fileio.c

   1 /*
   2  * File IO utilities used in rsync.
   3  *
   4  * Copyright (C) 1998 Andrew Tridgell
   5  * Copyright (C) 2002 Martin Pool
   6  * Copyright (C) 2004-2020 Wayne Davison
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 3 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, visit the http://fsf.org website.
  20  */
  21
  22 #include "rsync.h"
  23 #include "inums.h"
  24
  25 #ifndef ENODATA
  26 #define ENODATA EAGAIN
  27 #endif
  28
  29 /* We want all reads to be aligned on 1K boundaries. */
  30 #define ALIGN_BOUNDARY 1024
  31 /* How far past the boundary is an offset? */
  32 #define ALIGNED_OVERSHOOT(oft) ((oft) & (ALIGN_BOUNDARY-1))
  33 /* Round up a length to the next boundary */
  34 #define ALIGNED_LENGTH(len) ((((len) - 1) | (ALIGN_BOUNDARY-1)) + 1)
  35
  36 extern int sparse_files;
  37
  38 OFF_T preallocated_len = 0;
  39
  40 static OFF_T sparse_seek = 0;
  41 static OFF_T sparse_past_write = 0;
  42
  43 int sparse_end(int f, OFF_T size)
  44 {
  45         int ret;
  46
  47         sparse_past_write = 0;
  48
  49         if (!sparse_seek)
  50                 return 0;
  51
  52 #ifdef HAVE_FTRUNCATE
  53         ret = do_ftruncate(f, size);
  54 #else
  55         if (do_lseek(f, sparse_seek-1, SEEK_CUR) != size-1)
  56                 ret = -1;
  57         else {
  58                 do {
  59                         ret = write(f, "", 1);
  60                 } while (ret < 0 && errno == EINTR);
  61
  62                 ret = ret <= 0 ? -1 : 0;
  63         }
  64 #endif
  65
  66         sparse_seek = 0;
  67
  68         return ret;
  69 }
  70
  71 /* Note that the offset is just the caller letting us know where
  72  * the current file position is in the file. The use_seek arg tells
  73  * us that we should seek over matching data instead of writing it. */
  74 static int write_sparse(int f, int use_seek, OFF_T offset, const char *buf, int len)
  75 {
  76         int l1 = 0, l2 = 0;
  77         int ret;
  78
  79         for (l1 = 0; l1 < len && buf[l1] == 0; l1++) {}
  80         for (l2 = 0; l2 < len-l1 && buf[len-(l2+1)] == 0; l2++) {}
  81
  82         sparse_seek += l1;
  83
  84         if (l1 == len)
  85                 return len;
  86
  87         if (sparse_seek) {
  88                 if (sparse_past_write >= preallocated_len) {
  89                         if (do_lseek(f, sparse_seek, SEEK_CUR) < 0)
  90                                 return -1;
  91                 } else if (do_punch_hole(f, sparse_past_write, sparse_seek) < 0) {
  92                         sparse_seek = 0;
  93                         return -1;
  94                 }
  95         }
  96         sparse_seek = l2;
  97         sparse_past_write = offset + len - l2;
  98
  99         if (use_seek) {
 100                 /* The in-place data already matches. */
 101                 if (do_lseek(f, len - (l1+l2), SEEK_CUR) < 0)
 102                         return -1;
 103                 return len;
 104         }
 105
 106         while ((ret = write(f, buf + l1, len - (l1+l2))) <= 0) {
 107                 if (ret < 0 && errno == EINTR)
 108                         continue;
 109                 sparse_seek = 0;
 110                 return ret;
 111         }
 112
 113         if (ret != (int)(len - (l1+l2))) {
 114                 sparse_seek = 0;
 115                 return l1+ret;
 116         }
 117
 118         return len;
 119 }
 120
 121 static char *wf_writeBuf;
 122 static size_t wf_writeBufSize;
