commit 5a659ccc0ec217ab02a4c273a1f6d346a359560a

Author: Florian Weimer <fweimer@redhat.com>

Date:   Fri Jun 28 09:39:21 2019 +0200

    io: Remove copy_file_range emulation [BZ #24744]

    The kernel is evolving this interface (e.g., removal of the

    restriction on cross-device copies), and keeping up with that

    is difficult.  Applications which need the function should

    run kernels which support the system call instead of relying on

    the imperfect glibc emulation.

    Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

# Conflicts:

#	io/copy_file_range-compat.c

#	io/copy_file_range.c

#	io/tst-copy_file_range-compat.c

#	io/tst-copy_file_range.c

#	sysdeps/unix/sysv/linux/arm/kernel-features.h

#	sysdeps/unix/sysv/linux/microblaze/kernel-features.h

#	sysdeps/unix/sysv/linux/sh/kernel-features.h

diff --git a/io/Makefile b/io/Makefile

index 787a5c550ab64b17..62e71b4cbe879dbc 100644

--- a/io/Makefile

+++ b/io/Makefile

@@ -75,11 +75,6 @@ tests		:= test-utime test-stat test-stat2 test-lfs tst-getcwd \

 		   tst-fts tst-fts-lfs tst-open-tmpfile \

 		   tst-copy_file_range tst-getcwd-abspath \

-# This test includes the compat implementation of copy_file_range,

-# which uses internal, unexported libc functions.

-tests-static += tst-copy_file_range-compat

-tests-internal += tst-copy_file_range-compat

-

 # Likewise for statx, but we do not need static linking here.

 tests-internal += tst-statx

diff --git a/io/copy_file_range-compat.c b/io/copy_file_range-compat.c

deleted file mode 100644

index 4ab22cad19146ca9..0000000000000000

--- a/io/copy_file_range-compat.c

+++ /dev/null

@@ -1,160 +0,0 @@

-/* Emulation of copy_file_range.

-   Copyright (C) 2017-2018 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/>.  */

-

-/* The following macros should be defined before including this

-   file:

-

-   COPY_FILE_RANGE_DECL   Declaration specifiers for the function below.

-   COPY_FILE_RANGE        Name of the function to define.  */

-

-#include <errno.h>

-#include <fcntl.h>

-#include <inttypes.h>

-#include <limits.h>

-#include <sys/stat.h>

-#include <sys/types.h>

-#include <unistd.h>

-

-COPY_FILE_RANGE_DECL

-ssize_t

-COPY_FILE_RANGE (int infd, __off64_t *pinoff,

-                 int outfd, __off64_t *poutoff,

-                 size_t length, unsigned int flags)

-{

-  if (flags != 0)

-    {

-      __set_errno (EINVAL);

-      return -1;

-    }

-

-  {

-    struct stat64 instat;

-    struct stat64 outstat;

-    if (fstat64 (infd, &instat) != 0 || fstat64 (outfd, &outstat) != 0)

-      return -1;

-    if (S_ISDIR (instat.st_mode) || S_ISDIR (outstat.st_mode))

-      {

-        __set_errno (EISDIR);

-        return -1;

-      }

-    if (!S_ISREG (instat.st_mode) || !S_ISREG (outstat.st_mode))

-      {

-        /* We need a regular input file so that the we can seek

-           backwards in case of a write failure.  */

-        __set_errno (EINVAL);

-        return -1;

-      }

-    if (instat.st_dev != outstat.st_dev)

-      {

-        /* Cross-device copies are not supported.  */

-        __set_errno (EXDEV);

-        return -1;

-      }

-  }

-

-  /* The output descriptor must not have O_APPEND set.  */

-  {

-    int flags = __fcntl (outfd, F_GETFL);

-    if (flags & O_APPEND)

-      {

-        __set_errno (EBADF);

-        return -1;

-      }

-  }

-

-  /* Avoid an overflow in the result.  */

-  if (length > SSIZE_MAX)

-    length = SSIZE_MAX;

-

-  /* Main copying loop.  The buffer size is arbitrary and is a

-     trade-off between stack size consumption, cache usage, and

-     amortization of system call overhead.  */

-  size_t copied = 0;

-  char buf[8192];

-  while (length > 0)

-    {

-      size_t to_read = length;

-      if (to_read > sizeof (buf))

