Re: [PATCH v2] generic: test replacing a xattr with a larger value

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

On Fri, Sep 25, 2026 at 06:16:36PM +0100, fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> Test that replacing a xattr's value with a larger value works. This is a
> test that exercises a specific scenario on btrfs where two xattrs are
> stored in the same item, and for that to happen their names must result
> in the same crc32c hash.
> 
> This was recently fixed by the following patch:
> 
>   "btrfs: fix xattr replace when multiple xattrs are packed in the same item"
> 
> Signed-off-by: Filipe Manana <fdmanana@suse.com>
> 
> V2: Fix missing _ on _fixed_by_fs_commit call.
> 
>  tests/generic/806     | 43 +++++++++++++++++++++++++++++++++++++++++++
>  tests/generic/806.out | 11 +++++++++++
>  2 files changed, 54 insertions(+)
>  create mode 100755 tests/generic/806
>  create mode 100644 tests/generic/806.out
> 
> diff --git a/tests/generic/806 b/tests/generic/806
> new file mode 100755
> index 00000000..1fcf0145
> --- /dev/null
> +++ b/tests/generic/806
> @@ -0,0 +1,43 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2026 SUSE S.A.  All Rights Reserved.
> +#
> +# FS QA Test 806
> +#
> +# Test replacing a xattr's value with a larger value.
> +#
> +. ./common/preamble
> +_begin_fstest auto quick metadata attr
> +
> +. ./common/filter
> +. ./common/attr
> +
> +_require_scratch
> +_require_attrs
> +
> +_fixed_by_fs_commit btrfs xxxxxxxxxxxx \
> +   "btrfs: fix xattr replace when multiple xattrs are packed in the same item"
> +
> +_scratch_mkfs >>$seqres.full 2>&1 || _fail "mkfs failed"
> +_scratch_mount
> +
> +touch $SCRATCH_MNT/testfile
> +
> +# Add two xattrs that, on btrfs, have the same hash (crc32c) for their name
> +# and therefore are packed into the same btrfs_dir_item.
> +$SETFATTR_PROG -n user.foobar -v 123 $SCRATCH_MNT/testfile
> +$SETFATTR_PROG -n user.WvG1c1Td -v qwerty $SCRATCH_MNT/testfile

Heh, glad there's a test for this sort of collision thing. :)
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> +
> +# Verify the xattrs are present.
> +echo "xattrs before:"
> +_getfattr --absolute-names --dump $SCRATCH_MNT/testfile | _filter_scratch
> +
> +# Now replace the value of the foobar xattr with a significantly larger value.
> +$SETFATTR_PROG -n user.foobar -v abcdefghijklmnopqrstuvwxyz $SCRATCH_MNT/testfile
> +
> +# Check the xattrs have the expected values.
> +echo "xattrs after:"
> +_getfattr --absolute-names --dump $SCRATCH_MNT/testfile | _filter_scratch
> +
> +# success, all done
> +_exit 0
> diff --git a/tests/generic/806.out b/tests/generic/806.out
> new file mode 100644
> index 00000000..620a953e
> --- /dev/null
> +++ b/tests/generic/806.out
> @@ -0,0 +1,11 @@
> +QA output created by 806
> +xattrs before:
> +# file: SCRATCH_MNT/testfile
> +user.WvG1c1Td="qwerty"
> +user.foobar="123"
> +
> +xattrs after:
> +# file: SCRATCH_MNT/testfile
> +user.WvG1c1Td="qwerty"
> +user.foobar="abcdefghijklmnopqrstuvwxyz"
> +
> -- 
> 2.47.2
> 
>