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",
  93                          strerror(errno)));
  94                 return;
  95         }
  96
  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  Call SETLEASE. If we get EACCES then we try setting up the right capability and
 107  try again
 108 ****************************************************************************/
 109
 110 static int linux_setlease(int fd, int leasetype)
 111 {
 112         int ret;
 113
 114         if (fcntl(fd, F_SETSIG, RT_SIGNAL_LEASE) == -1) {
 115                 DEBUG(3,("Failed to set signal handler for kernel lease\n"));
 116                 return -1;
 117         }
 118
 119         ret = fcntl(fd, F_SETLEASE, leasetype);
 120         if (ret == -1 && errno == EACCES) {
 121                 set_capability(CAP_LEASE);
 122                 ret = fcntl(fd, F_SETLEASE, leasetype);
 123         }
 124
 125         return ret;
 126 }
 127
 128 /****************************************************************************
 129  * Deal with the Linux kernel <--> smbd
 130  * oplock break protocol.
 131 ****************************************************************************/
 132
 133 static files_struct *linux_oplock_receive_message(fd_set *fds)
 134 {
 135         int fd;
 136         files_struct *fsp;
 137
 138         BlockSignals(True, RT_SIGNAL_LEASE);
 139         fd = fd_pending_array[0];
 140         fsp = file_find_fd(fd);
 141         fd_pending_array[0] = (SIG_ATOMIC_T)-1;
 142         if (signals_received > 1)
 143                 memmove(CONST_DISCARD(void *, &fd_pending_array[0]),
 144                         CONST_DISCARD(void *, &fd_pending_array[1]),
 145                         sizeof(SIG_ATOMIC_T)*(signals_received-1));
 146         signals_received--;
 147         /* now we can receive more signals */
 148         BlockSignals(False, RT_SIGNAL_LEASE);
 149
 150         return fsp;
 151 }
 152
 153 /****************************************************************************
 154  Attempt to set an kernel oplock on a file.
 155 ****************************************************************************/
 156
 157 static BOOL linux_set_kernel_oplock(files_struct *fsp, int oplock_type)
 158 {
 159         if (linux_setlease(fsp->fh->fd, F_WRLCK) == -1) {
 160                 DEBUG(3,("linux_set_kernel_oplock: Refused oplock on file %s, "
 161                          "fd = %d, dev = %x, inode = %.0f. (%s)\n",
 162                          fsp->fsp_name, fsp->fh->fd,
 163                          (unsigned int)fsp->dev, (double)fsp->inode,
 164                          strerror(errno)));
 165                 return False;
 166         }
 167
 168         DEBUG(3,("linux_set_kernel_oplock: got kernel oplock on file %s, "
 169                  "dev = %x, inode = %.0f, file_id = %lu\n",
 170                   fsp->fsp_name, (unsigned int)fsp->dev, (double)fsp->inode,
 171                  fsp->fh->file_id));
 172
 173         return True;
 174 }
 175
 176 /****************************************************************************
 177  Release a kernel oplock on a file.
 178 ****************************************************************************/
 179
 180 static void linux_release_kernel_oplock(files_struct *fsp)
 181 {
 182         if (DEBUGLVL(10)) {
 183                 /*
 184                  * Check and print out the current kernel
 185                  * oplock state of this file.
 186                  */
 187                 int state = fcntl(fsp->fh->fd, F_GETLEASE, 0);
 188                 dbgtext("linux_release_kernel_oplock: file %s, dev = %x, "
 189                         "inode = %.0f file_id = %lu has kernel oplock state "
 190                         "of %x.\n", fsp->fsp_name, (unsigned int)fsp->dev,
 191                         (double)fsp->inode, fsp->fh->file_id, state );
 192         }
 193
 194         /*
 195          * Remove the kernel oplock on this file.
 196          */
 197         if (linux_setlease(fsp->fh->fd, F_UNLCK) == -1) {
 198                 if (DEBUGLVL(0)) {
 199                         dbgtext("linux_release_kernel_oplock: Error when "
 200                                 "removing kernel oplock on file " );
 201                         dbgtext("%s, dev = %x, inode = %.0f, file_id = %lu. "
 202                                 "Error was %s\n", fsp->fsp_name,
 203                                 (unsigned int)fsp->dev, (double)fsp->inode,
 204                                 fsp->fh->file_id, strerror(errno) );
 205                 }
 206         }
 207 }
 208
 209 /****************************************************************************
 210  See if a oplock message is waiting.
 211 ****************************************************************************/
 212
 213 static BOOL linux_oplock_msg_waiting(fd_set *fds)
 214 {
 215         return signals_received != 0;
 216 }
 217
 218 /****************************************************************************
 219  See if the kernel supports oplocks.
 220 ****************************************************************************/
 221
 222 static BOOL linux_oplocks_available(void)
 223 {
 224         int fd, ret;
 225         fd = open("/dev/null", O_RDONLY);
 226         if (fd == -1)
 227                 return False; /* uggh! */
 228         ret = fcntl(fd, F_GETLEASE, 0);
 229         close(fd);
 230         return ret == F_UNLCK;
 231 }
 232
 233 /****************************************************************************
 234  Setup kernel oplocks.
 235 ****************************************************************************/
 236
 237 struct kernel_oplocks *linux_init_kernel_oplocks(void)
 238 {
 239         static struct kernel_oplocks koplocks;
 240         struct sigaction act;
 241
 242         if (!linux_oplocks_available()) {
 243                 DEBUG(3,("Linux kernel oplocks not available\n"));
 244                 return NULL;
 245         }
 246
 247         ZERO_STRUCT(act);
 248
 249         act.sa_handler = NULL;
 250         act.sa_sigaction = signal_handler;
 251         act.sa_flags = SA_SIGINFO;
 252         sigemptyset( &act.sa_mask );
 253         if (sigaction(RT_SIGNAL_LEASE, &act, NULL) != 0) {
 254                 DEBUG(0,("Failed to setup RT_SIGNAL_LEASE handler\n"));
 255                 return NULL;
 256         }
 257
 258         koplocks.receive_message = linux_oplock_receive_message;
 259         koplocks.set_oplock = linux_set_kernel_oplock;
 260         koplocks.release_oplock = linux_release_kernel_oplock;
 261         koplocks.msg_waiting = linux_oplock_msg_waiting;
 262         koplocks.notification_fd = -1;
 263
 264         /* the signal can start off blocked due to a bug in bash */
 265         BlockSignals(False, RT_SIGNAL_LEASE);
 266
 267         DEBUG(3,("Linux kernel oplocks enabled\n"));
 268
 269         return &koplocks;
 270 }
 271 #else
 272  void oplock_linux_dummy(void);
 273
 274  void oplock_linux_dummy(void) {}
 275 #endif /* HAVE_KERNEL_OPLOCKS_LINUX */