[PATCH v1.3 1/2] xfs: make sure that we handle empty xattr leaf blocks ok

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

Make sure that the kernel can handle empty xattr leaf blocks properly,
since we've screwed this up enough times.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
v1.1: adopt maintainer's refactoring suggestions, skip v4 filesystems
from the start, and check that we really get an attr leaf block.
v1.2: eliminate dead code
v1.3: actually add golden output
---
 tests/xfs/845     |  117 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/xfs/845.out |    7 +++
 2 files changed, 124 insertions(+)
 create mode 100755 tests/xfs/845
 create mode 100644 tests/xfs/845.out

diff --git a/tests/xfs/845 b/tests/xfs/845
new file mode 100755
index 00000000..c142fba1
--- /dev/null
+++ b/tests/xfs/845
@@ -0,0 +1,117 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2022 Oracle.  All Rights Reserved.
+#
+# FS QA Test 845
+#
+# Make sure that XFS can handle empty leaf xattr blocks correctly.  These
+# blocks can appear in files as a result of system crashes in the middle of
+# xattr operations, which means that we /must/ handle them gracefully.
+# Check that read and write verifiers won't trip, that the get/list/setxattr
+# operations don't stumble over them, and that xfs_repair will offer to remove
+# the entire xattr fork if the root xattr leaf block is empty.
+#
+# Regression test for kernel commit:
+#
+# af866926d865 ("xfs: empty xattr leaf header blocks are not corruption")
+#
+. ./common/preamble
+_begin_fstest auto quick attr
+
+# Import common functions.
+. ./common/filter
+. ./common/attr
+
+# real QA test starts here
+
+_supported_fs xfs
+_require_scratch
+_require_scratch_xfs_crc # V4 is deprecated
+_fixed_by_kernel_commit af866926d865 "xfs: empty xattr leaf header blocks are not corruption"
+
+_scratch_mkfs_xfs | _filter_mkfs >$seqres.full 2>$tmp.mkfs
+cat $tmp.mkfs >> $seqres.full
+source $tmp.mkfs
+_scratch_mount
+
+$XFS_IO_PROG -f -c 'pwrite -S 0x58 0 64k' $SCRATCH_MNT/largefile >> $seqres.full
+$XFS_IO_PROG -f -c "pwrite -S 0x58 0 $isize" $SCRATCH_MNT/smallfile >> $seqres.full
+
+smallfile_md5=$(_md5_checksum $SCRATCH_MNT/smallfile)
+largefile_md5=$(_md5_checksum $SCRATCH_MNT/largefile)
+
+# Try to force the creation of a single leaf block in each of three files.
+# The first one gets a local attr, the second a remote attr, and the third
+# is left for scrub and repair to find.
+touch $SCRATCH_MNT/e0
+touch $SCRATCH_MNT/e1
+touch $SCRATCH_MNT/e2
+
+$ATTR_PROG -s x $SCRATCH_MNT/e0 < $SCRATCH_MNT/smallfile >> $seqres.full
+$ATTR_PROG -s x $SCRATCH_MNT/e1 < $SCRATCH_MNT/smallfile >> $seqres.full
+$ATTR_PROG -s x $SCRATCH_MNT/e2 < $SCRATCH_MNT/smallfile >> $seqres.full
+
+e0_ino=$(stat -c '%i' $SCRATCH_MNT/e0)
+e1_ino=$(stat -c '%i' $SCRATCH_MNT/e1)
+e2_ino=$(stat -c '%i' $SCRATCH_MNT/e2)
+
+_scratch_unmount
+
+# We used to think that it wasn't possible for empty xattr leaf blocks to
+# exist, but it turns out that setting a large xattr on a file that has no
+# xattrs can race with a log flush and crash, which results in an empty
+# leaf block being logged and recovered.  This is rather hard to trip, so we
+# use xfs_db to turn a regular leaf block into an empty one.
+make_empty_leaf() {
+	local inum="$1"
+
+	echo "editing inode $inum" >> $seqres.full
+
+	magic=$(_scratch_xfs_get_metadata_field hdr.info.hdr.magic "inode $inum" "ablock 0")
+	if [ "$magic" != "0x3bee" ]; then
+		_scratch_xfs_db -x -c "inode $inum" -c "ablock 0" -c print >> $seqres.full
+		_fail "inode $inum ablock 0 is not a leaf block?"
+	fi
+
+	base=$(_scratch_xfs_get_metadata_field "hdr.freemap[0].base" "inode $inum" "ablock 0")
+
+	_scratch_xfs_db -x -c "inode $inum" -c "ablock 0" \
+		-c "write -d hdr.count 0" \
+		-c "write -d hdr.usedbytes 0" \
+		-c "write -d hdr.firstused $dbsize" \
+		-c "write -d hdr.freemap[0].size $((dbsize - base))" \
+		-c print >> $seqres.full
+}
+
+make_empty_leaf $e0_ino
+make_empty_leaf $e1_ino
+make_empty_leaf $e2_ino
+
+_scratch_mount
+
+# Check that listxattr/getxattr/removexattr do nothing.
+$ATTR_PROG -l $SCRATCH_MNT/e0 2>&1 | _filter_scratch
+$ATTR_PROG -g x $SCRATCH_MNT/e0 2>&1 | _filter_scratch
+$ATTR_PROG -r x $SCRATCH_MNT/e0 2>&1 | _filter_scratch
+
+# Add a small attr to e0
+$ATTR_PROG -s x $SCRATCH_MNT/e0 < $SCRATCH_MNT/smallfile > /dev/null
+$ATTR_PROG -l $SCRATCH_MNT/e0 2>&1 | sed -e 's/\([0-9]*\) byte/XXX byte/g' | _filter_scratch
+small_md5="$($GETFATTR_PROG -n user.x --absolute-names --only-values $SCRATCH_MNT/e0 | _md5_checksum)"
+test "$small_md5" = "$smallfile_md5" || \
+	echo "smallfile $smallfile_md5 does not match small attr $small_md5"
+
+# Add a large attr to e1
+$ATTR_PROG -s x $SCRATCH_MNT/e1 < $SCRATCH_MNT/largefile > /dev/null
+$ATTR_PROG -l $SCRATCH_MNT/e1 2>&1 | _filter_scratch
+large_md5="$($GETFATTR_PROG -n user.x --absolute-names --only-values $SCRATCH_MNT/e1 | _md5_checksum)"
+test "$large_md5" = "$largefile_md5" || \
+	echo "largefile $largefile_md5 does not match large attr $large_md5"
+
+
+# Leave e2 to try to trip the repair tools, since xfs_repair used to flag
+# empty leaf blocks incorrectly too.
+
+# success, all done
+status=0
+exit
diff --git a/tests/xfs/845.out b/tests/xfs/845.out
new file mode 100644
index 00000000..be4e5b7c
--- /dev/null
+++ b/tests/xfs/845.out
@@ -0,0 +1,7 @@
+QA output created by 845
+attr_get: No data available
+Could not get "x" for SCRATCH_MNT/e0
+attr_remove: No data available
+Could not remove "x" for SCRATCH_MNT/e0
+Attribute "x" has a XXX byte value for SCRATCH_MNT/e0
+Attribute "x" has a 65536 byte value for SCRATCH_MNT/e1