source3/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 /* these can be removed when they are in glibc headers */
  26 struct  cap_user_header {
  27         uint32 version;
  28         int pid;
  29 } header;
  30 struct cap_user_data {
  31         uint32 effective;
  32         uint32 permitted;
  33         uint32 inheritable;
  34 } data;
  35
  36 extern int capget(struct cap_user_header * hdrp,
  37                   struct cap_user_data * datap);
  38 extern int capset(struct cap_user_header * hdrp,
  39                   const struct cap_user_data * datap);
  40
  41 static SIG_ATOMIC_T signals_received;
  42 #define FD_PENDING_SIZE 100
  43 static SIG_ATOMIC_T fd_pending_array[FD_PENDING_SIZE];
  44
  45 #ifndef F_SETLEASE
  46 #define F_SETLEASE      1024
  47 #endif
  48
  49 #ifndef F_GETLEASE
  50 #define F_GETLEASE      1025
  51 #endif
  52
  53 #ifndef CAP_LEASE
  54 #define CAP_LEASE 28
  55 #endif
  56
  57 #ifndef RT_SIGNAL_LEASE
  58 #define RT_SIGNAL_LEASE (SIGRTMIN+1)
  59 #endif
  60
  61 #ifndef F_SETSIG
  62 #define F_SETSIG 10
  63 #endif
  64
  65 /****************************************************************************
  66  Handle a LEASE signal, incrementing the signals_received and blocking the signal.
  67 ****************************************************************************/
  68
  69 static void signal_handler(int sig, siginfo_t *info, void *unused)
  70 {
  71         if (signals_received < FD_PENDING_SIZE - 1) {
  72                 fd_pending_array[signals_received] = (SIG_ATOMIC_T)info->si_fd;
  73                 signals_received++;
  74         } /* Else signal is lost. */
  75         sys_select_signal(RT_SIGNAL_LEASE);
  76 }
  77
  78 /****************************************************************************
  79  Try to gain a linux capability.
  80 ****************************************************************************/
  81
  82 static void set_capability(unsigned capability)
  83 {
  84 #ifndef _LINUX_CAPABILITY_VERSION
  85 #define _LINUX_CAPABILITY_VERSION 0x19980330
  86 #endif
  87         header.version = _LINUX_CAPABILITY_VERSION;
  88         header.pid = 0;
  89
  90         if (capget(&header, &data) == -1) {
  91                 DEBUG(3,("Unable to get kernel capabilities (%s)\n",
  92                          strerror(errno)));
  93                 return;
  94         }
  95
  96         if (0 == (data.effective & (1<<capability))) {
  97                 data.effective |= (1<<capability);
  98
  99                 if (capset(&header, &data) == -1) {
 100                         DEBUG(3,("Unable to set %d capability (%s)\n",
 101                                  capability, strerror(errno)));
 102                 }
 103         }
 104 }
 105
 106 /*
 107  * public function to get linux lease capability. Needed by some VFS modules (eg. gpfs.c)
 108  */
 109 void linux_set_lease_capability(void)
 110 {
 111         set_capability(CAP_LEASE);
 112 }
 113
 114 /*
 115  * Call to set the kernel lease signal handler
 116  */
 117 int linux_set_lease_sighandler(int fd)
 118 {
 119         if (fcntl(fd, F_SETSIG, RT_SIGNAL_LEASE) == -1) {
 120                 DEBUG(3,("Failed to set signal handler for kernel lease\n"));
 121                 return -1;
 122         }
 123
 124         return 0;
 125 }
 126
 127 /****************************************************************************
 128  Call SETLEASE. If we get EACCES then we try setting up the right capability and
 129  try again.
 130  Use the SMB_VFS_LINUX_SETLEASE instead of this call directly.
 131 ****************************************************************************/
 132
 133 int linux_setlease(int fd, int leasetype)
 134 {
 135         int ret;
 136
 137         ret = fcntl(fd, F_SETLEASE, leasetype);
 138         if (ret == -1 && errno == EACCES) {
 139                 set_capability(CAP_LEASE);
 140                 ret = fcntl(fd, F_SETLEASE, leasetype);
 141         }
 142
 143         return ret;
 144 }
 145
 146 /****************************************************************************
 147  * Deal with the Linux kernel <--> smbd
 148  * oplock break protocol.