-        to_read = sizeof (buf);

-

-      /* Fill the buffer.  */

-      ssize_t read_count;

-      if (pinoff == NULL)

-        read_count = read (infd, buf, to_read);

-      else

-        read_count = __libc_pread64 (infd, buf, to_read, *pinoff);

-      if (read_count == 0)

-        /* End of file reached prematurely.  */

-        return copied;

-      if (read_count < 0)

-        {

-          if (copied > 0)

-            /* Report the number of bytes copied so far.  */

-            return copied;

-          return -1;

-        }

-      if (pinoff != NULL)

-        *pinoff += read_count;

-

-      /* Write the buffer part which was read to the destination.  */

-      char *end = buf + read_count;

-      for (char *p = buf; p < end; )

-        {

-          ssize_t write_count;

-          if (poutoff == NULL)

-            write_count = write (outfd, p, end - p);

-          else

-            write_count = __libc_pwrite64 (outfd, p, end - p, *poutoff);

-          if (write_count < 0)

-            {

-              /* Adjust the input read position to match what we have

-                 written, so that the caller can pick up after the

-                 error.  */

-              size_t written = p - buf;

-              /* NB: This needs to be signed so that we can form the

-                 negative value below.  */

-              ssize_t overread = read_count - written;

-              if (pinoff == NULL)

-                {

-                  if (overread > 0)

-                    {

-                      /* We are on an error recovery path, so we

-                         cannot deal with failure here.  */

-                      int save_errno = errno;

-                      (void) __libc_lseek64 (infd, -overread, SEEK_CUR);

-                      __set_errno (save_errno);

-                    }

-                }

-              else /* pinoff != NULL */

-                *pinoff -= overread;

-

-              if (copied + written > 0)

-                /* Report the number of bytes copied so far.  */

-                return copied + written;

-              return -1;

-            }

-          p += write_count;

-          if (poutoff != NULL)

-            *poutoff += write_count;

-        } /* Write loop.  */

-

-      copied += read_count;

-      length -= read_count;

-    }

-  return copied;

-}

diff --git a/io/copy_file_range.c b/io/copy_file_range.c

index 98bff8bd2615b214..59fb979773b2b202 100644

--- a/io/copy_file_range.c

+++ b/io/copy_file_range.c

@@ -1,5 +1,5 @@

-/* Generic implementation of copy_file_range.

-   Copyright (C) 2017-2018 Free Software Foundation, Inc.

+/* Stub implementation of copy_file_range.

+   Copyright (C) 2017-2019 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

@@ -16,7 +16,15 @@

    License along with the GNU C Library; if not, see

    <http://www.gnu.org/licenses/>.  */

-#define COPY_FILE_RANGE_DECL

-#define COPY_FILE_RANGE copy_file_range

+#include <errno.h>

+#include <unistd.h>

-#include <io/copy_file_range-compat.c>

+ssize_t

+copy_file_range (int infd, __off64_t *pinoff,

+                 int outfd, __off64_t *poutoff,

+                 size_t length, unsigned int flags)

+{

+  __set_errno (ENOSYS);

+  return -1;

+}

+stub_warning (copy_file_range)

diff --git a/io/tst-copy_file_range-compat.c b/io/tst-copy_file_range-compat.c

deleted file mode 100644

index 00c109a74d3c9d64..0000000000000000

--- a/io/tst-copy_file_range-compat.c

+++ /dev/null

@@ -1,30 +0,0 @@

-/* Test the fallback implementation of copy_file_range.

-   Copyright (C) 2017-2018 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/>.  */

-

-/* Get the declaration of the official copy_of_range function.  */

-#include <unistd.h>

-

-/* Compile a local version of copy_file_range.  */

-#define COPY_FILE_RANGE_DECL static

-#define COPY_FILE_RANGE copy_file_range_compat

-#include <io/copy_file_range-compat.c>

-

-/* Re-use the test, but run it against copy_file_range_compat defined

-   above.  */

-#define copy_file_range copy_file_range_compat

-#include "tst-copy_file_range.c"

