smbd/oplock_linux.c

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/* 
   Unix SMB/CIFS implementation.
   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.
*/

#define DBGC_CLASS DBGC_LOCKING
#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 (SIGRTMIN+1)
#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(RT_SIGNAL_LEASE);
}

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

        return 0;
}

/****************************************************************************
 Call SETLEASE. If we get EACCES then we try setting up the right capability and
 try again.
 Use the SMB_VFS_LINUX_SETLEASE instead of this call directly.
****************************************************************************/

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

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

        return ret;
}

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

static files_struct *linux_oplock_receive_message(fd_set *fds)
{
        int fd;
        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(CONST_DISCARD(void *, &fd_pending_array[0]),
                        CONST_DISCARD(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);

        return fsp;
}

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

static BOOL linux_set_kernel_oplock(files_struct *fsp, int oplock_type)
{
        if ( SMB_VFS_LINUX_SETLEASE(fsp,fsp->fh->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->fh->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->fh->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->fh->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->fh->file_id, state );
        }

        /*
         * Remove the kernel oplock on this file.
         */
        if ( SMB_VFS_LINUX_SETLEASE(fsp,fsp->fh->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->fh->file_id, strerror(errno) );
                }
        }
}

/****************************************************************************
 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;
        }

        ZERO_STRUCT(act);

        act.sa_handler = NULL;
        act.sa_sigaction = signal_handler;
        act.sa_flags = SA_SIGINFO;
        sigemptyset( &act.sa_mask );
        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.msg_waiting = linux_oplock_msg_waiting;
        koplocks.notification_fd = -1;

        /* the signal can start off blocked due to a bug in bash */
        BlockSignals(False, RT_SIGNAL_LEASE);

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

        return &koplocks;
}
#else
 void oplock_linux_dummy(void);

 void oplock_linux_dummy(void) {}
#endif /* HAVE_KERNEL_OPLOCKS_LINUX */

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