Re: [PATCH v3] btrfs: test block group size class loading logic

[Zorro Lang <zlang@redhat.com>]

On Thu, Jan 26, 2023 at 09:48:17AM -0800, Boris Burkov wrote:
> Add a new test which checks that size classes in freshly loaded block
> groups after a cycle mount match size classes before going down
> 
> Depends on the kernel patch:
> btrfs: add size class stats to sysfs
> 
> Signed-off-by: Boris Burkov <boris@bur.io>
> ---
> Changelog:
> v3:
> Re-add fixed_by_kernel_commit, but for the stats patch which is
> required, but not a fix in the strictest sense.
> 
> v2:
> Drop the fixed_by_kernel_commit since the fix is not out past the btrfs
> development tree, so the fix is getting rolled in to the original broken
> commit. Modified the commit message to note the dependency on the new
> sysfs counters.
> 
>  tests/btrfs/283     | 50 +++++++++++++++++++++++++++++++++++++++++++++
>  tests/btrfs/283.out |  2 ++
>  2 files changed, 52 insertions(+)
>  create mode 100755 tests/btrfs/283
>  create mode 100644 tests/btrfs/283.out
> 
> diff --git a/tests/btrfs/283 b/tests/btrfs/283
> new file mode 100755
> index 00000000..d250a389
> --- /dev/null
> +++ b/tests/btrfs/283
> @@ -0,0 +1,50 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2023 Meta Platforms, Inc.  All Rights Reserved.
> +#
> +# FS QA Test 283
> +#
> +# Test that mounting a btrfs filesystem properly loads block group size classes.
> +#
> +. ./common/preamble
> +_begin_fstest auto quick mount
> +fixed_by_kernel_commit xxxxxxxx "btrfs: add size class stats to sysfs".

    +/root/git/xfstests/tests/btrfs/283: line 11: fixed_by_kernel_commit: command not found

It's "_fixed_by_kernel_commit", you missed the "_" prefix.

> +
> +sysfs_size_classes() {
> +	local uuid="$(findmnt -n -o UUID "$SCRATCH_MNT")"
> +	cat "/sys/fs/btrfs/$uuid/allocation/data/size_classes"

I hit below error:
    +cat: /sys/fs/btrfs/7df0dfa8-b1cd-4646-bd30-8683bbf0a4f1/allocation/data/size_classes: No such file or directory
    +cat: /sys/fs/btrfs/7df0dfa8-b1cd-4646-bd30-8683bbf0a4f1/allocation/data/size_classes: No such file or directory

I think btrfs not always support the "allocation/data/size_classes" file. So
we need to check if current kernel supports that, and _notrun if not. The
_require_fs_sysfs might help you a bit.

Thanks,
Zorro

> +}
> +
> +_supported_fs btrfs
> +_require_scratch
> +_require_btrfs_fs_sysfs
> +
> +f="$SCRATCH_MNT/f"
> +small=$((16 * 1024))
> +medium=$((1024 * 1024))
> +large=$((16 * 1024 * 1024))
> +
> +_scratch_mkfs >/dev/null
> +_scratch_mount
> +# Write files with extents in each size class
> +$XFS_IO_PROG -fc "pwrite -q 0 $small" $f.small
> +$XFS_IO_PROG -fc "pwrite -q 0 $medium" $f.medium
> +$XFS_IO_PROG -fc "pwrite -q 0 $large" $f.large
> +# Sync to force the extent allocation
> +sync
> +pre=$(sysfs_size_classes)
> +
> +# cycle mount to drop the block group cache
> +_scratch_cycle_mount
> +
> +# Another write causes us to actually load the block groups
> +$XFS_IO_PROG -fc "pwrite -q 0 $large" $f.large.2
> +sync
> +
> +post=$(sysfs_size_classes)
> +diff <(echo $pre) <(echo $post)
> +
> +echo "Silence is golden"
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/btrfs/283.out b/tests/btrfs/283.out
> new file mode 100644
> index 00000000..efb2c583
> --- /dev/null
> +++ b/tests/btrfs/283.out
> @@ -0,0 +1,2 @@
> +QA output created by 283
> +Silence is golden
> -- 
> 2.39.1
>