diff --git a/io/tst-copy_file_range.c b/io/tst-copy_file_range.c

index 3d531a19370911e5..4504020d2ee7d2ee 100644

--- a/io/tst-copy_file_range.c

+++ b/io/tst-copy_file_range.c

@@ -20,22 +20,15 @@

 #include <errno.h>

 #include <fcntl.h>

 #include <inttypes.h>

-#include <libgen.h>

-#include <poll.h>

-#include <sched.h>

 #include <stdbool.h>

 #include <stdio.h>

 #include <stdlib.h>

 #include <string.h>

 #include <support/check.h>

-#include <support/namespace.h>

 #include <support/support.h>

 #include <support/temp_file.h>

 #include <support/test-driver.h>

 #include <support/xunistd.h>

-#ifdef CLONE_NEWNS

-# include <sys/mount.h>

-#endif

 /* Boolean flags which indicate whether to use pointers with explicit

    output flags.  */

@@ -49,10 +42,6 @@ static int infd;

 static char *outfile;

 static int outfd;

-/* Like the above, but on a different file system.  xdevfile can be

-   NULL if no suitable file system has been found.  */

-static char *xdevfile;

-

 /* Input and output offsets.  Set according to do_inoff and do_outoff

    before the test.  The offsets themselves are always set to

    zero.  */

@@ -61,13 +50,10 @@ static off64_t *pinoff;

 static off64_t outoff;

 static off64_t *poutoff;

-/* These are a collection of copy sizes used in tests.  The selection

-   takes into account that the fallback implementation uses an

-   internal buffer of 8192 bytes.  */

+/* These are a collection of copy sizes used in tests.    */

 enum { maximum_size = 99999 };

 static const int typical_sizes[] =

-  { 0, 1, 2, 3, 1024, 2048, 4096, 8191, 8192, 8193, 16383, 16384, 16385,

-    maximum_size };

+  { 0, 1, 2, 3, 1024, 2048, 4096, 8191, 8192, 8193, maximum_size };

 /* The random contents of this array can be used as a pattern to check

    for correct write operations.  */

@@ -76,101 +62,6 @@ static unsigned char random_data[maximum_size];

 /* The size chosen by the test harness.  */

 static int current_size;

-/* Maximum writable file offset.  Updated by find_maximum_offset

-   below.  */

-static off64_t maximum_offset;

-

-/* Error code when crossing the offset.  */

-static int maximum_offset_errno;

-

-/* If true: Writes which cross the limit will fail.  If false: Writes

-   which cross the limit will result in a partial write.  */

-static bool maximum_offset_hard_limit;

-

-/* Fills maximum_offset etc. above.  Truncates outfd as a side

-   effect.  */

-static void

-find_maximum_offset (void)

-{

-  xftruncate (outfd, 0);

-  if (maximum_offset != 0)

-    return;

-

-  uint64_t upper = -1;

-  upper >>= 1;                  /* Maximum of off64_t.  */

-  TEST_VERIFY ((off64_t) upper > 0);

-  TEST_VERIFY ((off64_t) (upper + 1) < 0);

-  if (lseek64 (outfd, upper, SEEK_SET) >= 0)

-    {

-      if (write (outfd, "", 1) == 1)

-        FAIL_EXIT1 ("created a file larger than the off64_t range");

-    }

-

-  uint64_t lower = 1024 * 1024; /* A reasonable minimum file size.  */

-  /* Loop invariant: writing at lower succeeds, writing at upper fails.  */

-  while (lower + 1 < upper)

-    {

-      uint64_t middle = (lower + upper) / 2;

-      if (test_verbose > 0)

-        printf ("info: %s: remaining test range %" PRIu64 " .. %" PRIu64

-                ", probe at %" PRIu64 "\n", __func__, lower, upper, middle);

-      xftruncate (outfd, 0);

-      if (lseek64 (outfd, middle, SEEK_SET) >= 0

-          && write (outfd, "", 1) == 1)

-        lower = middle;

-      else

-        upper = middle;

-    }

-  TEST_VERIFY (lower + 1 == upper);

-  maximum_offset = lower;

-  printf ("info: maximum writable file offset: %" PRIu64 " (%" PRIx64 ")\n",

-          lower, lower);

-

-  /* Check that writing at the valid offset actually works.  */

-  xftruncate (outfd, 0);

-  xlseek (outfd, lower, SEEK_SET);

-  TEST_COMPARE (write (outfd, "", 1), 1);

-

-  /* Cross the boundary with a two-byte write.  This can either result

-     in a short write, or a failure.  */

-  xlseek (outfd, lower, SEEK_SET);

