generic: fallocate against a file range with a mix of holes and extents

Test that if we call fallocate against a file range that has a mix
of holes and written extents, the fallocate succeeds if the
filesystem has enough free space to allocate extents for the holes.

This test currently fails on btrfs and is fixed by a patch that has the
following subject:

    "btrfs: only reserve the needed data space amount during fallocate"

The test also fails on xfs, and after some discussion with Darrick,
it seems it's due to technical reasons that would require a
significant effort to xfs's implementation, and at the moment there
isn't enough motivation to do such change. The relevent thread is at:

    https://lore.kernel.org/linux-btrfs/20220315164011.GF8241@magnolia/

Therefore the test is intentionally skipped on xfs only. Ext4 and
f2fs pass this test.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

2 files changed, 83 insertions, 0 deletions

diff --git a/tests/generic/679 b/tests/generic/679
new file mode 100755
index 0000000000..440f0c081c
--- /dev/null
+++ b/tests/generic/679
@@ -0,0 +1,63 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2022 SUSE Linux Products GmbH.  All Rights Reserved.
+#
+# FS QA Test 679
+#
+# Test that if we call fallocate against a file range that has a mix of holes
+# and written extents, the fallocate succeeds if the filesystem has enough free
+# space to allocate extents for the holes.
+#
+. ./common/preamble
+_begin_fstest auto quick prealloc
+
+. ./common/rc
+. ./common/filter
+. ./common/punch
+
+# real QA test starts here
+
+_supported_fs generic
+_require_scratch
+_require_xfs_io_command "falloc"
+_require_xfs_io_command "fiemap"
+
+# This test is currently not valid for xfs, see the following thread for details:
+#
+#   https://lore.kernel.org/linux-btrfs/20220315164011.GF8241@magnolia/
+#
+[ $FSTYP == "xfs" ] && _notrun "test not valid for xfs"
+
+rm -f $seqres.full
+
+# Create a 1G filesystem.
+_scratch_mkfs_sized $((1024 * 1024 * 1024)) >>$seqres.full 2>&1
+_scratch_mount
+
+# Create a file with a size of 600M and two holes, each with a size of 1M and
+# at file ranges [200, 201M[ and [401M, 402M[.
+$XFS_IO_PROG -f -c "pwrite -S 0xab 0 200M" \
+                -c "pwrite -S 0xcd 201M 200M" \
+                -c "pwrite -S 0xef 402M 198M" \
+		$SCRATCH_MNT/foobar | _filter_xfs_io
+
+# Now call fallocate against the whole file range.
+# It should succeed, because only 2M of data space needs to be allocated,
+# and not 600M (which isn't available since our fs has a size of 1G).
+$XFS_IO_PROG -c "falloc 0 600M" $SCRATCH_MNT/foobar
+
+# Unmount and mount again the filesystem. We want to verify that the fallocate
+# results were persisted and that all the file data on disk are also correct.
+_scratch_cycle_mount
+
+echo -n "Number of unwritten extents in the file: "
+$XFS_IO_PROG -c "fiemap -v" $SCRATCH_MNT/foobar | _filter_fiemap | \
+    grep "unwritten" | wc -l
+
+# Verify we don't have any corruption caused by the fallocate.
+echo "File content after fallocate:"
+od -A d -t x1 $SCRATCH_MNT/foobar
+
+# success, all done
+status=0
+exit
diff --git a/tests/generic/679.out b/tests/generic/679.out
new file mode 100644
index 0000000000..fbf264b4b7
--- /dev/null
+++ b/tests/generic/679.out
@@ -0,0 +1,20 @@
+QA output created by 679
+wrote 209715200/209715200 bytes at offset 0
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 209715200/209715200 bytes at offset 210763776
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 207618048/207618048 bytes at offset 421527552
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+Number of unwritten extents in the file: 2
+File content after fallocate:
+0000000 ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab
+*
+209715200 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
+*
+210763776 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd
+*
+420478976 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
+*
+421527552 ef ef ef ef ef ef ef ef ef ef ef ef ef ef ef ef
+*
+629145600