Use SEEK_HOLE for hole detection

Based on patch by Pavel Raiskup.

Use SEEK_HOLE/SEEK_DATA feature of lseek on systems that support
it.  This can make archiving of sparse files much faster.

Implement the --hole-detection option to allow users to select
hole-detection method.

* src/common.h (hole_detection_method): New enum.
(hole_detection): New global.
* src/sparse.c  (sparse_scan_file_wholesparse): New function as a
method for detecting sparse files without any data.
(sparse_scan_file_raw): Rename from sparse_scan_file; with edits.
(sparse_scan_file_seek): New function.
(sparse_scan_file): Reimplement function.
* src/tar.c: New option --hole-detection

* tests/checkseekhole.c: New file.
* tests/.gitignore: Mention two test binaries.
* tests/Makefile.am: Add new tests.
* tests/testsuite.at (AT_SEEKHOLE_PREREQ): New macro.
Include sparse06.at.
* tests/sparse06.at: New test case.
* tests/sparse02.at: Force raw hole-detection method.
* tests/sparsemv.at: Likewise.
* tests/sparsemvp.at: Likewise.

* doc/tar.1: Document --hole-detection option.
* doc/tar.texi: Document hole-detection algorithms and
command-line options.
* NEWS: Document hole-detection.

14 files changed, 426 insertions, 79 deletions

diff --git a/NEWS b/NEWS
index 2dd9f195..d2cb0752 100644
--- a/NEWS
+++ b/NEWS
@@ -1,4 +1,4 @@
-GNU tar NEWS - User visible changes. 2015-11-02
+GNU tar NEWS - User visible changes. 2015-12-06
 Please send GNU tar bug reports to <bug-tar@gnu.org>
 
 
@@ -48,6 +48,25 @@ read from null-delimited file lists is treated as a file name.
 This restores the documented behavior, which was broken in version
 1.27.
 
+* Sparse file detection
+
+Tar now uses SEEK_DATA/SEEK_HOLE on systems that support it.  This
+allows for considerable speed-up in sparse-file detection.
+
+New option --hole-detection is provided, that allows the user to
+select the algorithm used for hole detection.  Available arguments
+are:
+
+  --hole-detection=seek
+     Use lseek(2) SEEK_DATA and SEEK_HOLE "whence" parameters.
+
+  --hole-detection=raw
+     Scan entire file before storing it to determine where holes
+     are located.
+
+The default is to use "seek" whenever possible, and fall back to
+"raw" otherwise.
+
 
 version 1.28, 2014-07-28
 
diff --git a/doc/tar.1 b/doc/tar.1
index 6e2aa745..18fdc9d7 100644
--- a/doc/tar.1
+++ b/doc/tar.1
@@ -13,7 +13,7 @@
 .\"
 .\" You should have received a copy of the GNU General Public License
 .\" along with this program.  If not, see <http://www.gnu.org/licenses/>.
-.TH TAR 1 "November 2, 2015" "TAR" "GNU TAR Manual"
+.TH TAR 1 "December 5, 2015" "TAR" "GNU TAR Manual"
 .SH NAME
 tar \- an archiving utility
 .SH SYNOPSIS
@@ -259,6 +259,12 @@ When listing or extracting, the actual contents of \fIFILE\fR is not
 inspected, it is needed only due to syntactical requirements.  It is
 therefore common practice to use \fB/dev/null\fR in its place.
 .TP
+\fB\-\-hole\-detection\fR=\fIMETHOD\fR
+Use \fIMETHOD\fR to detect holes in sparse files.  This option implies
+\fB\-\-sparse\fR.  Valid values for \fIMETHOD\fR are \fBseek\fR and
+\fBraw\fR.  Default is \fBseek\fR with fallback to \fBraw\fR when not
+applicable.
+.TP
 \fB\-G\fR, \fB\-\-incremental\fR
 Handle old GNU-format incremental backups.
 .TP
@@ -821,7 +827,8 @@ environment variable.  If it is not set, \fBexisting\fR is assumed.
 .RE
 .TP
 \fB\-C\fR, \fB\-\-directory\fR=\fIDIR\fR
-Change to directory DIR.
+Change to \fIDIR\fR before performing any operations.  This option is
+order-sensitive, i.e. it affects all options that follow.
 .TP
 \fB\-\-exclude\fR=\fIPATTERN\fR
 Exclude files matching \fIPATTERN\fR, a
diff --git a/doc/tar.texi b/doc/tar.texi
index 9713cb09..e3bfd665 100644
--- a/doc/tar.texi
+++ b/doc/tar.texi
@@ -2782,6 +2782,13 @@ they refer to, instead of creating usual hard link members.
 @command{tar} will print out a short message summarizing the operations and
 options to @command{tar} and exit. @xref{help}.
 
