io/fadvise.c

   1 /*
   2  * Copyright (c) 2004-2005 Silicon Graphics, Inc.
   3  * All Rights Reserved.
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License as
   7  * published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it would 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 the Free Software Foundation,
  16  * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  17  */
  18
  19 #include <xfs/libxfs.h>
  20 #include <xfs/command.h>
  21 #include <xfs/input.h>
  22 #include "init.h"
  23 #include "io.h"
  24
  25 static cmdinfo_t fadvise_cmd;
  26
  27 static void
  28 fadvise_help(void)
  29 {
  30         printf(_(
  31 "\n"
  32 " advise the page cache about expected I/O patterns on the current file\n"
  33 "\n"
  34 " Modifies kernel page cache behaviour when operating on the current file.\n"
  35 " The range arguments are required by some advise commands ([*] below).\n"
  36 " With no arguments, the POSIX_FADV_NORMAL advice is implied.\n"
  37 " -d -- don't need these pages (POSIX_FADV_DONTNEED) [*]\n"
  38 " -n -- data will be accessed once (POSIX_FADV_NOREUSE) [*]\n"
  39 " -r -- expect random page references (POSIX_FADV_RANDOM)\n"
  40 " -s -- expect sequential page references (POSIX_FADV_SEQUENTIAL)\n"
  41 " -w -- will need these pages (POSIX_FADV_WILLNEED) [*]\n"
  42 " Notes: these interfaces are not supported in Linux kernels before 2.6.\n"
  43 "   NORMAL sets the default readahead setting on the file.\n"
  44 "   RANDOM sets the readahead setting on the file to zero.\n"
  45 "   SEQUENTIAL sets double the default readahead setting on the file.\n"
  46 "   WILLNEED and NOREUSE are equivalent, and force the maximum readahead.\n"
  47 "\n"));
  48 }
  49
  50 static int
  51 fadvise_f(
  52         int             argc,
  53         char            **argv)
  54 {
  55         off64_t         offset = 0;
  56         size_t          length = 0;
  57         int             c, range = 0, advise = POSIX_FADV_NORMAL;
  58
  59         while ((c = getopt(argc, argv, "dnrsw")) != EOF) {
  60                 switch (c) {
  61                 case 'd':       /* Don't need these pages */
  62                         advise = POSIX_FADV_DONTNEED;
  63                         range = 1;
  64                         break;
  65                 case 'n':       /* Data will be accessed once */
  66                         advise = POSIX_FADV_NOREUSE;
  67                         range = 1;
  68                         break;
  69                 case 'r':       /* Expect random page references */
  70                         advise = POSIX_FADV_RANDOM;
  71                         range = 0;
  72                         break;
  73                 case 's':       /* Expect sequential page references */
  74                         advise = POSIX_FADV_SEQUENTIAL;
  75                         range = 0;
  76                         break;
  77                 case 'w':       /* Will need these pages */
  78                         advise = POSIX_FADV_WILLNEED;
  79                         range = 1;
  80                         break;
  81                 default:
  82                         return command_usage(&fadvise_cmd);
  83                 }
  84         }
  85         if (range) {
  86                 size_t  blocksize, sectsize;
  87
  88                 if (optind != argc - 2)
  89                         return command_usage(&fadvise_cmd);
  90                 init_cvtnum(&blocksize, &sectsize);
  91                 offset = cvtnum(blocksize, sectsize, argv[optind]);
  92                 if (offset < 0) {
  93                         printf(_("non-numeric offset argument -- %s\n"),
  94                                 argv[optind]);
  95                         return 0;
  96                 }
  97                 optind++;
  98                 length = cvtnum(blocksize, sectsize, argv[optind]);
  99                 if (length < 0) {
 100                         printf(_("non-numeric length argument -- %s\n"),
 101                                 argv[optind]);
 102                         return 0;
 103                 }
 104         } else if (optind != argc) {
 105                 return command_usage(&fadvise_cmd);
 106         }
 107
 108         if (posix_fadvise64(file->fd, offset, length, advise) < 0) {
 109                 perror("fadvise");
 110                 return 0;
 111         }
 112         return 0;
 113 }
 114
 115 void
 116 fadvise_init(void)
 117 {
 118         fadvise_cmd.name = _("fadvise");
 119         fadvise_cmd.cfunc = fadvise_f;
 120         fadvise_cmd.argmin = 0;
 121         fadvise_cmd.argmax = -1;
 122         fadvise_cmd.flags = CMD_NOMAP_OK | CMD_FOREIGN_OK;
 123         fadvise_cmd.args = _("[-dnrsw] [off len]");
 124         fadvise_cmd.oneline = _("advisory commands for sections of a file");
 125         fadvise_cmd.help = fadvise_help;
 126
 127         add_command(&fadvise_cmd);
 128 }