, F_SETLEASE, leasetype);
  94         if (ret == -1 && errno == EACCES) {
  95                 set_effective_capability(LEASE_CAPABILITY);
  96                 ret = fcntl(fd, F_SETLEASE, leasetype);
  97         }
  98
  99         return ret;
 100 }
 101
 102 /****************************************************************************
 103  * Deal with the Linux kernel <--> smbd
 104  * oplock break protocol.
 105 ****************************************************************************/
 106
 107 static files_struct *linux_oplock_receive_message(fd_set *fds)
 108 {
 109         int fd;
 110         files_struct *fsp;
 111
 112         BlockSignals(True, RT_SIGNAL_LEASE);
 113         fd = fd_pending_array[0];
 114         fsp = file_find_fd(fd);
 115         fd_pending_array[0] = (SIG_ATOMIC_T)-1;
 116         if (signals_received > 1)
 117                 memmove(CONST_DISCARD(void *, &fd_pending_array[0]),
 118                         CONST_DISCARD(void *, &fd_pending_array[1]),
 119                         sizeof(SIG_ATOMIC_T)*(signals_received-1));
 120         signals_received--;
 121         /* now we can receive more signals */
 122         BlockSignals(False, RT_SIGNAL_LEASE);
 123
 124         return fsp;
 125 }
 126
 127 /****************************************************************************
 128  Attempt to set an kernel oplock on a file.
 129 ****************************************************************************/
 130
 131 static bool linux_set_kernel_oplock(files_struct *fsp, int oplock_type)
 132 {
 133         if ( SMB_VFS_LINUX_SETLEASE(fsp, F_WRLCK) == -1) {
 134                 DEBUG(3,("linux_set_kernel_oplock: Refused oplock on file %s, "
 135                          "fd = %d, file_id = %s. (%s)\n",
 136                          fsp->fsp_name, fsp->fh->fd,
 137                          file_id_string_tos(&fsp->file_id),
 138                          strerror(errno)));
 139                 return False;
 140         }
 141
 142         DEBUG(3,("linux_set_kernel_oplock: got kernel oplock on file %s, "
 143                  "file_id = %s gen_id = %lu\n",
 144                  fsp->fsp_name, file_id_string_tos(&fsp->file_id),
 145                  fsp->fh->gen_id));
 146
 147         return True;
 148 }
 149
 150 /****************************************************************************
 151  Release a kernel oplock on a file.
 152 ****************************************************************************/
 153
 154 static void linux_release_kernel_oplock(files_struct *fsp)
 155 {
 156         if (DEBUGLVL(10)) {
 157                 /*
 158                  * Check and print out the current kernel
 159                  * oplock state of this file.
 160                  */
 161                 int state = fcntl(fsp->fh->fd, F_GETLEASE, 0);
 162                 dbgtext("linux_release_kernel_oplock: file %s, file_id = %s "
 163                         "gen_id = %lu has kernel oplock state "
 164                         "of %x.\n", fsp->fsp_name, file_id_string_tos(&fsp->file_id),
 165                         fsp->fh->gen_id, state );
 166         }
 167
 168         /*
 169          * Remove the kernel oplock on this file.
 170          */
 171         if ( SMB_VFS_LINUX_SETLEASE(fsp, F_UNLCK) == -1) {
 172                 if (DEBUGLVL(0)) {
 173                         dbgtext("linux_release_kernel_oplock: Error when "
 174                                 "removing kernel oplock on file " );
 175                         dbgtext("%s, file_id = %s, gen_id = %lu. "
 176                                 "Error was %s\n", fsp->fsp_name,
 177                                 file_id_string_tos(&fsp->file_id),
 178                                 fsp->fh->gen_id, strerror(errno) );
 179                 }
 180         }
 181 }
 182
 183 /****************************************************************************
 184  See if a oplock message is waiting.
 185 ****************************************************************************/
 186
 187 static bool linux_oplock_msg_waiting(fd_set *fds)
 188 {
 189         return signals_received != 0;
 190 }
 191
 192 /****************************************************************************
 193  See if the kernel supports oplocks.
 194 ****************************************************************************/
 195
 196 static bool linux_oplocks_available(void)
 197 {
 198         int fd, ret;
 199         fd = open("/dev/null", O_RDONLY);
 200         if (fd == -1)
 201                 return False; /* uggh! */
 202         ret = fcntl(fd, F_GETLEASE, 0);
 203         close(fd);
 204         return ret == F_UNLCK;
 205 }
 206
 207 /****************************************************************************
 208  Setup kernel oplocks.
 209 ****************************************************************************/
 210
 211 struct kernel_oplocks *linux_init_kernel_oplocks(void)
 212 {
 213         static struct kernel_oplocks koplocks;
 214         struct sigaction act;
 215
 216         if (!linux_oplocks_available()) {
 217                 DEBUG(3,("Linux kernel oplocks not available\n"));
 218                 return NULL;
 219         }
 220
 221         ZERO_STRUCT(act);
 222
 223         act.sa_handler = NULL;
 224         act.sa_sigaction = signal_handler;
 225         act.sa_flags = SA_SIGINFO;
 226         sigemptyset( &act.sa_mask );
 227         if (sigaction(RT_SIGNAL_LEASE, &act, NULL) != 0) {
 228                 DEBUG(0,("Failed to setup RT_SIGNAL_LEASE handler\n"));
 229                 return NULL;
 230         }
 231
 232         koplocks.receive_message = linux_oplock_receive_message;
 233         koplocks.set_oplock = linux_set_kernel_oplock;
 234         koplocks.release_oplock = linux_release_kernel_oplock;
 235         koplocks.msg_waiting = linux_oplock_msg_waiting;
 236         koplocks.notification_fd = -1;
 237
 238         /* the signal can start off blocked due to a bug in bash */
 239         BlockSignals(False, RT_SIGNAL_LEASE);
 240
 241         DEBUG(3,("Linux kernel oplocks enabled\n"));
 242
 243         return &koplocks;
 244 }
 245 #else
 246  void oplock_linux_dummy(void);
 247
 248  void oplock_linux_dummy(void) {}
 249 #endif /* HAVE_KERNEL_OPLOCKS_LINUX */