+@opsummary{hole-detection}
+@item --hole-detection=@var{method}
+Use @var{method} to detect holes in sparse files.  This option implies
+@option{--sparse}.  Valid methods are @samp{seek} and @samp{raw}.
+Default is @samp{seek} with fallback to @samp{raw} when not
+applicable. @xref{sparse}.
+
 @opsummary{ignore-case}
 @item --ignore-case
 Ignore case when matching member or file names with
@@ -9536,13 +9543,15 @@ could create an archive longer than the original.  To have @command{tar}
 attempt to recognize the holes in a file, use @option{--sparse}
 (@option{-S}).  When you use this option, then, for any file using
 less disk space than would be expected from its length, @command{tar}
-searches the file for consecutive stretches of zeros.  It then records
-in the archive for the file where the consecutive stretches of zeros
-are, and only archives the ``real contents'' of the file.  On
-extraction (using @option{--sparse} is not needed on extraction) any
-such files have holes created wherever the continuous stretches of zeros
-were found.  Thus, if you use @option{--sparse}, @command{tar} archives
-won't take more space than the original.
+searches the file for holes.  It then records in the archive for the file where
+the holes (consecutive stretches of zeros) are, and only archives the
+``real contents'' of the file.  On extraction (using @option{--sparse} is not
+needed on extraction) any such files have also holes created wherever the holes
+were found.  Thus, if you use @option{--sparse}, @command{tar} archives won't
+take more space than the original.
+
+@GNUTAR{} uses two methods for detecting holes in sparse files.  These
+methods are described later in this subsection.
 
 @table @option
 @opindex sparse
@@ -9568,37 +9577,12 @@ will never take more space on the media than the files take on disk
 (otherwise, archiving a disk filled with sparse files might take
 hundreds of tapes).  @xref{Incremental Dumps}.
 
-However, be aware that @option{--sparse} option presents a serious
-drawback.  Namely, in order to determine if the file is sparse
-@command{tar} has to read it before trying to archive it, so in total
-the file is read @strong{twice}.  So, always bear in mind that the
-time needed to process all files with this option is roughly twice
-the time needed to archive them without it.
-@FIXME{A technical note:
-
-Programs like @command{dump} do not have to read the entire file; by
-examining the file system directly, they can determine in advance
-exactly where the holes are and thus avoid reading through them.  The
-only data it need read are the actual allocated data blocks.
-@GNUTAR{} uses a more portable and straightforward
-archiving approach, it would be fairly difficult that it does
-otherwise.  Elizabeth Zwicky writes to @file{comp.unix.internals}, on
-1990-12-10:
-
-@quotation
-What I did say is that you cannot tell the difference between a hole and an
-equivalent number of nulls without reading raw blocks.  @code{st_blocks} at
-best tells you how many holes there are; it doesn't tell you @emph{where}.
-Just as programs may, conceivably, care what @code{st_blocks} is (care
-to name one that does?), they may also care where the holes are (I have
-no examples of this one either, but it's equally imaginable).
-
-I conclude from this that good archivers are not portable.  One can
-arguably conclude that if you want a portable program, you can in good
-conscience restore files with as many holes as possible, since you can't
-get it right.
-@end quotation
-}
+However, be aware that @option{--sparse} option may present a serious
+drawback.  Namely, in order to determine the positions of holes in a file
+@command{tar} may have to read it before trying to archive it, so in total
+the file may be read @strong{twice}.  This may happen when your OS or your FS
+does not support @dfn{SEEK_HOLE/SEEK_DATA} feature in @dfn{lseek} (See
+@option{--hole-detection}, below).
 
