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 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 #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", strerror(errno)));
  92                 return;
  93         }
  94
  95         data.effective |= (1<<capability);
  96
  97         if (capset(&header, &data) == -1) {
  98                 DEBUG(3,("Unable to set %d capability (%s)\n",
  99                          capability, strerror(errno)));
 100         }
 101 }
 102
 103 /****************************************************************************
 104  Call SETLEASE. If we get EACCES then we try setting up the right capability and
 105  try again
 106 ****************************************************************************/
 107
 108 static int linux_setlease(int fd, int leasetype)
 109 {
 110         int ret;
 111
 112         if (fcntl(fd, F_SETSIG, RT_SIGNAL_LEASE) == -1) {
 113                 DEBUG(3,("Failed to set signal handler for kernel lease\n"));
 114                 return -1;
 115         }
 116
 117         ret = fcntl(fd, F_SETLEASE, leasetype);
 118         if (ret == -1 && errno == EACCES) {
 119                 set_capability(CAP_LEASE);
 120                 ret = fcntl(fd, F_SETLEASE, leasetype);
 121         }
 122
 123         return ret;
 124 }
 125
 126 /****************************************************************************
 127  * Deal with the Linux kernel <--> smbd
 128  * oplock break protocol.
 129 ****************************************************************************/
 130
 131 static files_struct *linux_oplock_receive_message(fd_set *fds)
 132 {
 133         int fd;
 134         files_struct *fsp;
 135
 136         BlockSignals(True, RT_SIGNAL_LEASE);
 137         fd = fd_pending_array[0];
 138         fsp = file_find_fd(fd);
 139         fd_pending_array[0] = (SIG_ATOMIC_T)-1;
 140         if (signals_received > 1)
 141                 memmove(CONST_DISCARD(void *, &fd_pending_array[0]),
 142                         CONST_DISCARD(void *, &fd_pending_array[1]),
 143                         sizeof(SIG_ATOMIC_T)*(signals_received-1));
 144         signals_received--;
 145         /* now we can receive more signals */
 146         BlockSignals(False, RT_SIGNAL_LEASE);
 147
 148         return fsp;
 149 }
 150
 151 /****************************************************************************
 152  Attempt to set an kernel oplock on a file.
 153 ****************************************************************************/
 154
 155 static BOOL linux_set_kernel_oplock(files_struct *fsp, int oplock_type)
 156 {
 157         if (linux_setlease(fsp->fh->fd, F_WRLCK) == -1) {
 158                 DEBUG(3,("linux_set_kernel_oplock: Refused oplock on file %s, fd = %d, dev = %x, \
 159 inode = %.0f. (%s)\n",
 160                          fsp->fsp_name, fsp->fh->fd,
 161                          (unsigned int)fsp->dev, (double)fsp->inode, strerror(errno)));
 162                 return False;
 163         }
 164
 165         DEBUG(3,("linux_set_kernel_oplock: got kernel oplock on file %s, dev = %x, inode = %.0f, file_id = %lu\n",
 166                   fsp->fsp_name, (unsigned int)fsp->dev, (double)fsp->inode, fsp->file_id));
 167
 168         return True;
 169 }
 170
 171 /****************************************************************************
 172  Release a kernel oplock on a file.
 173 ****************************************************************************/
 174
 175 static void linux_release_kernel_oplock(files_struct *fsp)
 176 {
 177         if (DEBUGLVL(10)) {
 178                 /*
 179                  * Check and print out the current kernel
 180                  * oplock state of this file.
 181                  */
 182                 int state = fcntl(fsp->fh->fd, F_GETLEASE, 0);
 183                 dbgtext("linux_release_kernel_oplock: file %s, dev = %x, inode = %.0f file_id = %lu has kernel \
 184 oplock state of %x.\n", fsp->fsp_name, (unsigned int)fsp->dev,
 185                         (double)fsp->inode, fsp->file_id, state );
 186         }
 187
 188         /*
 189          * Remove the kernel oplock on this file.
 190          */
 191         if (linux_setlease(fsp->fh->fd, F_UNLCK) == -1) {
 192                 if (DEBUGLVL(0)) {
 193                         dbgtext("linux_release_kernel_oplock: Error when removing kernel oplock on file " );
 194                         dbgtext("%s, dev = %x, inode = %.0f, file_id = %lu. Error was %s\n",
 195                                 fsp->fsp_name, (unsigned int)fsp->dev,
 196                                 (double)fsp->inode, fsp->file_id, strerror(errno) );
 197                 }
 198         }
 199 }
 200
 201 /****************************************************************************
 202  See if a oplock message is waiting.
 203 ****************************************************************************/
 204
 205 static BOOL linux_oplock_msg_waiting(fd_set *fds)
 206 {
 207         return signals_received != 0;
 208 }
 209
 210 /****************************************************************************
 211  See if the kernel supports oplocks.
 212 ****************************************************************************/
 213
 214 static BOOL linux_oplocks_available(void)
 215 {
 216         int fd, ret;
 217         fd = open("/dev/null", O_RDONLY);
 218         if (fd == -1)
 219                 return False; /* uggh! */
 220         ret = fcntl(fd, F_GETLEASE, 0);
 221         close(fd);
 222         return ret == F_UNLCK;
 223 }
 224
 225 /****************************************************************************
 226  Setup kernel oplocks.
 227 ****************************************************************************/
 228
 229 struct kernel_oplocks *linux_init_kernel_oplocks(void)
 230 {
 231         static struct kernel_oplocks koplocks;
 232         struct sigaction act;
 233
 234         if (!linux_oplocks_available()) {
 235                 DEBUG(3,("Linux kernel oplocks not available\n"));
 236                 return NULL;
 237         }
 238
 239         ZERO_STRUCT(act);
 240
 241         act.sa_handler = NULL;
 242         act.sa_sigaction = signal_handler;
 243         act.sa_flags = SA_SIGINFO;
 244         sigemptyset( &act.sa_mask );
 245         if (sigaction(RT_SIGNAL_LEASE, &act, NULL) != 0) {
 246                 DEBUG(0,("Failed to setup RT_SIGNAL_LEASE handler\n"));
 247                 return NULL;
 248         }
 249
 250         koplocks.receive_message = linux_oplock_receive_message;
 251         koplocks.set_oplock = linux_set_kernel_oplock;
 252         koplocks.release_oplock = linux_release_kernel_oplock;
 253         koplocks.msg_waiting = linux_oplock_msg_waiting;
 254         koplocks.notification_fd = -1;
 255
 256         /* the signal can start off blocked due to a bug in bash */
 257         BlockSignals(False, RT_SIGNAL_LEASE);
 258
 259         DEBUG(3,("Linux kernel oplocks enabled\n"));
 260
 261         return &koplocks;
 262 }
 263 #else
 264  void oplock_linux_dummy(void);
 265
 266  void oplock_linux_dummy(void) {}
 267 #endif /* HAVE_KERNEL_OPLOCKS_LINUX */