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
  21 /* Commit data module.
  22  *
  23  * The purpose of this module is to flush data to disk at regular intervals,
  24  * just like the NFS commit operation. There's two rationales for this. First,
  25  * it minimises the data loss in case of a power outage without incurring
  26  * the poor performance of synchronous I/O. Second, a steady flush rate
  27  * can produce better throughput than suddenly dumping massive amounts of
  28  * writes onto a disk.
  29  *
  30  * Tunables:
  31  *
  32  *  commit: dthresh         Amount of dirty data that can accumulate
  33  *                          before we commit (sync) it.
  34  *
  35  *  commit: debug           Debug level at which to emit messages.
  36  *
  37  *  commit: eof mode        String. Tunes how the module tries to guess when
  38  *                          the client has written the last bytes of the file.
  39  *                          Possible values (default = hinted):
  40  *
  41  *     (*)  = hinted        Some clients (i.e. Windows Explorer) declare the
  42  *                          size of the file before transferring it. With this
  43  *                          option, we remember that hint, and commit after
  44  *                          writing in that file position. If the client
  45  *                          doesn't declare the size of file, commiting on EOF
  46  *                          is not triggered.
  47  *
  48  *          = growth        Commits after a write operation has made the file
  49  *                          size grow. If the client declares a file size, it
  50  *                          refrains to commit until the file has reached it.
  51  *                          Useful for defeating writeback on NFS shares.
  52  *
  53  */
  54
  55 #define MODULE "commit"
  56
  57 static int module_debug;
  58
  59 enum eof_mode
  60 {
  61     EOF_NONE = 0x0000,
  62     EOF_HINTED = 0x0001,
  63     EOF_GROWTH = 0x0002
  64 };
  65
  66 struct commit_info
  67 {
  68         /* For chunk-based commits */
  69         SMB_OFF_T dbytes;       /* Dirty (uncommitted) bytes */
  70         SMB_OFF_T dthresh;      /* Dirty data threshold */
  71         /* For commits on EOF */
  72         enum eof_mode on_eof;
  73         SMB_OFF_T eof;          /* Expected file size */
  74 };
  75
  76 static int commit_do(
  77         struct commit_info *            c,
  78         int                             fd)
  79 {
  80         int result;
  81
  82         DEBUG(module_debug,
  83                 ("%s: flushing %lu dirty bytes\n",
  84                  MODULE, (unsigned long)c->dbytes));
  85
  86 #if HAVE_FDATASYNC
  87         result = fdatasync(fd);
  88 #elif HAVE_FSYNC
  89         result = fsync(fd);
  90 #else
  91         DEBUG(0, ("%s: WARNING: no commit support on this platform\n",
  92                 MODULE));
  93         result = 0
  94 #endif
  95         if (result == 0) {
  96                 c->dbytes = 0;  /* on success, no dirty bytes */
  97         }
  98         return result;
  99 }
 100
 101 static int commit_all(
 102         struct vfs_handle_struct *      handle,
 103         files_struct *                  fsp)
 104 {
 105         struct commit_info *c;
 106
 107         if ((c = (struct commit_info *)VFS_FETCH_FSP_EXTENSION(handle, fsp))) {
 108                 if (c->dbytes) {
 109                         DEBUG(module_debug,
 110                                 ("%s: flushing %lu dirty bytes\n",
 111                                  MODULE, (unsigned long)c->dbytes));
 112
 113                         return commit_do(c, fsp->fh->fd);
 114                 }
 115         }
 116         return 0;
 117 }
 118
 119 static int commit(
 120         struct vfs_handle_struct *      handle,
 121         files_struct *                  fsp,
 122         SMB_OFF_T                       offset,
 123         ssize_t                         last_write)
 124 {
 125         struct commit_info *c;
 126
 127         if ((c = (struct commit_info *)VFS_FETCH_FSP_EXTENSION(handle, fsp))
 128             == NULL) {
 129                 return 0;
 130         }
 131
 132         c->dbytes += last_write;        /* dirty bytes always counted */
 133
 134         if (c->dthresh && (c->dbytes > c->dthresh)) {
 135                 return commit_do(c, fsp->fh->fd);
 136         }
 137
 138         /* Return if we are not in EOF mode or if we have temporarily opted
 139          * out of it.