-  ssize_t ret = write (outfd, " ", 2);

-  if (ret < 0)

-    {

-      maximum_offset_errno = errno;

-      maximum_offset_hard_limit = true;

-    }

-  else

-    maximum_offset_hard_limit = false;

-

-  /* Check that writing at the next offset actually fails.  This also

-     obtains the expected errno value.  */

-  xftruncate (outfd, 0);

-  const char *action;

-  if (lseek64 (outfd, lower + 1, SEEK_SET) != 0)

-    {

-      if (write (outfd, "", 1) != -1)

-        FAIL_EXIT1 ("write to impossible offset %" PRIu64 " succeeded",

-                    lower + 1);

-      action = "writing";

-      int errno_copy = errno;

-      if (maximum_offset_hard_limit)

-        TEST_COMPARE (errno_copy, maximum_offset_errno);

-      else

-        maximum_offset_errno = errno_copy;

-    }

-  else

-    {

-      action = "seeking";

-      maximum_offset_errno = errno;

-    }

-  printf ("info: %s out of range fails with %m (%d)\n",

-          action, maximum_offset_errno);

-

-  xftruncate (outfd, 0);

-  xlseek (outfd, 0, SEEK_SET);

-}

-

 /* Perform a copy of a file.  */

 static void

 simple_file_copy (void)

@@ -247,390 +138,6 @@ simple_file_copy (void)

   free (bytes);

 }

-/* Test that reading from a pipe willfails.  */

-static void

-pipe_as_source (void)

-{

-  int pipefds[2];

-  xpipe (pipefds);

-

-  for (int length = 0; length < 2; ++length)

-    {

-      if (test_verbose > 0)

-        printf ("info: %s: length=%d\n", __func__, length);

-

-      /* Make sure that there is something to copy in the pipe.  */

-      xwrite (pipefds[1], "@", 1);

-

-      TEST_COMPARE (copy_file_range (pipefds[0], pinoff, outfd, poutoff,

-                                     length, 0), -1);

-      /* Linux 4.10 and later return EINVAL.  Older kernels return

-         EXDEV.  */

-      TEST_VERIFY (errno == EINVAL || errno == EXDEV);

-      TEST_COMPARE (inoff, 0);

-      TEST_COMPARE (outoff, 0);

-      TEST_COMPARE (xlseek (outfd, 0, SEEK_CUR), 0);

-

-      /* Make sure that nothing was read.  */

-      char buf = 'A';

-      TEST_COMPARE (read (pipefds[0], &buf, 1), 1);

-      TEST_COMPARE (buf, '@');

-    }

-

-  xclose (pipefds[0]);

-  xclose (pipefds[1]);

-}

-

-/* Test that writing to a pipe fails.  */

-static void

-pipe_as_destination (void)

-{

-  /* Make sure that there is something to read in the input file.  */

-  xwrite (infd, "abc", 3);

-  xlseek (infd, 0, SEEK_SET);

-

-  int pipefds[2];

-  xpipe (pipefds);

-

-  for (int length = 0; length < 2; ++length)

-    {

-      if (test_verbose > 0)

-        printf ("info: %s: length=%d\n", __func__, length);

-

-      TEST_COMPARE (copy_file_range (infd, pinoff, pipefds[1], poutoff,

-                                     length, 0), -1);

-      /* Linux 4.10 and later return EINVAL.  Older kernels return

-         EXDEV.  */

-      TEST_VERIFY (errno == EINVAL || errno == EXDEV);

-      TEST_COMPARE (inoff, 0);

-      TEST_COMPARE (outoff, 0);

-      TEST_COMPARE (xlseek (infd, 0, SEEK_CUR), 0);

-

-      /* Make sure that nothing was written.  */

-      struct pollfd pollfd = { .fd = pipefds[0], .events = POLLIN, };

-      TEST_COMPARE (poll (&pollfd, 1, 0), 0);

-    }

-

-  xclose (pipefds[0]);

-  xclose (pipefds[1]);

-}

-

-/* Test a write failure after (potentially) writing some bytes.

