gnu/packages/patches/tar-remove-wholesparse-check.patch

   1 This patch is needed in order to build Guix on a Btrfs file system.
   2
   3
   4 From da922703282b0d3b8837a99a9c7fdd32f1d20d49 Mon Sep 17 00:00:00 2001
   5 From: Mark H Weaver <mhw@netris.org>
   6 Date: Tue, 9 Jan 2018 20:16:14 -0500
   7 Subject: [PATCH] Remove nonportable check for files containing only zeroes.
   8
   9 This check benefitted only one unlikely case (large files containing
  10 only zeroes, on systems that do not support SEEK_HOLE) and was based
  11 on an assumption about file system behavior that is not mandated by
  12 POSIX and no longer holds in practice, namely that for sufficiently
  13 large files, (st_blocks == 0) implies that the file contains only
  14 zeroes.  Examples of file systems that violate this assumption include
  15 Linux's /proc file system and Btrfs.
  16
  17 * src/sparse.c (sparse_scan_file_wholesparse): Remove this function.
  18 (sparse_scan_file_seek): Remove the initial check for files containing
  19 only zeroes.
  20 ---
  21  src/sparse.c | 24 ------------------------
  22  1 file changed, 24 deletions(-)
  23
  24 diff --git a/src/sparse.c b/src/sparse.c
  25 index d41c0ea..3de6560 100644
  26 --- a/src/sparse.c
  27 +++ b/src/sparse.c
  28 @@ -261,26 +261,6 @@ sparse_scan_file_raw (struct tar_sparse_file *file)
  29    return tar_sparse_scan (file, scan_end, NULL);
  30  }
  31
  32 -static bool
  33 -sparse_scan_file_wholesparse (struct tar_sparse_file *file)
  34 -{
  35 -  struct tar_stat_info *st = file->stat_info;
  36 -  struct sp_array sp = {0, 0};
  37 -
  38 -  /* Note that this function is called only for truly sparse files of size >= 1
  39 -     block size (checked via ST_IS_SPARSE before).  See the thread
  40 -     http://www.mail-archive.com/bug-tar@gnu.org/msg04209.html for more info */
  41 -  if (ST_NBLOCKS (st->stat) == 0)
  42 -    {
  43 -      st->archive_file_size = 0;
  44 -      sp.offset = st->stat.st_size;
  45 -      sparse_add_map (st, &sp);
  46 -      return true;
  47 -    }
  48 -
  49 -  return false;
  50 -}
  51 -
  52  #ifdef SEEK_HOLE
  53  /* Try to engage SEEK_HOLE/SEEK_DATA feature. */
  54  static bool
  55 @@ -343,10 +323,6 @@ sparse_scan_file_seek (struct tar_sparse_file *file)
  56  static bool
  57  sparse_scan_file (struct tar_sparse_file *file)
  58  {
  59 -  /* always check for completely sparse files */
  60 -  if (sparse_scan_file_wholesparse (file))
  61 -    return true;
  62 -
  63    switch (hole_detection)
  64      {
  65      case HOLE_DETECTION_DEFAULT:
  66 --
  67 2.15.1
  68