 @cindex sparse formats, defined
 When using @samp{POSIX} archive format, @GNUTAR{} is able to store
@@ -9612,7 +9596,6 @@ use an earlier format, you can select it using
 @table @option
 @opindex sparse-version
 @item --sparse-version=@var{version}
-
 Select the format to store sparse files in.  Valid @var{version} values
 are: @samp{0.0}, @samp{0.1} and @samp{1.0}.  @xref{Sparse Formats},
 for a detailed description of each format.
@@ -9620,6 +9603,39 @@ for a detailed description of each format.
 
 Using @option{--sparse-format} option implies @option{--sparse}.
 
+@table @option
+@opindex hole-detection
+@cindex hole detection
+@item --hole-detection=@var{method}
+Enforce concrete hole detection method.  Before the real contents of sparse
+file are stored, @command{tar} needs to gather knowledge about file
+sparseness.  This is because it needs to have the file's map of holes
+stored into tar header before it starts archiving the file contents.
+Currently, two methods of hole detection are implemented:
+
+@itemize @bullet
+@item @option{--hole-detection=seek}
+Seeking the file for data and holes.  It uses enhancement of the @code{lseek}
+system call (@code{SEEK_HOLE} and @code{SEEK_DATA}) which is able to
+reuse file system knowledge about sparse file contents - so the
+detection is usually very fast.  To use this feature, your file system
+and operating system must support it.  At the time of this writing
+(2015) this feature, in spite of not being accepted by POSIX, is
+fairly widely supported by different operating systems.
+
+@item @option{--hole-detection=raw}
+Reading byte-by-byte the whole sparse file before the archiving.  This
+method detects holes like consecutive stretches of zeroes.  Comparing to
+the previous method, it is usually much slower, although more
+portable.
+@end itemize
+@end table
+
+When no @option{--hole-detection} option is given, @command{tar} uses
+the @samp{seek}, if supported by the operating system.
+
+Using @option{--hole-detection} option implies @option{--sparse}.
+
 @node Attributes
 @section Handling File Attributes
 @cindex attributes, files
diff --git a/src/common.h b/src/common.h
index 72ad4c13..02ef1795 100644
--- a/src/common.h
+++ b/src/common.h
@@ -280,6 +280,15 @@ GLOBAL bool sparse_option;
 GLOBAL unsigned tar_sparse_major;
 GLOBAL unsigned tar_sparse_minor;
 
+enum hole_detection_method
+  {
+    HOLE_DETECTION_DEFAULT,
+    HOLE_DETECTION_RAW,
+    HOLE_DETECTION_SEEK
+  };
+
+GLOBAL enum hole_detection_method hole_detection;
+
 GLOBAL bool starting_file_option;
 
 /* Specified maximum byte length of each tape volume (multiple of 1024).  */
diff --git a/src/sparse.c b/src/sparse.c
index 6a976763..b04acee2 100644
--- a/src/sparse.c
+++ b/src/sparse.c
@@ -1,6 +1,6 @@
 /* Functions for dealing with sparse files
 
-   Copyright 2003-2007, 2010, 2013-2014 Free Software Foundation, Inc.
+   Copyright 2003-2007, 2010, 2013-2015 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by the
@@ -208,9 +208,9 @@ sparse_add_map (struct tar_stat_info *st, struct sp_array const *sp)
   st->sparse_map_avail = avail + 1;
 }
 
-/* Scan the sparse file and create its map */
+/* Scan the sparse file byte-by-byte and create its map. */
 static bool
-sparse_scan_file (struct tar_sparse_file *file)
+sparse_scan_file_raw (struct tar_sparse_file *file)
 {
   struct tar_stat_info *st = file->stat_info;
   int fd = file->fd;
@@ -221,41 +221,38 @@ sparse_scan_file (struct tar_sparse_file *file)
 
   st->archive_file_size = 0;
 