 123 static size_t wf_writeBufCnt;
 124
 125 int flush_write_file(int f)
 126 {
 127         int ret = 0;
 128         char *bp = wf_writeBuf;
 129
 130         while (wf_writeBufCnt > 0) {
 131                 if ((ret = write(f, bp, wf_writeBufCnt)) < 0) {
 132                         if (errno == EINTR)
 133                                 continue;
 134                         return ret;
 135                 }
 136                 wf_writeBufCnt -= ret;
 137                 bp += ret;
 138         }
 139         return ret;
 140 }
 141
 142 /* write_file does not allow incomplete writes.  It loops internally
 143  * until len bytes are written or errno is set.  Note that use_seek and
 144  * offset are only used in sparse processing (see write_sparse()). */
 145 int write_file(int f, int use_seek, OFF_T offset, const char *buf, int len)
 146 {
 147         int ret = 0;
 148
 149         while (len > 0) {
 150                 int r1;
 151                 if (sparse_files > 0) {
 152                         int len1 = MIN(len, SPARSE_WRITE_SIZE);
 153                         r1 = write_sparse(f, use_seek, offset, buf, len1);
 154                         offset += r1;
 155                 } else {
 156                         if (!wf_writeBuf) {
 157                                 wf_writeBufSize = WRITE_SIZE * 8;
 158                                 wf_writeBufCnt  = 0;
 159                                 wf_writeBuf = new_array(char, wf_writeBufSize);
 160                         }
 161                         r1 = (int)MIN((size_t)len, wf_writeBufSize - wf_writeBufCnt);
 162                         if (r1) {
 163                                 memcpy(wf_writeBuf + wf_writeBufCnt, buf, r1);
 164                                 wf_writeBufCnt += r1;
 165                         }
 166                         if (wf_writeBufCnt == wf_writeBufSize) {
 167                                 if (flush_write_file(f) < 0)
 168                                         return -1;
 169                                 if (!r1 && len)
 170                                         continue;
 171                         }
 172                 }
 173                 if (r1 <= 0) {
 174                         if (ret > 0)
 175                                 return ret;
 176                         return r1;
 177                 }
 178                 len -= r1;
 179                 buf += r1;
 180                 ret += r1;
 181         }
 182         return ret;
 183 }
 184
 185 /* An in-place update found identical data at an identical location. We either
 186  * just seek past it, or (for an in-place sparse update), we give the data to
 187  * the sparse processor with the use_seek flag set. */
 188 int skip_matched(int fd, OFF_T offset, const char *buf, int len)
 189 {
 190         OFF_T pos;
 191
 192         if (sparse_files > 0) {
 193                 if (write_file(fd, 1, offset, buf, len) != len)
 194                         return -1;
 195                 return 0;
 196         }
 197
 198         if (flush_write_file(fd) < 0)
 199                 return -1;
 200
 201         if ((pos = do_lseek(fd, len, SEEK_CUR)) != offset + len) {
 202                 rsyserr(FERROR_XFER, errno, "lseek returned %s, not %s",
 203                         big_num(pos), big_num(offset));
 204                 return -1;
 205         }
 206
 207         return 0;
 208 }
 209
 210 /* This provides functionality somewhat similar to mmap() but using read().
