source3/modules/vfs_commit.c

   1 /*
   2  * Copyright (c) James Peach 2006, 2007
   3  * Copyright (c) David Losada Carballo 2007
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 3 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 #include "includes.h"
  20 #include "system/filesys.h"
  21 #include "smbd/smbd.h"
  22 #include "lib/util/tevent_unix.h"
  23
  24 /* Commit data module.
  25  *
  26  * The purpose of this module is to flush data to disk at regular intervals,
  27  * just like the NFS commit operation. There's two rationales for this. First,
  28  * it minimises the data loss in case of a power outage without incurring
  29  * the poor performance of synchronous I/O. Second, a steady flush rate
  30  * can produce better throughput than suddenly dumping massive amounts of
  31  * writes onto a disk.
  32  *
  33  * Tunables:
  34  *
  35  *  commit: dthresh         Amount of dirty data that can accumulate
  36  *                          before we commit (sync) it.
  37  *
  38  *  commit: debug           Debug level at which to emit messages.
  39  *
  40  *  commit: eof mode        String. Tunes how the module tries to guess when
  41  *                          the client has written the last bytes of the file.
  42  *                          Possible values (default = hinted):
  43  *
  44  *     (*)  = hinted        Some clients (i.e. Windows Explorer) declare the
  45  *                          size of the file before transferring it. With this
  46  *                          option, we remember that hint, and commit after
  47  *                          writing in that file position. If the client
  48  *                          doesn't declare the size of file, commiting on EOF
  49  *                          is not triggered.
  50  *
  51  *          = growth        Commits after a write operation has made the file
  52  *                          size grow. If the client declares a file size, it
  53  *                          refrains to commit until the file has reached it.
  54  *                          Useful for defeating writeback on NFS shares.
  55  *
  56  */
  57
  58 #define MODULE "commit"
  59
  60 static int module_debug;
  61
  62 enum eof_mode
  63 {
  64     EOF_NONE = 0x0000,
  65     EOF_HINTED = 0x0001,
  66     EOF_GROWTH = 0x0002
  67 };
  68
  69 struct commit_info
  70 {
  71         /* For chunk-based commits */
  72         off_t dbytes;   /* Dirty (uncommitted) bytes */
  73         off_t dthresh;  /* Dirty data threshold */
  74         /* For commits on EOF */
  75         enum eof_mode on_eof;
  76         off_t eof;              /* Expected file size */
  77 };
  78
  79 static int commit_do(
  80         struct commit_info *            c,
  81         int                             fd)
  82 {
  83         int result;
  84
  85         DEBUG(module_debug,
  86                 ("%s: flushing %lu dirty bytes\n",
  87                  MODULE, (unsigned long)c->dbytes));
  88
  89 #if defined(HAVE_FDATASYNC)
  90         result = fdatasync(fd);
  91 #elif defined(HAVE_FSYNC)
  92         result = fsync(fd);
  93 #else
  94         DEBUG(0, ("%s: WARNING: no commit support on this platform\n",
  95                 MODULE));
  96         result = 0
  97 #endif
  98         if (result == 0) {
  99                 c->dbytes = 0;  /* on success, no dirty bytes */
 100         }
 101         return result;
 102 }
 103
 104 static int commit_all(
 105         struct vfs_handle_struct *      handle,
 106         files_struct *                  fsp)
 107 {
 108         struct commit_info *c;
 109
 110         if ((c = (struct commit_info *)VFS_FETCH_FSP_EXTENSION(handle, fsp))) {
 111                 if (c->dbytes) {
 112                         DEBUG(module_debug,
 113                                 ("%s: flushing %lu dirty bytes\n",
 114                                  MODULE, (unsigned long)c->dbytes));
 115
 116                         return commit_do(c, fsp->fh->fd);
 117                 }
 118         }
 119         return 0;
 120 }
 121
 122 static int commit(
 123         struct vfs_handle_struct *      handle,
 124         files_struct *                  fsp,
 125         off_t                   offset,
 126         ssize_t                         last_write)
 127 {
 128         struct commit_info *c;
 129
 130         if ((c = (struct commit_info *)VFS_FETCH_FSP_EXTENSION(handle, fsp))
 131             == NULL) {
 132                 return 0;
 133         }
 134
 135         c->dbytes += last_write;        /* dirty bytes always counted */
 136
 137         if (c->dthresh && (c->dbytes > c->dthresh)) {
 138                 return commit_do(c, fsp->fh->fd);
 139         }
 140
 141         /* Return if we are not in EOF mode or if we have temporarily opted
 142          * out of it.
