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 3 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, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #define DBGC_CLASS DBGC_LOCKING
  21 #include "includes.h"
  22 #include "system/filesys.h"
  23 #include "smbd/smbd.h"
  24 #include "smbd/globals.h"
  25
  26 #ifdef HAVE_KERNEL_OPLOCKS_LINUX
  27
  28 #ifndef RT_SIGNAL_LEASE
  29 #define RT_SIGNAL_LEASE (SIGRTMIN+1)
  30 #endif
  31
  32 /*
  33  * Call to set the kernel lease signal handler
  34  */
  35 int linux_set_lease_sighandler(int fd)
  36 {
  37         if (fcntl(fd, F_SETSIG, RT_SIGNAL_LEASE) == -1) {
  38                 DBG_NOTICE("Failed to set signal handler for kernel lease\n");
  39                 return -1;
  40         }
  41
  42         return 0;
  43 }
  44
  45 /****************************************************************************
  46  Call SETLEASE. If we get EACCES then we try setting up the right capability and
  47  try again.
  48  Use the SMB_VFS_LINUX_SETLEASE instead of this call directly.
  49 ****************************************************************************/
  50
  51 int linux_setlease(int fd, int leasetype)
  52 {
  53         int ret;
  54         int saved_errno = 0;
  55
  56         /*
  57          * Ensure the lease owner is root to allow
  58          * correct delivery of lease-break signals.
  59          */
  60
  61         become_root();
  62
  63         /* First set the signal handler. */
  64         if (linux_set_lease_sighandler(fd) == -1) {
  65                 saved_errno = errno;
  66                 ret = -1;
  67                 goto out;
  68         }
  69         ret = fcntl(fd, F_SETLEASE, leasetype);
  70         if (ret == -1) {
  71                 saved_errno = errno;
  72         }
  73
  74   out:
  75
  76         unbecome_root();
  77
  78         if (ret == -1) {
  79                 errno = saved_errno;
  80         }
  81         return ret;
  82 }
  83
  84 /****************************************************************************
  85  * Deal with the Linux kernel <--> smbd
  86  * oplock break protocol.
  87 ****************************************************************************/
  88
  89 static void linux_oplock_signal_handler(struct tevent_context *ev_ctx,
  90                                         struct tevent_signal *se,
  91                                         int signum, int count,
  92                                         void *_info, void *private_data)
  93 {
  94         struct kernel_oplocks *ctx =
  95                 talloc_get_type_abort(private_data,
  96                 struct kernel_oplocks);
  97         struct smbd_server_connection *sconn =
  98                 talloc_get_type_abort(ctx->private_data,
  99                 struct smbd_server_connection);
 100         siginfo_t *info = (siginfo_t *)_info;
 101         int fd = info->si_fd;
 102         files_struct *fsp;
 103
 104         fsp = file_find_fd(sconn, fd);
 105         if (fsp == NULL) {
 106                 DBG_ERR("linux_oplock_signal_handler: failed to find fsp for file fd=%d (file was closed ?)\n", fd );
 107                 return;
 108         }
 109         break_kernel_oplock(sconn->msg_ctx, fsp);
 110 }
 111
 112 /****************************************************************************
 113  Attempt to set an kernel oplock on a file.
 114 ****************************************************************************/
 115
 116 static bool linux_set_kernel_oplock(struct kernel_oplocks *ctx,
 117                                     files_struct *fsp, int oplock_type)
 118 {
 119         struct file_id_buf idbuf;
 120
 121         if ( SMB_VFS_LINUX_SETLEASE(fsp, F_WRLCK) == -1) {
 122                 DBG_NOTICE("Refused oplock on file %s, "
 123                            "fd = %d, file_id = %s. (%s)\n",
 124                            fsp_str_dbg(fsp),
 125                            fsp_get_io_fd(fsp),
 126                            file_id_str_buf(fsp->file_id, &idbuf),
 127                            strerror(errno));
 128                 return False;
 129         }
 130
 131         DBG_NOTICE("got kernel oplock on file %s, "
 132                    "file_id = %s gen_id = %"PRIu64"\n",
 133                    fsp_str_dbg(fsp),
 134                    file_id_str_buf(fsp->file_id, &idbuf),
 135                    fh_get_gen_id(fsp->fh));
 136
 137         return True;
 138 }
 139
 140 /****************************************************************************
 141  Release a kernel oplock on a file.
 142 ****************************************************************************/
 143
 144 static void linux_release_kernel_oplock(struct kernel_oplocks *ctx,
 145                                         files_struct *fsp, int oplock_type)
 146 {
 147         struct file_id_buf idbuf;
 148
 149         if (DEBUGLVL(DBGLVL_DEBUG)) {
 150                 /*
 151                  * Check and print out the current kernel
 152                  * oplock state of this file.
