source/modules/vfs_prealloc.c

   1 /*
   2  * XFS preallocation support module.
   3  *
   4  * Copyright (c) James Peach 2006
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  */
  20
  21 #include "includes.h"
  22
  23 /* Extent preallocation module.
  24  *
  25  * The purpose of this module is to preallocate space on the filesystem when
  26  * we have a good idea of how large files are supposed to be. This lets writes
  27  * proceed without having to allocate new extents and results in better file
  28  * layouts on disk.
  29  *
  30  * Currently only implemented for XFS. This module is based on an original idea
  31  * and implementation by Sebastian Brings.
  32  *
  33  * Tunables.
  34  *
  35  *      prealloc: <ext>     Number of bytes to preallocate for a file with
  36  *                          the matching extension.
  37  *      prealloc:debug      Debug level at which to emit messages.
  38  *
  39  * Example.
  40  *
  41  *      prealloc:mpeg = 500M  # Preallocate *.mpeg to 500 MiB.
  42  */
  43
  44 #ifdef HAVE_XFS_LIBXFS_H
  45 #include <xfs/libxfs.h>
  46 #define lock_type xfs_flock64_t
  47 #else
  48 #define lock_type struct flock64
  49 #endif
  50
  51 #define MODULE "prealloc"
  52 static int module_debug;
  53
  54 static int preallocate_space(int fd, SMB_OFF_T size)
  55 {
  56         lock_type fl = {0};
  57         int err;
  58
  59         if (size <= 0) {
  60                 return 0;
  61         }
  62
  63         fl.l_whence = SEEK_SET;
  64         fl.l_start = 0;
  65         fl.l_len = size;
  66
  67         /* IMPORTANT: We use RESVSP because we want the extents to be
  68          * allocated, but we don't want the allocation to show up in
  69          * st_size or persist after the close(2).
  70          */
  71
  72 #if defined(XFS_IOC_RESVSP64)
  73         /* On Linux this comes in via libxfs.h. */
  74         err = xfsctl(NULL, fd, XFS_IOC_RESVSP64, &fl);
  75 #elif defined(F_RESVSP64)
  76         /* On IRIX, this comes from fcntl.h. */
  77         err = fcntl(fd, F_RESVSP64, &fl);
  78 #else
  79         err = -1;
  80         errno = ENOSYS;
  81 #endif
  82
  83         if (err) {
  84                 DEBUG(module_debug,
  85                         ("%s: preallocate failed on fd=%d size=%lld: %s\n",
  86                         MODULE, fd, (long long)size, strerror(errno)));
  87         }
  88
  89         return err;
  90 }
  91
  92 static int prealloc_connect(
  93                 struct vfs_handle_struct *  handle,
  94                 const char *                service,
  95                 const char *                user)
  96 {
  97             module_debug = lp_parm_int(SNUM(handle->conn),
  98                                         MODULE, "debug", 100);
  99
 100             return SMB_VFS_NEXT_CONNECT(handle, service, user);
 101 }
 102
 103 static int prealloc_open(vfs_handle_struct* handle,
 104                         const char *        fname,
 105                         files_struct *      fsp,
 106                         int                 flags,
 107                         mode_t              mode)
 108 {
 109         int fd;
 110         off64_t size = 0;
 111
 112         const char * dot;
 113         char fext[10];
 114
 115         if (!(flags & (O_CREAT|O_TRUNC))) {
 116                 /* Caller is not intending to rewrite the file. Let's not mess
 117                  * with the allocation in this case.
 118                  */
 119                 goto normal_open;
 120         }
 121
 122         *fext = '\0';
 123         dot = strrchr(fname, '.');
 124         if (dot && *++dot) {
 125                 if (strlen(dot) < sizeof(fext)) {
 126                         strncpy(fext, dot, sizeof(fext));
 127                         strnorm(fext, CASE_LOWER);
 128                 }
 129         }
 130
 131         if (*fext == '\0') {
 132                 goto normal_open;
 133         }
 134
 135         /* Syntax for specifying preallocation size is:
 136          *      MODULE: <extension> = <size>
 137          * where
 138          *      <extension> is the file extension in lower case
 139          *      <size> is a size like 10, 10K, 10M
 140          */
 141         size = conv_str_size(lp_parm_const_string(SNUM(handle->conn), MODULE,
 142                                                     fext, NULL));
 143         if (size <= 0) {
 144                 /* No need to preallocate this file. */
 145                 goto normal_open;
 146         }
 147
 148         fd = SMB_VFS_NEXT_OPEN(handle, fname, fsp, flags, mode);
 149         if (fd < 0) {
 150                 return fd;
 151         }
 152
 153         /* Prellocate only if the file is being created or replaced. Note that
 154          * Samba won't ever pass down O_TRUNC, which is why we have to handle
 155          * truncate calls specially.
 156          */
 157         if ((flags & O_CREAT) || (flags & O_TRUNC)) {
 158                 SMB_OFF_T * psize;
 159
 160                 psize = VFS_ADD_FSP_EXTENSION(handle, fsp, SMB_OFF_T);
 161                 if (psize == NULL || *psize == -1) {
 162                         return fd;
 163                 }
 164
 165                 DEBUG(module_debug,
 166                         ("%s: preallocating %s (fd=%d) to %lld bytes\n",
 167                         MODULE, fname, fd, (long long)size));
 168
 169                 *psize = size;
 170                 if (preallocate_space(fd, *psize) < 0) {
 171                         VFS_REMOVE_FSP_EXTENSION(handle, fsp);
 172                 }
 173         }
 174
 175         return fd;
 176
 177 normal_open:
 178         /* We are not creating or replacing a file. Skip the
 179          * preallocation.
 180          */
 181         DEBUG(module_debug, ("%s: skipping preallocation for %s\n",
 182                     MODULE, fname));
 183         return SMB_VFS_NEXT_OPEN(handle, fname, fsp, flags, mode);
 184 }
 185
 186 static int prealloc_ftruncate(vfs_handle_struct * handle,
 187                         files_struct *  fsp,
 188                         int             fd,
 189                         SMB_OFF_T       offset)
 190 {
 191         SMB_OFF_T *psize;
 192         int ret = SMB_VFS_NEXT_FTRUNCATE(handle, fsp, fd, offset);
 193
 194         /* Maintain the allocated space even in the face of truncates. */
 195         if ((psize = VFS_FETCH_FSP_EXTENSION(handle, fsp))) {
 196                 preallocate_space(fd, *psize);
 197         }
 198
 199         return ret;
 200 }
 201
 202 static vfs_op_tuple prealloc_op_tuples[] = {
 203         {SMB_VFS_OP(prealloc_open), SMB_VFS_OP_OPEN, SMB_VFS_LAYER_TRANSPARENT},
 204         {SMB_VFS_OP(prealloc_ftruncate), SMB_VFS_OP_FTRUNCATE, SMB_VFS_LAYER_TRANSPARENT},
 205         {SMB_VFS_OP(prealloc_connect), SMB_VFS_OP_CONNECT, SMB_VFS_LAYER_TRANSPARENT},
 206         {NULL,  SMB_VFS_OP_NOOP, SMB_VFS_LAYER_NOOP}
 207 };
 208
 209 NTSTATUS vfs_prealloc_init(void);
 210 NTSTATUS vfs_prealloc_init(void)
 211 {
 212         return smb_register_vfs(SMB_VFS_INTERFACE_VERSION,
 213                 MODULE, prealloc_op_tuples);
 214 }
 215