 140          */
 141         if (c->on_eof == EOF_NONE || c->eof < 0) {
 142                 return 0;
 143         }
 144
 145         /* This write hit or went past our cache the file size. */
 146         if ((offset + last_write) >= c->eof) {
 147                 if (commit_do(c, fsp->fh->fd) == -1) {
 148                         return -1;
 149                 }
 150
 151                 /* Hinted mode only commits the first time we hit EOF. */
 152                 if (c->on_eof == EOF_HINTED) {
 153                     c->eof = -1;
 154                 } else if (c->on_eof == EOF_GROWTH) {
 155                     c->eof = offset + last_write;
 156                 }
 157         }
 158
 159         return 0;
 160 }
 161
 162 static int commit_connect(
 163         struct vfs_handle_struct *  handle,
 164         const char *                service,
 165         const char *                user)
 166 {
 167         int ret = SMB_VFS_NEXT_CONNECT(handle, service, user);
 168
 169         if (ret < 0) {
 170                 return ret;
 171         }
 172
 173         module_debug = lp_parm_int(SNUM(handle->conn), MODULE, "debug", 100);
 174         return 0;
 175 }
 176
 177 static int commit_open(
 178         vfs_handle_struct * handle,
 179         struct smb_filename *smb_fname,
 180         files_struct *      fsp,
 181         int                 flags,
 182         mode_t              mode)
 183 {
 184         SMB_OFF_T dthresh;
 185         const char *eof_mode;
 186         struct commit_info *c = NULL;
 187         int fd;
 188
 189         /* Don't bother with read-only files. */
 190         if ((flags & O_ACCMODE) == O_RDONLY) {
 191                 return SMB_VFS_NEXT_OPEN(handle, smb_fname, fsp, flags, mode);
 192         }
 193
 194         /* Read and check module configuration */
 195         dthresh = conv_str_size(lp_parm_const_string(SNUM(handle->conn),
 196                                         MODULE, "dthresh", NULL));
 197
 198         eof_mode = lp_parm_const_string(SNUM(handle->conn),
 199                                         MODULE, "eof mode", "none");
 200
 201         if (dthresh > 0 || !strequal(eof_mode, "none")) {
 202                 c = (struct commit_info *)VFS_ADD_FSP_EXTENSION(
 203                         handle, fsp, struct commit_info, NULL);
 204                 /* Process main tunables */
 205                 if (c) {
 206                         c->dthresh = dthresh;
 207                         c->dbytes = 0;
 208                         c->on_eof = EOF_NONE;
 209                         c->eof = 0;
 210                 }
 211         }
 212         /* Process eof_mode tunable */
 213         if (c) {
 214                 if (strequal(eof_mode, "hinted")) {
 215                         c->on_eof = EOF_HINTED;
 216                 } else if (strequal(eof_mode, "growth")) {
 217                         c->on_eof = EOF_GROWTH;
 218                 }
 219         }
 220
 221         fd = SMB_VFS_NEXT_OPEN(handle, smb_fname, fsp, flags, mode);
 222         if (fd == -1) {
 223                 VFS_REMOVE_FSP_EXTENSION(handle, fsp);
 224                 return fd;
 225         }
 226
 227         /* EOF commit modes require us to know the initial file size. */
 228         if (c && (c->on_eof != EOF_NONE)) {
 229                 SMB_STRUCT_STAT st;
 230                 if (SMB_VFS_FSTAT(fsp, &st) == -1) {
 231                         return -1;
 232                 }
 233                 c->eof = st.st_ex_size;
 234         }
 235
 236         return 0;
 237 }
 238
 239 static ssize_t commit_write(
 240         vfs_handle_struct * handle,
 241         files_struct *      fsp,
 242         const void *        data,
 243         size_t              count)
 244 {
 245         ssize_t ret;
 246         ret = SMB_VFS_NEXT_WRITE(handle, fsp, data, count);
 247
 248         if (ret > 0) {
 249                 if (commit(handle, fsp, fsp->fh->pos, ret) == -1) {
 250                         return -1;
 251                 }
 252         }
 253
 254         return ret;
 255 }
 256
 257 static ssize_t commit_pwrite(
 258         vfs_handle_struct * handle,
 259         files_struct *      fsp,
 260         const void *        data,
 261         size_t              count,
 262         SMB_OFF_T           offset)
 263 {
 264         ssize_t ret;
 265
 266         ret = SMB_VFS_NEXT_PWRITE(handle, fsp, data, count, offset);
 267         if (ret > 0) {
 268                 if (commit(handle, fsp, offset, ret) == -1) {
 269                         return -1;
 270                 }
 271         }
 272
 273         return ret;
 274 }
 275
 276 static int commit_close(
 277         vfs_handle_struct * handle,
 278         files_struct *      fsp)
 279 {
 280         /* Commit errors not checked, close() will find them again */
 281         commit_all(handle, fsp);
 282         return SMB_VFS_NEXT_CLOSE(handle, fsp);
 283 }
 284
 285 static int commit_ftruncate(
 286         vfs_handle_struct * handle,
 287         files_struct *      fsp,
 288         SMB_OFF_T           len)
 289 {
 290         int result;
 291
 292         result = SMB_VFS_NEXT_FTRUNCATE(handle, fsp, len);
 293         if (result == 0) {
 294                 struct commit_info *c;
 295                 if ((c = (struct commit_info *)VFS_FETCH_FSP_EXTENSION(
 296                              handle, fsp))) {
 297                         commit(handle, fsp, len, 0);
 298                         c->eof = len;
 299                 }
 300         }
 301
 302         return result;
 303 }
 304
 305 static struct vfs_fn_pointers vfs_commit_fns = {
 306         .open = commit_open,
 307         .close_fn = commit_close,
 308         .write = commit_write,
 309         .pwrite = commit_pwrite,
 310         .connect_fn = commit_connect,
 311         .ftruncate = commit_ftruncate
 312 };
 313
 314 NTSTATUS vfs_commit_init(void);
 315 NTSTATUS vfs_commit_init(void)
 316 {
 317         return smb_register_vfs(SMB_VFS_INTERFACE_VERSION, MODULE,
 318                                 &vfs_commit_fns);
 319 }
 320
 321