samba-mirror/source3/smbd/oplock_linux.c

/* 
   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

/* these can be removed when they are in glibc headers */
struct  cap_user_header {
	uint32 version;
	int pid;
} header;
struct cap_user_data {
	uint32 effective;
	uint32 permitted;
	uint32 inheritable;
} data;

extern int capget(struct cap_user_header * hdrp,
		  struct cap_user_data * datap);
extern int capset(struct cap_user_header * hdrp,
		  const struct cap_user_data * datap);

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);
}

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

static void set_capability(unsigned capability)
{
#ifndef _LINUX_CAPABILITY_VERSION
#define _LINUX_CAPABILITY_VERSION 0x19980330
#endif
	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 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 (linux_setlease(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 (linux_setlease(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 */