-   Failure occurs near the start of the buffer.  */

-static void

-delayed_write_failure_beginning (void)

-{

-  /* We need to write something to provoke the error.  */

-  if (current_size == 0)

-    return;

-  xwrite (infd, random_data, sizeof (random_data));

-  xlseek (infd, 0, SEEK_SET);

-

-  /* Write failure near the start.  The actual error code varies among

-     file systems.  */

-  find_maximum_offset ();

-  off64_t where = maximum_offset;

-

-  if (current_size == 1)

-    ++where;

-  outoff = where;

-  if (do_outoff)

-    xlseek (outfd, 1, SEEK_SET);

-  else

-    xlseek (outfd, where, SEEK_SET);

-  if (maximum_offset_hard_limit || where > maximum_offset)

-    {

-      TEST_COMPARE (copy_file_range (infd, pinoff, outfd, poutoff,

-                                     sizeof (random_data), 0), -1);

-      TEST_COMPARE (errno, maximum_offset_errno);

-      TEST_COMPARE (xlseek (infd, 0, SEEK_CUR), 0);

-      TEST_COMPARE (inoff, 0);

-      if (do_outoff)

-        TEST_COMPARE (xlseek (outfd, 0, SEEK_CUR), 1);

-      else

-        TEST_COMPARE (xlseek (outfd, 0, SEEK_CUR), where);

-      TEST_COMPARE (outoff, where);

-      struct stat64 st;

-      xfstat (outfd, &st);

-      TEST_COMPARE (st.st_size, 0);

-    }

-  else

-    {

-      /* The offset is not a hard limit.  This means we write one

-         byte.  */

-      TEST_COMPARE (copy_file_range (infd, pinoff, outfd, poutoff,

-                                     sizeof (random_data), 0), 1);

-      if (do_inoff)

-        {

-          TEST_COMPARE (inoff, 1);

-          TEST_COMPARE (xlseek (infd, 0, SEEK_CUR), 0);

-        }

-      else

-        {

-          TEST_COMPARE (xlseek (infd, 0, SEEK_CUR), 1);

-          TEST_COMPARE (inoff, 0);

-        }

-      if (do_outoff)

-        {

-          TEST_COMPARE (xlseek (outfd, 0, SEEK_CUR), 1);

-          TEST_COMPARE (outoff, where + 1);

-        }

-      else

-        {

-          TEST_COMPARE (xlseek (outfd, 0, SEEK_CUR), where + 1);

-          TEST_COMPARE (outoff, where);

-        }

-      struct stat64 st;

-      xfstat (outfd, &st);

-      TEST_COMPARE (st.st_size, where + 1);

-    }

-}

-

-/* Test a write failure after (potentially) writing some bytes.

-   Failure occurs near the end of the buffer.  */

-static void

-delayed_write_failure_end (void)

-{

-  if (current_size <= 1)

-    /* This would be same as the first test because there is not

-       enough data to write to make a difference.  */

-    return;

-  xwrite (infd, random_data, sizeof (random_data));

-  xlseek (infd, 0, SEEK_SET);

-

-  find_maximum_offset ();

-  off64_t where = maximum_offset - current_size + 1;

-  if (current_size == sizeof (random_data))

-    /* Otherwise we do not reach the non-writable byte.  */

-    ++where;

-  outoff = where;

-  if (do_outoff)

-    xlseek (outfd, 1, SEEK_SET);

-  else

-    xlseek (outfd, where, SEEK_SET);

-  ssize_t ret = copy_file_range (infd, pinoff, outfd, poutoff,

-                                 sizeof (random_data), 0);

-  if (ret < 0)

-    {

-      TEST_COMPARE (ret, -1);

-      TEST_COMPARE (errno, maximum_offset_errno);

-      struct stat64 st;

-      xfstat (outfd, &st);

-      TEST_COMPARE (st.st_size, 0);

-    }

-  else

-    {

-      /* The first copy succeeded.  This happens in the emulation

-         because the internal buffer of limited size does not

-         necessarily cross the off64_t boundary on the first write

-         operation.  */

-      if (test_verbose > 0)

-        printf ("info:   copy_file_range (%zu) returned %zd\n",

-                sizeof (random_data), ret);

-      TEST_VERIFY (ret > 0);

-      TEST_VERIFY (ret < maximum_size);

-      struct stat64 st;

-      xfstat (outfd, &st);

-      TEST_COMPARE (st.st_size, where + ret);

-      if (do_inoff)

-        {

-          TEST_COMPARE (inoff, ret);

-          TEST_COMPARE (xlseek (infd, 0, SEEK_CUR), 0);

