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
  23 /* Commit data module.
  24  *
  25  * The purpose of this module is to flush data to disk at regular intervals,
  26  * just like the NFS commit operation. There's two rationales for this. First,
  27  * it minimises the data loss in case of a power outage without incurring
  28  * the poor performance of synchronous I/O. Second, a steady flush rate
  29  * can produce better throughput than suddenly dumping massive amounts of
  30  * writes onto a disk.
  31  *
  32  * Tunables:
  33  *
  34  *  commit: dthresh         Amount of dirty data that can accumulate
  35  *                          before we commit (sync) it.
  36  *
  37  *  commit: debug           Debug level at which to emit messages.
  38  *
  39  *  commit: eof mode        String. Tunes how the module tries to guess when
  40  *                          the client has written the last bytes of the file.
  41  *                          Possible values (default = hinted):
  42  *
  43  *     (*)  = hinted        Some clients (i.e. Windows Explorer) declare the
  44  *                          size of the file before transferring it. With this
  45  *                          option, we remember that hint, and commit after
  46  *                          writing in that file position. If the client
  47  *                          doesn't declare the size of file, commiting on EOF
  48  *                          is not triggered.
  49  *
  50  *          = growth        Commits after a write operation has made the file
  51  *                          size grow. If the client declares a file size, it
  52  *                          refrains to commit until the file has reached it.
  53  *                          Useful for defeating writeback on NFS shares.
  54  *
  55  */
  56
  57 #define MODULE "commit"
  58
  59 static int module_debug;
  60
  61 enum eof_mode
  62 {
  63     EOF_NONE = 0x0000,
  64     EOF_HINTED = 0x0001,
  65     EOF_GROWTH = 0x0002
  66 };
  67
  68 struct commit_info
  69 {
  70         /* For chunk-based commits */
  71         SMB_OFF_T dbytes;       /* Dirty (uncommitted) bytes */
  72         SMB_OFF_T dthresh;      /* Dirty data threshold */
  73         /* For commits on EOF */
  74         enum eof_mode on_eof;
  75         SMB_OFF_T eof;          /* Expected file size */
  76 };
  77
  78 static int commit_do(
  79         struct commit_info *            c,
  80         int                             fd)
  81 {
  82         int result;
  83
  84         DEBUG(module_debug,
  85                 ("%s: flushing %lu dirty bytes\n",
  86                  MODULE, (unsigned long)c->dbytes));
  87
  88 #if HAVE_FDATASYNC
  89         result = fdatasync(fd);
  90 #elif HAVE_FSYNC
  91         result = fsync(fd);
  92 #else
  93         DEBUG(0, ("%s: WARNING: no commit support on this platform\n",
  94                 MODULE));
  95         result = 0
  96 #endif
  97         if (result == 0) {
  98                 c->dbytes = 0;  /* on success, no dirty bytes */
  99         }
 100         return result;
 101 }
 102
 103 static int commit_all(
 104         struct vfs_handle_struct *      handle,
 105         files_struct *                  fsp)
 106 {
 107         struct commit_info *c;
 108
 109         if ((c = (struct commit_info *)VFS_FETCH_FSP_EXTENSION(handle, fsp))) {
 110                 if (c->dbytes) {
 111                         DEBUG(module_debug,
 112                                 ("%s: flushing %lu dirty bytes\n",
 113                                  MODULE, (unsigned long)c->dbytes));
 114
 115                         return commit_do(c, fsp->fh->fd);
 116                 }
 117         }
 118         return 0;
 119 }
 120
 121 static int commit(
 122         struct vfs_handle_struct *      handle,
 123         files_struct *                  fsp,
 124         SMB_OFF_T                       offset,
 125         ssize_t                         last_write)
 126 {
 127         struct commit_info *c;
 128
 129         if ((c = (struct commit_info *)VFS_FETCH_FSP_EXTENSION(handle, fsp))
 130             == NULL) {
 131                 return 0;
 132         }
 133
 134         c->dbytes += last_write;        /* dirty bytes always counted */
 135
 136         if (c->dthresh && (c->dbytes > c->dthresh)) {
 137                 return commit_do(c, fsp->fh->fd);
 138         }
 139
 140         /* Return if we are not in EOF mode or if we have temporarily opted
 141          * out of it.