 149 ****************************************************************************/
 150
 151 static files_struct *linux_oplock_receive_message(fd_set *fds)
 152 {
 153         int fd;
 154         files_struct *fsp;
 155
 156         BlockSignals(True, RT_SIGNAL_LEASE);
 157         fd = fd_pending_array[0];
 158         fsp = file_find_fd(fd);
 159         fd_pending_array[0] = (SIG_ATOMIC_T)-1;
 160         if (signals_received > 1)
 161                 memmove(CONST_DISCARD(void *, &fd_pending_array[0]),
 162                         CONST_DISCARD(void *, &fd_pending_array[1]),
 163                         sizeof(SIG_ATOMIC_T)*(signals_received-1));
 164         signals_received--;
 165         /* now we can receive more signals */
 166         BlockSignals(False, RT_SIGNAL_LEASE);
 167
 168         return fsp;
 169 }
 170
 171 /****************************************************************************
 172  Attempt to set an kernel oplock on a file.
 173 ****************************************************************************/
 174
 175 static bool linux_set_kernel_oplock(files_struct *fsp, int oplock_type)
 176 {
 177         if ( SMB_VFS_LINUX_SETLEASE(fsp, F_WRLCK) == -1) {
 178                 DEBUG(3,("linux_set_kernel_oplock: Refused oplock on file %s, "
 179                          "fd = %d, file_id = %s. (%s)\n",
 180                          fsp->fsp_name, fsp->fh->fd,
 181                          file_id_string_tos(&fsp->file_id),
 182                          strerror(errno)));
 183                 return False;
 184         }
 185
 186         DEBUG(3,("linux_set_kernel_oplock: got kernel oplock on file %s, "
 187                  "file_id = %s gen_id = %lu\n",
 188                  fsp->fsp_name, file_id_string_tos(&fsp->file_id),
 189                  fsp->fh->gen_id));
 190
 191         return True;
 192 }
 193
 194 /****************************************************************************
 195  Release a kernel oplock on a file.
 196 ****************************************************************************/
 197
 198 static void linux_release_kernel_oplock(files_struct *fsp)
 199 {
 200         if (DEBUGLVL(10)) {
 201                 /*
 202                  * Check and print out the current kernel
 203                  * oplock state of this file.
 204                  */
 205                 int state = fcntl(fsp->fh->fd, F_GETLEASE, 0);
 206                 dbgtext("linux_release_kernel_oplock: file %s, file_id = %s "
 207                         "gen_id = %lu has kernel oplock state "
 208                         "of %x.\n", fsp->fsp_name, file_id_string_tos(&fsp->file_id),
 209                         fsp->fh->gen_id, state );
 210         }
 211
 212         /*
 213          * Remove the kernel oplock on this file.
 214          */
 215         if ( SMB_VFS_LINUX_SETLEASE(fsp, F_UNLCK) == -1) {
 216                 if (DEBUGLVL(0)) {
 217                         dbgtext("linux_release_kernel_oplock: Error when "
 218                                 "removing kernel oplock on file " );
 219                         dbgtext("%s, file_id = %s, gen_id = %lu. "
 220                                 "Error was %s\n", fsp->fsp_name,
 221                                 file_id_string_tos(&fsp->file_id),
 222                                 fsp->fh->gen_id, strerror(errno) );
 223                 }
 224         }
 225 }
 226
 227 /****************************************************************************
 228  See if a oplock message is waiting.
 229 ****************************************************************************/
 230
 231 static bool linux_oplock_msg_waiting(fd_set *fds)
 232 {
 233         return signals_received != 0;
 234 }
 235
 236 /****************************************************************************
 237  See if the kernel supports oplocks.
 238 ****************************************************************************/
 239
 240 static bool linux_oplocks_available(void)
 241 {
 242         int fd, ret;
 243         fd = open("/dev/null", O_RDONLY);
 244         if (fd == -1)
 245                 return False; /* uggh! */
 246         ret = fcntl(fd, F_GETLEASE, 0);
 247         close(fd);
 248         return ret == F_UNLCK;
 249 }
 250
 251 /****************************************************************************
 252  Setup kernel oplocks.
 253 ****************************************************************************/
 254
 255 struct kernel_oplocks *linux_init_kernel_oplocks(void)
 256 {
 257         static struct kernel_oplocks koplocks;
 258         struct sigaction act;
 259
 260         if (!linux_oplocks_available()) {
 261                 DEBUG(3,("Linux kernel oplocks not available\n"));
 262                 return NULL;
 263         }
 264
 265         ZERO_STRUCT(act);
 266
 267         act.sa_handler = NULL;
 268         act.sa_sigaction = signal_handler;
 269         act.sa_flags = SA_SIGINFO;
 270         sigemptyset( &act.sa_mask );
 271         if (sigaction(RT_SIGNAL_LEASE, &act, NULL) != 0) {
 272                 DEBUG(0,("Failed to setup RT_SIGNAL_LEASE handler\n"));
 273                 return NULL;
 274         }
 275
 276         koplocks.receive_message = linux_oplock_receive_message;
 277         koplocks.set_oplock = linux_set_kernel_oplock;
 278         koplocks.release_oplock = linux_release_kernel_oplock;
 279         koplocks.msg_waiting = linux_oplock_msg_waiting;
 280         koplocks.notification_fd = -1;
 281
 282         /* the signal can start off blocked due to a bug in bash */
 283         BlockSignals(False, RT_SIGNAL_LEASE);
 284
 285         DEBUG(3,("Linux kernel oplocks enabled\n"));
 286
 287         return &koplocks;
 288 }
 289 #else
 290  void oplock_linux_dummy(void);
 291
 292  void oplock_linux_dummy(void) {}
 293 #endif /* HAVE_KERNEL_OPLOCKS_LINUX */