Re: [PATCH] generic: add a test case for fallocate i_size extension

[Zorro Lang <zlang@kernel.org>]

On Tue, May 19, 2026 at 06:14:10PM +0100, fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> Test an i_size expanding fallocate into a range beyond current i_size that
> already has a preallocated extent, with an unmount and mount after each
> fallocate to verify that no metadata (i_size) and extents were lost.
> 
> This used to fail on btrfs when not using the no-holes feature (which is
> a default since btrfs-progs 5.15) before this recent kernel fix:
> 
>   c562ba61fc5e ("btrfs: fix incorrect i_size after remount caused by KEEP_SIZE prealloc gap")
> 
> So in order to reproduce the failure when using an unpatched kernel and
> a btrfs-progs >= 5.15, one must run the test with:
> 
>   MKFS_OPTIONS="-O ^no-holes"
> 
> Signed-off-by: Filipe Manana <fdmanana@suse.com>
> ---

Classic, Filipe! As standard as always. Even the tiny details like comments,
groups, _require_congruent_file_oplen and so on are perfect.

Reviewed-by: Zorro Lang <zlang@kernel.org>

>  tests/generic/795     | 52 +++++++++++++++++++++++++++++++++++++++++++
>  tests/generic/795.out |  5 +++++
>  2 files changed, 57 insertions(+)
>  create mode 100755 tests/generic/795
>  create mode 100644 tests/generic/795.out
> 
> diff --git a/tests/generic/795 b/tests/generic/795
> new file mode 100755
> index 00000000..299c8134
> --- /dev/null
> +++ b/tests/generic/795
> @@ -0,0 +1,52 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2026 SUSE S.A.  All Rights Reserved.
> +#
> +# FS QA Test 795
> +#
> +# Test an i_size expanding fallocate into a range beyond current i_size that
> +# already has a preallocated extent, with an unmount and mount after each
> +# fallocate to verify that no metadata (i_size) and extents were lost.
> +#
> +. ./common/preamble
> +_begin_fstest auto quick prealloc fiemap
> +
> +. ./common/punch # for _filter_fiemap
> +
> +_require_scratch
> +_require_xfs_io_command "falloc" "-k"
> +_require_xfs_io_command "fiemap"
> +
> +_fixed_by_fs_commit btrfs c562ba61fc5e \
> +	"btrfs: fix incorrect i_size after remount caused by KEEP_SIZE prealloc gap"
> +
> +_scratch_mkfs >>$seqres.full 2>&1
> +_scratch_mount
> +
> +# The fiemap results in the golden output requires file allocations to align to
> +# 1M boundaries.
> +_require_congruent_file_oplen $SCRATCH_MNT 1048576
> +
> +# Create our file with a size of 0 and a prealloc extent in the range [4M, 8M].
> +$XFS_IO_PROG -f -c "falloc -k 4M 4M" $SCRATCH_MNT/foo
> +
> +# Unmount and mount again to remove any in memory state of the inode. We will
> +# verify later that neither metadata nor extents were lost during unmount.
> +_scratch_cycle_mount
> +
> +# Do an i_size expanding fallocate that overlaps the previous prealloc range
> +# and extents past it. This increases the file size to 9M and allocates an
> +# extent in the range [8M, 9M].
> +$XFS_IO_PROG -c "falloc 7M 2M" $SCRATCH_MNT/foo
> +
> +# Unmount and mount again to remove any in memory state of the inode. We will
> +# verify later that neither metadata nor extents were lost during unmount.
> +_scratch_cycle_mount
> +
> +# File size should be 9M and we should have unwritten extents in range [4M, 9M].
> +echo "File size after cycle mounts: $(stat -c %s $SCRATCH_MNT/foo)"
> +echo "Fiemap output:"
> +$XFS_IO_PROG -c "fiemap -v" $SCRATCH_MNT/foo | _filter_fiemap
> +
> +# Success, all done.
> +_exit 0
> diff --git a/tests/generic/795.out b/tests/generic/795.out
> new file mode 100644
> index 00000000..b2f78ac0
> --- /dev/null
> +++ b/tests/generic/795.out
> @@ -0,0 +1,5 @@
> +QA output created by 795
> +File size after cycle mounts: 9437184
> +Fiemap output:
> +0: [0..8191]: hole
> +1: [8192..18431]: unwritten
> -- 
> 2.47.2
> 
>