Re: [RFC PATCH] fstests: test fix for an agbno overflow in __xfs_getfsmap_datadev

[Dave Chinner <david@fromorbit.com>]

On Tue, Aug 22, 2023 at 06:02:39PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> Dave Chinner reported that xfs/273 fails if the AG size happens to be an
> exact power of two.  I traced this to an agbno integer overflow when the
> current GETFSMAP call is a continuation of a previous GETFSMAP call, and
> the last record returned was non-shareable space at the end of an AG.
> 
> This is the regression test for that bug.
> 
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---
>  tests/xfs/935     |   55 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  tests/xfs/935.out |    2 ++
>  2 files changed, 57 insertions(+)
>  create mode 100755 tests/xfs/935
>  create mode 100644 tests/xfs/935.out
> 
> diff --git a/tests/xfs/935 b/tests/xfs/935
> new file mode 100755
> index 0000000000..a06f2fc8dc
> --- /dev/null
> +++ b/tests/xfs/935
> @@ -0,0 +1,55 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2023 Oracle.  All Rights Reserved.
> +#
> +# FS QA Test 935
> +#
> +# Regression test for an agbno overflow bug in XFS GETFSMAP involving an
> +# fsmap_advance call.  Userspace can indicate that a GETFSMAP call is actually
> +# a continuation of a previous call by setting the "low" key to the last record
> +# returned by the previous call.
> +#
> +# If the last record returned by GETFSMAP is a non-shareable extent at the end
> +# of an AG and the AG size is exactly a power of two, the startblock in the low
> +# key of the rmapbt query can be set to a value larger than EOAG.  When this
> +# happens, GETFSMAP will return EINVAL instead of returning records for the
> +# next AG.
> +#
> +. ./common/preamble
> +_begin_fstest auto quick fsmap
> +
> +. ./common/filter
> +
> +_fixed_by_git_commit kernel XXXXXXXXXXXXX \
> +	"xfs: fix an agbno overflow in __xfs_getfsmap_datadev"
> +
> +# Modify as appropriate.
> +_supported_fs generic
> +_require_xfs_io_command fsmap
> +_require_xfs_scratch_rmapbt
> +
> +_scratch_mkfs | _filter_mkfs 2> $tmp.mkfs >> $seqres.full
> +source $tmp.mkfs
> +
> +# Find the next power of two agsize smaller than whatever the default is.
> +for ((p = 31; p > 0; p--)); do
> +	desired_agsize=$((2 ** p))
> +	test "$desired_agsize" -lt "$agsize" && break
> +done
> +
> +echo "desired asize=$desired_agsize" >> $seqres.full
                 agsize

Otherwise looks fine.

Reviewed-by: Dave Chinner <dchinner@redhat.com>
-- 
Dave Chinner
david@fromorbit.com