source/modules/vfs_commit.c

   1 /*
   2  * Copyright (c) James Peach 2006
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  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  */
  38
  39 #define MODULE "commit"
  40
  41 static int module_debug;
  42
  43 struct commit_info
  44 {
  45         SMB_OFF_T dbytes;       /* Dirty (uncommitted) bytes */
  46         SMB_OFF_T dthresh;      /* Dirty data threshold */
  47 };
  48
  49 static void commit_all(
  50         struct vfs_handle_struct *      handle,
  51         files_struct *                  fsp)
  52 {
  53         struct commit_info *c;
  54
  55         if ((c = VFS_FETCH_FSP_EXTENSION(handle, fsp))) {
  56                 if (c->dbytes) {
  57                         DEBUG(module_debug,
  58                                 ("%s: flushing %lu dirty bytes\n",
  59                                  MODULE, (unsigned long)c->dbytes));
  60
  61                         fdatasync(fsp->fh->fd);
  62                         c->dbytes = 0;
  63                 }
  64         }
  65 }
  66
  67 static void commit(
  68         struct vfs_handle_struct *      handle,
  69         files_struct *                  fsp,
  70         ssize_t                         last_write)
  71 {
  72         struct commit_info *c;
  73
  74         if ((c = VFS_FETCH_FSP_EXTENSION(handle, fsp))) {
  75
  76                 if (last_write > 0) {
  77                         c->dbytes += last_write;
  78                 }
  79
  80                 if (c->dbytes > c->dthresh) {
  81                         DEBUG(module_debug,
  82                                 ("%s: flushing %lu dirty bytes\n",
  83                                  MODULE, (unsigned long)c->dbytes));
  84
  85                         fdatasync(fsp->fh->fd);
  86                         c->dbytes = 0;
  87                 }
  88         }
  89 }
  90
  91 static int commit_connect(
  92         struct vfs_handle_struct *  handle,
  93         const char *                service,
  94         const char *                user)
  95 {
  96         module_debug = lp_parm_int(SNUM(handle->conn), MODULE, "debug", 100);
  97         return SMB_VFS_NEXT_CONNECT(handle, service, user);
  98 }
  99
 100 static int commit_open(
 101         vfs_handle_struct * handle,
 102         const char *        fname,
 103         files_struct *      fsp,
 104         int                 flags,
 105         mode_t              mode)
 106 {
 107         SMB_OFF_T dthresh;
 108
 109         /* Don't bother with read-only files. */
 110         if ((flags & O_ACCMODE) == O_RDONLY) {
 111                 return SMB_VFS_NEXT_OPEN(handle, fname, fsp, flags, mode);
 112         }
 113
 114         dthresh = conv_str_size(lp_parm_const_string(SNUM(handle->conn),
 115                                         MODULE, "dthresh", NULL));
 116
 117         if (dthresh > 0) {
 118                 struct commit_info * c;
 119                 c = VFS_ADD_FSP_EXTENSION(handle, fsp, struct commit_info);
 120                 if (c) {
 121                         c->dthresh = dthresh;
 122                         c->dbytes = 0;
 123                 }
 124         }
 125
 126         return SMB_VFS_NEXT_OPEN(handle, fname, fsp, flags, mode);
 127 }
 128
 129 static ssize_t commit_write(
 130         vfs_handle_struct * handle,
 131         files_struct *      fsp,
 132         int                 fd,
 133         void *              data,
 134         size_t              count)
 135 {
 136         ssize_t ret;
 137
 138         ret = SMB_VFS_NEXT_WRITE(handle, fsp, fd, data, count);
 139         commit(handle, fsp, ret);
 140
 141         return ret;
 142 }
 143
 144 static ssize_t commit_pwrite(
 145         vfs_handle_struct * handle,
 146         files_struct *      fsp,
 147         int                 fd,
 148         void *              data,
 149         size_t              count,
 150         SMB_OFF_T           offset)
 151 {
 152         ssize_t ret;
 153
 154         ret = SMB_VFS_NEXT_PWRITE(handle, fsp, fd, data, count, offset);
 155         commit(handle, fsp, ret);
 156
 157         return ret;
 158 }
 159
 160 static ssize_t commit_close(
 161         vfs_handle_struct * handle,
 162         files_struct *      fsp,
 163         int                 fd)
 164 {
 165         commit_all(handle, fsp);
 166         return SMB_VFS_NEXT_CLOSE(handle, fsp, fd);
 167 }
 168
 169 static vfs_op_tuple commit_ops [] =
 170 {
 171         {SMB_VFS_OP(commit_open),
 172                 SMB_VFS_OP_OPEN, SMB_VFS_LAYER_TRANSPARENT},
 173         {SMB_VFS_OP(commit_close),
 174                 SMB_VFS_OP_CLOSE, SMB_VFS_LAYER_TRANSPARENT},
 175         {SMB_VFS_OP(commit_write),
 176                 SMB_VFS_OP_WRITE, SMB_VFS_LAYER_TRANSPARENT},
 177         {SMB_VFS_OP(commit_pwrite),
 178                 SMB_VFS_OP_PWRITE, SMB_VFS_LAYER_TRANSPARENT},
 179         {SMB_VFS_OP(commit_connect),
 180                 SMB_VFS_OP_CONNECT,  SMB_VFS_LAYER_TRANSPARENT},
 181
 182         {SMB_VFS_OP(NULL), SMB_VFS_OP_NOOP, SMB_VFS_LAYER_NOOP}
 183 };
 184
 185 NTSTATUS vfs_commit_init(void);
 186 NTSTATUS vfs_commit_init(void)
 187 {
 188         return smb_register_vfs(SMB_VFS_INTERFACE_VERSION, MODULE, commit_ops);
 189 }
 190