-  if (ST_NBLOCKS (st->stat) == 0)
-    offset = st->stat.st_size;
-  else
-    {
-      if (!tar_sparse_scan (file, scan_begin, NULL))
-	return false;
-
-      while ((count = blocking_read (fd, buffer, sizeof buffer)) != 0
-	     && count != SAFE_READ_ERROR)
-	{
-	  /* Analyze the block.  */
-	  if (zero_block_p (buffer, count))
-	    {
-	      if (sp.numbytes)
-		{
-		  sparse_add_map (st, &sp);
-		  sp.numbytes = 0;
-		  if (!tar_sparse_scan (file, scan_block, NULL))
-		    return false;
-		}
-	    }
-	  else
-	    {
-	      if (sp.numbytes == 0)
-		sp.offset = offset;
-	      sp.numbytes += count;
-	      st->archive_file_size += count;
-	      if (!tar_sparse_scan (file, scan_block, buffer))
-		return false;
-	    }
+  if (!tar_sparse_scan (file, scan_begin, NULL))
+    return false;
 
-	  offset += count;
-	}
+  while ((count = blocking_read (fd, buffer, sizeof buffer)) != 0
+         && count != SAFE_READ_ERROR)
+    {
+      /* Analyze the block.  */
+      if (zero_block_p (buffer, count))
+        {
+          if (sp.numbytes)
+            {
+              sparse_add_map (st, &sp);
+              sp.numbytes = 0;
+              if (!tar_sparse_scan (file, scan_block, NULL))
+                return false;
+            }
+        }
+      else
+        {
+          if (sp.numbytes == 0)
+            sp.offset = offset;
+          sp.numbytes += count;
+          st->archive_file_size += count;
+          if (!tar_sparse_scan (file, scan_block, buffer))
+            return false;
+        }
+
+      offset += count;
     }
 
+  /* save one more sparse segment of length 0 to indicate that
+     the file ends with a hole */
   if (sp.numbytes == 0)
     sp.offset = offset;
 
@@ -264,6 +261,114 @@ sparse_scan_file (struct tar_sparse_file *file)
   return tar_sparse_scan (file, scan_end, NULL);
 }
 
+static bool
+sparse_scan_file_wholesparse (struct tar_sparse_file *file)
+{
+  struct tar_stat_info *st = file->stat_info;
+  struct sp_array sp = {0, 0};
+
+  /* Note that this function is called only for truly sparse files of size >= 1
+     block size (checked via ST_IS_SPARSE before).  See the thread
+     http://www.mail-archive.com/bug-tar@gnu.org/msg04209.html for more info */
+  if (ST_NBLOCKS (st->stat) == 0)
+    {
+      st->archive_file_size = 0;
+      sp.offset = st->stat.st_size;
+      sparse_add_map (st, &sp);
+      return true;
+    }
+
+  return false;
+}
+
+#ifdef SEEK_HOLE
+/* Try to engage SEEK_HOLE/SEEK_DATA feature. */
+static bool
+sparse_scan_file_seek (struct tar_sparse_file *file)
+{
+  struct tar_stat_info *st = file->stat_info;
+  int fd = file->fd;
+  struct sp_array sp = {0, 0};
+  off_t offset = 0;
+  off_t data_offset;
+  off_t hole_offset;
+
+  st->archive_file_size = 0;
+
+  for (;;)
+    {
+      /* locate first chunk of data */
+      data_offset = lseek (fd, offset, SEEK_DATA);
+
+      if (data_offset == (off_t)-1)
+        /* ENXIO == EOF; error otherwise */
+        {
+          if (errno == ENXIO)
+            {
+              /* file ends with hole, add one more empty chunk of data */
+              sp.numbytes = 0;
+              sp.offset = st->stat.st_size;
+              sparse_add_map (st, &sp);
+              return true;
+            }
+          return false;
+        }
+
+      hole_offset = lseek (fd, data_offset, SEEK_HOLE);
+
+      /* according to specs, if FS does not fully support
+	 SEEK_DATA/SEEK_HOLE it may just implement kind of "wrapper" around
+	 classic lseek() call.  We must detect it here and try to use other
+	 hole-detection methods. */
+      if (offset == 0 /* first loop */
+          && data_offset == 0
+          && hole_offset == st->stat.st_size)
+        {
+          lseek (fd, 0, SEEK_SET);
+          return false;
+        }
+
+      sp.offset = data_offset;
+      sp.numbytes = hole_offset - data_offset;
+      sparse_add_map (st, &sp);
+
+      st->archive_file_size += sp.numbytes;
+      offset = hole_offset;
+    }
+
+  return true;
+}
+#endif
+
+static bool
+sparse_scan_file (struct tar_sparse_file *file)
+{
+  /* always check for completely sparse files */
+  if (sparse_scan_file_wholesparse (file))
+    return true;
+
+  switch (hole_detection)
+    {
+    case HOLE_DETECTION_DEFAULT:
+    case HOLE_DETECTION_SEEK:
+#ifdef SEEK_HOLE
+      if (sparse_scan_file_seek (file))
+        return true;
+#else
+      if (hole_detection == HOLE_DETECTION_SEEK)
+	WARN((0, 0,
+	      _("\"seek\" hole detection is not supported, using \"raw\".")));
+      /* fall back to "raw" for this and all other files */
+      hole_detection = HOLE_DETECTION_RAW;
+#endif
+    case HOLE_DETECTION_RAW:
+      if (sparse_scan_file_raw (file))
+	return true;
+    }
+  
+  return false;
+}
+
 static struct tar_sparse_optab const oldgnu_optab;
 static struct tar_sparse_optab const star_optab;
 static struct tar_sparse_optab const pax_optab;
diff --git a/src/tar.c b/src/tar.c
index 21b0a3bf..6be62e05 100644
--- a/src/tar.c
+++ b/src/tar.c
@@ -362,6 +362,7 @@ enum
   SHOW_TRANSFORMED_NAMES_OPTION,
   SKIP_OLD_FILES_OPTION,
   SORT_OPTION,
+  HOLE_DETECTION_OPTION,
   SPARSE_VERSION_OPTION,
   STRIP_COMPONENTS_OPTION,
   SUFFIX_OPTION,
@@ -451,6 +452,8 @@ static struct argp_option options[] = {
 
