source3/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 3 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, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include "includes.h"
  21 #include "system/filesys.h"
  22 #include "smbd/smbd.h"
  23
  24 /* Extent preallocation module.
  25  *
  26  * The purpose of this module is to preallocate space on the filesystem when
  27  * we have a good idea of how large files are supposed to be. This lets writes
  28  * proceed without having to allocate new extents and results in better file
  29  * layouts on disk.
  30  *
  31  * Currently only implemented for XFS. This module is based on an original idea
  32  * and implementation by Sebastian Brings.
  33  *
  34  * Tunables.
  35  *
  36  *      prealloc: <ext>     Number of bytes to preallocate for a file with
  37  *                          the matching extension.
  38  *      prealloc:debug      Debug level at which to emit messages.
  39  *
  40  * Example.
  41  *
  42  *      prealloc:mpeg = 500M  # Preallocate *.mpeg to 500 MiB.
  43  */
  44
  45 #ifdef HAVE_XFS_LIBXFS_H
  46 #include <xfs/libxfs.h>
  47 #define lock_type xfs_flock64_t
  48 #else
  49 #define lock_type struct flock64
  50 #endif
  51
  52 #define MODULE "prealloc"
  53 static int module_debug;
  54
  55 static int preallocate_space(int fd, off_t size)
  56 {
  57         int err;
  58         lock_type fl = {0};
  59
  60         if (size <= 0) {
  61                 return 0;
  62         }
  63
  64         fl.l_whence = SEEK_SET;
  65         fl.l_start = 0;
  66         fl.l_len = size;
  67
  68         /* IMPORTANT: We use RESVSP because we want the extents to be
  69          * allocated, but we don't want the allocation to show up in
  70          * st_size or persist after the close(2).
  71          */
  72
  73 #if defined(XFS_IOC_RESVSP64)
  74         /* On Linux this comes in via libxfs.h. */
  75         err = xfsctl(NULL, fd, XFS_IOC_RESVSP64, &fl);
  76 #elif defined(F_RESVSP64)
  77         /* On IRIX, this comes from fcntl.h. */
  78         err = fcntl(fd, F_RESVSP64, &fl);
  79 #else
  80         err = -1;
  81         errno = ENOSYS;
  82 #endif
  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         int ret = SMB_VFS_NEXT_CONNECT(handle, service, user);
  98
  99         if (ret < 0) {
 100                 return ret;
 101         }
 102
 103         module_debug = lp_parm_int(SNUM(handle->conn),
 104                                         MODULE, "debug", 100);
 105
 106         return 0;
 107 }
 108
 109 static int prealloc_openat(struct vfs_handle_struct* handle,
 110                            const struct files_struct *dirfsp,
 111                            const struct smb_filename *smb_fname,
 112                            files_struct *fsp,
 113                            const struct vfs_open_how *how)
 114 {
 115         int fd;
 116         off_t size = 0;
 117         const char * dot;
 118         char fext[10];
 119
 120         if (!(how->flags & (O_CREAT|O_TRUNC))) {
 121                 /* Caller is not intending to rewrite the file. Let's not mess
 122                  * with the allocation in this case.
 123                  */
 124                 goto normal_open;
 125         }
 126
 127         *fext = '\0';
 128         dot = strrchr(smb_fname->base_name, '.');
 129         if (dot && *++dot) {
 130                 if (strlen(dot) < sizeof(fext)) {
 131                         bool ok;
 132                         strncpy(fext, dot, sizeof(fext));
 133                         ok = strlower_m(fext);
 134                         if (!ok);
 135                                 goto normal_open;
 136                         }
 137                 }
 138         }
 139
 140         if (*fext == '\0') {
 141                 goto normal_open;
 142         }
 143
 144         /* Syntax for specifying preallocation size is:
 145          *      MODULE: <extension> = <size>
 146          * where
 147          *      <extension> is the file extension in lower case
 148          *      <size> is a size like 10, 10K, 10M
 149          */
 150         size = conv_str_size(lp_parm_const_string(SNUM(handle->conn), MODULE,
 151                                                     fext, NULL));
 152         if (size <= 0) {
 153                 /* No need to preallocate this file. */
 154                 goto normal_open;
 155         }
 156
 157         fd = SMB_VFS_NEXT_OPENAT(handle, dirfsp, smb_fname, fsp, how);
 158         if (fd < 0) {
 159                 return fd;
 160         }
 161
 162         /* Preallocate only if the file is being created or replaced. Note that
 163          * Samba won't ever pass down O_TRUNC, which is why we have to handle
 164          * truncate calls specially.
 165          */
 166         if ((how->flags & O_CREAT) || (how->flags & O_TRUNC)) {
 167                 off_t * psize;
 168
 169                 psize = VFS_ADD_FSP_EXTENSION(handle, fsp, off_t, NULL);
 170                 if (psize == NULL || *psize == -1) {
 171                         return fd;
 172                 }
 173
 174                 DEBUG(module_debug,
 175                         ("%s: preallocating %s (fd=%d) to %lld bytes\n",
 176                             MODULE, smb_fname_str_dbg(smb_fname), fd,
 177                             (long long)size));
 178
 179                 *psize = size;
 180                 if (preallocate_space(fd, *psize) < 0) {
 181                         VFS_REMOVE_FSP_EXTENSION(handle, fsp);
 182                 }
 183         }
 184
 185         return fd;
 186
 187 normal_open:
 188         /* We are not creating or replacing a file. Skip the
 189          * preallocation.
 190          */
 191         DEBUG(module_debug, ("%s: skipping preallocation for %s\n",
 192                 MODULE, smb_fname_str_dbg(smb_fname)));
 193         return SMB_VFS_NEXT_OPENAT(handle, dirfsp, smb_fname, fsp, how);
 194 }
 195
 196 static int prealloc_ftruncate(vfs_handle_struct * handle,
 197                         files_struct *  fsp,
 198                         off_t   offset)
 199 {
 200         off_t *psize;
 201         int ret = SMB_VFS_NEXT_FTRUNCATE(handle, fsp, offset);
 202
 203         /* Maintain the allocated space even in the face of truncates. */
 204         if ((psize = VFS_FETCH_FSP_EXTENSION(handle, fsp))) {
 205                 preallocate_space(fsp_get_io_fd(fsp), *psize);
 206         }
 207
 208         return ret;
 209 }
 210
 211 static struct vfs_fn_pointers prealloc_fns = {
 212         .openat_fn = prealloc_openat,
 213         .ftruncate_fn = prealloc_ftruncate,
 214         .connect_fn = prealloc_connect,
 215 };
 216
 217 static_decl_vfs;
 218 NTSTATUS vfs_prealloc_init(TALLOC_CTX *ctx)
 219 {
 220         return smb_register_vfs(SMB_VFS_INTERFACE_VERSION,
 221                                 MODULE, &prealloc_fns);
 222 }