 142          */
 143         if (c->on_eof == EOF_NONE || c->eof < 0) {
 144                 return 0;
 145         }
 146
 147         /* This write hit or went past our cache the file size. */
 148         if ((offset + last_write) >= c->eof) {
 149                 if (commit_do(c, fsp->fh->fd) == -1) {
 150                         return -1;
 151                 }
 152
 153                 /* Hinted mode only commits the first time we hit EOF. */
 154                 if (c->on_eof == EOF_HINTED) {
 155                     c->eof = -1;
 156                 } else if (c->on_eof == EOF_GROWTH) {
 157                     c->eof = offset + last_write;
 158                 }
 159         }
 160
 161         return 0;
 162 }
 163
 164 static int commit_connect(
 165         struct vfs_handle_struct *  handle,
 166         const char *                service,
 167         const char *                user)
 168 {
 169         int ret = SMB_VFS_NEXT_CONNECT(handle, service, user);
 170
 171         if (ret < 0) {
 172                 return ret;
 173         }
 174
 175         module_debug = lp_parm_int(SNUM(handle->conn), MODULE, "debug", 100);
 176         return 0;
 177 }
 178
 179 static int commit_open(
 180         vfs_handle_struct * handle,
 181         struct smb_filename *smb_fname,
 182         files_struct *      fsp,
 183         int                 flags,
 184         mode_t              mode)
 185 {
 186         SMB_OFF_T dthresh;
 187         const char *eof_mode;
 188         struct commit_info *c = NULL;
 189         int fd;
 190
 191         /* Don't bother with read-only files. */
 192         if ((flags & O_ACCMODE) == O_RDONLY) {
 193                 return SMB_VFS_NEXT_OPEN(handle, smb_fname, fsp, flags, mode);
 194         }
 195
 196         /* Read and check module configuration */
 197         dthresh = conv_str_size(lp_parm_const_string(SNUM(handle->conn),
 198                                         MODULE, "dthresh", NULL));
 199
 200         eof_mode = lp_parm_const_string(SNUM(handle->conn),
 201                                         MODULE, "eof mode", "none");
 202
 203         if (dthresh > 0 || !strequal(eof_mode, "none")) {
 204                 c = (struct commit_info *)VFS_ADD_FSP_EXTENSION(
 205                         handle, fsp, struct commit_info, NULL);
 206                 /* Process main tunables */
 207                 if (c) {
 208                         c->dthresh = dthresh;
 209                         c->dbytes = 0;
 210                         c->on_eof = EOF_NONE;
 211                         c->eof = 0;
 212                 }
 213         }
 214         /* Process eof_mode tunable */
 215         if (c) {
 216                 if (strequal(eof_mode, "hinted")) {
 217                         c->on_eof = EOF_HINTED;
 218                 } else if (strequal(eof_mode, "growth")) {
 219                         c->on_eof = EOF_GROWTH;
 220                 }
 221         }
 222
 223         fd = SMB_VFS_NEXT_OPEN(handle, smb_fname, fsp, flags, mode);
 224         if (fd == -1) {
 225                 VFS_REMOVE_FSP_EXTENSION(handle, fsp);
 226                 return fd;
 227         }
 228
 229         /* EOF commit modes require us to know the initial file size. */
 230         if (c && (c->on_eof != EOF_NONE)) {
 231                 SMB_STRUCT_STAT st;
 232                 if (SMB_VFS_FSTAT(fsp, &st) == -1) {
 233                         return -1;
 234                 }
 235                 c->eof = st.st_ex_size;
 236         }
 237
 238         return 0;
 239 }
 240
 241 static ssize_t commit_write(
 242         vfs_handle_struct * handle,
 243         files_struct *      fsp,
 244         const void *        data,
 245         size_t              count)
 246 {
 247         ssize_t ret;
 248         ret = SMB_VFS_NEXT_WRITE(handle, fsp, data, count);
 249
 250         if (ret > 0) {
 251                 if (commit(handle, fsp, fsp->fh->pos, ret) == -1) {
 252                         return -1;
 253                 }
 254         }
 255
 256         return ret;
 257 }
 258
 259 static ssize_t commit_pwrite(
 260         vfs_handle_struct * handle,
 261         files_struct *      fsp,
 262         const void *        data,
 263         size_t              count,
 264         SMB_OFF_T           offset)
 265 {
 266         ssize_t ret;
 267
 268         ret = SMB_VFS_NEXT_PWRITE(handle, fsp, data, count, offset);
 269         if (ret > 0) {
 270                 if (commit(handle, fsp, offset, ret) == -1) {
 271                         return -1;
 272                 }
 273         }
 274
 275         return ret;
 276 }
 277
 278 static int commit_close(
 279         vfs_handle_struct * handle,
 280         files_struct *      fsp)
 281 {
 282         /* Commit errors not checked, close() will find them again */
 283         commit_all(handle, fsp);
 284         return SMB_VFS_NEXT_CLOSE(handle, fsp);
 285 }
 286
 287 static int commit_ftruncate(
 288         vfs_handle_struct * handle,
 289         files_struct *      fsp,
 290         SMB_OFF_T           len)
 291 {
 292         int result;
 293
 294         result = SMB_VFS_NEXT_FTRUNCATE(handle, fsp, len);
 295         if (result == 0) {
 296                 struct commit_info *c;
 297                 if ((c = (struct commit_info *)VFS_FETCH_FSP_EXTENSION(
 298                              handle, fsp))) {
 299                         commit(handle, fsp, len, 0);
 300                         c->eof = len;
 301                 }
 302         }
 303
 304         return result;
 305 }
 306
 307 static struct vfs_fn_pointers vfs_commit_fns = {
 308         .open_fn = commit_open,
 309         .close_fn = commit_close,
 310         .write = commit_write,
 311         .pwrite = commit_pwrite,
 312         .connect_fn = commit_connect,
 313         .ftruncate = commit_ftruncate
 314 };
 315
 316 NTSTATUS vfs_commit_init(void);
 317 NTSTATUS vfs_commit_init(void)
 318 {
 319         return smb_register_vfs(SMB_VFS_INTERFACE_VERSION, MODULE,
 320                                 &vfs_commit_fns);
 321 }
 322
 323