[PATCH] fstests: btrfs: add a test case to verify fsverity on compressed files

[PATCH] fstests: btrfs: add a test case to verify fsverity on compressed files

[Qu Wenruo]

There is a bug report that with the recently enabled large folios
support, compressed files on btrfs can give random but reproducible
warnings about file corruption.

It turns out to be a bug in the verification range, where blocks not
included in the read range are passed to be verified.

Add a new regression test case for it, the workload is pretty simple:

- Create a 64M file with compressed file extents
- Enable fsverity digest on that file
- Drop page cache
- Read that file
- Verify there is no "FILE CORRUPTED!" warning

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 tests/btrfs/359     | 45 +++++++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/359.out |  6 ++++++
 2 files changed, 51 insertions(+)
 create mode 100755 tests/btrfs/359
 create mode 100644 tests/btrfs/359.out

diff --git a/tests/btrfs/359 b/tests/btrfs/359
new file mode 100755
index 00000000..2047d965
--- /dev/null
+++ b/tests/btrfs/359
@@ -0,0 +1,45 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2026 SUSE S.A.  All Rights Reserved.
+#
+# FS QA Test 359
+#
+# Test if btrfs handles fsverity read correctly without corruption warning
+#
+. ./common/preamble
+_begin_fstest auto quick verity compress
+
+_fixed_by_kernel_commit xxxxxxxxxxxx \
+	"btrfs: fix the fsverity callback where unexpected range is verified"
+
+. ./common/filter
+. ./common/verity
+
+_require_scratch_verity
+
+_scratch_mkfs_verity >> $seqres.full
+
+# We need a read range that doesn't cover the full folio, the easiest way
+# to create such read is compression, which limits the extent size to 128K,
+# much smaller than the supported large folio size (256K or 2M for 4K page size).
+_scratch_mount -o compress
+
+# Create a large enough file that can contain multiple compressed file extents.
+_pwrite_byte "0xcd" 0 64m "$SCRATCH_MNT/foobar" | _filter_xfs_io
+
+# Enable verity on that file
+_fsv_enable "$SCRATCH_MNT/foobar"
+
+# Cycle mount to drop page cache
+_scratch_cycle_mount
+
+# Read the file, unpatched kernel will race and trigger fs-verity warnings.
+# But the read itself should still be fine, as the failed part will be retried.
+_hexdump "$SCRATCH_MNT/foobar"
+
+# Check for any kernel warnings from fs-verity on file corruption.
+if _check_dmesg_for "FILE CORRUPTED!"; then
+	echo "fs-verity detected corruption"
+fi
+
+_exit 0
diff --git a/tests/btrfs/359.out b/tests/btrfs/359.out
new file mode 100644
index 00000000..96bd78d7
--- /dev/null
+++ b/tests/btrfs/359.out
@@ -0,0 +1,6 @@
+QA output created by 359
+wrote 67108864/67108864 bytes at offset 0
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+000000 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd  >................<
+*
+4000000
-- 
2.56.0

Re: [PATCH] fstests: btrfs: add a test case to verify fsverity on compressed files

[Eric Biggers]

On Sat, Oct 10, 2026 at 01:55:08PM +1030, Qu Wenruo wrote:
> There is a bug report that with the recently enabled large folios
> support, compressed files on btrfs can give random but reproducible
> warnings about file corruption.
> 
> It turns out to be a bug in the verification range, where blocks not
> included in the read range are passed to be verified.
> 
> Add a new regression test case for it, the workload is pretty simple:
> 
> - Create a 64M file with compressed file extents
> - Enable fsverity digest on that file
> - Drop page cache
> - Read that file
> - Verify there is no "FILE CORRUPTED!" warning
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
>  tests/btrfs/359     | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  tests/btrfs/359.out |  6 ++++++
>  2 files changed, 51 insertions(+)
>  create mode 100755 tests/btrfs/359
>  create mode 100644 tests/btrfs/359.out
> 
> diff --git a/tests/btrfs/359 b/tests/btrfs/359
> new file mode 100755
> index 00000000..2047d965
> --- /dev/null
> +++ b/tests/btrfs/359
> @@ -0,0 +1,45 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2026 SUSE S.A.  All Rights Reserved.
> +#
> +# FS QA Test 359
> +#
> +# Test if btrfs handles fsverity read correctly without corruption warning
> +#
> +. ./common/preamble
> +_begin_fstest auto quick verity compress
> +
> +_fixed_by_kernel_commit xxxxxxxxxxxx \
> +	"btrfs: fix the fsverity callback where unexpected range is verified"
> +
> +. ./common/filter
> +. ./common/verity
> +
> +_require_scratch_verity

