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oplock_linux.c

/* 
   Unix SMB/Netbios implementation.
   Version 3.0
   kernel oplock processing for Linux
   Copyright (C) Andrew Tridgell 2000
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"

#if HAVE_KERNEL_OPLOCKS_LINUX

static SIG_ATOMIC_T signals_received;
#define FD_PENDING_SIZE 100
static SIG_ATOMIC_T fd_pending_array[FD_PENDING_SIZE];

#ifndef F_SETLEASE
#define F_SETLEASE      1024
#endif

#ifndef F_GETLEASE
#define F_GETLEASE      1025
#endif

#ifndef CAP_LEASE
#define CAP_LEASE 28
#endif

#ifndef RT_SIGNAL_LEASE
#define RT_SIGNAL_LEASE 33
#endif

#ifndef F_SETSIG
#define F_SETSIG 10
#endif

/****************************************************************************
 Handle a LEASE signal, incrementing the signals_received and blocking the signal.
****************************************************************************/

static void signal_handler(int sig, siginfo_t *info, void *unused)
{
      if (signals_received < FD_PENDING_SIZE - 1) {
            fd_pending_array[signals_received] = (SIG_ATOMIC_T)info->si_fd;
            signals_received++;
      } /* Else signal is lost. */
      sys_select_signal();
}

/****************************************************************************
 Try to gain a linux capability.
****************************************************************************/

static void set_capability(unsigned capability)
{
#ifndef _LINUX_CAPABILITY_VERSION
#define _LINUX_CAPABILITY_VERSION 0x19980330
#endif
      /* these can be removed when they are in glibc headers */
      struct  {
            uint32 version;
            int pid;
      } header;
      struct {
            uint32 effective;
            uint32 permitted;
            uint32 inheritable;
      } data;

      header.version = _LINUX_CAPABILITY_VERSION;
      header.pid = 0;

      if (capget(&header, &data) == -1) {
            DEBUG(3,("Unable to get kernel capabilities (%s)\n", strerror(errno)));
            return;
      }

      data.effective |= (1<<capability);

      if (capset(&header, &data) == -1) {
            DEBUG(3,("Unable to set %d capability (%s)\n", 
                   capability, strerror(errno)));
      }
}

/****************************************************************************
 Call SETLEASE. If we get EACCES then we try setting up the right capability and
 try again
****************************************************************************/

static int linux_setlease(int fd, int leasetype)
{
      int ret;

      if (fcntl(fd, F_SETSIG, RT_SIGNAL_LEASE) == -1) {
            DEBUG(3,("Failed to set signal handler for kernel lease\n"));
            return -1;
      }

      ret = fcntl(fd, F_SETLEASE, leasetype);
      if (ret == -1 && errno == EACCES) {
            set_capability(CAP_LEASE);
            ret = fcntl(fd, F_SETLEASE, leasetype);
      }

      return ret;
}

/****************************************************************************
 * Deal with the Linux kernel <--> smbd
 * oplock break protocol.
****************************************************************************/

static BOOL linux_oplock_receive_message(fd_set *fds, char *buffer, int buffer_len)
{
      int fd;
      struct files_struct *fsp;

      BlockSignals(True, RT_SIGNAL_LEASE);
      fd = fd_pending_array[0];
      fsp = file_find_fd(fd);
      fd_pending_array[0] = (SIG_ATOMIC_T)-1;
      if (signals_received > 1)
      memmove((void *)&fd_pending_array[0], (void *)&fd_pending_array[1],
                  sizeof(SIG_ATOMIC_T)*(signals_received-1));
      signals_received--;
      /* now we can receive more signals */
      BlockSignals(False, RT_SIGNAL_LEASE);

      if (fsp == NULL) {
            DEBUG(0,("Invalid file descriptor %d in kernel oplock break!\n", (int)fd));
            return False;
      }

      DEBUG(3,("linux_oplock_receive_message: kernel oplock break request received for \
dev = %x, inode = %.0f fd = %d, fileid = %lu \n", (unsigned int)fsp->dev, (double)fsp->inode,
                  fd, fsp->file_id));
     
      /*
       * Create a kernel oplock break message.
       */
     
      /* Setup the message header */
      SIVAL(buffer,OPBRK_CMD_LEN_OFFSET,KERNEL_OPLOCK_BREAK_MSG_LEN);
      SSVAL(buffer,OPBRK_CMD_PORT_OFFSET,0);
     
      buffer += OPBRK_CMD_HEADER_LEN;
     
      SSVAL(buffer,OPBRK_MESSAGE_CMD_OFFSET,KERNEL_OPLOCK_BREAK_CMD);
     
      memcpy(buffer + KERNEL_OPLOCK_BREAK_DEV_OFFSET, (char *)&fsp->dev, sizeof(fsp->dev));
      memcpy(buffer + KERNEL_OPLOCK_BREAK_INODE_OFFSET, (char *)&fsp->inode, sizeof(fsp->inode));     
      memcpy(buffer + KERNEL_OPLOCK_BREAK_FILEID_OFFSET, (char *)&fsp->file_id, sizeof(fsp->file_id));      

      return True;
}

/****************************************************************************
 Attempt to set an kernel oplock on a file.
****************************************************************************/

static BOOL linux_set_kernel_oplock(files_struct *fsp, int oplock_type)
{
      if (linux_setlease(fsp->fd, F_WRLCK) == -1) {
            DEBUG(3,("linux_set_kernel_oplock: Refused oplock on file %s, fd = %d, dev = %x, \
inode = %.0f. (%s)\n",
                   fsp->fsp_name, fsp->fd, 
                   (unsigned int)fsp->dev, (double)fsp->inode, strerror(errno)));
            return False;
      }
      