   {"sparse", 'S', 0, 0,
    N_("handle sparse files efficiently"), GRID+1 },
+  {"hole-detection", HOLE_DETECTION_OPTION, N_("TYPE"), 0,
+   N_("technique to detect holes"), GRID+1 },
   {"sparse-version", SPARSE_VERSION_OPTION, N_("MAJOR[.MINOR]"), 0,
    N_("set version of the sparse format to use (implies --sparse)"), GRID+1},
   {"incremental", 'G', 0, 0,
@@ -1464,6 +1467,19 @@ static int sort_mode_flag[] = {
 };
 
 ARGMATCH_VERIFY (sort_mode_arg, sort_mode_flag);
+
+static char const *const hole_detection_args[] =
+{
+  "raw", "seek", NULL
+};
+
+static int const hole_detection_types[] =
+{
+  HOLE_DETECTION_RAW, HOLE_DETECTION_SEEK
+};
+
+ARGMATCH_VERIFY (hole_detection_args, hole_detection_types);
+
 
 static void
 set_old_files_option (int code, struct option_locus *loc)
@@ -1753,6 +1769,12 @@ parse_opt (int key, char *arg, struct argp_state *state)
       set_old_files_option (SKIP_OLD_FILES, args->loc);
       break;
 
+    case HOLE_DETECTION_OPTION:
+      hole_detection = XARGMATCH ("--hole-detection", arg,
+				  hole_detection_args, hole_detection_types);
+      sparse_option = true;
+      break;
+
     case SPARSE_VERSION_OPTION:
       sparse_option = true;
       {
@@ -2523,6 +2545,7 @@ decode_options (int argc, char **argv)
   blocking_factor = DEFAULT_BLOCKING;
   record_size = DEFAULT_BLOCKING * BLOCKSIZE;
   excluded = new_exclude ();
+  hole_detection = HOLE_DETECTION_DEFAULT;
 
   newer_mtime_option.tv_sec = TYPE_MINIMUM (time_t);
   newer_mtime_option.tv_nsec = -1;
diff --git a/tests/.gitignore b/tests/.gitignore
index 9d836a81..2a721ba6 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -9,3 +9,5 @@ argcv.h
 genfile.c
 genfile
 download
+ttyemu
+checkseekhole
diff --git a/tests/Makefile.am b/tests/Makefile.am
index f1d12410..6093d447 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -207,6 +207,7 @@ TESTSUITE_AT = \
  sparse03.at\
  sparse04.at\
  sparse05.at\
+ sparse06.at\
  sparsemv.at\
  sparsemvp.at\
  spmvp00.at\
@@ -275,13 +276,14 @@ installcheck-local: $(check_PROGRAMS)
 ## genfile      ##
 ## ------------ ##
 
