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         result = 0
  92 #endif
  93         if (result == 0) {
  94                 c->dbytes = 0;  /* on success, no dirty bytes */
  95         }
  96         return result;
  97 }
  98
  99 static int commit_all(
 100         struct vfs_handle_struct *      handle,
 101         files_struct *                  fsp)
 102 {
 103         struct commit_info *c;
 104
 105         if ((c = (struct commit_info *)VFS_FETCH_FSP_EXTENSION(handle, fsp))) {
 106                 if (c->dbytes) {
 107                         DEBUG(module_debug,
 108                                 ("%s: flushing %lu dirty bytes\n",
 109                                  MODULE, (unsigned long)c->dbytes));
 110
 111                         return commit_do(c, fsp->fh->fd);
 112                 }
 113         }
 114         return 0;
 115 }
 116
 117 static int commit(
 118         struct vfs_handle_struct *      handle,
 119         files_struct *                  fsp,
 120         SMB_OFF_T                       offset,
 121         ssize_t                         last_write)
 122 {
 123         struct commit_info *c;
 124
 125         if ((c = (struct commit_info *)VFS_FETCH_FSP_EXTENSION(handle, fsp))
 126             == NULL) {
 127                 return 0;
 128         }
 129
 130         c->dbytes += last_write;        /* dirty bytes always counted */
 131
 132         if (c->dthresh && (c->dbytes > c->dthresh)) {
 133                 return commit_do(c, fsp->fh->fd);
 134         }
 135
 136         /* Return if we are not in EOF mode or if we have temporarily opted
 137          * out of it.
 138          */
 139         if (c->on_eof == EOF_NONE || c->eof < 0) {
 140                 return 0;
 141         }
 142
 143         /* This write hit or went past our cache the file size. */
 144         if ((offset + last_write) >= c->eof) {
 145                 if (commit_do(c, fsp->fh->fd) == -1) {
 146                         return -1;
 147                 }
 148
 149                 /* Hinted mode only commits the first time we hit EOF. */
 150                 if (c->on_eof == EOF_HINTED) {
 151                     c->eof = -1;
 152                 } else if (c->on_eof == EOF_GROWTH) {
 153                     c->eof = offset + last_write;
 154                 }
 155         }
 156
 157         return 0;
 158 }
 159
 160 static int commit_connect(
 161         struct vfs_handle_struct *  handle,
 162         const char *                service,
 163         const char *                user)
 164 {
 165         int ret = SMB_VFS_NEXT_CONNECT(handle, service, user);
 166
 167         if (ret < 0) {
 168                 return ret;
 169         }
 170
 171         module_debug = lp_parm_int(SNUM(handle->conn), MODULE, "debug", 100);
 172         return 0;
 173 }
 174
 175 static int commit_open(
 176         vfs_handle_struct * handle,
 177         struct smb_filename *smb_fname,
 178         files_struct *      fsp,
 179         int                 flags,
 180         mode_t              mode)
 181 {
 182         SMB_OFF_T dthresh;
 183         const char *eof_mode;
 184         struct commit_info *c = NULL;
 185         int fd;
 186
 187         /* Don't bother with read-only files. */
 188         if ((flags & O_ACCMODE) == O_RDONLY) {
 189                 return SMB_VFS_NEXT_OPEN(handle, smb_fname, fsp, flags, mode);
 190         }
 191
 192         /* Read and check module configuration */
 193         dthresh = conv_str_size(lp_parm_const_string(SNUM(handle->conn),
 194                                         MODULE, "dthresh", NULL));
 195
 196         eof_mode = lp_parm_const_string(SNUM(handle->conn),
 197                                         MODULE, "eof mode", "none");
 198
 199         if (dthresh > 0 || !strequal(eof_mode, "none")) {
 200                 c = (struct commit_info *)VFS_ADD_FSP_EXTENSION(
