[PATCH v4] btrfs: test block group size class loading logic

[PATCH v4] btrfs: test block group size class loading logic

[Boris Burkov]

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:
v4:
Fix dump typo in _fixed_by_kernel_commit (left out leading underscore
copy+pasting). Re-tested happy and sad case...

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..2176c8e4
--- /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".
+
+sysfs_size_classes() {
+	local uuid="$(findmnt -n -o UUID "$SCRATCH_MNT")"
+	cat "/sys/fs/btrfs/$uuid/allocation/data/size_classes"
+}
+
+_supported_fs btrfs
+_require_scratch
+_require_btrfs_fs_sysfs
+
+f="$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

Re: [PATCH v4] btrfs: test block group size class loading logic

[Filipe Manana]

On Thu, Jan 26, 2023 at 6:02 PM Boris Burkov <boris@bur.io> 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:
> v4:
> Fix dump typo in _fixed_by_kernel_commit (left out leading underscore
> copy+pasting). Re-tested happy and sad case...
>
> 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..2176c8e4
> --- /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

Why the mount group? We aren't testing mount options.
It's a bit odd to me.

> +_fixed_by_kernel_commit xxxxxxxx "btrfs: add size class stats to sysfs".

Should be _wants_kernel_commit here, because it's a new feature and
not a bug fix.

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

This alone is not enough.

What if we are running in a kernel with btrfs' sysfs support but
without the size classes?
I.e. the allocation/data/size_classes path does not exist.

Then the test fails with:

cat: /sys/fs/btrfs/95da1e36-8411-468a-abeb-71652dc2092b/allocation/data/size_classes:
No such file or directory

Instead the test just be skipped, i.e. calling:  _notrun "allocation
size classes not supported"

Thanks.

> +
> +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
>