source: vendor/3.6.9/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 3 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, see <http://www.gnu.org/licenses/>.
*/

#define DBGC_CLASS DBGC_LOCKING
#include "includes.h"
#include "system/filesys.h"
#include "smbd/smbd.h"
#include "smbd/globals.h"

#if HAVE_KERNEL_OPLOCKS_LINUX

#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

/*
 * public function to get linux lease capability. Needed by some VFS modules (eg. gpfs.c)
 */
void linux_set_lease_capability(void)
{
        set_effective_capability(LEASE_CAPABILITY);
}

/* 
 * 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;

        /* First set the signal handler. */
        if (linux_set_lease_sighandler(fd) == -1) {
                return -1;
        }
        ret = fcntl(fd, F_SETLEASE, leasetype);
        if (ret == -1 && errno == EACCES) {
                set_effective_capability(LEASE_CAPABILITY);
                /*
                 * Bug 8974 - work around Linux kernel bug
                 * https://bugzilla.kernel.org/show_bug.cgi?id=43336.
                 * "fcntl(F_SETLEASE) resets signal number when
                 *  called multiple times"
                 */
                if (linux_set_lease_sighandler(fd) == -1) {
                        return -1;
                }
                ret = fcntl(fd, F_SETLEASE, leasetype);
        }

        return ret;
}

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

static void linux_oplock_signal_handler(struct tevent_context *ev_ctx,
                                        struct tevent_signal *se,
                                        int signum, int count,
                                        void *_info, void *private_data)
{
        siginfo_t *info = (siginfo_t *)_info;
        int fd = info->si_fd;
        files_struct *fsp;

        fsp = file_find_fd(smbd_server_conn, fd);
        if (fsp == NULL) {
                DEBUG(0,("linux_oplock_signal_handler: failed to find fsp for file fd=%d (file was closed ?)\n", fd ));
                return;
        }
        break_kernel_oplock(fsp->conn->sconn->msg_ctx, fsp);
}

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

static bool linux_set_kernel_oplock(struct kernel_oplocks *ctx,
                                    files_struct *fsp, int oplock_type)
{
        if ( SMB_VFS_LINUX_SETLEASE(fsp, F_WRLCK) == -1) {
                DEBUG(3,("linux_set_kernel_oplock: Refused oplock on file %s, "
                         "fd = %d, file_id = %s. (%s)\n",
                         fsp_str_dbg(fsp), fsp->fh->fd,
                         file_id_string_tos(&fsp->file_id),
                         strerror(errno)));
                return False;
        }
        
        DEBUG(3,("linux_set_kernel_oplock: got kernel oplock on file %s, "
                 "file_id = %s gen_id = %lu\n",
                 fsp_str_dbg(fsp), file_id_string_tos(&fsp->file_id),
                 fsp->fh->gen_id));

        return True;
}

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

static void linux_release_kernel_oplock(struct kernel_oplocks *ctx,
                                        files_struct *fsp, int oplock_type)
{
        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, file_id = %s "
                        "gen_id = %lu has kernel oplock state "
                        "of %x.\n", fsp_str_dbg(fsp),
                        file_id_string_tos(&fsp->file_id),
                        fsp->fh->gen_id, state );
        }

        /*
         * Remove the kernel oplock on this file.
         */
        if ( SMB_VFS_LINUX_SETLEASE(fsp, F_UNLCK) == -1) {
                if (DEBUGLVL(0)) {
                        dbgtext("linux_release_kernel_oplock: Error when "
                                "removing kernel oplock on file " );
                        dbgtext("%s, file_id = %s, gen_id = %lu. "
                                "Error was %s\n", fsp_str_dbg(fsp),
                                file_id_string_tos(&fsp->file_id),
                                fsp->fh->gen_id, strerror(errno) );
                }
        }
}

/****************************************************************************
 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.
****************************************************************************/

static const struct kernel_oplocks_ops linux_koplocks = {
        .set_oplock                     = linux_set_kernel_oplock,
        .release_oplock                 = linux_release_kernel_oplock,
        .contend_level2_oplocks_begin   = NULL,
        .contend_level2_oplocks_end     = NULL,
};

struct kernel_oplocks *linux_init_kernel_oplocks(TALLOC_CTX *mem_ctx)
{
        struct kernel_oplocks *ctx;
        struct tevent_signal *se;

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

        ctx = talloc_zero(mem_ctx, struct kernel_oplocks);
        if (!ctx) {
                DEBUG(0,("Linux Kernel oplocks talloc_Zero failed\n"));
                return NULL;
        }

        ctx->ops = &linux_koplocks;

        se = tevent_add_signal(smbd_event_context(),
                               ctx,
                               RT_SIGNAL_LEASE, SA_SIGINFO,
                               linux_oplock_signal_handler,
                               ctx);
        if (!se) {
                DEBUG(0,("Failed to setup RT_SIGNAL_LEASE handler"));
                TALLOC_FREE(ctx);
                return NULL;
        }

        ctx->private_data = se;

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

        return ctx;
}
#else
 void oplock_linux_dummy(void);

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