-check_PROGRAMS = genfile
+check_PROGRAMS = genfile checkseekhole
 
 if TAR_COND_GRANTPT
 check_PROGRAMS += ttyemu
 endif
 
 genfile_SOURCES = genfile.c argcv.c argcv.h
+checkseekhole_SOURCES = checkseekhole.c
 
 ttyemu_SOURCES = ttyemu.c
 
diff --git a/tests/checkseekhole.c b/tests/checkseekhole.c
new file mode 100644
index 00000000..38c03630
--- /dev/null
+++ b/tests/checkseekhole.c
@@ -0,0 +1,92 @@
+/* Test suite for GNU tar - SEEK_HOLE detector.
+
+   Copyright 2015 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by the
+   Free Software Foundation; either version 3, or (at your option) any later
+   version.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
+   Public License for more details.
+
+   You should have received a copy of the GNU General Public License along
+   with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+   Description:  detect whether it is possible to work with SEEK_HOLE on
+   particular operating system and file system. */
+
+#include "config.h"
+
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <fcntl.h>
+
+enum {
+    EX_OK = 0,    /* SEEK_HOLE support */
+    EX_FAIL,      /* test failed - no SEEK_HOLE support */
+    EX_BAD,       /* test is not relevant */
+};
+
+int
+check_seek_hole (int fd)
+{
+#ifdef SEEK_HOLE
+  struct stat stat;
+  off_t offset;
+
+  /* hole of 100MB */
+  if (lseek (fd, 100*1024*1024, SEEK_END) < 0)
+    return EX_BAD;
+
+  /* piece of data */
+  if (write (fd, "data\n", 5) != 5)
+    return EX_BAD;
+
+  /* another hole */
+  if (lseek (fd, 100*1024*1024, SEEK_END) < 0)
+    return EX_BAD;
+
+  /* piece of data */
+  if (write (fd, "data\n", 5) != 5)
+    return EX_BAD;
+
+  if (fstat (fd, &stat))
+    return EX_BAD;
+
+  offset = lseek (fd, 0, SEEK_DATA);
+  if (offset == (off_t)-1)
+    return EX_FAIL;
+
+  offset = lseek (fd, offset, SEEK_HOLE);
+  if (offset == (off_t)-1 || offset == stat.st_size)
+    return EX_FAIL;
+
+  return EX_OK;
+#else
+  return EX_BAD;
+#endif
+}
+
+int
+main ()
+{
+#ifdef SEEK_HOLE
+  int rc;
+  char template[] = "testseekhole-XXXXXX";
+  int fd = mkstemp (template);
+  if (fd == -1)
+    return EX_BAD;
+  rc = check_seek_hole (fd);
+  close (fd);
+  unlink (template);
+
+  return rc;
+#else
+  return EX_FAIL;
+#endif
+}
diff --git a/tests/sparse02.at b/tests/sparse02.at
index 1f044914..16bb31bd 100644
--- a/tests/sparse02.at
+++ b/tests/sparse02.at
@@ -27,7 +27,7 @@ AT_KEYWORDS([sparse sparse02])
 