 153                  */
 154                 int state = fcntl(fsp_get_io_fd(fsp), F_GETLEASE, 0);
 155                 dbgtext("linux_release_kernel_oplock: file %s, file_id = %s "
 156                         "gen_id = %"PRIu64" has kernel oplock state "
 157                         "of %x.\n",
 158                         fsp_str_dbg(fsp),
 159                         file_id_str_buf(fsp->file_id, &idbuf),
 160                         fh_get_gen_id(fsp->fh),
 161                         state);
 162         }
 163
 164         /*
 165          * Remove the kernel oplock on this file.
 166          */
 167         if ( SMB_VFS_LINUX_SETLEASE(fsp, F_UNLCK) == -1) {
 168                 if (DEBUGLVL(DBGLVL_ERR)) {
 169                         dbgtext("linux_release_kernel_oplock: Error when "
 170                                 "removing kernel oplock on file " );
 171                         dbgtext("%s, file_id = %s, gen_id = %"PRIu64". "
 172                                 "Error was %s\n",
 173                                 fsp_str_dbg(fsp),
 174                                 file_id_str_buf(fsp->file_id, &idbuf),
 175                                 fh_get_gen_id(fsp->fh),
 176                                 strerror(errno));
 177                 }
 178         }
 179 }
 180
 181 /****************************************************************************
 182  See if the kernel supports oplocks.
 183 ****************************************************************************/
 184
 185 static bool linux_oplocks_available(void)
 186 {
 187         int fd, ret;
 188         fd = open("/dev/null", O_RDONLY);
 189         if (fd == -1)
 190                 return False; /* uggh! */
 191         ret = fcntl(fd, F_GETLEASE, 0);
 192         close(fd);
 193         return ret == F_UNLCK;
 194 }
 195
 196 /****************************************************************************
 197  Setup kernel oplocks.
 198 ****************************************************************************/
 199
 200 static const struct kernel_oplocks_ops linux_koplocks = {
 201         .set_oplock                     = linux_set_kernel_oplock,
 202         .release_oplock                 = linux_release_kernel_oplock,
 203 };
 204
 205 struct kernel_oplocks *linux_init_kernel_oplocks(struct smbd_server_connection *sconn)
 206 {
 207         struct kernel_oplocks *ctx;
 208         struct tevent_signal *se;
 209
 210         if (!linux_oplocks_available()) {
 211                 DBG_NOTICE("Linux kernel oplocks not available\n");
 212                 return NULL;
 213         }
 214
 215         ctx = talloc_zero(sconn, struct kernel_oplocks);
 216         if (!ctx) {
 217                 DBG_ERR("Linux Kernel oplocks talloc_Zero failed\n");
 218                 return NULL;
 219         }
 220
 221         ctx->ops = &linux_koplocks;
 222         ctx->private_data = sconn;
 223
 224         se = tevent_add_signal(sconn->ev_ctx,
 225                                ctx,
 226                                RT_SIGNAL_LEASE, SA_SIGINFO,
 227                                linux_oplock_signal_handler,
 228                                ctx);
 229         if (!se) {
 230                 DBG_ERR("Failed to setup RT_SIGNAL_LEASE handler\n");
 231                 TALLOC_FREE(ctx);
 232                 return NULL;
 233         }
 234
 235         DBG_NOTICE("Linux kernel oplocks enabled\n");
 236
 237         return ctx;
 238 }
 239 #else
 240  void oplock_linux_dummy(void);
 241
 242  void oplock_linux_dummy(void) {}
 243 #endif /* HAVE_KERNEL_OPLOCKS_LINUX */