Avoid running some tests if the file system does not support holes

Otherwise, these tests fills up the entire disk (or just run very
slowly and eventually time out).

10 files changed, 135 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index d834107..496fd1f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,22 @@
 2018-08-21  Florian Weimer  <fweimer@redhat.com>
 
+	* support/support.h (support_descriptor_supports_holes): Declare.
+	* support/Makefile (libsupport-routines): Add
+	support_descriptor_supports_holes.
+	* support/support_descriptor_supports_holes.c: New file.
+	* io/tst-copy_file_range.c: Call support_descriptor_supports_holes
+	and stop testing if holes are not supported.
+	* io/test-lfs.c (do_prepare): Likewise.
+	* sysdeps/unix/sysv/linux/tst-fallocate-common.c (do_prepare):
+	Likewise.
+	* timezone/tst-tzset.c (create_tz_file): Likewise.
+	* misc/tst-preadvwritev-common.c (temp_fd_supports_holes) New
+	variable.
+	(do_prepare): Set it.
+	* misc/tst-preadvwritev64.c (do_test): Use temp_fd_supports_holes.
+
+2018-08-21  Florian Weimer  <fweimer@redhat.com>
+
 	[BZ #17248]
 	* Makeconfig (+cflags): Do not sort (and deduplicate).
 
diff --git a/io/test-lfs.c b/io/test-lfs.c
index f7721a5..52120e9 100644
--- a/io/test-lfs.c
+++ b/io/test-lfs.c
@@ -25,6 +25,7 @@
 #include <error.h>
 #include <errno.h>
 #include <sys/resource.h>
+#include <support/check.h>
 
 /* Prototype for our test function.  */
 extern void do_prepare (int argc, char *argv[]);
@@ -70,6 +71,8 @@ do_prepare (int argc, char *argv[])
       else
 	error (EXIT_FAILURE, errno, "cannot create temporary file");
     }
+  if (!support_descriptor_supports_holes (fd))
+    FAIL_UNSUPPORTED ("File %s does not support holes", name);
   add_temp_file (name);
 
   if (getrlimit64 (RLIMIT_FSIZE, &rlim) != 0)
diff --git a/io/tst-copy_file_range.c b/io/tst-copy_file_range.c
index 3d531a1..e5b46f9 100644
--- a/io/tst-copy_file_range.c
+++ b/io/tst-copy_file_range.c
@@ -739,7 +739,12 @@ do_test (void)
     *p = rand () >> 24;
 
   infd = create_temp_file ("tst-copy_file_range-in-", &infile);
-  xclose (create_temp_file ("tst-copy_file_range-out-", &outfile));
+  {
+    int outfd = create_temp_file ("tst-copy_file_range-out-", &outfile);
+    if (!support_descriptor_supports_holes (outfd))
+      FAIL_UNSUPPORTED ("File %s does not support holes", outfile);
+    xclose (outfd);
+  }
 
   /* Try to find a different directory from the default input/output
      file.  */
diff --git a/misc/tst-preadvwritev-common.c b/misc/tst-preadvwritev-common.c
index b59a3de..4a5e53a 100644
--- a/misc/tst-preadvwritev-common.c
+++ b/misc/tst-preadvwritev-common.c
@@ -17,6 +17,7 @@
    <http://www.gnu.org/licenses/>.  */
 
 #include <array_length.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdint.h>
 #include <errno.h>
@@ -26,10 +27,12 @@
 
 #include <support/check.h>
 #include <support/temp_file.h>
+#include <support/support.h>
 #include <support/xunistd.h>
 
 static char *temp_filename;
 static int temp_fd;
+static bool temp_fd_supports_holes;
 
 static int do_test (void);
 
@@ -39,6 +42,7 @@ do_prepare (int argc, char **argv)
   temp_fd = create_temp_file ("tst-preadvwritev.", &temp_filename);
   if (temp_fd == -1)
     FAIL_EXIT1 ("cannot create temporary file");
+  temp_fd_supports_holes = support_descriptor_supports_holes (temp_fd);
 }
 #define PREPARE do_prepare
 
diff --git a/misc/tst-preadvwritev64.c b/misc/tst-preadvwritev64.c
index b718da6..451d03e 100644
--- a/misc/tst-preadvwritev64.c
+++ b/misc/tst-preadvwritev64.c
@@ -26,6 +26,12 @@ do_test (void)
 
   ret = do_test_with_offset (0);
 
+  if (!temp_fd_supports_holes)
+    {
+      puts ("warning: partial test due to lack of support for holes");
+      return ret;
+    }
+
   /* Create a sparse file larger than 4GB to check if offset is handled
      correctly in p{write,read}v64. */
   off_t base_offset = UINT32_MAX + 2048LL;
diff --git a/support/Makefile b/support/Makefile
index 652d2cd..9063046 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -43,6 +43,7 @@ libsupport-routines = \
   support_capture_subprocess \
   support_capture_subprocess_check \
   support_chroot \
+  support_descriptor_supports_holes \
   support_enter_mount_namespace \
   support_enter_network_namespace \
   support_format_address_family \
diff --git a/support/support.h b/support/support.h
index b61fe07..34ae6e1 100644
--- a/support/support.h
+++ b/support/support.h
@@ -65,6 +65,12 @@ void support_write_file_string (const char *path, const char *contents);
    the result).  */
 char *support_quote_blob (const void *blob, size_t length);
 