 143          */
 144         if (c->on_eof == EOF_NONE || c->eof < 0) {
 145                 return 0;
 146         }
 147
 148         /* This write hit or went past our cache the file size. */
 149         if ((offset + last_write) >= c->eof) {
 150                 if (commit_do(c, fsp->fh->fd) == -1) {
 151                         return -1;
 152                 }
 153
 154                 /* Hinted mode only commits the first time we hit EOF. */
 155                 if (c->on_eof == EOF_HINTED) {
 156                     c->eof = -1;
 157                 } else if (c->on_eof == EOF_GROWTH) {
 158                     c->eof = offset + last_write;
 159                 }
 160         }
 161
 162         return 0;
 163 }
 164
 165 static int commit_connect(
 166         struct vfs_handle_struct *  handle,
 167         const char *                service,
 168         const char *                user)
 169 {
 170         int ret = SMB_VFS_NEXT_CONNECT(handle, service, user);
 171
 172         if (ret < 0) {
 173                 return ret;
 174         }
 175
 176         module_debug = lp_parm_int(SNUM(handle->conn), MODULE, "debug", 100);
 177         return 0;
 178 }
 179
 180 static int commit_openat(struct vfs_handle_struct *handle,
 181                          const struct files_struct *dirfsp,
 182                          const struct smb_filename *smb_fname,
 183                          files_struct *fsp,
 184                          int flags,
 185                          mode_t mode)
 186 {
 187         off_t dthresh;
 188         const char *eof_mode;
 189         struct commit_info *c = NULL;
 190         int fd;
 191
 192         /* Don't bother with read-only files. */
 193         if ((flags & O_ACCMODE) == O_RDONLY) {
 194                 return SMB_VFS_NEXT_OPENAT(handle,
 195                                            dirfsp,
 196                                            smb_fname,
 197                                            fsp,
 198                                            flags,
 199                                            mode);
 200         }
 201
 202         /* Read and check module configuration */
 203         dthresh = conv_str_size(lp_parm_const_string(SNUM(handle->conn),
 204                                         MODULE, "dthresh", NULL));
 205
 206         eof_mode = lp_parm_const_string(SNUM(handle->conn),
 207                                         MODULE, "eof mode", "none");
 208
 209         if (dthresh > 0 || !strequal(eof_mode, "none")) {
 210                 c = VFS_ADD_FSP_EXTENSION(
 211                         handle, fsp, struct commit_info, NULL);
 212                 /* Process main tunables */
 213                 if (c) {
 214                         c->dthresh = dthresh;
 215                         c->dbytes = 0;
 216                         c->on_eof = EOF_NONE;
 217                         c->eof = 0;
 218                 }
 219         }
 220         /* Process eof_mode tunable */
 221         if (c) {
 222                 if (strequal(eof_mode, "hinted")) {
 223                         c->on_eof = EOF_HINTED;
 224                 } else if (strequal(eof_mode, "growth")) {
 225                         c->on_eof = EOF_GROWTH;
 226                 }
 227         }
 228
 229         fd = SMB_VFS_NEXT_OPENAT(handle, dirfsp, smb_fname, fsp, flags, mode);
 230         if (fd == -1) {
 231                 VFS_REMOVE_FSP_EXTENSION(handle, fsp);
 232                 return fd;
 233         }
 234
 235         /* EOF commit modes require us to know the initial file size. */
 236         if (c && (c->on_eof != EOF_NONE)) {
 237                 SMB_STRUCT_STAT st;
 238                 /*
 239                  * Setting the fd of the FSP is a hack
 240                  * but also practiced elsewhere -
 241                  * needed for calling the VFS.