 211  * It gives sliding window access to a file.  mmap() is not used because of
 212  * the possibility of another program (such as a mailer) truncating the
 213  * file thus giving us a SIGBUS. */
 214 struct map_struct *map_file(int fd, OFF_T len, int32 read_size, int32 blk_size)
 215 {
 216         struct map_struct *map;
 217
 218         map = new0(struct map_struct);
 219
 220         if (blk_size && (read_size % blk_size))
 221                 read_size += blk_size - (read_size % blk_size);
 222
 223         map->fd = fd;
 224         map->file_size = len;
 225         map->def_window_size = ALIGNED_LENGTH(read_size);
 226
 227         return map;
 228 }
 229
 230
 231 /* slide the read window in the file */
 232 char *map_ptr(struct map_struct *map, OFF_T offset, int32 len)
 233 {
 234         OFF_T window_start, read_start;
 235         int32 window_size, read_size, read_offset, align_fudge;
 236
 237         if (len == 0)
 238                 return NULL;
 239         if (len < 0) {
 240                 rprintf(FERROR, "invalid len passed to map_ptr: %ld\n",
 241                         (long)len);
 242                 exit_cleanup(RERR_FILEIO);
 243         }
 244
 245         /* in most cases the region will already be available */
 246         if (offset >= map->p_offset && offset+len <= map->p_offset+map->p_len)
 247                 return map->p + (offset - map->p_offset);
 248
 249         /* nope, we are going to have to do a read. Work out our desired window */
 250         align_fudge = (int32)ALIGNED_OVERSHOOT(offset);
 251         window_start = offset - align_fudge;
 252         window_size = map->def_window_size;
 253         if (window_start + window_size > map->file_size)
 254                 window_size = (int32)(map->file_size - window_start);
 255         if (window_size < len + align_fudge)
 256                 window_size = ALIGNED_LENGTH(len + align_fudge);
 257
 258         /* make sure we have allocated enough memory for the window */
 259         if (window_size > map->p_size) {
 260                 map->p = realloc_array(map->p, char, window_size);
 261                 map->p_size = window_size;
 262         }
 263
 264         /* Now try to avoid re-reading any bytes by reusing any bytes from the previous buffer. */
 265         if (window_start >= map->p_offset && window_start < map->p_offset + map->p_len
 266          && window_start + window_size >= map->p_offset + map->p_len) {
 267                 read_start = map->p_offset + map->p_len;
 268                 read_offset = (int32)(read_start - window_start);
 269                 read_size = window_size - read_offset;
 270                 memmove(map->p, map->p + (map->p_len - read_offset), read_offset);
 271         } else {
 272                 read_start = window_start;
 273                 read_size = window_size;
 274                 read_offset = 0;
 275         }
 276
 277         if (read_size <= 0) {
 278                 rprintf(FERROR, "invalid read_size of %ld in map_ptr\n",
 279                         (long)read_size);
 280                 exit_cleanup(RERR_FILEIO);
 281         }
 282
 283         if (map->p_fd_offset != read_start) {
 284                 OFF_T ret = do_lseek(map->fd, read_start, SEEK_SET);
 285                 if (ret != read_start) {
 286                         rsyserr(FERROR, errno, "lseek returned %s, not %s",
 287                                 big_num(ret), big_num(read_start));
 288                         exit_cleanup(RERR_FILEIO);
 289                 }
 290                 map->p_fd_offset = read_start;
 291         }
 292         map->p_offset = window_start;
 293         map->p_len = window_size;
 294
 295         while (read_size > 0) {
 296                 int32 nread = read(map->fd, map->p + read_offset, read_size);
 297                 if (nread <= 0) {
 298                         if (!map->status)
 299                                 map->status = nread ? errno : ENODATA;
 300                         /* The best we can do is zero the buffer -- the file
 301                          * has changed mid transfer! */
 302                         memset(map->p + read_offset, 0, read_size);
 303                         break;
 304                 }
 305                 map->p_fd_offset += nread;
 306                 read_offset += nread;
 307                 read_size -= nread;
 308         }
 309
 310         return map->p + align_fudge;
 311 }
 312
 313 int unmap_file(struct map_struct *map)
 314 {
 315         int     ret;
 316
 317         if (map->p) {
 318                 free(map->p);
 319                 map->p = NULL;
 320         }
 321         ret = map->status;
 322 #if 0 /* I don't think we really need this. */
 323         force_memzero(map, sizeof map[0]);
 324 #endif
 325         free(map);
 326
 327         return ret;
 328 }