 AT_TAR_CHECK([
 genfile --sparse --file sparsefile --block-size 512 0 ABCD 1M EFGH 2000K IJKL || AT_SKIP_TEST
-tar -c -f archive --sparse sparsefile || exit 1
+tar --hole-detection=raw -c -f archive --sparse sparsefile || exit 1
 echo separator
 
 tar xfO archive | cat - > sparsecopy || exit 1
diff --git a/tests/sparse06.at b/tests/sparse06.at
new file mode 100644
index 00000000..1888436d
--- /dev/null
+++ b/tests/sparse06.at
@@ -0,0 +1,56 @@
+# Process this file with autom4te to create testsuite. -*- Autotest -*-
+#
+# Test suite for GNU tar.
+# Copyright 2014 Free Software Foundation, Inc.
+
+# This file is part of GNU tar.
+
+# GNU tar is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+
+# GNU tar is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+AT_SETUP([storing sparse file using seek method])
+AT_KEYWORDS([sparse sparse06])
+
+m4_define([check_pattern],[
+rm -rf out archive.tar smallsparse && mkdir out
+genfile --sparse --file smallsparse $1
+tar -cSf archive.tar smallsparse
+tar -xf archive.tar -C out
+cmp smallsparse out/smallsparse
+])
+
+AT_TAR_CHECK([
+AT_SEEKHOLE_PREREQ
+AT_TIMEOUT_PREREQ
+
+TAR_OPTIONS="$TAR_OPTIONS --hole-detection=seek"
+genfile --sparse --file bigsparse 0 ABC 8G DEF
+timeout 2 tar -cSf a bigsparse
+test $? -eq 0 || exit 1
+
+check_pattern([0 ABC])
+check_pattern([0 ABC 10M])
+check_pattern([0 ABC 10M DEF])
+
+check_pattern([10M])
+check_pattern([10M ABC])
+check_pattern([10M ABC 20M])
+
+check_pattern([10M DEF 20M GHI 30M JKL 40M])
+
+],
+[0],,
+[genfile: created file is not sparse
+],,,[posix])
+
+AT_CLEANUP
diff --git a/tests/sparsemv.at b/tests/sparsemv.at
index 958f04e1..47e71e8f 100644
--- a/tests/sparsemv.at
+++ b/tests/sparsemv.at
@@ -30,6 +30,7 @@ AT_KEYWORDS([sparse multiv sparsemv])
 
 AT_TAR_CHECK([
 exec <&-
+TAR_OPTIONS="$TAR_OPTIONS --hole-detection=raw"
 genfile --sparse --file sparsefile 0 ABCDEFGHIJK 1M ABCDEFGHI || AT_SKIP_TEST
 echo "Pass 1: Split between data blocks"
 echo "Create archive"
diff --git a/tests/sparsemvp.at b/tests/sparsemvp.at
index 29ee224b..0fd6e33b 100644
--- a/tests/sparsemvp.at
+++ b/tests/sparsemvp.at
@@ -26,6 +26,7 @@ dnl TAR_MVP_TEST version map1 map2
 m4_define([TAR_MVP_TEST],[
 AT_TAR_CHECK([
 exec <&-
+TAR_OPTIONS="$TAR_OPTIONS --hole-detection=raw"
 genfile --sparse --file sparsefile $2 || AT_SKIP_TEST
 echo "Pass 1: Split between data blocks"
 echo "Create archive"
diff --git a/tests/testsuite.at b/tests/testsuite.at
index a08dc771..df8c14cb 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -112,6 +112,19 @@ rm -f $[]$
 test $result -eq 0 || AT_SKIP_TEST
 ])
 
+dnl AT_SEEKHOLE_PREREQ
+m4_define([AT_SEEKHOLE_PREREQ],[
+checkseekhole || AT_SKIP_TEST
+])
+
+m4_define([AT_TIMEOUT_PREREQ],[
+timeout 100 true
+if test $? -ne 0; then
+    echo >&2 "the 'timeout' utility not found"
+    AT_SKIP_TEST
+fi
+])
+
 m4_define([AT_TAR_MKHIER],[
 install-sh -d $1 >/dev/null dnl
 m4_if([$2],,,&& genfile --file [$1]/[$2]) || AT_SKIP_TEST])
@@ -358,6 +371,7 @@ m4_include([sparse02.at])
 m4_include([sparse03.at])
 m4_include([sparse04.at])
 m4_include([sparse05.at])
+m4_include([sparse06.at])
 m4_include([sparsemv.at])
 m4_include([spmvp00.at])
 m4_include([spmvp01.at])