      DEBUG(3,("linux_set_kernel_oplock: got kernel oplock on file %s, dev = %x, inode = %.0f, file_id = %lu\n",
              fsp->fsp_name, (unsigned int)fsp->dev, (double)fsp->inode, fsp->file_id));

      return True;
}

/****************************************************************************
 Release a kernel oplock on a file.
****************************************************************************/

static void linux_release_kernel_oplock(files_struct *fsp)
{
      if (DEBUGLVL(10)) {
            /*
             * Check and print out the current kernel
             * oplock state of this file.
             */
            int state = fcntl(fsp->fd, F_GETLEASE, 0);
            dbgtext("linux_release_kernel_oplock: file %s, dev = %x, inode = %.0f file_id = %lu has kernel \
oplock state of %x.\n", fsp->fsp_name, (unsigned int)fsp->dev,
                        (double)fsp->inode, fsp->file_id, state );
      }

      /*
       * Remove the kernel oplock on this file.
       */
      if (linux_setlease(fsp->fd, F_UNLCK) == -1) {
            if (DEBUGLVL(0)) {
                  dbgtext("linux_release_kernel_oplock: Error when removing kernel oplock on file " );
                  dbgtext("%s, dev = %x, inode = %.0f, file_id = %lu. Error was %s\n",
                        fsp->fsp_name, (unsigned int)fsp->dev, 
                        (double)fsp->inode, fsp->file_id, strerror(errno) );
            }
      }
}

/****************************************************************************
 Parse a kernel oplock message.
****************************************************************************/

static BOOL linux_kernel_oplock_parse(char *msg_start, int msg_len, SMB_INO_T *inode,
            SMB_DEV_T *dev, unsigned long *file_id)
{
      /* Ensure that the msg length is correct. */
      if (msg_len != KERNEL_OPLOCK_BREAK_MSG_LEN) {
            DEBUG(0,("incorrect length for KERNEL_OPLOCK_BREAK_CMD (was %d, should be %d).\n", 
                   msg_len, KERNEL_OPLOCK_BREAK_MSG_LEN));
            return False;
      }

      memcpy((char *)inode, msg_start+KERNEL_OPLOCK_BREAK_INODE_OFFSET, sizeof(*inode));
      memcpy((char *)dev, msg_start+KERNEL_OPLOCK_BREAK_DEV_OFFSET, sizeof(*dev));
      memcpy((char *)file_id, msg_start+KERNEL_OPLOCK_BREAK_FILEID_OFFSET, sizeof(*file_id));

      DEBUG(3,("kernel oplock break request for file dev = %x, inode = %.0f, file_id = %lu\n", 
            (unsigned int)*dev, (double)*inode, *file_id));

      return True;
}

/****************************************************************************
 See if a oplock message is waiting.
****************************************************************************/

static BOOL linux_oplock_msg_waiting(fd_set *fds)
{
      return signals_received != 0;
}

/****************************************************************************
 See if the kernel supports oplocks.
****************************************************************************/

static BOOL linux_oplocks_available(void)
{
      int fd, ret;
      fd = open("/dev/null", O_RDONLY);
      if (fd == -1)
            return False; /* uggh! */
      ret = fcntl(fd, F_GETLEASE, 0);
      close(fd);
      return ret == F_UNLCK;
}

/****************************************************************************
 Setup kernel oplocks.
****************************************************************************/

struct kernel_oplocks *linux_init_kernel_oplocks(void) 
{
      static struct kernel_oplocks koplocks;
        struct sigaction act;

      if (!linux_oplocks_available()) {
            DEBUG(3,("Linux kernel oplocks not available\n"));
            return NULL;
      }

      act.sa_handler = NULL;
      act.sa_sigaction = signal_handler;
      act.sa_flags = SA_SIGINFO;
      if (sigaction(RT_SIGNAL_LEASE, &act, NULL) != 0) {
            DEBUG(0,("Failed to setup RT_SIGNAL_LEASE handler\n"));
            return NULL;
      }

      koplocks.receive_message = linux_oplock_receive_message;
      koplocks.set_oplock = linux_set_kernel_oplock;
      koplocks.release_oplock = linux_release_kernel_oplock;
      koplocks.parse_message = linux_kernel_oplock_parse;
      koplocks.msg_waiting = linux_oplock_msg_waiting;
      koplocks.notification_fd = -1;

      DEBUG(3,("Linux kernel oplocks enabled\n"));

      return &koplocks;
}
#else
 void oplock_linux_dummy(void) {}
#endif /* HAVE_KERNEL_OPLOCKS_LINUX */

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