[PATCH v4 1/2] common: new helper to alloacate fixed size files

[Pavel Reichl <preichl@redhat.com>]

Helper that creates files of specified size using falloc if supported,
otherwise pwrite is used.

Signed-off-by: Pavel Reichl <preichl@redhat.com>
---
 common/rc         | 22 ++++++++++++++++++++++
 tests/generic/694 |  8 +++++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/common/rc b/common/rc
index a25cbcd0..3d4587b7 100644
--- a/common/rc
+++ b/common/rc
@@ -4925,6 +4925,28 @@ hexdump()
 	_fail "Use _hexdump(), please!"
 }
 
+# Try to create a file with inode->i_blocks = $length. There may be some small
+# overhead, e.g. ext2 filesystem allocates a substantial number of blocks
+# to store block mappings. Those are accounted to i_blocks.
+_create_file_sized()
+{
+	local length=$1
+	local file=$2
+	local tmp=`mktemp -u`
+	local ret=0
+
+	$XFS_IO_PROG -ft -c "falloc 0 $length" $file >$tmp.out 2>&1
+	ret=$?
+	if (grep -Eq "Operation not supported|command .* not found" $tmp.out);then
+		# fallocate isn't supported, fallback to general buffer write
+		$XFS_IO_PROG -ft -c "pwrite 0 $length" $file >$tmp.out 2>&1
+		ret=$?
+	fi
+	[ $ret -ne 0 ] && cat $tmp.out
+	rm -f $tmp.out
+	return $ret
+}
+
 init_rc
 
 ################################################################################
diff --git a/tests/generic/694 b/tests/generic/694
index dfd988df..09fb9e71 100755
--- a/tests/generic/694
+++ b/tests/generic/694
@@ -21,6 +21,9 @@ _cleanup()
 }
 
 _supported_fs generic
+_fixed_by_kernel_commit 0c336d6e33f4 \
+	"exfat: fix incorrect loading of i_blocks for large file"
+
 _require_test
 _require_fs_space $TEST_DIR $((4 * 1024 * 1024)) #kB
 
@@ -30,7 +33,10 @@ junk_dir=$TEST_DIR/$seq
 junk_file=$junk_dir/junk
 mkdir -p $junk_dir
 
-$XFS_IO_PROG -f -c "pwrite -W 0 4G" $junk_file > /dev/null
+_create_file_sized 4G $junk_file
+if [ $? -ne 0 ]; then
+	echo "_create_file_sized failed"
+fi
 
 iblocks=`stat -c '%b' $junk_file`
 
-- 
2.37.3