 242                  */
 243                 fsp_set_fd(fsp, fd);
 244                 if (SMB_VFS_FSTAT(fsp, &st) == -1) {
 245                         int saved_errno = errno;
 246                         SMB_VFS_CLOSE(fsp);
 247                         errno = saved_errno;
 248                         return -1;
 249                 }
 250                 c->eof = st.st_ex_size;
 251         }
 252
 253         return fd;
 254 }
 255
 256 static ssize_t commit_pwrite(
 257         vfs_handle_struct * handle,
 258         files_struct *      fsp,
 259         const void *        data,
 260         size_t              count,
 261         off_t       offset)
 262 {
 263         ssize_t ret;
 264
 265         ret = SMB_VFS_NEXT_PWRITE(handle, fsp, data, count, offset);
 266         if (ret > 0) {
 267                 if (commit(handle, fsp, offset, ret) == -1) {
 268                         return -1;
 269                 }
 270         }
 271
 272         return ret;
 273 }
 274
 275 struct commit_pwrite_state {
 276         struct vfs_handle_struct *handle;
 277         struct files_struct *fsp;
 278         ssize_t ret;
 279         struct vfs_aio_state vfs_aio_state;
 280 };
 281
 282 static void commit_pwrite_written(struct tevent_req *subreq);
 283
 284 static struct tevent_req *commit_pwrite_send(struct vfs_handle_struct *handle,
 285                                              TALLOC_CTX *mem_ctx,
 286                                              struct tevent_context *ev,
 287                                              struct files_struct *fsp,
 288                                              const void *data,
 289                                              size_t n, off_t offset)
 290 {
 291         struct tevent_req *req, *subreq;
 292         struct commit_pwrite_state *state;
 293
 294         req = tevent_req_create(mem_ctx, &state, struct commit_pwrite_state);
 295         if (req == NULL) {
 296                 return NULL;
 297         }
 298         state->handle = handle;
 299         state->fsp = fsp;
 300
 301         subreq = SMB_VFS_NEXT_PWRITE_SEND(state, ev, handle, fsp, data,
 302                                           n, offset);
 303         if (tevent_req_nomem(subreq, req)) {
 304                 return tevent_req_post(req, ev);
 305         }
 306         tevent_req_set_callback(subreq, commit_pwrite_written, req);
 307         return req;
 308 }
 309
 310 static void commit_pwrite_written(struct tevent_req *subreq)
 311 {
 312         struct tevent_req *req = tevent_req_callback_data(
 313                 subreq, struct tevent_req);
 314         struct commit_pwrite_state *state = tevent_req_data(
 315                 req, struct commit_pwrite_state);
 316         int commit_ret;
 317
 318         state->ret = SMB_VFS_PWRITE_RECV(subreq, &state->vfs_aio_state);
 319         TALLOC_FREE(subreq);
 320
 321         if (state->ret <= 0) {
 322                 tevent_req_done(req);
 323                 return;
 324         }
 325
 326         /*
 327          * Ok, this is a sync fake. We should make the sync async as well, but
 328          * I'm too lazy for that right now -- vl
 329          */
 330         commit_ret = commit(state->handle, state->fsp, state->fsp->fh->pos,
 331                             state->ret);
 332
 333         if (commit_ret == -1) {
 334                 state->ret = -1;
 335         }
 336
 337         tevent_req_done(req);
 338 }
 339
 340 static ssize_t commit_pwrite_recv(struct tevent_req *req,
 341                                   struct vfs_aio_state *vfs_aio_state)
 342 {
 343         struct commit_pwrite_state *state =
 344                 tevent_req_data(req, struct commit_pwrite_state);
 345
 346         if (tevent_req_is_unix_error(req, &vfs_aio_state->error)) {
 347                 return -1;
 348         }
 349         *vfs_aio_state = state->vfs_aio_state;
 350         return state->ret;
 351 }
 352
 353 static int commit_close(
 354         vfs_handle_struct * handle,
 355         files_struct *      fsp)
 356 {
 357         /* Commit errors not checked, close() will find them again */
 358         commit_all(handle, fsp);
 359         return SMB_VFS_NEXT_CLOSE(handle, fsp);
 360 }
 361
 362 static int commit_ftruncate(
 363         vfs_handle_struct * handle,
 364         files_struct *      fsp,
 365         off_t           len)
 366 {
 367         int result;
 368
 369         result = SMB_VFS_NEXT_FTRUNCATE(handle, fsp, len);
 370         if (result == 0) {
 371                 struct commit_info *c;
 372                 if ((c = (struct commit_info *)VFS_FETCH_FSP_EXTENSION(
 373                              handle, fsp))) {
 374                         commit(handle, fsp, len, 0);
 375                         c->eof = len;
 376                 }
 377         }
 378
 379         return result;
 380 }
 381
 382 static struct vfs_fn_pointers vfs_commit_fns = {
 383         .openat_fn = commit_openat,
 384         .close_fn = commit_close,
 385         .pwrite_fn = commit_pwrite,
 386         .pwrite_send_fn = commit_pwrite_send,
 387         .pwrite_recv_fn = commit_pwrite_recv,
 388         .connect_fn = commit_connect,
 389         .ftruncate_fn = commit_ftruncate
 390 };
 391
 392 static_decl_vfs;
 393 NTSTATUS vfs_commit_init(TALLOC_CTX *ctx)
 394 {
 395         return smb_register_vfs(SMB_VFS_INTERFACE_VERSION, MODULE,
 396                                 &vfs_commit_fns);
 397 }
 398
 399