+/* Returns non-zero if the file descriptor is a regular file on a file
+   system which supports holes (that is, seeking and writing does not
+   allocate storage for the range of zeros).  FD must refer to a
+   regular file open for writing, and initially empty.  */
+int support_descriptor_supports_holes (int fd);
+
 /* Error-checking wrapper functions which terminate the process on
    error.  */
 
diff --git a/support/support_descriptor_supports_holes.c b/support/support_descriptor_supports_holes.c
new file mode 100644
index 0000000..c7099ca
--- /dev/null
+++ b/support/support_descriptor_supports_holes.c
@@ -0,0 +1,87 @@
+/* Test for file system hole support.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <stdbool.h>
+#include <support.h>
+#include <support/check.h>
+#include <sys/stat.h>
+#include <xunistd.h>
+
+int
+support_descriptor_supports_holes (int fd)
+{
+  enum
+    {
+      /* Write offset for the enlarged file.  This value is arbitrary
+         and hopefully large enough to trigger the creation of holes.
+         We cannot use the file system block size as a reference here
+         because it is incorrect for network file systems.  */
+      write_offset = 16 * 1024 * 1024,
+
+      /* Our write may add this number of additional blocks (see
+         block_limit below).  */
+      block_headroom = 8,
+    };
+
+  struct stat64 st;
+  xfstat (fd, &st);
+  if (!S_ISREG (st.st_mode))
+    FAIL_EXIT1 ("descriptor %d does not refer to a regular file", fd);
+  if (st.st_size != 0)
+    FAIL_EXIT1 ("descriptor %d does not refer to an empty file", fd);
+  if (st.st_blocks > block_headroom)
+    FAIL_EXIT1 ("descriptor %d refers to a pre-allocated file (%lld blocks)",
+                fd, (long long int) st.st_blocks);
+
+  /* Write a single byte at the start of the file to compute the block
+     usage for a single byte.  */
+  xlseek (fd, 0, SEEK_SET);
+  char b = '@';
+  xwrite (fd, &b, 1);
+  /* Attempt to bypass delayed allocation.  */
+  TEST_COMPARE (fsync (fd), 0);
+  xfstat (fd, &st);
+
+  /* This limit is arbitrary.  The file system needs to store
+     somewhere that data exists at the write offset, and this may
+     moderately increase the number of blocks used by the file, in
+     proportion to the initial block count, but not in proportion to
+     the write offset.  */
+  unsigned long long int block_limit = 2 * st.st_blocks + block_headroom;
+
+  /* Write a single byte at 16 megabytes.  */
+  xlseek (fd, write_offset, SEEK_SET);
+  xwrite (fd, &b, 1);
+  /* Attempt to bypass delayed allocation.  */
+  TEST_COMPARE (fsync (fd), 0);
+  xfstat (fd, &st);
+  bool supports_holes = st.st_blocks <= block_limit;
+
+  /* Also check that extending the file does not fill up holes.  */
+  xftruncate (fd, 2 * write_offset);
+  /* Attempt to bypass delayed allocation.  */
+  TEST_COMPARE (fsync (fd), 0);
+  xfstat (fd, &st);
+  supports_holes = supports_holes && st.st_blocks <= block_limit;
+
+  /* Return to a zero-length file.  */
+  xftruncate (fd, 0);
+  xlseek (fd, 0, SEEK_SET);
+
+  return supports_holes;
+}
diff --git a/sysdeps/unix/sysv/linux/tst-fallocate-common.c b/sysdeps/unix/sysv/linux/tst-fallocate-common.c
index a6ba403..bc54cf5 100644
--- a/sysdeps/unix/sysv/linux/tst-fallocate-common.c
+++ b/sysdeps/unix/sysv/linux/tst-fallocate-common.c
@@ -41,6 +41,8 @@ do_prepare (int argc, char **argv)
   temp_fd = create_temp_file ("tst-fallocate.", &temp_filename);
   if (temp_fd == -1)
     FAIL_EXIT1 ("cannot create temporary file: %m");
+  if (!support_descriptor_supports_holes (temp_fd))
+    FAIL_UNSUPPORTED ("File %s does not support holes", temp_filename);
 }
 #define PREPARE do_prepare
 
diff --git a/timezone/tst-tzset.c b/timezone/tst-tzset.c
index 27f986b..744c583 100644
--- a/timezone/tst-tzset.c
+++ b/timezone/tst-tzset.c
@@ -24,6 +24,7 @@
 #include <sys/resource.h>
 #include <time.h>
 #include <unistd.h>
+#include <support/check.h>
 
 #define TIMEOUT 5
 static int do_test (void);
@@ -38,6 +39,8 @@ create_tz_file (off64_t size)
   int fd = create_temp_file ("tst-tzset-", &path);
   if (fd < 0)
     exit (1);
+  if (!support_descriptor_supports_holes (fd))
+    FAIL_UNSUPPORTED ("File %s does not support holes", path);
 
   // Reopen for large-file support.
   close (fd);