 201                         handle, fsp, struct commit_info, NULL);
 202                 /* Process main tunables */
 203                 if (c) {
 204                         c->dthresh = dthresh;
 205                         c->dbytes = 0;
 206                         c->on_eof = EOF_NONE;
 207                         c->eof = 0;
 208                 }
 209         }
 210         /* Process eof_mode tunable */
 211         if (c) {
 212                 if (strequal(eof_mode, "hinted")) {
 213                         c->on_eof = EOF_HINTED;
 214                 } else if (strequal(eof_mode, "growth")) {
 215                         c->on_eof = EOF_GROWTH;
 216                 }
 217         }
 218
 219         fd = SMB_VFS_NEXT_OPEN(handle, smb_fname, fsp, flags, mode);
 220         if (fd == -1) {
 221                 VFS_REMOVE_FSP_EXTENSION(handle, fsp);
 222                 return fd;
 223         }
 224
 225         /* EOF commit modes require us to know the initial file size. */
 226         if (c && (c->on_eof != EOF_NONE)) {
 227                 SMB_STRUCT_STAT st;
 228                 if (SMB_VFS_FSTAT(fsp, &st) == -1) {
 229                         return -1;
 230                 }
 231                 c->eof = st.st_ex_size;
 232         }
 233
 234         return fd;
 235 }
 236
 237 static ssize_t commit_write(
 238         vfs_handle_struct * handle,
 239         files_struct *      fsp,
 240         const void *        data,
 241         size_t              count)
 242 {
 243         ssize_t ret;
 244         ret = SMB_VFS_NEXT_WRITE(handle, fsp, data, count);
 245
 246         if (ret > 0) {
 247                 if (commit(handle, fsp, fsp->fh->pos, ret) == -1) {
 248                         return -1;
 249                 }
 250         }
 251
 252         return ret;
 253 }
 254
 255 static ssize_t commit_pwrite(
 256         vfs_handle_struct * handle,
 257         files_struct *      fsp,
 258         const void *        data,
 259         size_t              count,
 260         SMB_OFF_T           offset)
 261 {
 262         ssize_t ret;
 263
 264         ret = SMB_VFS_NEXT_PWRITE(handle, fsp, data, count, offset);
 265         if (ret > 0) {
 266                 if (commit(handle, fsp, offset, ret) == -1) {
 267                         return -1;
 268                 }
 269         }
 270
 271         return ret;
 272 }
 273
 274 static int commit_close(
 275         vfs_handle_struct * handle,
 276         files_struct *      fsp)
 277 {
 278         /* Commit errors not checked, close() will find them again */
 279         commit_all(handle, fsp);
 280         return SMB_VFS_NEXT_CLOSE(handle, fsp);
 281 }
 282
 283 static int commit_ftruncate(
 284         vfs_handle_struct * handle,
 285         files_struct *      fsp,
 286         SMB_OFF_T           len)
 287 {
 288         int result;
 289
 290         result = SMB_VFS_NEXT_FTRUNCATE(handle, fsp, len);
 291         if (result == 0) {
 292                 struct commit_info *c;
 293                 if ((c = (struct commit_info *)VFS_FETCH_FSP_EXTENSION(
 294                              handle, fsp))) {
 295                         commit(handle, fsp, len, 0);
 296                         c->eof = len;
 297                 }
 298         }
 299
 300         return result;
 301 }
 302
 303 static struct vfs_fn_pointers vfs_commit_fns = {
 304         .open = commit_open,
 305         .close_fn = commit_close,
 306         .write = commit_write,
 307         .pwrite = commit_pwrite,
 308         .connect_fn = commit_connect,
 309         .ftruncate = commit_ftruncate
 310 };
 311
 312 NTSTATUS vfs_commit_init(void);
 313 NTSTATUS vfs_commit_init(void)
 314 {
 315         return smb_register_vfs(SMB_VFS_INTERFACE_VERSION, MODULE,
 316                                 &vfs_commit_fns);
 317 }
 318
 319