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

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

On Sat, Jul 09, 2022 at 01:27:20AM +0800, Zorro Lang wrote:
> On Sat, Jul 09, 2022 at 01:08:27AM +0800, Zorro Lang wrote:
> > On Fri, Jul 08, 2022 at 10:02:04AM -0700, Darrick J. Wong wrote:
> > > 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>
> > > ---
> > 
> > This version looks good to me, thanks for this new case!
> > 
> > Reviewed-by: Zorro Lang <zlang@redhat.com>
> 
> Errr.. I just noticed that there's not .out file in this patch, and it's not
> simple "Silence is golden" I think.

<sigh> guess who forgot to git add? :(

--D

> Thanks,
> Zorro
> 
> > 
> > > 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
> > > ---
> > >  tests/xfs/845 |  117 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 117 insertions(+)
> > >  create mode 100755 tests/xfs/845
> > > 
> > > 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
> > > 
>