Re: [RFC,2/2] xfstests: common/rc: add cluster size support for ext4

Sorry for digging this really old post [1]. The overall background is
that, @offset and @len need to be aligned with cluster size when doing
fallocate(), or several xfstests cases calling fsx will fail if the
tested filesystem enabling 'bigalloc' feature.

On April 27, 2020, 5:33 p.m. UTC Darrick J. Wong wrote:

On Fri, Apr 24, 2020 at 05:33:50PM +0800, Jeffle Xu wrote:

quoted

Inserting and collapsing range on ext4 with 'bigalloc' feature will
fail due to the offset and size should be alligned with the cluster
size.

The previous patch has add support for cluster size in fsx. Detect and
pass the cluster size parameter to fsx if the underlying filesystem
is ext4 with bigalloc.

Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
---
 common/rc | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/common/rc b/common/rc
index 2000bd9..71dde5f 100644
--- a/common/rc
+++ b/common/rc

@@ -3908,6 +3908,15 @@ run_fsx()
 {
 	echo fsx $@
 	local args=`echo $@ | sed -e "s/ BSIZE / $bsize /g" -e "s/ PSIZE / $psize /g"`
+
+	if [ "$FSTYP" == "ext4" ]; then
+		local cluster_size=$(tune2fs -l $TEST_DEV | grep 'Cluster size' | awk '{print $3}')
+		if [ -n $cluster_size ]; then
+			echo "cluster size: $cluster_size"
+			args="$args -u $cluster_size"
+		fi
+	fi

Computing the file allocation block size ought to be a separate helper.

I wonder if there's a standard way to report cluster sizes, seeing as
fat, ext4, ocfs2, and xfs can all have minimum space allocation units
that are larger than the base fs block size.

In fact only for insert_range and collapse range of ext4 and xfs (in
realtime mode), @offset and @len need to be aligned with cluster size.

Though fat and ocfs2 also support cluster size, ocfs2 only supports
preallocate and punch_hole, and fat only supports preallocate, in which
case @offset and @len needn't be aligned with cluster size.


So we need to align @offset and @len with cluster size only for ext4 and
xfs (in realtime mode) at a minimum cost, to fix this issue. But the
question is, there's no standard programming interface exporting cluster
size. For both ext4 and xfs, it's stored as a binary data in disk
version superblock, e.g., tune2fs could detect the cluster size of ext4.


Any idea on how to query the cluster size?


[1]
https://patchwork.kernel.org/project/fstests/cover/1587720830-11955-1-git-send-email-jefflexu@linux.alibaba.com/

-- 
Thanks,
Jeffle