-        }

-      else

-          TEST_COMPARE (xlseek (infd, 0, SEEK_CUR), ret);

-

-      char *buffer = xmalloc (ret);

-      TEST_COMPARE (pread64 (outfd, buffer, ret, where), ret);

-      TEST_VERIFY (memcmp (buffer, random_data, ret) == 0);

-      free (buffer);

-

-      /* The second copy fails.  */

-      TEST_COMPARE (copy_file_range (infd, pinoff, outfd, poutoff,

-                                     sizeof (random_data), 0), -1);

-      TEST_COMPARE (errno, maximum_offset_errno);

-    }

-}

-

-/* Test a write failure across devices.  */

-static void

-cross_device_failure (void)

-{

-  if (xdevfile == NULL)

-    /* Subtest not supported due to missing cross-device file.  */

-    return;

-

-  /* We need something to write.  */

-  xwrite (infd, random_data, sizeof (random_data));

-  xlseek (infd, 0, SEEK_SET);

-

-  int xdevfd = xopen (xdevfile, O_RDWR | O_LARGEFILE, 0);

-  TEST_COMPARE (copy_file_range (infd, pinoff, xdevfd, poutoff,

-                                 current_size, 0), -1);

-  TEST_COMPARE (errno, EXDEV);

-  TEST_COMPARE (xlseek (infd, 0, SEEK_CUR), 0);

-  struct stat64 st;

-  xfstat (xdevfd, &st);

-  TEST_COMPARE (st.st_size, 0);

-

-  xclose (xdevfd);

-}

-

-/* Try to exercise ENOSPC behavior with a tempfs file system (so that

-   we do not have to fill up a regular file system to get the error).

-   This function runs in a subprocess, so that we do not change the

-   mount namespace of the actual test process.  */

-static void

-enospc_failure_1 (void *closure)

-{

-#ifdef CLONE_NEWNS

-  support_become_root ();

-

-  /* Make sure that we do not alter the file system mounts of the

-     parents.  */

-  if (! support_enter_mount_namespace ())

-    {

-      printf ("warning: ENOSPC test skipped\n");

-      return;

-    }

-

-  char *mountpoint = closure;

-  if (mount ("none", mountpoint, "tmpfs", MS_NODEV | MS_NOEXEC,

-             "size=500k") != 0)

-    {

-      printf ("warning: could not mount tmpfs at %s: %m\n", mountpoint);

-      return;

-    }

-

-  /* The source file must reside on the same file system.  */

-  char *intmpfsfile = xasprintf ("%s/%s", mountpoint, "in");

-  int intmpfsfd = xopen (intmpfsfile, O_RDWR | O_CREAT | O_LARGEFILE, 0600);

-  xwrite (intmpfsfd, random_data, sizeof (random_data));

-  xlseek (intmpfsfd, 1, SEEK_SET);

-  inoff = 1;

-

-  char *outtmpfsfile = xasprintf ("%s/%s", mountpoint, "out");

-  int outtmpfsfd = xopen (outtmpfsfile, O_RDWR | O_CREAT | O_LARGEFILE, 0600);

-

-  /* Fill the file with data until ENOSPC is reached.  */

-  while (true)

-    {

-      ssize_t ret = write (outtmpfsfd, random_data, sizeof (random_data));

-      if (ret < 0 && errno != ENOSPC)

-        FAIL_EXIT1 ("write to %s: %m", outtmpfsfile);

-      if (ret < sizeof (random_data))

-        break;

-    }

-  TEST_COMPARE (write (outtmpfsfd, "", 1), -1);

-  TEST_COMPARE (errno, ENOSPC);

-  off64_t maxsize = xlseek (outtmpfsfd, 0, SEEK_CUR);

-  TEST_VERIFY_EXIT (maxsize > sizeof (random_data));

-

-  /* Constructed the expected file contents.  */

-  char *expected = xmalloc (maxsize);

-  TEST_COMPARE (pread64 (outtmpfsfd, expected, maxsize, 0), maxsize);

-  /* Go back a little, so some bytes can be written.  */

-  enum { offset = 20000 };

-  TEST_VERIFY_EXIT (offset < maxsize);

-  TEST_VERIFY_EXIT (offset < sizeof (random_data));

-  memcpy (expected + maxsize - offset, random_data + 1, offset);