Missing _require_check_dmesg?

Also, sourcing common/verity adds nodatasum to the mount options.
Doesn't that disable compression too?

- Eric

Re: [PATCH] fstests: btrfs: add a test case to verify fsverity on compressed files

[Qu Wenruo]

在 2026/10/10 18:32, Eric Biggers 写道:
> On Sat, Oct 10, 2026 at 01:55:08PM +1030, Qu Wenruo wrote:
>> There is a bug report that with the recently enabled large folios
>> support, compressed files on btrfs can give random but reproducible
>> warnings about file corruption.
>>
>> It turns out to be a bug in the verification range, where blocks not
>> included in the read range are passed to be verified.
>>
>> Add a new regression test case for it, the workload is pretty simple:
>>
>> - Create a 64M file with compressed file extents
>> - Enable fsverity digest on that file
>> - Drop page cache
>> - Read that file
>> - Verify there is no "FILE CORRUPTED!" warning
>>
>> Signed-off-by: Qu Wenruo <wqu@suse.com>
>> ---
>>   tests/btrfs/359     | 45 +++++++++++++++++++++++++++++++++++++++++++++
>>   tests/btrfs/359.out |  6 ++++++
>>   2 files changed, 51 insertions(+)
>>   create mode 100755 tests/btrfs/359
>>   create mode 100644 tests/btrfs/359.out
>>
>> diff --git a/tests/btrfs/359 b/tests/btrfs/359
>> new file mode 100755
>> index 00000000..2047d965
>> --- /dev/null
>> +++ b/tests/btrfs/359
>> @@ -0,0 +1,45 @@
>> +#! /bin/bash
>> +# SPDX-License-Identifier: GPL-2.0
>> +# Copyright (c) 2026 SUSE S.A.  All Rights Reserved.
>> +#
>> +# FS QA Test 359
>> +#
>> +# Test if btrfs handles fsverity read correctly without corruption warning
>> +#
>> +. ./common/preamble
>> +_begin_fstest auto quick verity compress
>> +
>> +_fixed_by_kernel_commit xxxxxxxxxxxx \
>> +	"btrfs: fix the fsverity callback where unexpected range is verified"
>> +
>> +. ./common/filter
>> +. ./common/verity
>> +
>> +_require_scratch_verity
> 
> Missing _require_check_dmesg?

Right, thanks for pointing out this.
> 
> Also, sourcing common/verity adds nodatasum to the mount options.
> Doesn't that disable compression too?

It can still be override by the extra "-o compress" option at later 
_scratch_mount() call.

In fact after the run, the fs still has compressed extents, e.g:

	item 201 key (257 EXTENT_DATA 66977792) itemoff 5577 itemsize 53
		generation 9 type 1 (regular)
		extent data disk byte 15724544 nr 4096
		extent data offset 0 nr 131072 ram 131072
		extent compression 1 (zlib)
		extent encryption 0

On the hand, I believe it's possible to craft a generic test case that 
doesn't require any btrfs specific mount option.

Using holes can still force btrfs to split the reads and trigger the 
warning.

I'll send out a generic test instead.

Thanks,
Qu





> 
> - Eric