[PATCH v2] generic: test fsync after punching hole adjacent to an existing hole

* [PATCH v2] generic: test fsync after punching hole adjacent to an existing hole
@ 2022-09-01 16:10 fdmanana
  2022-09-02  2:38 ` Zorro Lang
  0 siblings, 1 reply; 2+ messages in thread
From: fdmanana @ 2022-09-01 16:10 UTC (permalink / raw)
  To: fstests; +Cc: linux-btrfs, Filipe Manana

From: Filipe Manana <fdmanana@suse.com>

Test that if we punch a hole adjacent to an existing hole, fsync the file
and then power fail, the new hole exists after mounting again the
filesystem.

This currently fails on btrfs with kernels 5.18 and 5.19 when not using
the "no-holes" feature. The "no-holes" feature is enabled by default at
mkfs time starting with btrfs-progs 5.15, so to trigger the issue with
btrfs-progs 5.15+ and kernel 5.18 or kernel 5.19, one must set
"-O ^no-holes" in the MKFS_OPTIONS environment variable (part of the
btrfs test matrix).

The issue is fixed for btrfs with the following kernel patch:

   "btrfs: update generation of hole file extent item when merging holes"

Signed-off-by: Filipe Manana <fdmanana@suse.com>
---

v2: Added kernel commit tag (now that's merged in Linus' tree),
    added auto group, added the new odd _require_congruent_file_oplen
    requirement.

 tests/generic/695     | 91 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/695.out | 15 +++++++
 2 files changed, 106 insertions(+)
 create mode 100755 tests/generic/695
 create mode 100644 tests/generic/695.out

diff --git a/tests/generic/695 b/tests/generic/695
new file mode 100755
index 00000000..b46e35cf
--- /dev/null
+++ b/tests/generic/695
@@ -0,0 +1,91 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2022 SUSE Linux Products GmbH. All Rights Reserved.
+#
+# FS QA Test 695
+#
+# Test that if we punch a hole adjacent to an existing hole, fsync the file and
+# then power fail, the new hole exists after mounting again the filesystem.
+#
+# This is motivated by a regression on btrfs, fixed by the commit mentioned
+# below, when not using the no-holes feature (which is enabled by default since
+# btrfs-progs 5.15).
+#
+. ./common/preamble
+_begin_fstest auto quick log punch
+
+_cleanup()
+{
+	_cleanup_flakey
+	cd /
+	rm -r -f $tmp.*
+}
+
+. ./common/filter
+. ./common/dmflakey
+. ./common/punch
+
+_supported_fs generic
+_fixed_by_kernel_commit e6e3dec6c3c288 \
+        "btrfs: update generation of hole file extent item when merging holes"
+_require_scratch
+_require_dm_target flakey
+_require_xfs_io_command "fpunch"
+_require_xfs_io_command "fiemap"
+
+_scratch_mkfs >>$seqres.full 2>&1
+_require_metadata_journaling $SCRATCH_DEV
+_init_flakey
+_mount_flakey
+
+# We punch 2M holes and require extent allocations to align to 2M in fiemap
+# results.
+_require_congruent_file_oplen $SCRATCH_MNT $((2 * 1024 * 1024))
+
+# Create our test file with the following layout:
+#
+# [0, 2M)    - hole
+# [2M, 10M)  - extent
+# [10M, 12M) - hole
+$XFS_IO_PROG -f -c "truncate 12M" \
+	     -c "pwrite -S 0xab 2M 8M" \
+	     $SCRATCH_MNT/foobar | _filter_xfs_io
+
+# Persist everything, commit the filesystem's transaction.
+sync
+
+# Now punch two holes in the file:
+#
+# 1) For the range [2M, 4M), which is adjacent to the existing hole in the range
+#    [0, 2M);
+# 2) For the range [8M, 10M), which is adjacent to the existing hole in the
+#    range [10M, 12M).
+#
+# These operations start a new filesystem transaction.
+# Then finally fsync the file.
+$XFS_IO_PROG -c "fpunch 2M 2M" \
+	     -c "fpunch 8M 2M" \
+	     -c "fsync" $SCRATCH_MNT/foobar
+
+# Simulate a power failure and mount the filesystem to check that everything
+# is in the same state as before the power failure.
+_flakey_drop_and_remount
+
+# We expect the following file layout:
+#
+# [0, 4M)    - hole
+# [4M, 8M)   - extent
+# [8M, 12M)  - hole
+echo "File layout after power failure:"
+$XFS_IO_PROG -c "fiemap -v" $SCRATCH_MNT/foobar | _filter_fiemap
+
+# When reading the file we expect to get the range [4M, 8M) filled with bytes
+# that have a value of 0xab and 0x00 for anything outside that range.
+echo "File content after power failure:"
+_hexdump $SCRATCH_MNT/foobar
+
+_unmount_flakey
+
+# success, all done
+status=0
+exit
diff --git a/tests/generic/695.out b/tests/generic/695.out
new file mode 100644
index 00000000..447ef5cf
--- /dev/null
+++ b/tests/generic/695.out
@@ -0,0 +1,15 @@
+QA output created by 695
+wrote 8388608/8388608 bytes at offset 2097152
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+File layout after power failure:
+0: [0..8191]: hole
+1: [8192..16383]: data
+2: [16384..24575]: hole
+File content after power failure:
+000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  >................<
+*
+400000 ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab  >................<
+*
+800000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  >................<
+*
+c00000
-- 
2.35.1


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